Glossary of oceanographic terms

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SPECIAL PUBLICATION

Glossary of
Oceanographic Terms

2d Edition
1966

Edited by B. B. BAKER, Jr.,
W. R. DEEBEL, R. D. GEISENDERFER

Oceanographic Analysis Division
Marine Sciences Department

U.S. NAVAL OCEANOGRAPHIC OFFICE
Washington, D.C. 20390

For sale by authorized sales agents of the U.S. Naval Oceanographic Office; also by Superintendent
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Foreword

The increasing application of oceanography to naval opera-
tions, planning, and research is resulting in the dissemination
to the Fleet of many types of publications by this Office. The
intent of this glossary is to provide the users of our publications
with current basic definitions of the technical terms used therein
as an md to the understanding, interpretation, and application
of the environmental data presented. Hopefully, others in the
oceanographic community will find this glossary helpful.

To improve future editions of this publication, users are
urged to submit comments, suggestions, and pertinent material.

O. D. WATERS, JR.
Rear Admiral, U.S. Navy
Commander

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PREFACE

This glossary attempts to provide the
U.S. Fleet; Naval shore facilities, lab-
oratories, planning staffs, and instruc-
tional components; other governmental
agencies concerned with the marine en-
vironment; foreign hydrographic/ocean-
ographie activities; merchant marine;
ocean engineering industry; and the
oceanographic community in general
with definitions of technical terms used
in oceanography and allied marine
sciences.

As the field of oceanography encom-
passes practically all of the scientific
disciplines, the compilers of this glos-
sary recognized from the outset that,
within the prescribed framework of
time, manpower, and funds, this publi-
cation could not possibly include the
entire complex lexicon which has evolved
from the marine sciences over the past
few decades. For the most part, the
terms and definitions cited here repre-
sent current and, in some places, past
usage in the marine aspects of physics,
chemistry, biology, geology, geophysics,
geography, mathematics, and meteorol-
ogy, particularly in the manner that
these terms are used in the U.S. Naval
Oceanographic Office research, opera-
tions, and publications.

The selection of terms for inclusion,
together with their definitions, was left
to the discretion of the several subject
specialists employed at this Office who
contributed the bulk of this volume.
Generally, terms and their definitions
were selected from existing sources or
publications dealing with specific aspects
of oceanography, as well as the few
available related glossaries. Some terms
in borderline subject areas were included
arbitrarily, and the tendency here was
probably toward overinclusion. In ad-

dition to compilation, review, consolida-
tion, and design of format by the editing
committee, another substantive review of
the entire manuscript was performed by
the various components of this Office,
among whom draft copies were circu-
lated.

In order that this glossary may serve
the user with minimum effort of his
part, the terms are arranged alphabeti-
caliy and followed immediately by a
definition or a reference to the preferred
synonym. Jn some entries the user is
referred to a related term whose defini-
tion contains an explanation of the term
in question. Synonyms, symbols, and
scientific names are italicized. An aster-
isk indicates a copyrighted name. Nearly
all terms are singular nouns; verbs and
adjectives have been kept to a minimum.
Also, mathematical equations have been
kept to a minimum and, where possible,
stated in sentence form. Where a term
has more than one definition, each defi-
nition is numbered, the first definition
representing the term’s applicability to
oceanography or its use in this Office;
otherwise, the sequence is arbitrary. As
a further aid to the user, some words
(in boldface type) within a definition
indicate an internal cross reference
whereby the user can go to a term de-
fined elsewhere in this glossary. Every
effort was made to keep the definitions
as uncomplicated as possible, since this
glossary is not intended to be ‘‘encyclo-
pedic.’”’ Illustrations have been used
sparingly and confined to the simplest
forms of representation.

Although the references used in pre-
paring this glossary represent only a
small portion of the extensive literature
devoted to the marine sciences, the List
of Sources can serve the user by: 1)

giving the authoritative source of a defi-
nition and 2) giving sources from which
a review of a specific subject can be
made. Where the definition given re-
flects substantially that given in the
source, a number in parentheses corre-
sponding to that item in the List of
Sources follows the definition. If a
term has multiple definitions, the loca-
tion of the source number underneath
the entry on the left indicates that this
source supports all definitions; other-
wise, each definition has its own refer-
ence number, if applicable. Definitions
containing no source number represent
_the opinion of the contributing specialist

vi

or a major modification of an existing
definition.

As a further guide to the user, ap-
pendixes are included which contain in-
formation of possible interest, although
not necessarily within the basic scope
of a glossary. Appendix A contains
abbreviations and acronyms related to
oceanography-oriented Navy projects,
operations, and equipment and scientific
usage in general. Appendix B contains
abbreviations, titles, and locations of in-
stitutions, agencies, activities, and
groups currently engaged either directly
in oceanography or in work in closely
allied marine sciences.

abioseston—See tripton.

ablation—1. The combined processes (such as sub-
limation, melting, evaporation) which remove
snow or ice from the surface of a glacier, snow-
field, etc.; in this sense, the opposite of alimen-
tation. Particularly in glaciology, the term
may be applied to reduction of the entire snow-
ice mass, and may also include losses by wind
action and by calving.

Air temperature is the dominant factor in con-
trolling ablation; precipitation amounts exer-
cise only secondary control. During the abla-
tion season, an ablation rate of about two milli-
meters per hour is typical of most glaciers.

2. The amount of snow or ice removed by the
above processes; in this sense, the opposite of
accumulation.

(5)

abnormal—Opposed to normal in whatever sense
the latter term is used. When normal signifies
typical, abnormal means unusual, lying outside
the range of common occurrence. When normal
signifies an arithmetic mean or median value,
abnormal implies a deviation, however slight,
from the mean or median. (5)

abrasion—The wearing away or rounding of sur-
faces by friction; for example, the action of
glaciers, wind, and waterborne sand on rocks
or rock fragments.

abrasion platform—A surface of marine denuda-
tion formed by wave erosion which is still in its
original position at or near the wave base, with
the marine forces still operating on it.

absolute index of refraction—=Sce index of re-
fraction (sense 1).

absolute refractive index—wSce index of refrac-
tion (sense 1).

absolute temperature scale—(abbreviated A).
See Kelvin temperature scale.

absorptance—The ratio of the radiant flux lost
from a beam by means of absorption to the in-
cident flux. (8)

absorption—1. The process in which incident ra-
diant energy is retained by a substance. A fur-
ther processs always results from absorption,
that 1s, the irreversible conversion of the ab-
sorbed radiation into some other form of energy
within and according to the nature of the ab-
sorbing medium. The absorbing medium itself
may emit radiation, but only after an energy
conversion has occurred.

A substance which absorbs energy may also be
a medium of reflection, refraction, diffraction,
or Scattering ; these processes, however, involve
no energy retention or transformation and are
to be clearly differentiated from absorption.
See attenuation.

2. In general, the taking up or assimilation of
one substance by another, where the two sub-
stances chemically or physically combine.

(5)

absorption coefficient—1. A measure of the
amount of normally incident radiant energy
absorbed through a unit distance or by a mass
of absorbing medium. (5)

2. For dissolved gases: Maximum volume of
gas that can be dissolved in a unit volume of
water. The absorption coefficient of gases gen-
erally decreases with increasing temperature and
salinity.

absorption factor —See absorptivity.

absorption loss—That part of the transmission
loss which is due to dissipation or the conversion
of sound energy into some other form of energy,
usually heat. This conversion may take place
within the medium itself or upon a reflection at
one of its boundaries. (3)

absorptivity—(also called absorption factor).
A measure of the amount of radiant energy ab-
sorbed by a given substance of definite dimen-
sions; defined as the ratio of the amount of ra-
diant energy absorbed to the total amount inci-
dent upon that substance. (5)

abyss—A particularly deep part of the ocean, or
any part below 300 fathoms. (68)

abyssal—(or abyssobenthic). Pertaining to the
great depths of the ocean, generally below 2,000
fathoms (3,700 meters). (See figure for clas-
sification of marine environments.)

abyssalbenthic—According to some authorities
corresponding to the approximate lower half of
the bathyal and all of the abyssal and hadal.
See classification of marine environments.

Pertaining to a deep sea zone extending below
400 to 600 fathoms (800 to 1,100 meters) and
comprising all of the deep sea benthic system
below the archibenthic zone.

abyssal gap—This term is not recommended by
ACUF. See gap.

abyssal hill—This term is not recommended by
ACUF. See knoll.

abyssal plain—This term is not recommended by
ACUF. See plain.

ABYSSOBENTHIC

abyssobenthic—Scee abyssal.

abyssopelagic—Pertaining to that portion of the
ocean which lies below depths of 2,000 fathoms
(3,700 meters). (See figure for classification
of marine environments.)

acceleration—The rate of change with time of
speed and/or velocity ; strictly, the rate of change
with time of the velocity of a particle. (5)

In the egs system of physical measurements, it
is expressed in terms of centimeters per second
per second. See gal. (37)

acceleration of gravity—The acceleration of a
freely falling body due to the gravitational at-
traction of the earth. Its true value varies with
latitude, altitude, and the nature of the under-
lying rocks.

accelerometer—A device which measures the
forces of acceleration acting on a body within
the instrument. Among many uses it can be
used to measure wave effect on a ship at sea.

accepted depth—(sometimes called observed
depth). The best possible determination of the
true depth of each Nansen bottle at the time of
reversal. (67)

accretion—1. Natural accretion is the gradual
build-up of land over a long period of time
solely by the action of the forces of nature, on a
beach by deposition of water or airborne ma-
terial. Artificial accretion is a similar build-up
of land by reason of an act of man, such as the
accretion formed by a groin, breakwater, or
beach fill deposited by mechanical means. (61)
See aggradation.

2. The process by which inorganic masses
grow larger, by the addition of fresh particles to
the outside. (2)

accretionary limestone—A limestone which has
formed in situ by slow accumulation of organic
remains such as coral or shells. (2) See bio-
strome, bioherm, organic reef.

accumulation—In glaciology, the quantity of
snow or other solid form of water added to a
glacier or snowfield by alimentation; the op-
posite of ablation. (5)

accuracy—The degree of conformity with a stand-
ard. Accuracy relates to the quality of a result,
and is distinguished from precision which re-
lates to the quality of the operation by which the
result is obtained. (37)

acicular ice—(also called fibrous ice, satin ice).
Fresh water ice consisting of numerous long
crystals and hollow tubes having variable form,
layered arrangement, and a content of air bub-
bles. This ice often forms at the bottom of an
ice layer near its contact with water. (59)

acid rock—Igneous rock containing a high pro-
portion of silica, contrasted with basic rock in a
two-division classification of rocks. (2)

aclinic line—(or dip equator, magnetic equator).
The line through those points on the earth’s sur-
face at which the magnetic inclination is zero.

The aclinic line is a particular case of an iso-
clinic line.

In South America the aclinic line lies at about
15°S; while from central Africa to about Viet-
nam it coincides approximately with the parallel
of 10°N. (5)

acorn barnacle—(or rock barnacle). A barna-
cle (Blanidae) whose shell is attached or
cemented directly to a firm surface.

acoustic, acoustical—These two qualifying ad-
jectives can be confused and, in fact, are often
misused. The qualifying adjective acoustic is
used when the term which it modifies desig-
nates something which has the properties,
dimensions, or physical characteristics, asso-
ciated with sound waves. The adjective acousti-
cal, on the other hand, is used when the term
being qualified does not innately contain some
property, dimension, or physical characteristic
which is intimately associated with sound.
Thus, we speak of an acoustic impedance, but
a speak of the Acoustical Society of America.

3)

acoustic bearing—Sce sonic bearing.

acoustic dispersion—1. The scattering or
spreading of sound with frequency.

2. The separation of a complex sound wave
into its various frequency components, usually
caused by a variation with frequency of the
wave velocity of the medium. The rate of
change of the velocity with frequency is used as
a measure of the dispersion. (6)

acoustic impedance—For a given surface area of
an acoustic medium perpendicular, at every
point, to the direction of propagation of
sinusoidal acoustic waves of given frequency,
and having equal acoustic pressures and equal
volume velocities per unit area at every point
of the surface at any instant, the acoustic
impedance is the quotient obtained by dividing
(1) the phasor corresponding to the acoustic
pressure by (2) the phasor corresponding to
the volume velocity. (28)

acoustic intensity—The limit approached by the
quotient obtained by dividing the power of the
acoustic energy being transmitted at a given
time through a given area by the magnitude of
this area as the magnitude of this area ap-
proaches zero.

pe

where intensity, 7, in root mean square pressure,
P, of a plane wave, p is the density, and ¢ the
sound velocity. Units are energy per square
centimeter per second. (28)

acoustic pressure—The difference at a point be-
tween the instantaneous sound pressure and the
hydrostatic pressure.

acoustics—The science of sound, including its
production, transmission, and effects.

acoustic scattering—The irregular reflection,
refraction, or diffraction of a sound in many
directions. (3)

acoustic screen—A blanket of air bubbles that
effectively entraps backscattered sound energy.

acoustic signature—The graphic noise output
characteristic of and identified with a specific
noise source, for example, the noise output of a
particular class of submarine.

acoustic sounding—=wSce echo sounding.

acoustic wave—Sce sound wave.

acre-foot—The volume of water required to cover
one acre to a depth of one foot, hence 43,560 cubic
feet ; a convenient unit for measuring irrigation
water, runoff volume, and reservoir capacity.

5

Moree i pie science of measurement of
radiant energy, particularly that of the sun,
in its thermal, chemical (actinic), and luminous
aspects. (5)

actinotrocha—The planktonic larva of the bottom
dwelling worm Phoronas.

activated water—A transient chemically reactive
state created in water by absorbed ionizing radia-
tions. The passage of ionizing radiation
through water produces, temporarily, ions,
atoms, radicals, or molecules in a chemically
reactive state. The combined effect of all such
entities is said to be due to activated water.
Their identity has not been established with cer-
tainty, although evidence exists of the presence
of eo hydroxyl radicals and hydrogen atoms.
(41, 70)

activation—The process of inducing radioactiv-
ity through neutron bombardment or by other
types ofirradiation. (41)

activation analysis—A method of elemental
analysis, especially for small traces of material,
based on the detection of characteristic radio-
nuclides following a nuclear bombardment.
(41)

active glacier—A glacier which has an aceumu-
lation area, in contrast to a stagnant glacier.
An active glacier need not have an advancing
front. (59

active material—Fissionable material, such as
plutonium, uranium enriched in the isotope 233
or 235, and any other material capable of releas-
ing substantial quantities of atomic energy. In
the military field of atomic energy, the term
refers to the nuclear components of nuclear
weapons exclusive of the natural uranium parts;
or, in the field of nuclear power, it refers to the
nuclear fuel in atomic reactors. (63)

active sonar—The method or equipment by which
information concerning a distant object is ob-
tained through evaluation of the sound signal
reflected from the object to the generating
equipment. See passive sonar.

activity—1. The number of atoms decaying per
unit of time. The unit of activity is the curie,
3.7 X 10?° disintegrations persecond. (41)

AEOLIAN SANDS

2. A measure of the intensity of emission
from a radioactive substance in terms of ob-
servable effects, often expressed in counts per
unit of time. (41)

3. A term frequently used to designate a par-
ticular radioactive nuclide. (41)

4. A term frequently used to designate a par-
ticular radiation component, for example, the
gamma activity of asource. (41)

5. A term commonly used for radioactivity.
(41)

6. In practice, activity is often expressed in
terms of observable effects, such as counts per
minute or roentgens per hour at one meter.
(41)

7. Chemical activity of dissolution of salts.

adfreezing—The process by which one object be-
comes adhered to another by the binding action
ofice. (5)

adiabatic phenomena—Those phenomena which
occur without a gain or loss of heat.

adiabatic process—A thermodynamic change of
state of a system in which there is no transfer of
heat or mass across the boundaries of the system.
In an adiabatic process, compression always
results in warming, expansion in cooling. (5)

adiabatic temperature changes—The compres-
sion of a fluid without gain or loss of heat to the
surroundings is work performed on the system
and produces a rise or fall of temperature. Such
a rise or fall of temperature occurs with chang-
ing depth.

adjacent seas—Sce marginal seas.

adrift—Floating without moorings or anchor:
drifting at the mercy of the sea and weather.
See stopped.

adsorption—The adhesion of a thin film of liquid
or gas to a solid substance. The solid does not
chemically combine with the adsorbed sub-
stance. (5)

advance (of a shoreline)—1. A continuing sea-
ward movement of the shoreline.

2. A net seaward movement of the shoreline
over aspecified time. (61)

advection—1. In oceanography, advection refers
to the horizontal or vertical flow of sea water as
acurrent.

2. The process of transport of an atmospheric
property solely by the mass motion (velocity
field) of the atmosphere. In meteorology, ad-
vection describes the predominantly —hori-
zontal, large-scale motions of the atmosphere.

advection fog—1. A type of fog caused by the
advection of moist air over a cold surface, and
the consequent cooling of that air to below its
dew point.

A very common advection fog is that caused
by moist air in transport over a cold body of
water (sea fog).

; Sometimes applied to steam fog.
5

aeolian sands—S¢ee eolian sands.

AEROBE

aerobe—(also called aerobiont). An organism
which can live and grow only in the presence of
oxygen. An organism which employs aerobic
respiration.

aerobiont—Sce aerobe.

A-frame—A steel frame used for outboard sus-
pension of oceanographic gear in shipboard sur-
vey work, so named because of its A-shape.

afternoon effect—The solar heating of the surface
water, which causes a shallow negative tempera-
ture gradient. The net result is downward
refraction of sound rays and reduction in near-
surface ranges.

aftershock—An earthquake which follows a
larger earthquake and originates at or near the
focus of the largerearthquake. (2)

age—1. See age of phase inequality.

2. The stage of development of sea ice. The
term usually refers to the length of time since its
formation and toits thickness.

age dating—The calculation of the absolute age
of a material by such means as the fossil record
or by radioactive determination of the number
of atoms of a stable radiogenic end product rela-
tive to the number of atoms of its radioactive
parent.

age of diurnal inequality—(or age of diurnal
tide). The time interval between the maximum
semimonthly north or south declination of the
moon and the maximum effect of the declination
upon the range of tide or speed of the tidal
current. (50)

age of diurnal tide—Sce age of diurnal inequal-
ity.

age of moon—The time elapsed since the preced-
ingnewmoon. (50)

age of parallax inequality—The time interval
between the perigee of the moon and the maxi-
mum effect of the parallax (distance of the
moon) upon the range of tide or speed of tidal
current. (50)

age of phase inequality—(or age, age of tide).
The time interval between the new or full moon
and the maximum effect of these phases upon the
range of tide or speed of tidal current. (50)

age of tide—See age of phase inequality.

age of water—The time elapsed since a water mass
was last at the surface and in contact with the
atmosphere. The water’s age gives an indica-
tion of the rate of overturn of ocean water, an
important factor in the use of the oceans for
dumping radioactive wastes and determining
the rate of replenishment of nutrients.

The most commonly used method for deter-
mining the age of water involves the decay
rate of carbon™ whose half-life is 5,600 years.
This method gives the following approximate
ages to an accuracy of +100 years: North
Atlantic Central Water, 600 years; North At-
lantic Bottom Water, 900 years; North Atlantic
Deep Water, 700 years; Antarctic Intermediate

and Bottom Water (South Atlantic), less than
350 years.

Another method for determining the age of
water makes use of the depletion rate of dis-
solved oxygen. This method assumes that the
water was saturated with oxygen while at the
surface and that its oxygen was consumed at a
any rate by chemical combination with detritus.

45

agger—wScee double tide.

agglomerate—-see breccia.

aggradation—The process of building up a sur-
face by continuous or intermittent deposition.

aggregate sample—Sce compound sample.

agonic line—The line through all points on the
earth’s surface at which the magnetic declina-
tion is zero; that is, the locus of all points at
which magnetic north and true north coincide.
This line is a particular case of an isogonic line.
The position of this line exhibits variations in
time. (5)

agua enferma—See aguaje.

agua je—(also called salgaso, aqua enferma). An
annual condition noted in the coastal water of
Peru which results in discolored water (usually
red or yellow) and various degrees of destruc-
tion of marine life. Aguaje usually occurs
from April through June and is a local term
used along certain portions of the Peruvian
coast. The immediate cause of this condition is
the increase in water temperature when warmer
oceanic currents are carried inshore. Marine
organisms unaccustomed to warm water die and
decompose. Coincidentally large concentra-
tions of dinoflagellates form discolored water
patches. Dinoflagellates, in turn may destroy
marine organisms, possibly due to toxins they
contain. This is not the same as the massively
catastrophic condition associated with El Nino
which occurs approximately every seven years.

Agulhas Current—(sometimes called Agulhas
Stream). A fast current flowing southwest-
ward along the southeast coast of Africa.

Throughout the year, part of the South
Equatorial Current turns south along the east
coast of Africa and feeds the strong Agulhas
Current. To the south of 30°S the Agulhas
Current is a narrow, well-defined current that
extends less than 100 kilometers from the coast;
south of 35°S a major portion of the current
turns counterclockwise and joins the prevailing
eastward flow across the southern part of the
Indian Ocean. However, a small portion of the
Agulhas Current rounds the Cape of Good Hope
into the Atlantic Ocean.

Agulhas Stream—See Agulhas Current.

aid to navigation—1. A device external to a boat
or ship designed to assist in determination of
position, a safe course, or to warn of dangers.
Examples are: lighthouses, lights, buoys, day-
beacons, radio beacons, and electronic devices.
(51)

2. The expression “aid to navigation” should
not be confused with “navigational aid,” a broad
expression covering any instrument, device,
chart, method, ete. intended to assist in the navi-
gation of a craft. (68)

air bladder—(also called swim bladder, gas blad-
der). A membranous sac of atmospheric gases
lying in the body cavity between the vertebral
column and the alimentary tract of certain
fishes. It serves a hydrostatic function in most
fishes that possess it; in some it participates in
sound production.

airborne expendable bathythermograph—A
buoyant canister which is ejected into the water
from an aircraft to provide measurements of
water temperature with depth. The tempera-
ture information is transmitted to the aircraft.
The instrument is designed to measure the tem-
perature from the surface to 1,000 feet with an
accuracy of +5 percent in depth and a tempera-
ture accuracy of +0.5°F within the range of
28° to 90°F.

airborne oceanography—The use of airborne
platforms such as aircraft and helicopters to
study physical parameters of the ocean.

airborne radiation thermometer—An infrared-
sensing device which measures the sea surface
temperature from an aircraft.

airborne sea and swell recorder—A frequency
modulated continuous wave radar system used to
measure wave height from an aircraft.

air embolism—(also called trawmatic air em-
bolism). The blocking of an artery by an air
bubble. A serious potential injury among
divers or personnel escaping from submarines.
It is caused by an expansion of air inside the
lungs, which increases when the breath is held
during ascent. Lung tissues rupture, air is
forced into the capillaries of the lung, and the
resulting air bubbles are carried to the heart
and into the arterial system.

airglow—(also called night-sky light, permanent
aurora). The quasi-steady radiant emission
from the upper atmosphere over middle and low
latitudes; as distinguished from the sporadic
emission of auroras which occur over high lati-
tudes. Airglow is not to be confused with air-
light. (5)

airlight—In determinations of visual range, light
from sun and sky which is scattered into the eyes
of an observer by atmospheric suspensoids (and,
to slight extent, by air molecules) lying in the
observer’s cone of vision. That is, airlight
reaches the eye in the same manner that diffuse
sky radiation reaches the earth’s surface. Air-
light is not to be confused with airglow. (5)

air mass—A widespread body of air, the proper-
ties of which can be identified as (a) having been
established while that air was situated over a
particular region of the earth’s surface (air-
mass source region), and (b) undergoing spe-
cific modifications while in transit away from

ALEUTIAN LOW

the source region. An air mass is often defined
as a widespread body of air that is approxi-
mately homogeneous in its horizontal extent,
particularly with reference to temperature and
moisture distribution; in addition, the vertical
temperature and moisture variations are ap-
proximately the same over its horizontal extent.

The stagnation or long-continued motion of
air over a source region permits the vertical tem-
perature and moisture distribution of the air to
reach relative equilibrium with the underlying
surface. (5)

air-mass source region—An extensive area of the

earth’s surface over which bodies of air fre-
quently remain for a sufficient time to acquire
characteristic temperature and moisture proper-
ties imparted by that surface. Air so modified
becomes identifiable as a distinct air mass. (5)

aktological—Refers to nearshore shallow water

areas, environment, sediments, or life. (2)

Alaska Current—A current that flows northwest-

ward and westward along the coasts of Canada
and Alaska to the Aleutian Islands.

It contains water from the North Pacific Cur-
rent, and has the character of a warm current;
it therefore exercises an influence on climatic
conditions of the region similar, but on a smaller
scale, to that which the North Atlantic and
Norway Currents exercise on the climates of
northwestern Europe.

albedo—The ratio of the amount of electromag-

netic radiation reflected by a body to the
amount incident upon it, commonly expressed as
a percentage. The albedo is to be distinguished
from the reflectivity, which refers to one spe-
cific wavelength (monochromatic radiation).
(5)

In the oceans the albedo of the water’s sur-
face (direct solar radiation) ranges from about
6 to 11 percent between 40°N and 40°S; the
reflectivity for diffuse sky radiation is some-
what larger.

Alberta low—A low pressure area centered on the

eastern slope of the Canadian Rockies in the
province of Alberta, Canada.

Formerly, it was thought that such lows ac-
tually originated (more or less independently)
over this location. It isnow recognized that de-
pressions moving inland from the Pacific are
the actual parent systems. Alberta lows appear
as these systems enhance, or are enhanced by, the
dynamic trough that is atypical, almost semi-
permanent, feature of this region. (5)

Aleutian Current—A current setting southwest-

ward along the south coasts of the Aleutian
Islands.

Aleutian low—The low pressure center located

near the Aleutian Islands on mean charts of sea
level pressure. It represents one of the main
centers of action in the atmospheric circula-
tion of the Northern Hemisphere.

ALEXANDER’S ACRES

The Aleutian low is most intense in the winter
months; in summer it is displaced toward the
North Pole and is almost nonexistent. On a
daily basis, the area of the Aleutian low is
marked by alternating high and low pressure
centers, moving generally to the eastward; it is
not the scene of an intense stationary low. (5)

Alexander’s Acres—An unusual, but easily rec-
ognizable type of deep scattering layer record
(possibly caused by tent fish) in which the train
of echoes forms a series of crescentic or mound-
shaped traces. This type of layer record usually
occurs at a depth of about 180 fathoms and has
been recorded most consistently in the slope
water off the northeastern United States by
means of an echo sounder using 12-ke sound.

alga(e)—A thallophyte possessing chlorophyll;
includes almost all seaweeds. See red alga,
blue-green alga, brown alga, green alga.
algal ball—WSee algal biscuits.

algal biscuits— (also called algal ball, marl ball).
Spherical and disk-shaped bodies up to 20 centi-
meters in diameter, composed of algal lime-
stone and often dolomitic. (2)

algal limestone—A limestone composed largely of
the remains of calicum-secreting algae. (2)

algal reef—A reef composed largely of algal re-
mains.

algal ridge—The elevated margin of a windward
reef built by actively growing calcareous
algae. (2)

algal rim—A low rim built by actively growing
calcareous algae on the lagoonal side of a lee-
ward reef, or on the windward side of a reef
patchinalagoon. (2)

alignment —(also spelled alinement). In a near-
shore wave study, a line drawn on a chart par-
allel to the general direction of a section of
coast. The waves calculated to strike the mid-
point of the alignment are assumed to be char-
acteristic of those reaching the shallow water
of the entire section.

alignment chart—See nomogram.

alimentation—Generally, the process of provid-
ing nourishment or sustenance; thus in glaciol-
ogy, the combined processes which serve to in-
crease the mass of a glacier or snowfield; the
opposite of ablation. The deposition of snow
is the major form of glacial alimentation, but
other forms of precipitation along with sub-
limation, refreezing of melt water, etc. also
contribute.

The additional mass produced by alimenta-
tion is termed accumulation. (5)

alinement—WSee alignment.

alkalinity—In sea water, the excess of hydroxyl
ions over hydrogen ions, generally expressed as
milliequivalents per liter. (5)

allochem—Marine sediment formed by chemical
or biochemical precipitation; includes intra-
clasts, odlites, fossils, and pellets. (2)

allogenic—The term applied to rock or sediment
constituents which originated at a different
place and at a previous time to the rock of which
they now constitute a part. Examples are
pebbles in a conglomerate.

alluvium—The detrital deposits eroded, trans-
ported, and deposited by streams; an important
constituent of shelf deposits.

alpha particle—1. A positively charged particle
emitted from a nucleus and composed of two
protons and two neutrons. It is identical in all
measured properties with the nucleus of a helium
atom.

2. By extension, the nucleus of a helium atom,
especially when it is in rapid motion, as when
artificially accelerated.

(41)

alpha ray—A synonym for alpha particle. (70)

alternating current—See reversing current,
tidal current.

altitude—1. The vertical distance between a point
and a datum surface, such as mean sea level.

2. The vertical angle between the plane of the
horizon and the line to the observed point, as a
star.

3. See elevation.

(2)

ambient—The environment surrounding a body
but undisturbed or unaffected by it.

ambient noise—The noise produced in the sea by
marine animals, ship and industrial activity, ter-
restrial movements, precipitation, and other un-
derwater or surface activity outside the measur-
ing platform and detection equipment itself.

ambient temperature—The temperature of the
medium surrounding an object.

American Mediterranean—A name for the Car-
ibbean Sea and the Gulf of Mexico region.

ammonia nitrogen—An intermediate product of
the nitrogen cycle of the sea which is present
where organic matter decomposes in quantity.

amphidromic point—A no-tide or nodal point on
a chart of cotidal lines from which the cotidal
lines radiate. (See figure for cotidal chart.)

amphidromic region—An area surrounding an
amphidromic point in which the cotidal lines
radiate from the no-tide point and progress
through all hours of the tide cycle. (See figure
for cotidal chart.)

amphidromic system—Scee amphidromic region.

amphipod—One of an order (Amphipoda) of
elongate and usually laterally compressed
crustaceans. The species live in a variety of
habitats from the parasitic state to the deep
pelagic. Some species are semipermanent
members of fouling communities.

amphitrite—A large inflatable ship. Sixty-five
feet long, weighing 6 tons, it draws only 14
inches when fully loaded. It has been used as
a tender in sea-diving operations.

amplitude—1. The magnitude of the displacement
of a wave from a mean value. For a simple
harmonic wave, it is the maximum displace-
ment from the mean. For more complex wave
motion, amplitude is usually taken as one-half
the mean distance (or difference) between maxi-
mums and minimums.

An ocean surface wave has an amplitude equal
to the vertical distance from still water level to
wave crest, that is, one-half the wave height.

5)
2. In engineering usage, loosely, the wave
height from crest to trough. (61)
3. The semirange of a constituent tide. (50)

anadromous—A form of life cycle among fishes
in which maturity is attained in the ocean, and
the adults ascend streams and rivers to spawn
in fresh water. Salmon and shad are two ex-
amples.

anaerobe—(also called anaerobiont). Organisms
for whose life processes a complete or (in some
forms) nearly complete absence of oxygen is es-
sential. Facultative anaerobes can utilize free
oxygen; obligate anaerobes are poisoned by it.

anaerobic—Conditions in which oxygen is ex-
cluded, and as a result normal life that depends
on the presence of oxygen is not possible. Some
bacteria can, however, live in these conditions.
(32)

anaerobic sediment—A highly organic sediment
rich in 7,8 formed in the absence of free oxygen.
Characteristic of some fiords and marine basins
where little or no circulation or mixing of the
bottom water occurs.

anaerobiont—Sce anaerobe.

anchorage—1. An area where a ship anchors or
may anchor, either because of suitability or
designation.

2. Explosives anchorage—an area set part for
anchored ships discharging or receiving explo-
slves.

3. Exposed anchorage—an anchorage that is
unprotected from such dangers as weather, sea,
or Ice.

-4, Prohibited anchorage—a section of a har-
bor kept free of anchored ships.

5. Temporary anchorage—a place where ships
can anchor only under favorable conditions and
where ships must have power ready to get under
way.

anchorage stone—Scee anchor stone.

anchor ice—(also called bottom ice, depth ice,
ground ice, lappered ice, underwater ice). Ice
found attached or anchored to the bottom ir-
respective of its nature of formation. (74)

anchor stone—(or anchorage stone). A pebble
or boulder to which marine plants have attached
themselves. (2)

andesite line—The postulated geographic and
petrographic boundary between the andesite-
dacite-rhyolite rock association of the margin
of the Pacific Ocean and the olivine basalt-

ANGLE OF REFRACTION

trachyte rock association of the Pacific Ocean
basin and its included islands. (2)

anemometer—The general name for instruments
designed to measure the speed (or force) of the
wind. (5)

anemone—Sce Sea anemone.

aneroid—1. Literally, “not wet,” containing no
liquid; applied to a kind of barometer which
contains no liquid, an aneroid barometer.
2. See aneroid barometer.

5)

aneroid barometer—(rarely called holosteric
barometer). An instrument for measuring at-
mospheric pressure. It is constructed on the
following principles: an aneroid capsule (a thin
corrugated hollow disk) is partially evacuated
of gas, and is restrained from collapsing by an
external or internal spring. The deflection of
the spring will be nearly proportional to the
difference between the internal and external
pressures. Magnification of the spring deflec-
tion is obtained both by connecting capsules in
series and by mechanical linkages.

The aneroid barometer is temperature com-
pensated at a given pressure level by adjust-
ment of the residual gas in the aneroid or by a
bimetallic link arrangement. The instrument is
subject to uncertainties due to variations in the
elastic properties of the spring and capsules,
a due to wear in the mechanical linkages.

5)
angel—A radar echo caused by a physical phe-
nomenon not discernible to the eye.

Studies indicate that a fair portion of angels
are caused by strong temperature and/or mois-
ture gradients such as might be found near the
boundaries of bubbles of especially warm or
moist air. They frequently occur in shallow
layers at or near temperature inversions within
the lowest few thousand feet of the atmosphere.
(5)

angle of bank—Scee angle of roll.

angle of deviation—The angle through which a
ray isbent by refraction. (68)

angle of incidence—The angle at which a ray of
energy, or an object, impinges upon a surface,
measured between the direction of propagation
of the energy (or object) and a perpendicular
to the surface at the point of impingement, or
incidence. See angle of reflection, angle of
refraction. (5)

angle of reflection—The angle at which a re-
flected ray of energy leaves a reflecting surface,
measured between the direction of the outgoing
ray and a perpendicular to the surface at the
point of reflection. (5)

angle of refraction—The angle at which a re-
fracted ray of energy leaves the interface at
which the refraction occurred, measured be-
tween the direction of the refracted ray and a
perpendicular to the interface at the point of
refraction. (5)

ANGLE OF ROLL

angle of roll—(also called angle of bank, roll
angle). The angle between the lateral axis of
a craft and the horizontal. It is considered
positive if the port side is higher than the star-
board side, but may be designated starboard or
port depending upon which side is lower. (68)

angle of yaw—(also called yaw angle). 1. The
horizontal angular displacement of the longi-
tudinal axis of a ship from its neutral position,
during a yaw. It is designated right or left
according to the direction of displacement of the
bow.

2. The angle between a line in the direction
of the relative wind and a plane through the
longitudinal and vertical axes of an aircraft.
It is considered positive if the nose is displaced
to the right.

(68)
angstrom—(abbreviated A, formerly A). A
unit of length used in the measurement of the
wavelength of light, X-rays, and other electro-
magnetic radiation and in the measurement of
molecular and atomic diameters. One angstrom
equals 10-* centimeter or 10-* micron. (5)
Angstrém compensation pyrheliometer—An
absolute instrument developed by K. Angstrom
for the measurement of direct solar radiation.
The radiation receiver station consists of two
identical manganic strips whose temperatures
are measured by attached thermocouples. One
of the strips is shaded, while the other is ex-
posed to sunlight. An electrical heating current
is passed through the shaded strip so as to raise
its temperature to that of the exposed strip.
The electric power required to accomplish this
is a measure of the solar radiation. (5)
Angstrém pyrgeometer—An instrument de-
veloped by K. Angstrém for measuring the ef-
fective terrestrial radiation. It consists of four
manganic strips, of which two are blackened and
two are polished. The blackened strips are al-
lowed to radiate to the atmosphere while the
polished strips are shielded. The electrical
power required to equalize the temperature of
the four strips is taken as a measure of the out-
going radiation. (5)
angular momentum—The moment of the linear
momentum of a particle about a point. If m
is the mass of the particle, V the velocity, and 7
the position vector from the given point O to the
particle, the angular momentum J/ about O is
given by,
M=r-mV

The angular momentum of a particle about an
axis is defined as that component, along the axis,
of the angular momentum of the particle about
any point on the axis.

The angular momentum of a continuous me-
dium is given by the integral of the product 7: V
over the mass of the medium.

In meteorology, it is conventional to deal with
the angular momentum per unit volume, which
is given by the product 7: p V, where p is the
density. (5)

angular spreading—The lateral extension of
ocean waves as they move out of the generating
area as Swell. (5)

angular-spreading factor—In ocean wave fore-
casting, the ratio of the actual wave energy pres-
ent at a point to that which would have been
eee in the absence of angular spreading.

5)

angular velocity—A representation of the rate of
rotation of a particle about the axis of rotation,
with magnitude equal to the time rate of angular
displacement of any point of the body.

The angular velocity of the earth (in the ab-
solute coordinate system) is directed along the
earth’s axis toward the pole star and is equal in
ae to 7.2921X10-° radian per second.

5

anion—A negatively charged ion.

anisotropic—Not isotropic; that is, exhibiting
different properties when tested along axes in
different directions.

annelid—(or segmented worm). One of a phy-
lum (Annelida or Annulata) of segmented
worms, with the majority of marine forms pos-
sessing a distinct head. Members of the group
are either free swimming, burrowing, or tube
building or may combine two of these modes of
living. Several tube-building species are no-
table fouling organisms.

anniversary winds—A general term for local
winds or larger-scale wind systems (such as the
monsoon, etesians, etc.) that recur annually.
(5)

annual inequality—The seasonal or yearly varia-
tion in the water level or in the tidal current
speed; more or less periodic, due chiefly to me-
tecrological causes. (50)

anomalistic tide cycle—The average period of
about 2714 days, measured from perigee to peri-
gee, during which the moon completes one revo-
lution around the earth.

anomalous—Not encompassed by rules governing
the majority of cases; distinguished from ab-
normal by implying a difference of kind rather
than a difference merely of degree. (5)

anomalous field—S¢ee residual magnetic field.

anomalous propagation—The propagation of en-
ergy (such as sound) when it arrives at a des-
tination via a path significantly different from
the normally expected path. (5)

anomaly—1. In oceanography, the difference be-
tween conditions actually observed at a serial
station and those that would have existed had
the water all been of a given arbitrary tempera-
ture and salinity. (5)

2. A deviation from a norm. (87)

3. In geophysics, the difference between the
theoretical or computed and actual value. (2)

anomaly of dynamic height—See dynamic
height anomaly.

anomaly of geopotential difference—See dy-
namic height anomaly.

anomaly of specific volume—Sce specific vol-
ume anomaly.

anoxemia—WSce anoxia.

anoxia— (also called anowemia). The absence of
oxygen; an abnormal condition produced by
breathing air which is deficient in oxygen. (5)

anstau—The process resulting in the piling up of
water, such as occurs in convergence. (14)

antagonism—A relationship between species in
which at least one species is harmed. See anti-
biosis, parasitism.

antarctic air—A type of air whose characteristics
are developed in an antarctic region. Antarctic
air appears to be colder at the surface in all sea-
sons, and at all levels in autumn and winter, than
artic air. (5)

antarctic anticyclone—(or antarctic high). The
glacial anticyclone which has been said to over-
lie the continent of Antarctica; analogous to the
Greenland anticyclone. (5)

Antarctic Bottom Water—Sce water mass.

Antarctic Circumpolar Current—See West
Wind Drift.

Antarctic Convergence—(or Antarctic Con-
vergence line, Antarctic Convergence zone).
The Southern Hemisphere polar convergence.
It is the best defined convergence line in the
oceans, being recognized by a relatively rapid
northward increase in the surface temperature.
It can be traced around the world in the broad
belt of open water between Antarctica to the
south and Africa, Australia, and South America
to the north. See convergence.

Antarctic Convergence line—Sce
Convergence.

Antarctic Convergence zone—Scee Antarctic
Convergence.

antarctic high—WSee antarctic anticyclone.

Antarctic Intermediate Water—Sce water
mass.

Antarctic Ocean—The name commonly applied to
those portions of the Atlantic, Pacific, and In-
dian Oceans which reach the Antaric Continent
on the south and are bounded on the north by
the Subtropical Convergence. This feature is
not a recognized ocean body.

antecedent platform theory—A theory of coral
atoll and barrier reef formation which postu-
lates a submarine platform 50 meters or more
below sea level from which barrier reefs and
atolls grow upward to the water surface without
changes in sea level. (2)

anthozoan—One of a class (Anthozoa) of coelen-
terates in which the medusoid stage is absent
and the polyp (hydroid) stage is better de-
veloped than in the other coelenterates. The
sea anemones, Sea pens, and corals are some
members of this group.

Antarctic

APHELION

antibiosis—The relationship between species in
which certain substances produced or excreted
by organisms are generally harmful to others.
The mass kills of fishes and other organisms due
to outbreaks of red tide are examples of anti-
biosis.

anticline—A fold or arch of rock in which the
strata dip in opposite directions away from the
plane of the axis. See syncline.

anticyclone—An atmospheric anticyclonic cir-
culation, a closed circulation. With respect to
the relative direction of its rotation, it is the
opposite of a cyclone.

Because anticyclonic circulation and relative
high atmospheric pressure usually coexist, the
terms anticyclone and high are used inter-
changeably in common practice. (5)

anticyclonic—Having a sense of rotation about
the local vertical opposite to that of the earth’s
rotation; that is, clockwise in the Northern
Hemisphere, counterclockwise in the Southern
Hemisphere, undefined at the Equator. It is
the opposite of cyclonic. (5)

antifouling coating—Scee antifouling paint.

antifouling paint—(or antifouling coating). A
substance applied to a surface to prevent the
attachment of fouling organisms when sub-
merged. The principle applied is the gradual
release of compounds toxic to fouling organisms;
effectiveness of the coating depends upon the
toxicity of the compound and the rate and
duration of release. Toxic compounds com-
monly used are cuprous oxide and mercuric
oxide.

Antilles Current—A current formed by part of
the North Equatorial Current that flows along
the northern side of the Greater Antilles. The
Antilles Current joins the Florida Current
north of Grand Bahama Island to form the
Gulf Stream.

antinode—Sce loop.

Antisubmarine Warfare—(abbreviated ASW).
Operations conducted against submarines, their
supporting forces and operating bases. (63)

Antisubmarine Warfare Environmental Pre-
diction System—(abbreviated ASWEPS).
An integrated system of men and machines to
predict and display oceanographic parameters
in support of antisubmarine warfare operations.

antitrades—(formerly, also called counter-
trades). A deep layer of westerly winds in the
troposphere above the surface trade winds of
the tropics. They comprise the equatorward
side of the mid-latitude westerlies, but are found
at upper levels rather than at the surface.

The antitrades are best developed in the
winter hemisphere, and also above the eastern
extremities of the subtropical highs. (5)

aperiodic motion—Any nonperiodic motion.

aphelion—The point in the earth’s orbit farthest
from the sun. (50)

APHOTIC ZONE

aphotic zone—That portion of the ocean waters
where light is insufficient for plants to carry on
photosynthesis. See euphotic zone. (See
figure for classification of marine environ-
ments.)

apogean range—(abbreviated An). Theaverage
of all monthly tide ranges occuring at the time
of apogee.

apogean tidal current—A tidal current of de-
creased speed occurring at the time of apogean
tide.

apogean tide—Tides of decreased range occurring
monthly near the time of the moon’s apogee.

apogee—That point on the orbit of the moon (or
any other earth satellite) farthest from the
earth; opposed to perigee. (5)

apparent contrast—The change in contrast that
depends upon the distance to an object, the
amount of light absorption, and the inclination
of line of sight to the vertical; expressed as
percentage.

apparent freezing point—Sce freezing point.

apparent luminance—With respect to the visual
range of a dark, distant object: luminance,
created by airlight, of that portion of the visual
field subtended by the object; that is, the light
scattered into the eye by particles, including air
molecules, lying along the optic path from eye
to object. (5)

apparent velocity—The velocity with which a
fixed phase of a seismic wave, usually its front
or beginning, passes an observer. (35)

appendicularian—One of a class (Larvacea) of
small, transparent, planktonic tunicates in
which the body is covered by a large tunic and
is composed of a trunk and a long tail. Some
species are luminescent.

approach—The area or space of indefinite extent
in immediate contact with an objective; par-
ticularly, that part of the sea adjacent to a
shoreline. (68)

approximate absolute temperature scale—(ab-
breviated AA). A temperature scale with the
ice point at 273 degrees and boiling point of
water at 373 degrees. (5)

apron—A sloping underwater extension of an ice-
berg, or an outspread deposit of ice or rock ma-
terial in front of a glacier. (68) See ram.

apsis—Hither of the two orbital points nearest
or farthest from the center of attraction, the
perihelion and aphelion in the case of an orbit
about the sun, and the perigee and apogee in
the case of an orbit about the earth. The line
connecting these two points is called line of
apsides. (68)

aquaculture—Fish, shellfish, and algae farming;
development of new sea foods, and methods of
rearing larvae of clams and oysters. Today
ee practiced in Japan and Southeast Asia.

35)

10

aquafact—An isolated boulder which has been
worn smooth on its seaward face by wave
abrasion.

Aqua-Lung*—Self-contained underwater breath-
ing apparatus (SCUBA) of the demand or open
circuit type; specifically, the Cousteau-Gagnan
apparatus. The trademark for SCUBA equip-
ment manufactured by a U.S. concern.

aqueous desert—A marine bottom environment
in which there is little or no macroscopic in-
vertebrate shelled life, usually a bottom of
shifting sands. (2)

aragonite—A mineral, orthorhombic CaCO;, a
major constituent of shallow muds on the
Bahama Banks and elsewhere.

arch—See rise.

arched iceberg—An iceberg with a large opening
at the water line, extending through the iceberg,
forming an arch. (68)

archibathyal—See archibenthic.

archibenthal—Sce archibenthic.

archibenthic—(also called archibenthal, archi-
bathyal).

1. According to some authorities a subdivision
of the benthic division. According to other au-
thorities it corresponds roughly to the upper
half of the bathyal.

2. Pertaining to a zone extending from a
depth of about 650 feet (200 meters) (con-
tinental shelf edge) to between 2,625 and 3,600
feet (800 and 1,100 meters). See classification
of marine environments.

Archimedean buoyant force—Sce buoyancy
(sense 2).

Archimedes’s principle—The statement that a
new upward or buoyant force, equal in magni-
tude to the weight of the displaced fluid, acts
upon a body either partly or wholly submerged
in a fluid at rest under the influence of gravity.

This force is known as the Archimedean
buoyant force (or buoyancy) and is independent
of the shape of the submerged body and does
not depend upon any special properties of the
fluid. (5)

archipelagic apron—A gently sloping sea floor
with a generally smooth surface on the sea floor,
particularly found around groups of islands or
seamounts. (62)

archipelago—A sea or part of a sea studded with
islands or island groups; often synonymous with
island group.

are shooting—(or fan shooting). A method of
refraction; seismic prospecting, in which the
variation of travel time with the azimuth from
a shot is used to infer geologic structure. (35)

arctic air—A type of air whose characteristics are
developed mostly in winter over arctic surfaces
of ice and snow. Arctic air is cold aloft and it
extends to great heights, but the surface
temperatures are often higher than those of
polar air. For two or three months in summer
arctic air masses are shallow and rapidly lose

their characteristics as they move southward.
5)

Sh anticyclone—See arctic high.

Arctic Convergence—(or Arctic Convergence
zone, Arctic Convergence line). The Northern
Hemisphere polar convergence. Because of
the configuration of the oceans in the northern
latitudes, this convergence zone is poorly defined.
See convergence.

Arctic Convergence line—See Arctic Conver-
gence.

Arctic Convergence zone—See Arctic Conver-
gence.

arctic high—(also called arctic anticyclone, polar
anticyclone, polar high). A weak high that
appears on mean charts of sea-level pressure over
the Arctic Basin during late spring, summer,
andearly autumn. (5)

Arctic Intermediate Water—Sce water mass.

arctic pack—1. (sometimes called many-year ice) .
Sea ice more than two years old. This nearly
salt-free ice has a smoothly undulating surface
due to the smoothing of pressure ice by weather-
ing. It also has a thickness of more than 2.5
meters (8.2 feet), and often is colored in differ-
ent tintsofblue. (74)

2. See polarice (sensel1). (59)

3. (sometimes called polarice). The drifting
ice floes of the Arctic Basin; specifically, the
thick, heavily hummocked polar ice of the cen-
tral Arctic Ocean. (59)

arctic sea smoke—Same as steam fog; but often
specifically applied to steam fog rising from
small areas of open water within sea ice. See
frost smoke, steam fog. (5)

arctic smoke—See steam fog, frost smoke.

arcuate delta—A curved or bowed delta with the
convex side toward the sea.

arenaceous—Applied to rocks or sediments de-
rived from or containing sand.

arenite—(also spelled arenyte). See sandstone.

argillaceous—A pplied to all rocks or sediment
composed partly or completely of clay.

argillite—A rock derived either from siltstone,
claystone, or shale.

argonaut—See nautilus.

Argus Island—An oceanographic research tower
erected on Plantagenet Bank 22 miles southwest
of Bermuda.

arithmetic mean—(also called mean, average).
The sum of a set of individual values of any
quantity, divided by the number of values in the
set.

arm—Any deep and comparatively narrow branch
of the sea extending inland, as opposed to gulfs
and firths.

array—aA group of two or more devices such as
hydrophones which feed into a common re-
ceiver. The purpose of thus grouping hydro-
phones is to increase coverage and sensitivity of
the listening unit and also to determine the bear-
ing of a target.

207-109 O—66——_2

11

ASCENDANT

arrival—The chronologic appearance (such as
first, second, third arrival) of different wave
energies on a seismic or acoustic record.

arrow worm—(or chaetognath, glass worm).
One of a phylum (Chaetognatha) of small, elon-
gate, transparent, wormlike animals pelagic in
all seas from the surface to great depths. They
are abundant and may multiply rapidly into vast
swarms. Some species of the group, especially
of the genus Sagitta, have been identified as
indicator species.

arthropod—One of a phylum (Arthropoda) of
animals, most with a segmented external skele-
ton of chitin but some with plates of calcium
carbonate, and with jointed appendages; for ex-
ample, the crustaceans, spiders, and insects.

artificial radioactivity—1. A term. used to denote
the phenomenon of radioactivity produced by
particle bombardment or electromagnetic irra-
diation.
_- 2. The radioactivity of synthetic nuclides.
See induced radioactivity.
(41)

artificial sea water—Prepared solutions that
duplicate sea water as exactly as possible. The
following table shows three formulas for arti-
ficialsea water: (54)

FORMULAS FOR ARTIFICIAL SEA WATER
(Cl=19.00°/,,)

McCLENDON BRUJEWICZ LYMAN AND
ET AL (1917) (SUBOW, 1931) FLEMING (1940)

SALT

TOTAL
WATER TO
1,000.0000

34.4406 | TOTAL
WATER TO

1,000.000

TOTAL
WATER TO
1,000.000

34.421 34.481

(SVERDRUP; ET. AL., 1949)

artificial upwelling—The concept of having a
nuclear reactor (or other unnatural source) sit-
ting on the bottom of the ocean in cold, low
productivity parts of the sea to create warmth
needed to generate turbulence and subsequent
fertility to the area.

ascendant—The vector representing the rate of
increase of a property. See gradient.

ASCIDIAN

ascidian—(or sea squirt). One of a class (As-
cidiacea) of attached or buried tunicates having
a saclike body covered by a tough flexible tunic,
called atest. They are widespread and notable
fouling organisms.

asea—On the sea; at sea; seaward.

aseismic—Not subject to earthquakes, as an
aseismic region. (35)

ash breeze—Absence of wind;calm. (68) |

ash fall—(also called ash shower). 1. A rain of
airborne volcanic ash falling from an eruption
cloud, characteristic of volcanic eruptions.

2. A deposit of volcanic ash resulting from

sucha fall. (2)

ash shower—Scee ash fall. ,

aspect—The angle made by a target with the line
joining it to the observation point is known as
the aspect of thetarget. (28)

astacin carotenoid—An animal pigment found
especially in the covering of adult planktonic
crustacea. Measurement of this carotenoid
in sea water samples gives some measure of
microscopic animal matter.

asthenosphere—S¢ce mantle.

astronomical meteor—Sce meteor.

astronomical position—A point on the earth
whose position has been determined by celestial
observations. (66)

astronomical tidal constituent—Sce constitu-
ent.

astronomical tide—(or astronomic tide). Tide
due to the attractions of the sun and moon, in
contrast to a meteorological tide, which is
caused mainly by wind and atmospheric pres-
sure. See equilibrium tide.

astronomic tide—Scee astronomical tide.

ASWEPS aircraft—A_ specially instrumented
flying laboratory which conducts thermal struc-
ture research in support of ASWEPS.

asymptotic radiance distribution—The radiance
distribution which is the limit of the distribution
in the hydrosphere as the depth increases in-
finitely. It is symmetrical around the vertical
and independent of sun zenith distance. (8)

<—— LEEWARD

REESE aE. L

HIGH TIDE -.--
LOW TIDE™

Atlantic Ocean—The Atlantic Ocean extends
from Antarctica northward to the southern
limits of the Greenland and Norwegian Seas.
It is separated from the Pacific Ocean by the
meridian of Cape Horn to the Antarctic Con-
tinent, and the boundary between the Atlantic
and Indian Oceans is placed at the meridian of
Cape Agulhas to the Antarctic Continent.

The Equator separates the Atlantic Ocean
into the North and South Atlantic Oceans.

The limits of the Atlantic Ocean exclude the
seas lying within it.

ATLANTIS—A long-range study to determine
the feasibility of large ocean surveillance sys-
tems.

atmosphere—This term when used as a pressure
term is defined as the pressure exerted per square
centimeter by a column of mercury 760 milli-
meters high at a temperature of 0°C where the
acceleration of gravity is 980.665 centimeters
per second per second. One atmosphere of pres-
sure equals 1.0133 X 10° dynes per square centi-
meter. The actual effect of atmospheric pres-
sure is ignored when considering pressures with-
in the ocean. Surface pressure is cuusidered to
be zero.

atmospheric pressure—(also called barometric
pressure). ‘The pressure exerted by the atmos-
phere as a consequence of gravitational force
exerted upon the “column” of air lying directly
above the point in question. (5)

atmospheric tide—Sce tide.

atoll—A ring-shaped organic reef that encloses a
lagoon in which there is no preexisting land,
and which is surrounded by the open sea. (56)

atoll lagoon—See barrier lagoon.

atollon—A large reef ring in the Maldive Islands
consisting of many smaller reef rings. The word
atoll was derived from thisname. (2)

atoll reef—A ring-shaped coral and limestone
reef often carrying low sand islands, enclosing
a body of water. (2)

atom—The smallest particle of an element which
can enter into a chemical combination. All

WINDWARD ——>
REE C .

,...— INTERTIDAL
“ZONE

2

ISLAND 12

5 WW

CONSPICUOUS FEATURES OF AN ATOLL AND ITS PERIPHERAL REEF

1. Outer slope;
7. Reef patch;

2. Reef front;

8. Lagoon floor; 9. Coral head;

3. Seaward reef margin;
10. Lagoon reef flat;

5. Lagoon reef margin; 6. Lagoon slope;
12. Seaward beach.

(AFTER TRACY; ET. AL., 1955)

4. Reef flat;
11. Lagoon beach;

chemical compounds are formed of atoms, the
difference between compounds being attributable
to the nature, number, and arrangement of their
constituent atoms. (27)

atomic energy—aAll forms of energy released in
the course of nuclear fission or nuclear transfor-
mation (P.L. 703, 83d Congress). (63)

atomic weight—The relative weight of the atom
on the basis of oxygen as16. Fora pure isotope,
the atomic weight rounded off to the nearest
integer gives the total number of nucleons
(neutrons and protons) making up the atomic
nucleus. If these weights are expressed in
grams they are called gram atomic weights.

27)

Note: According to the International Unified
Scale of 1961, the relative weight of the atom is
based on Carbon as 12.

attenuance—The sum of absorptance and scat-
terance. (8)

attenuation—1. In physics, any process in which
the flux density, power, amplitude, intensity,
illuminance, etc. of a “parallel beam” of energy
decreases with increasing distance from the en-
ergy source. Attenuation is always due to the
action of the transmitting medium itself. It
should not be applied to the divergence of flux
due to distance alone, as described by the in-
verse-square law. (5)

2. The reduction in sound or light intensity
caused by the absorption and scattering of
sound or light energy in air or water.

3. A lessening of the amplitude of a wave with
distance from the origin. (66)

4. The decrease of submarine motion with in-
creasing depth. Submarine motion resulting
from surface waves attenuates rapidly with
depth and practically disappears at a depth
equal to a surface wavelength.

attenuation coefficient—A measure of the space
rate of diminution, or attenuation, of any
transmitted electromagnetic radiation. This
quantity may be identified in a form of Bou-
guer’s law (or Beer’s law) :

dl=—cal dz;
I=I1,e-%

or

where J is the flux density at the selected point
in space, Z, is the flux density at the source, a is
the distance from the source, and a is the atten-
uation coefficient.

In general, the attenuation coefficient is speci-
fied only when the attenuation is known to be
due to both absorption and scattering or when
it is impossible to determine which is the cause.
More common is the use of either the absorption
coefficient or the scattering coefficient.

Extinction coefficient is a synonymous term,
but it is used mostly in reference to visible
radiation. (5)

13

AUTOCHTHONOUS

attenuation constant—(also called attenuation
factor, decay constant). A measure of the space
rate of attenuation, that is, the rate of flux-
density (or power) reduction as energy (visual,
electromagnetic, acoustic) propagates from its
source. (5)

attenuation factor—Sce attenuation constant.

Atterberg grade scale—(or Atterberg scale). A
decimal grade scale for particle size, with 2
millimeters as the reference point, and involv-
ing the fixed ratio 10. Subdivisions are the
geometric means of the grade limits: 0.2, 0.6, 2.0,
6.3, 20.0. (2)

Atterberg limits—The indices (LL, PL) of the
water content of a sediment at the boundary be-
tween the semiliquid and plastic state (liquid
limit) and the plastic ade the semisolid state
(plastic limit). (31)

Atterberg scale—Sce Atterberg grade scale.

attitude—The position of a body as determined
by the inclination of the axes to some frame of
reference. If not otherwise specified this frame
of reference is fixed totheearth. (63)

audio frequency—(also called sonic fregency).
A frequency within the audible range, about 20
to 20,000 cycles per second. (68)

augmenting factor—A factor used in the har-
monic analysis of tides or tidal currents. It
is a correction factor for tabulating the hourly
heights or speeds used in the summation for
constituents other than S which do not occur
on the exact constituent hours to which they are
assigned, but at times may differ by as much as
ahalfhour. (50)

aural null—A null detected by listening for a
minimum signal or the complete absence of an
audible signal. (68)

auricularia larva—The planktonic young of a
sea cucumber.

aurora—The sporadic radiant emission from the
upper atmosphere over middle and high lati-
tudes.

In northern latitudes these displays are called
aurora borealis, aurora polaris, or northern
lights; and in southern latitudes they are called
aurora australis. (5)

aurora australis—The aurora of southern lati-
tudes. (5)

aurora borealis—(also called aurora polaris,
northern lights). The aurora of northern lati-
tudes. (5)

aurora polaris—See aurora, aurora borealis.

auroral zone—A zone of maximum auroral activ-
ity at about 23 degrees from the geomagnetic
pole.

authalic projection—Scee equal area projection.

authigenic—A term applied to products of chemi-
cal and biochemical action which originated in
sediments at the time of or after deposition, and
before burial and consolidation, such as calcium
carbonate or manganese oxide deposition. (2)

autochthonous—Of local origin ; indigenous.

AUTOMATIC TIDE GAGE

automatic tide gage—An instrument that auto-
matically registers the rise and the fall of the
tide. (50)

automatic weather station—A weather station at
which the services of an observer are not re-
quired. Most automatic weather stations are
equipped with telemeter apparatus for trans-
mitting weather information at predetermined
times, or by use of an interrogation system.

autophytic nutrition—See autotrophic nutri-
tion.

autotrophic nutrition—That process by which
an organism manufactures its own food from
inorganic compounds. See holophytic nutri-
tion, chemotrophic nutrition, heterotrophic
nutrition, mixotrophic nutrition.

autumn ice—1. Sea ice in early stage of forma-
tion. It is comparatively brackish, and crystal-
line in appearance. Like young ice, it is not
yet affected by lateral pressure. (5)

2. A Russian term defining a specific form
of one-year ice (70 to 200 centimeters thick).
At the end of the growth season in spring the
thickest one-year ice is also called autumn ice
since it formed earliest the previous autumn.
Thus, it has been defined as 150 to 200 centi-
meters or more thick. Autumn ice usually does
not completely disappear during the summer.

autumn maximum—A secondary flowering of
phytoplankton. The flowering results from the
regeneration of nutrients after the decomposi-
tion of organisms that have died during the
summer and from vertical mixing after summer
stratification.

auxiliary thermometer—A mercury-in-glass
thermometer attached to the stem of a reversing
thermometer. It is read at the same time as the
reversing thermometer so that the correction to
the reading of the latter, resulting from change

14

in temperature after reversal, can be computed.
(5)

average—See arithmetic mean.

average current—Sce mean current.

average depth—The average water depths based
on soundings reduced to low water datum.

average limit of ice—Average seaward extent of
ice during a normal winter.

avulsion—Rapid erosion of shoreland by waves
duringastorm. (73)

awash—1. Tossed about or bathed by waves or
tide. (61)

2. A rock exposed or one just bare at any stage
of the tide between the datum of mean high
water and the sounding.

axis of acoustic symmetry—For many trans-
ducers the three-dimensional directivity is such
that it may be represented by the surface gen-
erated by rotating a two-dimensional directivity
pattern about the axis corresponding to the ref-
erence bearing of the transducer. This axis may
then be described as an axis of acoustic sym-
tae or, more briefly, as the acoustic axis.

28
one of channel—The center line of a channel.
30)

azoic—Without life; however, most ocean areas
described as azoic are known to contain at least
a bacterial flora.

Azores high—The semipermanent subtropical
high over the North Atlantic Ocean, so named
especially when it is located over the eastern part
of the ocean.

The same high, when displaced to the western
part of the Atlantic, or when it develops a sepa-
rate cell there, is known as the Bermuda high.
On mean charts of sea-level pressure, this high is
one of the principal centers of action in north-
ern latitudes. (5)

back bay—A small bay into which streams drain
and which is connected with the sea through
passes between barrier islands. (2)

backbeach—See backshore.

backdeep—An oceanic depression on the concave
sideofanislandare. (2)

background—Ever-present effects in physical ap-
paratus above which a phenomenon must mani-
fest itself in order to be measured. Background
can take various forms, depending on the nature
of the measurement. In electrical measure-
ments of radioactivity and nuclear phenomena,
the term usually refers to those undesired counts
or currents that arise from cosmic rays, local
contaminating radioactivity, insulator leakage,
amplifier noise, power-line fluctuations, etc. In
nuclear work and photographic emulsions, the
term refers to developable grains unrelated to
the tracks under investigation. (41)

background count—The evidence or effect on a
detector of radiation, other than that which it is
-desired to detect, caused by any agency. (63)

background noise—Noise made up of sound from
a variety of sources, other than the desired sig-
nal, as indicated by the block diagram below:

CIRCUIT NOISE
HYDROPHONE MOTION
NOISE FROM OWN SHIP)

AMPLIFIED
NOISE

BIOLOGICAL NOISE
TRAFFIC NOISE

BACKGROUND
NOISE
SPEECH

NOISE

GUNFIRE

CLASSIFICATION OF BACKGROUND NOISE

background radiation—1. Radiation arising
from radioactive material other than the one di-
rectly under consideration.

2. In the ocean environment when measuring
fission products or radioactive tracers, the
background radiation (radioactivity) is that
radiation (radioactivity) contributed by cosmic
rays and the natural radioactive constituents of
sea water.

(70)

B

15

backing—1. According to general internationally
accepted usage, a change in wind direction in a
counterclockwise sense (for example, south to
southeast to east) in either hemisphere of the
earth; the opposite of veering.

2. According to widespread usage among
United States meteorologists, a change in wind
direction in a counterclockwise sense in the
Northern Hemisphere, clockwise in the Southern
Hemisphere; the opposite of veering.

back radiation—Sce counterradiation.

back reef—The region behind a reef, between it
and the land. Variously applied to reef flat,
lagoonal deposits, or terrestrial deposits connec-
ting the reef and the land. (2)

backrush—The seaward return of water following
uprush of the waves. See backwash. (61)
(See figure for surf zone.)

backscattering—The part of the reflected sound
energy that returns to the transducer; equiva-
lent to reverberation.

backscattering—The part of the refiected sound
scattering cross section of an object is an area
equal to 47 times the product of the square of a
unit distance and the square of the sound pres-
sure scattered by the object back in the direction
from which the sound has come as observed at
unit distance from the acoustic center of the
object, divided by the square of the sound pres-
sure of the plane wave incident on the object.
The unit of the cross section is the square of the
unit distance. (6)

backshore—That part of a beach which is usually
dry, being reached only by the highest tides,
and, by extension, a narrow strip of relatively
flat coast bordering the sea. See foreshore.
(68) (See figure for shore profile.)

back-slope—The gentler sloping side of a ridge;
in contrast with escarpment, the steeper slope.
(2)

backward scatterance—The ratio of the radiant
flux scattered through angles 90 to 180 degrees
from a beam, to the incident flux. (8)

backward scattering coefficient—The coefficient

which relates to backward scatterance. Unit
of measurement ism?. (8)
backwash—(also called backrush). Water or

waves thrown back by an obstruction such as a
ship, breakwater, cliff, etc. (61)

backwater—1. Water turned back by an obstruc-
tion, opposing current, etc. (68)

BACTERIAL FILM

2. Water held back from the main flow, as
that which overflows the land and collects in low
places or that forming an inlet approximately
parallel to the main body and connected thereto
by anarrow outlet. (68)

3. An arm of the sea, usually lying parallel
a the coast, behind a narrow strip of land.

30

bacterial film—vSee primary film.

Baffin Bay pack—(or middle pack). The drift-
ing ice floes west of Greenland between Davis
Strait and the southern limit of North Open
Water, which is roughly a line from Cape York
to the entrance of Lancaster Sound. (59)

baffle area—An area of approximately 30 degrees
to either side of the stern in which the chance of
holding a sonar contact is nearly impossible.

Bahama Current—See Antilles Current.

balancing—A maneuver that enables a stationary
submarine to float in a density layer.

balancing layer—A density layer of sufficient
thickness, magnitude, intensity, and depth to
allow a submarine to balance safely.

baleen—(or whalebone). The horny material
growing down from the upper jaw of large
plankton-feeding whales, which forms a strainer
or filtering organ consisting of numerous plates
with fringed edges.

baleen whale—(also called mysticete, whalebone
whale). A member of the cetacean suborder
Mysticeti, which comprises the right whales,
gray whales, and rorquals.

ball—(also called dongshore bar). A low sand
ridge which extends generally parallel with the
shoreline and is submerged at least by high
tides. It is generally separated from the beach
by an intervening trough. (2) (See figure for
shore profile.)

ballast—Broken stone, gravel, or other heavy ma-
terial which is used in a ship to improve its
stability or control the draft. Frequently, jet-
tisoned ballast is found in marine sediment
‘samples. (9)

ball breaker—A device used in oceanographic op-
erations such as coring for determining when
the bottom is reached. It is a metal frame con-
taining a glass ball with a weight suspended
above it. When bottom contact is made the
weight drops on the glass ball and causes it to
implode. The sound wave generated by the im-
plosion is received aboard ship by a listening
device.

ball ice—Sea ice consisting of a large number of
soft, spongy spheres 1 to 2 inches in diameter.
This is a rare form of ice. (68)

meat whe bellicatter). An

59

band elimination filter—A wave filter which has
a large insertion loss for one frequency band
with the cutoff frequencies for this band neither
zero nor infinite.

ice foot.

band level—A given spectrum level is usually as-
sociated with a specific frequency. To identify
a transmission level measuring the power in a
specified frequency band, or the acoustic inten-
sity in a specified frequency band, it may be
designated as a band level. (28)

band-pass filter—A wave filter which has a single
transmission band extending from a lower cut-
off frequency greater than zero to a finite upper
cutoff frequency.

bandwidth—The number of units (cycles, kilo-
cycles, etc.) of frequency required for trans-
mission. (66)

bank—1. An elevation of the sea floor located on a
continental (or island) shelf and over which
the depth of water is relatively shallow but sufii-
cient for safe surface navigation. It may sup-
port shoals or bars on its surface which are
dangerous to navigation. (62)

2. In its secondary sense, a shallow area con-
sisting of shifting forms of silt, sand, mud,
gravel, etc., but in this case it is only used with
a qualifying word such as “sand-bank,” “gravel-
bank,” ete. (30)

Bankia—A genus of molluscan borers. See ship-
worm.

bank-inset reefs—Coral reefs which are situated
well within the unrimmed outer edges of con-
tinental and insular shelves. (2)

bank reef—A reef which les within the outer
margin of rimless shoals in contrast to bar-
rier and atoll reefs which rise directly from
deep water. (2)

bar—1. A submerged or emerged embankment of
sand, gravel, or mud built on the sea floor in
shallow water by waves and currents. A bar
may also be composed of mollusk shells. When
it is a ridge generally parallel to shore and sub-
merged by high tides, it is a longshore bar. Off-
shore bars or barrier bars or beaches are built
principally by wave action on sand or gravel at
a distance from shore and separated from it by
a lagoon. When a bar extends partly or com-
pletely across the entrance to a bay it 1s called a
baymouth bar. A crescentic bar commonly
found off the entrance to a harbor is a lunate
bar, (2)

2. A unit of pressure, defined as 1 bar equals

108 dynes per square centimeter.

barber—1. A severe storm at sea during which
spray and precipitation freeze onto the decks
and rigging of boats.

2. (also spelled berber). In the Gulf of St.
Lawrence, a local form of blizzard in which the
wind-borne ice particles almost cut the skin from
the face.

3. See frost smoke.

bare ice—Ice without snow cover. (74)

bar-finger sand—An elongated lenticular sand
body underlying a distributary in a bird-foot
delta. In the Mississippi delta it may be 15 to

SWASH CHANNEL

OFFSHORE BAR

RIVER MOUTH BAR

BARS

(BEB, TR-4, 1954)

20 miles long, 250 feet thick, and 5 miles
wide. (2)
barnacle—One of an order (Cirripedia) of crus-
taceans which are enclosed in a calcareous shell
and sessile during their adult life. They are
of two general types, the acorn barnacles and
the stalked barnacles. Barnacles are one of
the most notable groups of fouling organisms.
baroclinity—The state of stratification in a fluid
in which surfaces of constant pressure (isobaric)
intersect surfaces of constant density (isosteric).
The number, per unit area, of isobaric-isosteric
solenoids intersecting a given surface is a meas-
ure of the baroclinity. (5)
barometer—An instrument for measuring atmos-
pheric pressure. (35)
barometric pressure—See atmospheric pres-
sure.
barotrauma—Scee squeeze.
barotropy—The state of a fluid in which surfaces
of constant density (or temperature) are coin-
cident with surfaces of constant pressure; it is
the state of zero baroclinity. (5)
bar port—A harbor that can be entered only when
the tide rises sufficiently to permit passage of
shipsoverabar. (73)
barred basin—See silled basin.
barrier—1. In polar terminology, an early term
for ice Shelf ; first used by Sir James Clark Ross
for the face of the antarctic ice shelf named for
him, “Ross Barrier.” (5)
2. Barrier is being replaced by ice shelf and
ice front in publications and maps. (59)
barrier bar—See bar.
barrier basin—A basin produced by natural dam-
ming by glacial moraines, landslides, ete. (2)
barrier beach—(also called offshore barrier). A
_ bar essentially parallel to the shore, the crest
of which is above high water. (61)
barrier berg—~Scee tabular iceberg.

17

BASEMENT ROCK

LAGOON

BARRIER BEACH

(BEB, TR-4, 1954)

barrier chain—A series of barrier islands, bar-
rier spits, and barrier beaches which extends
along a considerable length of coast. (2)

barrier ice—(or shelf ice). See ice shelf.

barrier iceberg—(or barrier berg). 1. See tab-
ular iceberg.

2. A large tabular iceberg broken off an ice
shelf. (59)

barrier lagoon—A bay roughly parallel to the
coast and separated from the open ocean by bar-
rier islands. Also the body of water encircled
by coral islands and reefs, in which case it may
be called an atoll lagoon. (See figure for
atoll.)

barrier reef—A coral reef parallel to and sep-
arated from the coast by a lagoon that is too
deep for coral growth. Generally, barrier reefs
follow the coasts for long distances and are cut
through at irregular intervals by channels or
passes. (2)

barysphere—S¢ee centrosphere.

basalt—A basic igneous (extrusive) rock com-
posed primarily of calcic plagioclase, pyroxene,
and with or without olivine. Also an inner
layer of worldwide extent underlying the oceans
and the granitic continents. (2

base line—1. A surveyed line established with
more than usual care, to which surveys are re-
ferred for coordination and correlation. This
established line becomes the base for the com-
putation of the other two sides of a triangle (in
triangulation). (37)

2. The line between the master and slave sta-
tions in Loran or other hyperbolic navigation
systems.

basement—(also called basement complex, base-
ment rock). An igneous or metamorphic rock
complex underlying sedimentary or volcanic
rocks

basement complex—See basement.

basement rock—Sce basement.

BASE STATION

base station—A geographic position whose ab-
solute gravity value is known; also the point
from which a survey begins.

Tn exploration, particularly magnetic or grav-
ity surveys, a reference station where quanti-
ties under investigation have known values or
may be under repeated or continuous measure-
ment in order to establish additional stations in
relation to it. (2)

base surge—A cloud which rolls out from the bot-
tom of the column produced by a subsurface
burst of a nuclear weapon. For underwater
bursts the surge is, in effect, a cloud of liquid
droplets which has the property of flowing al-
most as if it were homogeneous fluid. (63)

basic rock—In geology, a term for igneous rocks
that are comparatively low in silica.

basin—A depression of the sea floor more or less
equidimensional in form and of variable extent.

2

bastard—A hard massive boulder or rock. Also
adjective meaning of abnormal shape or of un-
usual composition or proportion. (48)

bathy—An indicator group in the coded bathy-
thermograph message.

bathyal—Pertaining to ocean depths between 100
and 2,000 fathoms (180 and 3,700 meters) ; also
to the ocean bottom between those depths, some-
times identical with the continental slope en-
vironment. (See figure for classification of
marine environment.)

bathyconductograph (BC)—A device to measure
the electrical conductivity of sea water at var-
ious depths from a moving ship.

bathymeter—An instrument primarily designed
for measuring depth of water. Bathymetric
surveys, previously done by lead line, are now
performed by using an echo sounder and a pre-
cision depth recorder. (35)

ea or pertaining to bathymetry.

68)

bathymetric chart—A map delineating the form
of the bottom of a body of water, usually by
means of depth contours (isobaths). (5)

bathymetric low—Sce low (sense 2).

bathymetry—The science of measuring ocean
depths in order to determine the sea floor topog-
raphy.

bathypelagic—A depth zone of the ocean which
hes between depths of 500 and 2,000 fathoms
(900 and 3,700 meters). (See figure for clas-
sification of marine environment.)

bathypelagic fish—Any of a variety of oceanic
fishes which, at least part of the time, inhabit a
depth range between about 500 to 2,000 fathoms
(900 to 3,700 meters). Many of these fishes
characteristically undergo extensive diurnal ver-
tical migrations and are thought to contribute to
sound scattering layers in the sea.

Bathyscaphe—(also spelled Bathyscaph, Bathy-
scap). A free, manned vehicle for exploring the
deep ocean.

18

Bathysphere—A spherical chamber in which
persons are lowered for observation and study
of ocean depths. (68)

bathythermogram—The record made by a
bathythermograph, or a photographic print of
this record and accompanying meteorological
observations. Now rarely used. (68)

bathythermograph—(abbreviated BT). A de-
vice for obtaining a record of temperature
against depth (strictly speaking, pressure) in
the ocean, from a ship underway. For a ther-
mal element it has a xylene filled copper coil,
which actuates a stylus through a Bourdon
tube. The presure element is a copper aneriod
capsule which moves a coated glass slide at right
angle to the motion of the stylus. A double
analog record is thus obtained as the BT is low-
ered and recovered. (5)

bathythermograph (BT) grid—A transparent
glass slide, marked with calibration lines of tem-
perature and depth, which, when superimposed
against a bathythermograph slide, makes it
possible to read off observed values of tempera-
ture and depth. Each instrument has its own
grid. (5)

bathythermograph (BT) print—An enlarged
photographic print of a bathythermograph
slide superimposed against the appropriate
bathythermograph grid, annotated with par-
ticulars of location and data. (5)

bathythermograph (BT) slide—A 1-inch by 134-
inch glass slide with a coated (now usually gold
anodised, formerly smoked) surface on one side.

A stylus on the bathythermograph scratches
a depth versus temperature trace on the coated
surface.

bathythermograph (BT) viewer—A small mag-
nifying device used in reading temperature and
depth values from a bathythermograph slide
overlaid by a bathythermograph grid.

bathythermograph (BT) winch—A small elec-
tric winch primarily used for lowering and rais-
ing a bathythermograph. This winch is a
high-speed type holding about 2,500 feet of
345-Inch diameter stainless steel wire.

bay—1. A recess in the shore or an inlet of a sea
between two capes or headlands; not as large
asa gulf but larger thanacove. (2)

2. An inward bend in the ice edge formed
either by wind or current. (74)

bay deltas—Deltas formed at the mouths of
streams which discharge into bays or estuaries.
Their advance toward the bay mouths often ex-
tinguishes lagoons behind bay bars or com-
pletely fills open bays, thus simplifying the
shoreline. When the delta forms at the head of
the bay, it is a bay-head delta. (2)

bay-head delta—See bay deltas.

bay ice—1. Level ice of more than one winter’s
growth which has remained free of hummocks
and is nourished by surface layers of snow.

(74)

2. A Labrador term for one-year ice formed
in bays or inlets. (59)

3. In the antarctic, sometimes applied to
heavy floes recently broken away from an ice
shelf. (5)

4. Young flat sea ice sufficiently thick to im-
pede navigation. (59) Obsolete.

baymouth bar—A bar extending partially or en-
tirely across the mouth of a bay. (61)

BAYMOUTH BAR

(BEB, TR-4, 19.54)

bayou—A small sluggish stream or estuarial
creek, with a slow or imperceptible current, in
coastal swamps or river deltas. See slough.
68
neve ae seabeach). 1. The zone of uncon-
solidated material that extends landward from
the low water line to the place where there is
marked change in material or physiographic
form .... or to the line of permanent vegeta-
tion (usually the effective limit of storm waves).
A beach includes foreshore and backshore.
2. Sometimes, the material which is in more
or less active transport, alongshore or on-and-
off shore, rather than the zone. (See figure for
shore profile.)
3. See strand, shoreline, coastline, tideland.
(61)
beach berm—A nearly horizontal portion of the
beach or backshore formed by the deposit of
material by wave action. Some beaches have no
berms, others have one or several. (61)
beachcomber—Sce comber.
beach cusp—(also called cusp). One of a series
of low mounds of beach material separated by
crescent A-shaped troughs spaced at more or
a regular intervals along the beach face.
61)
beach erosion—The carrying away of beach ma-
terials by wave action, tidal currents, or lit-
toral currents, or by wind. (61)
beach face—The section of the beach normally
exposed to the action of the wave uprush. The

BEAM TRANSMITTANCE METER

foreshore zone of a beach.
with shoreface.) (Sce figures for surf zone
and shore profile.) (61)

beach profile—Sce shore profile.

beach ridge—An essentially continuous mound of
beach material behind the beach that has been
heaped up by wave or other action. Ridges may
occur singly or as a series of approximately
parallel deposits. In England they are called
fulls. (61)

beachrock—(or beach sandstone). <A friable to
well-cemented rock consisting of calcareous skel-
etal debris and, in many places, mineral grains
and rock fragments cemented by calcium car-
bonate. It is formed only in the intertidal
zone and occurs in thin beds dipping seaward
at angles of less than 15 degrees. See also cay
sandstone. (2)

beach sandstone—Sce beachrock.

beach scarp—An almost vertical slope along the
beach caused by erosion by wave action. It
may vary in height from a few inches to several
feet, depending on wave action and the nature
and composition of the beach. (See figure for
shore profile.) (61)

beach width—The horizontal dimension of the
ee as measured normal to the shoreline.

61

beam—A ray or collection of focused rays of ra-
diated energy. (5)

(beam) attenuance meter—(or beam transmit-
tance meter). A radiance meter which meas-
ures the beam transmittance, 7’, of a fixed path.
The beam attenuance (C=1-7. (8)

beam pattern—See directional response pat-
tern.

beam sea—Waves moving in a direction approxi-
mately 90 degrees from the heading. Those
moving in a direction approximately opposite
to the heading are called head sea, those moving
in the general direction of the heading are called
following sea, and those moving in a direction
approxiately 45 degrees from the heading
(striking the quarter) are called quartering sea.
See cross sea. (68)

beam tide—In navigational usage, a tidal current
setting in a direction approximately 90 degrees
from the heading of a ship. One setting in a
direction approximately 90 degrees from the
course is called a cross tide. In common usage
these two expressions are usually used synony-
mously. One setting in a direction approxi-
mately opposite to the heading is called a head
tide. One setting in such a direction as to in-
crease the speed of a ship is called a fair tide.
(68)

beam transmittance—The transmittance for a
beam the diameter of which is small compared
to its length. (8)

beam transmittance meter—Sce (beam) atten-
uance meter.

(Not synonymous

BEAM TRAWL

beam trawl—A type of trawl which has a rigid
front (or beam) fastened between two metal
shoes the soles of which slide over the bottom.
As the trawl passes over the bottom, fish and
other marine life are captured within the at-
tached net.

beam width—The beam width of a directional
transducer of a given frequency in a given
plane which includes the beam axis is the angle
included between the two directions, one to the
left and the other to the right of the axis, at
which the angular deviation loss has a specified
value.

beam wind—A nautical term for a crosswind, es-
pecially a wind blowing 90 degrees from a ship’s
heading.

bearing—The horizontal direction of one terres-
trial point from another. It is usually meas-
ured from 000 degrees at the reference direction
clockwise through 360 degrees. (66)

beat—The periodic variation that results from the
superposition of two simple harmonic oscilla-
tions whose frequencies differ by a small amount.
It involves a periodic increase and decrease of
amplitude at the beat frequency which is equal
to the difference in the frequencies of the two

arent signals. Thus, if two pure tones having
requencies of 300 and 400 cycles per second are

heard by a listener, he will also sense a frequency
equal to the difference, 100 cycles per second.
This is the beat frequency.

beating—A wave phenomenon which occurs when
two or more waves of different frequencies be-
come superimposed. The resultant wave has
amplitude maximum (“beats”) at the frequency
equal to the difference of the frequencies of the
initial waves. Seesurf beat. (5)

Beaufort force—(or Beaufort number). A num-
ber denoting the speed (or “strength”) of the
wind according to the Beaufort wind scale.

Beaufort number—See Beaufort force.

Beaufort scale—Sce Beaufort wind scale.

Beaufort wind scale—A system of estimating
and reporting wind speeds, devised in the early
nineteenth century (1806) by Admiral Beaufort
of the British Navy. It was originally based on
the effects of various wind speeds on the amount
of canvas that a full-rigged frigate of the period
could carry, but has since been modified and
modernized. In its present form for interna-
tional meteorological use it equates (a) Beau-
fort force (or Beaufort number), (b) wind
speed, (c) descriptive term, and (d) visible ef-
fects upon land objects orsea surface. (5)

bed—1. The smallest division of a layered rock
series separated from material above or below by
a more or less well defined change in character.

2. The ground upon which a body of water

rests. The term is usually used with a modifier
to indicate the type of water body, as sea bed.
See bottom. (68)

20

bedded—See bed.

bedding cleavage—A cleavage or break that is
parallel tothe bedding. (68) See bed.

bedding joint—A joint that is parallel to the bed-
ding. (68) Seebed.

bedding plane—Division planes which separate
the individual layers. (68) Seebed.

bed load—See load.

bedrock—Any solid rock underlying soil or un-
consolidated sediments.

bel—A unit of level when the base of the loga-
rithm is 10. Use of the bel is restricted to levels
of quantities proportional to power. See
decibel. (69)

bell—See umbrella.

bellicatter—Variant spelling of ballycadder,
meaning an ice foot.

59)
belt— (also called ice belt, sea bar). A long area
of sea ice bounded by open water or land. De-
pending on their length, belts can vary from a
few kilometers to more than 100 kilometers (54
n.miles) inwidth. (74)
bench—1. A level or gently sloping erosion plane
inclined seaward.
2. A nearly horizontal area at about the level
oe high water on the sea side of a
ike.

bench mark—A permanently fixed point of known
elevation. A primary bench mark is one close
toa tide station to which the tide staff and tidal
datum originally are referenced.

bending—Upward or downward motion in a sheet
of ice, caused by lateral pressure. This is the
first stage in the formation of pressure ice, and
is characteristic of thin and very plastic ice.
Seerafting, tenting. (68)

bends—See decompression sickness.

Benguela Current—A strong current flowing
northward along the southwest coast of Africa;
it is formed by the West Wind Drift and the
Agulhas Current. The Benguela Current
flows toward the Equator, gradually leaves the
coast, and becomes the South Equatorial Cur-
rent.

benthic—(also called benthonic). 1. That por-
tion of the marine environment inhabited by ma-
rine organisms which live permanently in or on
the bottom. (See figure for classification of
marine environments.)

2. Pertaining to all submarine bottom terrain
regardless of water depth.

benthic division—A primary division of the sea
which includes all of the ocean floor. (See fig-
ure for classification of marine environ-
ments.)

benthonic—wWSce benthic, benthos.

benthos—1. Bottom dwelling forms of marine life.
Many authorities include certain fishes, such as
stingrays and flounders, which spend much of

their lives in close association with the bottom,
in this category.
2. Also applied to the floor or deepest part of

aseaorocean. (2)

bentonite—A clay formed from the decomposition
of voleanic ash and composed of the clay
minerals montmorillonite and beidellite. (2)

berber—See barber.

berg—Scee iceberg.

bergy bit—A medium-sized piece of ice, generally
less than 5 meters (16.4 feet) high and about
the size of a small cottage. A bergy bit mainly
originates from glacier ice but occasionally
from a massive piece of sea ice or hummocked
ice. When it is known to be sea ice, the term
floeberg may beused. (74)

bergy seltzer—Sizzling sound comparable to that
of Seltzer water which icebergs emit when they
melt. It is caused by the release of air bubbles
that were retained in the berg at high pressure.

berm—The nearly horizontal portion of a beach
or backshore having an abrupt fall and formed
by deposition of material by wave action, and

marks the limit of ordinary high tides. (See
figure for shore profile.)
berm crest—(also called berm edge). The sea-

ward limit of a berm.
profile.) (61)

berm edge—Scee berm crest.

Bermuda high—The semipermanent subtropical
high of the North Atlantic Ocean, so named
especially when it is located in the western part
of the ocean.

This same high, when displaced toward the
eastern part of the Atlantic, is known as the
Azores high. On mean charts of sea-level pres-
sure, this high is a principal center of action.

(See figure for shore

beset—Surrounded so closely by sea ice that steer-
ing control is lost. The term does not imply
pressure. If the ship is incapable of proceed-
ing, it is icebound. If pressure is involved,
the ship is said to be nipped. (68)

best depth range—The detection range of a sub-
marine target which is at the best depth to escape
detection by a ship with hull-mounted sonar.

beta particle—A negative electron or a positive
electron (positron) emitted from a nucleus dur-
ing beta decay. The symbols B, 8°, and £* are
reserved for electrons of nuclear origin. (41)

beta ray—Synonym for beta particle.

biennial ice—Sea ice between one and two years
old. See young polar ice.

bifilar current indicator—An apparatus used for
obtaining only the direction of the current at
different depths. (37)

bifurcation—A forking, or division into two
branches; the point of forking; a branch.

big clearing—~Sce polynya.

bight—1. A concavity in the coastline which
forms a large open bay.

2. See bay (sense 2).

BIOMASS

big ice floe—Sec ice floe.

bilateral transducer—(or reversible transducer).
A transducer capable of transmission in either
direction between its terminations. (69)

bill—A narrow promontory or headland. (68)

Billion-electron-volts—(abbreviated Bev).
Equivalent to 10° electron-volts.

billow—Usually a great wave or surge of water;
any wave. (73)

binary scaler—A scaler whose scaling factor is
two per stage. (70)

biocenose—Sce community.

biocenosis—Sce community.

bioclastic rock—Rocks produced from material
broken or arranged by animals or plants and
consisting of fragmental organic remains.

biogenic deposit—A_ deposit resulting from the
physiological activities of organisms. (2)

bioherm—A reef or mound built principally by
sedimentary organisms such as porate mol-
lusks, etc. See also accretionary limestone,
biostrome, reef. (2)

Oe term for organic limestone.

2

biological half-life—The time required for the
body to eliminate one-half of an administered
dose of any substance by regular processes of
elimination. This time is approximately the
same for both stable and radioactive isotopes of
a particular element. (70)

biological oceanography—The study of the
ocean’s plant and animal life in relation to the
marine environment, including the effects of
habitat, sedimentation, physical and chemical
changes in the environment, and other factors on
the spatial and temporal distribution of marine
organisms, as well as the action of organisms on
the environment.

bioluminescence—(also called phosphorescence,
luminescence). The production of light with-
out sensible heat by living organisms as a result
of a chemical reaction either within certain cells
or organs or extracellularly in some form of
secretion. Luminescence usually is induced by
external stimuli, especially mechanical, such as
wave action or shock waves. It is produced by
a variety of marine organisms in displays of
three general types, namely, sheet type, spark
type, and glowing-ball type. See luciferin,
luciferase.

bioluminescent display—Production of biologi-
cal light of sufficient intensity to make the water
or disturbances of the water conspicuously illu-
minated. Displays may be weak and noted only
as a pale green luminosity of wave crests, or
they may be extremely intense and capable of
lighting large areas of ocean. Momentary
luminescence created by a few jellyfish when
disturbed is not considered a display.

biomass—(also called standing crop, standing
stock, live-weight). The amount of living mat-

BIOSPHERE

ter per unit of water surface or volume ex-
pressed in weight units.

biosphere—That transition zone between earth
and atmosphere within which most forms of ter-
restrial life are commonly found; the outer por-
tion of the geosphere and inner or lower portion
of the atmosphere.

biostromal limestone—Sce coquina.

biostrome—Bedded structures such as shell beds
consisting of and built mainly by sedentary or-
ganisms; not a moundlike or lenslike form. See
also accretionary limestone, bioherm, reef.
(2)

ne fauna and flora of a given region.

58)

biotic factors—Factors of a biological nature,
such as availability of food, competition be-
tween species, predator-prey relationships, etc.,
which, besides the purely physical and chemical
factors, also affect the distribution and abun-
con of a given species of plant or animal.

25)

biotic succession—The natural replacement of
one or more groups of marine organisms grow-
ing in a specific habitat by other groups, the
preceding groups in some way preparing or
favorably modifying the habitat for the suc-
ceeding groups.

bipinnaria larva—The usually planktonic young
of a Sea Star.

Birch discontinuity—Seismic discontinuity
within the earth’s mantle at a depth of about
900 kilometers (about 558 statute miles), pos-
sibly caused by a chemical or phase change, or
both. (2)

bird-foot delta—A delta formed by the out-
growth of pairs of natural levees making the
digitate or bird-foot form.

BIRD-FOOT DELTA

(AFTER: LOBECK, A.K., “GEOMORPHOLOGY, AN
INTRODUCTION TO THE STUDY OF LANDSCAPING.
NEW YORK: McGRAWHILL. 1939. p 230.)

bit—1. A small piece of sea ice; a single fragment
of brash ice.
2. A binary unit of information. (5)

bittern—The liquid remaining after sea water has
been concentrated by evaporation until salt has
crystallized. (5)

bivalve—(or pelecypod, lamellibranch). One of
a class (Pelecypoda or lamellibranch) of mol-
lusks generally sessile or burrowing into soft
sediment, rock, wood, or other materials. In-
dividuals possess a hinged shell and a hatchet-
shaped foot, which in some is used in digging.
The clams, oysters, and mussels belong to this
class; many of the latter two mollusks are no-
table fouling organisms; several are marine
borers.

black and white iceberg—An iceberg having a
dark, opaque portion containing sand and
stones, and separated from the white portion by
a definite line of demarcation. (68)

black body radiation—The electromagnetic ra-
diation emitted by an ideal black body; it is the
theoretical maximum amount of radiant energy
of all wavelengths which can be emitted by a
body ata giventemperature. (5)

black bottle—(also called dark bottle}. A con-
tainer used in measuring respiratory activity of
primary producers. The container is covered
or coated to exclude light and thereby prevent
photosynthetic activity. See light bottle.

black fish—See pilot whale.

black ice—Thin, new ice on fresh or salt water,
appearing dark in color because of its trans-
parency. (59)

black mud—(also called hydrogen sulfide mud).
A dark fine-grained sediment formed in poorly
aerated bays, lagoons, and fiords. This sedi-
ment contains large quantities of decaying or-
ganic matter and iron sulfides and generally
exudes hydrogen sulfide gas.

blade—The expanded or elongate leaflike part of
the larger algae, especially kelp. See lamina.

blanket deposit—A sedimentary deposit of uni-
form thickness which covers a wide region.

blast wave—A sharply defined wave of increased
pressure rapidly propagated through a sur-
rounding medium from a center of detonation
or similar disturbance. (63)

blind lead—(also called cul-de-sac, pocket). A
lead with only one outlet. (68)

blind rollers—Long, high swells which have in-
creased in height, almost to the breaking point,
as they pass over shoals or run in shoaling
water. (61)

blink—See ice blink, snow blink.

blizzard—A severe weather condition character-
ized by low temperatures and by strong winds
bearing a great amount of snow (mostly fine,
dry snow picked up from the ground). The
U.S. Weather Bureau specifies for blizzard, a
wind of 28 knots or higher, low temperatures,
and sufficient snow in the air to reduce visibility
to less than 500 feet. (5)

block—1. A sea ice fragment more than 6 feet but
less than 30 feet in diameter. See ice cake.

59
Note: The WMO is attempting to phase out
this term.

2. An angular rock fragment variously de-
fined as being larger than 4 millimeters, larger
than 32 millimeters, or larger than 256 milli-
meters. (2) %.

blocky iceberg—An iceberg with steep, precipi-
tous sides, and with an essentially horizontal
upper surface. (68)

bloom—See plankton bloom.

blowing spray—Spray lifted from the sea surface
by the wind and blown about in such quantities
that the horizontal visibility is restricted. (5)

blown sands—See eolian sands.

blue-green alga—One of a division or phylum
(Cyanophyta) (the Myxophyceae of another
scheme) of single-celled or simply filamentous
plants in which the blue color is imparted by a
water-soluble accessory pigment, c-phycocyanin.
In the planktonic form, Skujaella (Trichodes-
mium) erythraea, for whose color the Red Sea
was named, a red pigment dominates the others.
Attached forms have a characteristic scummy or
velvety growth on boat bottoms, rocks, and other
underwater surfaces. Large masses of plank-
tonic forms cause “sliming” of the water.

blue ice—The oldest and hardest form of glacier
ice. It is distinguished by a slightly bluish or
greenish color. (65)

blue mud—A combination of terrigenous and deep
sea sediments having a bluish gray color due to
the presence of organic matter and finely divided
iron sulfides. Calcium carbonate is present in
variable amounts up to 35 percent.

bluff—A headland or cliff with a bold almost per-
pendicular front.

boat channel—A shallow, narrow channel on a
reef flat which separates a fringing reef from
the shore. It is parallel to shore and generally
only a few feet deep.

body waves—Hither transverse or longitudinal
seismic waves transmitted in the interior of an
elastic solid or fluid, and not related to a bound-
ary surface. (35)

boiling point—The temperature at which the
equilibrium vapor pressure between a liquid and
its Vapor is equal to the external pressure on the
liquid.

“The boiling point of pure water at standard
atmospheric pressure is equal to 100°C (212°F)
and is a fiducial point for thermometer calibra-
tion. (5)

bold coast—A prominent landmass that rises
steeply from thesea. (61)

bolometer—An instrument for measuring ther-
mal radiation. (68)

bora—A fall wind whose source is so cold that
when the air reaches the lowlands or coast the
dynamic warming is insufficient to raise the air

23

BOTTOM FRICTION

temperature to the normal level for the region;
hence it appears as a cold wind.

The term was originally and still is applied
to the cold northeast wind on the Dalmatian
coast of Yugoslavia in winter when cold air from
Russia crosses the mountains and descends to the
relatively warm coast of the Atlantic. It is
very stormy and squally, the squalls sometimes
reaching 100 miles per hour or more. (5)

borderland—A not so commonly used term for the
declivity which marks the inner or landward
margin of the continental borderland; the
ACUF did not find sufficient evidence of this
type of feature to warrant inclusion in their rec-
ommended terms and definitions.

borderland slope—The declivity which marks the
inner or landward margin of the continental
borderland. (2)

bore—1. See hydraulic jump.

2. (also called eager, mascaret, or tidal bore).
A high breaking wave of water, advancing
rapidly up an estuary. Bores can occur at the
mouths of shallow rivers if the tide range at the
mouth is large. They can also be generated in
a river when tsunamis enter shallow coastal
water and propagate up the river. (5)

3. A submarine sand ridge in very shallow
water. It may build up to intertidal level. (2)

4. See borehole.

borehole—(or boring, bore). A hole drilled into
the earth to obtain samples of and measure the
physical properties of the rock and sediments
penetrated.

borer—See marine borer.

boring—1. Forcing a ship under power through
ice, by breaking a lead.

2. See borehole.

(68)

bottle paper—Scee drift bottle.

bottle post—WSee drift bottle.

bottom—Any ground covered by water. Bed
refers more specifically to the whole submerged
basin, and floor is the essentially horizontal sur-
face of the ground beneath the water.

bottom bounce—A technique by which acoustic
energy is reflected off the ocean bottom one or
more times before reaching the target.

bottom flow—(or wnderflow). A current denser
than any part of the surrounding fluid and
which flows along the sea bottom.

bottom friction—The force resulting from the in-
teraction between the ocean bottom and water
particle motion over it. In the case of currents,
it is a retarding force acting in a direction op-
posite to the current flow. It is proportional to
the roughness of the bottom, water density, ve-
locity of the current, and water depth. The ef-
fect of bottom friction is also of importance in
forecasting waves in shallow water. As the
waves travel over shallow water they lose con-
siderable energy because of the stress of moving

BOTTOM ICE

water against the bottom of the ocean, causing
the waves to decrease in height.

bottom ice—Scee anchor ice.

bottom load—WScee load.

bottom materials—Sce bottom sediments.

bottom pressure—The pressure at a point on the
bottom of a body of water due to the weight of
the column of water above it.

bottom pressure fluctuation—The change in
pressure at a point on the bottom of a body of
water as a surface wave passes over it.

bottom reflection—The return of transmitted
sound from the bottom of the ocean. The char-
acteristics of reflected sound depend on the na-
ture of the bottom and on the wavelength of
the sound.

bottom resistivity—The resistance, in ohms, be-
tween opposite faces of a unit cube of sediment.
It is governed more by the electrolyte concen-
tration of the liquid filling the interstices than
by the intrusive conductivity of the sediment
grains itself.

bottom reverberation—Sce reverberation.

bottom sample—A portion of the material form-
ing the bottom, brought up for inspection.
(68

enti sampler—Any instrument used to obtain
a bottom sample. See grab.

bottom sediments—(also called bottom ma-
terials). In general all sedimentary material
regardless of origin found on or in the subma-
rine bottom, including ballast or other material
dumped into the sea by man. More specifically
it is limited to unconsolidated mineral and or-
ganic material forming the sea bottom, not in-
cluding coral reefs or bedrock.

bottom-set beds—The layers of fine alluvial sedi-
ments carried out and deposited on the bottom
of the sea in front of a delta. (2)

BOTTOM-SET BEDS

1. Top-set beds; 2. Fore-set beds; 3. Water surface;
set beds

4. Bottom-

(AFTER: LEET, L. DON & JUDSON, SHELDON. PHYSICAL
GEOLOGY. NEW YORK: PRENTICE-HALL, INC. 1954. p. 139.)

bottom temperature—Temperature observed at
the bottom of the sea.

bottom water—The water mass at the deepest part
of the water column. It is the densest water
that is permitted to occupy that position by the
regional topography. See water mass.

Bouguer anomaly—A difference between an ob-
served value of gravity and a theoretical value
at the point of observation, which has been cor-
rected for the effect of topography only, the to-

24

pography being considered as resting on a plane
of indefinite extent. (37)

Bouguer correction—A correction made in ob-
served gravity values for the altitude (eleva-
tion) above sea level of the station and the rock
between the station and sea level.

boulder—(or bowlder). A rounded rock with a
diameter of 256 millimeters or larger. See phi
grade scale.

boulder barricade—A coast bordered with lines
of innumerable large boulders visible between
low water and half tide.

boulder clay—Unstratified or little stratified and
unsorted deposit of silty and clayey materials in
which are embedded particles of sand to boul-
der size. (2)

boulderet—See cobble.

boulder gravel—Deposit of uncemented boul-
ders. (2)

boundary layer—A term referring broadly to
the layer of fluid in the immediate vicinity of
a bounding’ surface. It is the layer in which
frictional forces are not negligible.

boundary surface—Sce interface.

Bourdon tube—Part of the temperature sensing
element in a bathythermograph. It consists
of a hollow brass coil connected to a xylene
filled tube, with one end fixed and the other free
to move with temperature expansion and con-
traction.

bowlder—See boulder.

box gage—(or float gage). A tide gage that is
operated by a float in a long, vertical stationary
box to which the tide is admitted through an
opening in the bottom. (50)

brachial—Pertaining to armlike structures, such
as to the rays of starfishes.

brachiolaria—A more advanced stage of the bi-
pinnaria larva of a sea star.

brachiopod—(or lamp shell). One of a phylum
(Brachiopoda) of sessile, marine, mollusklike
animals in which the body, whose construction
differs considerably from that of the mollusks,
is enclosed in calcareous or horny bivalve shell.
Most species live in shallow water. Many fossil
species are known.

brackish water—Water in which salinity values
range from approximately 0.50 to 17.00 parts
per thousand. ee

branch fiord—A bifurcation of a narrow deep
arm of the sea.

branchial—Pertaining to gills.

branching bay—See estuary.

brash ice—A fragment of sea ice or river ice less
than 2 meters (6.6 feet) in diameter. (74)

brave west winds—A nautical term for the strong
and rather persistent westerly winds over the
oceans in temperate latitudes.

They occur between 40° and 65°N in the
Northern Hemisphere and 35° to 65°S in the
Southern Hemisphere, where they are more
regular and are strongest between 40° and 50°S

(roaring forties). They are associated with
the strong pressure gradient on the equatorial
side of the frequent depressions passing east-
ward in subpolar temperate latitudes; hence
they fluctuate mainly between southwest and
northwest. (5)

Brazil Current—The warm ocean current that
flows southward along the Brazilian coast below
Natal.

Its origin is in the westward flowing South
Equatorial Current, part of which turns south
and flows along the eeath American coast as
the Brazil Current. At about 35° S it meets the
cold north-setting Falkland Current and the
two turn to set eastward across the South
Atlantic Ocean.

breaker—A wave breaking on the shore, over a
reef, etc. Breakers may be roughly classified
into three kinds, although the categories may
overlap:

Spilling breakers break gradually over a con-

siderable distance ;

Plunging breakers tend to curl over and break

with a crash; and

Surging breakers peak up, but then instead

of spilling or plunging they surge up on
the beach face.

In the figure on the following page, the
sketches consist of a series of profiles of the wave
form as it appears before, during, and after
breaking. The numbers opposite the profile
lines indicate the relative times of occurrence.

61

eben depth—(also called breaking depth).
The still water depth at the point where a wave
breaks. (See figure for surf zone.) (61)

breaker zone—Generally used for surf zone.

breaking depth—Sce breaker depth.

breakup—In general, the spring melting of snow,
ice, and frozen ground. Specifically, the
destruction of the ice cover on rivers and seas
during the spring thaw; or applied to the time
when the solid sheet of ice breaks into pieces that
move with the current.

Breakup connotes the end of winter to a resi-
dent of the north. (59)

breakwater—A structure protecting a shore area,
harbor, anchorage, or basin from waves. (61)

breecia—(or agglomerate). A fragmental rock
whose components are angular and therefore, as
distinguished from conglomerates, are not wa-
terworn. There are friction or fault-breccias,
talus-breccias, and eruptive or volcanic brec-
cias. (2)

bridge—A light formation of snow or ice join-
ing two heavier formations. Seeramp. (65)

brightness—S¢ee luminance.

brine—Sea water containing a higher concentra-
tion of dissolved salt than that of the ordinary
ocean.

__ Brine is produced by the evaporation or freez-
ing of sea water, for, in the latter case, the sea ice

BT SLUG

formed is much less saline than the initial liquid,
leaving the adjacent unfrozen water with in-
creased salinity. The liquid remaining after
sea water has been concentrated by evaporation
until salt has crystallized is called bittern. (5)
brine slush—A mixture of ice crystals and salt
water, which retards or prevents complete freez-
ing, often found between young sea ice and a
cover of newly fallensnow. (59)
brit—(sometimes spelled britt). 1. The young of
the common herring; any of certain small
herring.
2. The plankton upon which the right whales
feed.
3. Any of the silversides.

British thermal unit—(abbreviated B.T.U.,
Btu). A unit of energy defined as the heat re-
quired to raise the temperature of one pound
of water one degree Fahrenheit; it is equal to
252.1 calories or 1,055 Joules. (5)

brittle star—One of a class (Ophiuroidea) of
echinoderms having five, sometimes six, rarely
seven or eight, elongate, slender, cylindrical
arms radiating from a flat central disc; they
range from shallow water to great depths.

broad ice field—A Russian term for an ice field
of more than 10 kilometers (5.4 n. miles) in
width. It corresponds to the current WMO
definition of vast ice floe.

broken beit—The transition zone between open
water and consolidatedice. (68)

broken ice—(also called loose ice, loose pack ice,
open ice, open pack ice, slack ice). Ice that
covers from 5-tenths to 8-tenths of the sea sur-
face. Seeopenpackice. (68)

Note: This term is being superceded by the
term open pack ice by WMO.

broken water—Water having a surface covered
with ripples or eddies, and usually surrounded
by calm water. (68)

brown alga—One of a division or phylum (Phae-
ophyta) (the Phyophyceae of another scheme)
of greenish yellow to deep brown, filamentous to
massively complex plants, in which the color is
imparted by the predominance of carotenes and
xanthophylls over the chlorophylls. This
group includes the rockweeds, gulfweeds, and
the large kelp. Brown algae are most abundant
in the cooler waters of the world.

bryozoan—(or polyzoan, moss animal, sea mat).
One of a phylum (Bryozoa or Polyzoa) of mi-
nute, mostly colonial, aquatic animals with body
walls often hardened by calcium carbonate and
growing attached to aquatic plants, rocks, and
other firm surfaces. Colonies may be encrust-
ing, creeping, or erect and branching. Encrust-
ing colonies may be white, yellowish, or brick
red and consist of many tiny, beautifully formed
shells. Members of this phylum are widespread
and notable fouling organisms.

BT slug—Scee airborne expendable bathyther-
mograph.

BUBBLE PULSE

BREAKING
INT

STILL WATER LINE

BEACH _IS_USUALLY VERY FLAT

SPILLING BREAKERS GENERAL CHARACTER OF SPILLING BREAKERS

BREAKING
POINT

PLUNGING BREAKERS

FOAM LINE
OF 4

SURGING BREAKERS GENERAL CHARACTER OF SURGING BREAKERS

TYPES OF BREAKERS

(AFTER WIEGEL, 1953)

bubble pulse—A pulsation attributable to the bub- bucket thermometer—A thermometer used to

ble produced by a seismic charge fired in water. measure the temperature of a bucket of water
The bubble pulsates several times with a period drawn from the surface of the ocean. :
proportional to the cube root of the weight of Bug Battery—A bacteria-filled fuel cell in which
the charge; each oscillation produces an identical certain biological organisms act as supercata-
unwanted seismic effect. (4) lysts in promoting electrochemical reactions.
bucket temperature—The surface temperature of The Navy has sent radio signals more than 15
the sea as measured by a bucket thermometer. miles powered by this device. This new concept

26

developed from the discovery that electrodes
thrust in ocean mud could pick up electrical
energy from microorganisms under the bottom
slime.

built platform—A bank of sediment which flanks
the marine-cut terrace or wave cut platform on
its seaward margin. The sediment is derived
from marine erosion and from rivers. (2)

bulk modulus—Sce coefficient of compressibil-
ity.

bull kelp—1. One of a genus (Wereocystis) of
large brown algae, which consist of a massive
holdfast, a long tough stipe terminated by an
elongate bulbous pneumatocyst, from which
four lamina-bearing branches radiate. This
genus occurs only on the Pacific coast of North
America from southern California northward
into Alaska and may reach lengths of 100 feet or
more.

2. One of a genus (Durvillea) of large brown
algae with broad, massive, leathery laminae,
which grows on rocks in the intertidal zone in
the cold waters of South America and New Zea-
land.

bummock—From the point of view of the sub-
mariner, a downward projection from the un-
derside of the ice canopy; the submerged coun-
terpartofahummock. (7)

buoy—A float; especially a floating object moored
to the bottom, to mark a channel, anchor, shoal
rock, etc. Some common types are:

A nun or nut buoy is conical in shape;

A can buoy is squat, and cylindrical or nearly
cylindrical above water and conical below
water ;

A spar buoy is a vertical, slender spar an-
chored at one end ;

A bell buoy is one having a bell operated

207-109 O—66——_3

27

BYSSUS

mechanically or by the action of waves,
usually marking shoals or rocks;

A whistling buoy is similarly operated (by
wave action), marking shoals or channel
entrances;

A dan buoy carries a pole with a flag or light
on it.

(61)

buoyancy—1. That property of an object that en-
ables it to float on the surface of a liquid, or
ascend through and remain freely suspended in
a compressible fluid such as the atmosphere.
Quantitatively, it may be expressed as the ratio
of the specific weight of the fluid to the specific
weight of the object; or, in another manner, by
the weight of the fluid displaced minus the
weight of the object.

2. (or buoyant force; also called Archime-
dean buoyant force). The upward force ex-
erted upon a parcel of fluid (or an object within
the fluid) in a gravitational field by virtue of
the density difference between the parcel (or ob-
ject) and that of the surrounding fluid.

5

buoyant force—Sce buoyancy (sense 2).

burning of the sea—Scee sea fire.

Buys Ballot’s law—A law describing the rela-
tionship of the horizontal wind direction in the
atmosphere to the pressure distribution; if one
stands with his back to the wind, the pressure to
the left is lower than to the right in the Northern
Hemisphere. In the Southern Hemisphere, the
relation is reversed.

This law was formulated in 1857 by the Dutch
meteorologist Buys Ballot and is a qualitative
Aes of the geostrophic wind equation.

5)

byssal thread—A part of a byssus.

byssus—A hairy attachment structure secreted by
certain pelecypods. '

caballing—The mixing of two water masses of
identical in sttw densities but different in situ
temperatures and salinities, such that the result-
ing mixture is denser than its components.

cable—1. A chain of metal links or a strong hemp
or wire rope used to anchor ships or buoys; an
underwater or overhead ropelike wire carrying
an electric current.

2. A unit of distance equal to 720 feet in the
U.S. Navy.

3. A unit of distance equal to 608 feet in the
British Navy or exactly one-tenth of a British
Nautical Mile.

(68)

cable-laid rope— (also known as water-laid rope).
Three or four plain-laid, three-stranded ropes
twisted together in the opposite direction to the
twists in each rope. It 1s used for ropes much
exposed to water.

cadder—A short form of ballycadder, meaning an
icefoot. (59)

caisson disease—Sece decompression sickness.

cake—See ice cake.

cake ice—An ice pack composed of fragments of
flat sea ice. (59)

cake urchin—Sce sea urchin.

calcarenite—A limestone or dolomite rock com-
posed of 50 percent or more coral sand or shell
sand whose particle size ranges from 4g, to 2
millimeters. Sometimes designates calcareous
sand.

caleareous—Consisting of or containing calcium
or calcium carbonate; impregnated with calcium
carbonate. (13)

calcareous algae—Marine plants which form a
hard external covering of calcium compounds.
Calcareous algae are found in all oceans and
frequently form reefs.

calcareous grits—Sandy beds, intermixed with
calcareous matter. (48)

calcareous sponge—A sponge in which the in-
ternal skeletal elements (spicules) are com-
posed of calcium carbonate.

calcilutite—A very fine-grained limestone or cal-
careous sediment, often containing some clay
matter. The mean grain diameter is less than
0.0625 millimeter.

calcirudite—A limestone conglomerate or sedi-
ment composed of fragments of coral, shell, or
limestone, cemented by or mixed with calcite
and calcareous sand or mud. (2)

C

28

calcisiltite—Limestone or limy sediment com-
posed of silt-sized calcareous fragments.
calcite—Calcium carbonate, CaCO,, crystallized
in hexagonal-rhombohedral form; one of the
rincipal constituents of limestone.
calclithite—Limestone containing 50 percent or
more of fragments of older limestone eroded
from the land. (2)
cale-sapropel—Sediments containin
sapropel but also the remains Be
algae. (2)
caldera—A large basin-shaped volcanic depres-
sion, the diameter of which is many times
greater than that of the included volcanic vent
or vents. Calderas are classified into three ma-
jor types: explosion, collapse, and erosion.
Numerous islands are drowned remnants of
calderas. (2) (See figure for compound
volcano.)
caldron—This term is not recommended by
ACUF. See basin.
calf—A piece of floating ice which has broken
away from a larger piece of sea ice or land ice.
Specifically, a piece of ice which rises to the sur-
face after breaking away from the submerged
ortion of its parent formation. (59)
calibration—Comparison between two instru-
ments or devices, one of which is a standard of
known accuracy, to detect and to correlate or
adjust any variation in the accuracy of the in-
strument being compared. (22)
calibration correction—The value to be added to
or subtracted from the reading of an instrument
to obtain the correct reading. (68)
calibration error—(also called scale error).
That error in an instrument due to imperfection
of calibration or maladjustment of its parts.
68
caiatipa table—A list of calibration correc-
tions or calibrated values. A card having such
a table on it is called a calibration card. (68)
California Current—The ocean current that flows
southward along the west coast of the United
States to northern Baja California. It is
formed by parts of the North Pacific Current
and the Subarctie Current and is a wide cur-
rent that moves sluggishly toward the south-
east. Off Central America, the California Cur-
rent turns toward the west and becomes the
North Equatorial Current.
Callao Painter—(or Z7 Pintor). Mariners’ ref-
erence to the catastrophic destruction of marine
life which causes the blackening of paint on

principally
calcareous

ships within the harbor of Callao, Peru. Hy-
drogen sulfide released during the decomposi-
tion of the or ganisms 1s responsible for the phe-
nomenon. The immediate cause of this phe-
nomenon is the increase in water temperature
when warmer oceanic currents turn inshore; or-
ganisms normally accustomed to colder water
temperatures die because of this abrupt tempera-
ture change.

calm—1. The state or condition of the water sur-
face when there are no wind waves or swell.
(73)

2. The apparent absence of motion of the sur-
face water; the water is generally considered
calm if the ctirrent speed is less than 0.1 knot.
See slack water.

calm belt—A belt of latitude in which the winds
are generally light and variable. The principal
calm belts are the horse latitudes (the calms of
Cancer and Capricorn) and the doldrums.
(5

Pee uiveniated cal). A unit of heat orig-
inally defined as the amount of heat required
to raise the temperature of one gram of water
through one degree centigrade (the gram-cal-
orie or small calorie), but this proved to be in-
sufficiently precise. The 15-degree gram-cal-
orie (cal,;) is the amount of heat required to
raise the temperature of one gram of water from
14.5°C to 15.5°C, and is equal to 4.1855 Joules.
The kilogram-calorie or large calorie (Kcal, kg-
cal, or Cal) is 1,000 times as large as a calorie.
The Internation Table calorie (ITcal) equals
1.00032 cal,;. (5)

calve—To break off or discharge pieces of ice
om a larger ice mass, as from a tidal glacier.

59)

calved ice—(also called calf). A piece of ice
floating in a body of water after calving from
a mass of land ice or an iceberg.

The term calf sometimes is used specifically
for a piece that has broken loose from a sub-
merged portion of an iceberg and risen to the
sea surface. (5)

calving—The breaking off of a mass of ice from
its parent glacier, iceberg, or ice shelf. (5)
camber—A small basin, usually with a narrow
co generally situated inside a harbor.
30)
canal—1. An artificial watercourse cut through
land.

2. A long narrow arm of the sea extending in-
land, between islands, or between islands and
the mainland.

(2)

Canaries Current—See Canary Current.

Canary Current—The prevailing southward flow
along the northwest coast of Africa; it helps to
form.the North Equatorial Current.

candled ice—Scee candle ice.

candle ice—(or candled ice, penknife ice, needle
tice, frost columns of ice). A form of rotten

29

CARIBBEAN CURRENT

ice; disintegrating sea ice (or lake ice) consist-
ing "of ice prisms or r cylinders oriented per ‘pendic-
ular to the original ice surface; these “ice fin-
gers” may be equal in length to the thickness of
the original ice before its disintegration. (5)

candle-power—Scee luminous intensity.

canyon—A relatively narrow, deep depression
with steep slopes, the bottom of which grades
continuously downward. (62)

canyon delta—A variation and more specific
definition of a type of fan which is described as
a sloping cone-shaped accumulation of sedi-
ments at the mouth of a canyon having a single
deep seachannel and high natural levees on its
upper portion and multiple shallow distributary
seachannels on its lower portion; not recom-
mended by ACUF. See fan.

cape—A body of land jutting from a continent or
large island which prominently marks a change
in or interrupts the coastal trend.

Wind Drift flowing eastward in the immediate
vicinity of Cape Horn, and then curving north-
eastward to continue as the Falkland Current.
(68)

capillary forces—Sce surface tension.

capillary ripple—Same as capillary wave.

capillary wave—(also called ripple, capillary rip-

ple). A wave whose velocity of propagation is
controlled primarily by the surface tension of
the liquid in which the wave is travelling.
Water waves of length less than one inch are
considered to be capillary waves. (61)
carapace—A chitinous or bony shield covering
the whole or part of the back of certain animals,
such as many crustaceans and theturtles. (26)
carbon dioxide—A heavy, colorless gas of chemi-
cal formula CO,. It is the fourth most abund-
ant constituent of dry air, now present to the
extent of 0.033 percent by volume.

Over 99 percent of the terrestrial CO, is found
in the oceans, but its solubility is strongly tem-
perature-dependent, so changes in sea surface
temperatures can lead to marked local changes
in@O, content. (5)

Carbon method—A method of radioactive dat-
ing which utilizes the ratio of radiocarbon
(Carbon) to Carbon” to determine the age of
samples containing formerly living matter.

Carbon" technique-_A method of measuring
primary production by using the radioactive
isotope Ct asa tracer. The tracer, in the form
C#O,, is assimilated by marine phytoplankton
under appropriate test conditions. The amount
of this tracer that has been incorporated into the
organic matter of the phytoplankton is measured
to determine the gross primary production.

Caribbean Current—A current flowing westward
through the Caribbean Sea. It is formed prin-
cipally by the major part of the North Equa-
torial Current setting through the Lesser

CAROTENE

Antilles; it is quite strong as it passes through
Yucatan Channel and then turns clockwise to
form. the Florida Current.

carotene—A_ plant pigment.
carotenoid.

carrageen— See Irish moss.

carrageenin—(or carragheenin). An extract of
Irish moss or carrageen, with gel properties,
used in puddings and as a stabilizer in various
food products.

carragheenin—See carrageenin.

cartography—The art and science of making
charts or maps. (66)

cascade—The mass of spray thrown outward
from around the base of a waterspout. (5)

cascajo—Reef-derived material consisting of
coral debris and other sediment occurring in old
deposits. (2)

castings—~See fecal pellet.

catadromous—A form of life cycle among fishes
in which maturity is attained in fresh waters,
and the adults migrate into the ocean to spawn.
The common eel is an example.

catazone—The deepest zone of rock metamor-
phism where very high pressures and tempera-
tures both prevail. (: 2)

catenary—The curve assumed by a flexible cord
in equilibrium when suspended from both ends.
The wire on which instruments are lowered
into the sea forms half a catenary in the pres-
ence of currents.

cathode ray tube—A vacuum tube consisting es-
sentially of an electron gun producing a con-
centrated electron beam (or cathode ray) which
impinges on a phosphorescent coating on the
back of a viewing face (or screen). The excita-
tion of the phosphor produces light, the inten-
sity of which is controlled by regulating the
flow of electrons. Deflection of the beam is
achieved either electromagnetically by currents
in coils around the tube, or electrostatically by
voltages on internal deflection plates. (5)

cat ice—See shell ice.

cation—A positively charged ion.

cat’s paw—A puff of wind; a light breeze affecting
a small area, as one that causes patches of rip-
ples on the surface of a water area. (68)

catter—A short form of bellicatter, meaning an
ice foot. Seeicefoot. (59)

caustic—1. In refraction of waves, the name
given to the curve to which adjacent orthog-
onals of waves, refracted by a bottom whose
contour lines are curved, are tangent. The oc-
currence of a caustic always marks a region of
crossed orthogonals and high wave convergence.
(61) (See figure for wave refraction.)

2. The envelope of a sequence of underwater
sound rays which defines the boundary of the
sound field.

cavitation—The turbulent formation, generally
mechanically induced, including growth and col-
lapse of bubbles in a fluid, and occurring when

See nonastacin

30

the static pressure at any point in fluid flow is
less than fluid vapor pressure.

cavitation noise—The noise produced in a liquid
by the collapse of bubbles that have been created
by cavitation. (3)

cay—(also called key or kay). A low flat island
or mound of sand: built up on a reef flat slightly
above high tide which may contain a large ad-
mixture of coral or shell fragments. (2)

cay sandstone—A friable to firm sandstone ce-
mented by calcium carbonate and formed from
coral sand near the base of coral reefs and ex-
tending to above high tide. See also beach-
rock. (2)

celerity—=Scee wave celerity.

cellular convection—An organized, convective,
fluid motion characterized by the presence of
distant convection cells or convective units, usu-
ally with upward motion (away from the heat
source) in the central portions of the cell, and
sinking or downward flow in the cell’s outer
regions. (5)

Celsius temperature scale—(abbreviated C).
Same as centigrade temperature scale, by recent
convention. The Ninth General Conference on
Weights and Measures (1948) replaced the des-
ignation “degree centigrade” by “degree
Celsius.” (5)

cementation—The process of precipitation of a
binding material such as quartz, calcite, or dolo-
mite around grains or minerals in rocks. (2)

center of action—Any one of the semipermanent
highs and lows that appear on mean charts of
sea-level pressure. As originally used by L.
Teisserenc de Bort in 1881, this term was applied
to maximums and minimums of pressure on
daily charts.

The main centers of action in the Northern
Hemisphere are the Icelandic low, the Aleutian
low, the Azores high and/or Bermuda high,
the Pacific high, the Siberian high (in winter),
and the Asiatic low (in summer). Other less
intense or less consistent “mean” systems may
be considered. Fluctuations in the nature of
these centers are intimately associated with
relatively widespread and long-term weather
changes. (5)

center of gravity—A point at which the mass of
the entire body may be regarded as being con-
centrated.

centigrade temperature scale—Sce Celsius tem-
perature scale.

Central Water—Sce water mass.

centrifugal force—The force with which a body
moving under constraint along a curved path,
reacts to the constraint. Centrifugal force acts
in a direction away from the center of curvature
of the path of the moving body. As a force
caused by the rotation of the earth on its axis,
centrifugal force is opposed to gravitation, and
combines with it to form gravity. (37)

centrifuge plankton—See nannoplankton.

centrosphere—(also called barysphere, core).
The central core of the earth, composed of dense
material, and making up most of its mass. (2)
(See figure for earth structure.)

cephalopod—One of a class (Cephalopoda) of
benthic or free-swimming mollusks possessing
a large head, large eyes, and a circle of arms or
tentacles around the mouth; the shell is external,
internal, or absent, and an ink sac usually is
present. See squid, octopus, nautilus.

cetacean—A marine mammal of the order Ce-
tacea, which includes the whales, dolphins, and
porpoises.

cgs system—The system of physical measure-
ments in which the fundamental units of length,
mass, and time are the centimeter, gram, and
second, respectively. (37)

chaetognath—See arrow worm.

chain bag dredge—Sce chain mesh dredge.

chain mesh dredge—(also called chain bag
dredge). A bottom sampler constructed of a
rectangular steel collar attached to a chain mail
purse lined with screens or netting. It is used
on the continental shelf to collect coarse-grained
sediments and bottom dwelling organisms.

chain reaction—Any chemical or nuclear process
in which some of the products of the process or
energy released by the process are instrumental
in the continuation or magnification of the proc-
ess. (70)

chalk—A very soft white to light gray limestone
composed of the tests of floating microorga-
nisms and some shells of bottom dwelling ani-
mals in a matrix of finely crystalline calcite.
Chalk is classed as rock on bottom sediment
charts. (2)

Challenger Expedition—The expedition
mounted by the British in H.M/.S. Challenger,
1873-1876, which made the first extensive
oceanographic research cruise.

change of tide—(or turn of the tide). A re-
versal of the direction of motion (rising or fall-
ing) of a tide. Sometimes applied to a reversal
in the set of a tidal current.

channel—1. A natural or artificial waterway
which either periodically or continuously con-
tains moving water, or which forms a connect-
ing link between two bodies of water. (61)

2. The part of a body of water deep enough
to be used for navigation through an area other-
wise too shallow for navigation. (61)

( 5 A large strait, as the English Channel.
61

4. The deepest portion of a stream, bay, or
strait through which the main volume or current
of water flows. (61)

5. A lead in packice. (59)

6. An energy band of predetermined size used
in the discrimination and storage of electronic
pulses like those from a gamma ray spectrom-
eter probe. See pulse height analyzer.

31

CHIP LOG

channel wave—Any elastic wave propagated in a
sound channel because of a low velocity layer in
iis pee earth, the ocean, or the atmosphere.

5)

chapeirao—A Brazilian term for isolated coral
structures, which often rise to a height of 40 to
50 feet like towers, sometimes spreading out in
a mushroomlike top. (2)

characteristic wave height—Sce significant
wave height.

character of the bottom—(also called nature of
the bottom). The type of material of which the
bottom is composed and its physical character-
istics such as hard, sticky, and rough.

chart—A special-purpose map generally designed
for purposes of navigation. The term is some-
times used to describe other special-purpose
maps. (37)

chart datum—(or datum, datum plane, hydro-
graphic datum plane of reference, reference
plane, tidal datum). The permanently estab-
lished surface from which soundings or tide
heights are referenced (usually low water).
The surface is called a tidal datum when re-
ferred to a certain phase of the tide. In order
to provide a factor of safety, some level lower
than mean sea level is generally selected, such
as mean low water or mean lower low water.
(See figure for tide range.) .

charted depth—The vertical distance from the
tidal datum to the bottom. (68)

Charybdis—Sce Galofaro.

chemical oceanography—The study of the chem-
ical composition of the dissolved solids and
gases, material in suspension, and acidity of
ocean waters and their variability both geo-
graphically and temporally in relationship to
the adjoining domains, namely, the atmosphere
and the ocean bottom.

chemiluminescence—The production of light
during a chemical reaction at low temperatures.
Bioluminescence is a chemiluminescent reac-
tion.

chemistry of sea water—Scee constituents of
sea water.

chemoautotrophic nutrition—See chemotrophic
nutrition.

chemotrophic nutrition—(or chemoautotrophic
nutrition). ‘That process by which an orga-
nism manufactures its food by using the energy
derived from oxidizing organic matter. See
autotrophic nutrition.

Chile Current—See Peru Current.

chip log—A line marked at intervals (commonly
50 feet), and payed out over the stern of a mov-
ing ship. By timing the intervals at which the
markers appear as the line is pulled out by a
drag (the “chip”), the ship’s speed can be de-
termined. The wavelength of ocean waves can
be estimated by noting the position of wave
crests relative to the markers. (5)

CHI-SQUARE TEST

chi-square test—A statistical significance test
based on frequency of occurrence; it is appli-
cable both to qualitative attributes and quanti-
tative variables. Among its many uses, the
most common are tests of hypothesized proba-
bilities or probability distributions (goodness of
fit), statistical dependence or independence
(association), and common population homo-
geneity). (5)

chitin—A_ nitrogeneous carbohydrate derivative
forming the skeletal substance in arthropods.
(26)

chiton—One of a class (Amphineura) of flattened
mollusks protected either by calcareous
spicules or plates.

chlorine equivalent—Original definition of
chlorinity. It represents the total amount of
chlorine, bromine, and iodine in grams per kilo-
gram of sea water, with the assumption that
the bromine and iodine have been replaced by
chlorine. Chlorine equivalent is dependent on
changes in atomic weights, whereas chlorinity
is independent of such changes. (54)

chlorinity—(symbol Cl). A measure of the
chloride content, by mass, of sea water (grams
per kilogram of sea water, or per mille). Orig-
inally chlorinity was defined as the weight of
chlorine in grams per kilogram of sea water
after the bromides and the iodides had been re-
placed by chlorides. To make the definition
independent of atomic weight, chlorinity is now
defined as 0.3285233 times the weight of silver
equivalent to all the halides.

Because of the Law of Constancy of Relative
Proportions the amount of chlorinity in a sea
water sample is generally used to establish the
sample’s salinity. By using normal water as
a comparison standard, Knudsen burettes and
pipettes for the analysis, and Knudsen’s
Tables to compute the results, determinations
as accurate as those of a time-consuming gravi-
metric analysis can be made with a rapid titra-
tion of the sea water against silver nitrate solu-
tion, employing potassium chromate or other
suitable indicator for the end-point. ;

chlorophyll—A group of green pigments, identi-
fied as a, 6, and c, which occur chiefly in bodies
called chloroplasts and are active in photo-
synthesis. The concentration of each of these
pigments has been employed as a means of
estimating the rate of photosynthesis (primary
production) or as an index of the standing crop
of plant forms.

chloroplast—The green pigmented body or bodies
within the cells of green algae. (13)

chlorosity—The chlorine content of one liter of
sea water. It is equal to the chlorinity of the
sample times its density at 20°C. (5)

32

chlorosity factor—The ratio between the various
substances in sea water and the chlorosity. It
is obtained by dividing the concentration of the
substance in milligram-atoms per liter by the
chlorosity. (54)

chop—(or wind chop). The short-crested waves
that may spring up quickly in a fairly moderate
breeze and break easily at the crest. (61)

chopping sea—See choppy sea.

choppy sea—(also called chopping sea, cockling
sea). Short, rough waves tumbling with a short
and quick motion. (73)

chordate—One of a phylum (Chordata) of ani-
mals which possess a notochord (a middorsal
cylindrical rod), a series of paired gill slits,
both of which features are present only in the
embryo of air-breathing members, and a dorsal
central nervous system. Representative chord-
ates are the tunicates, fishes, and mammals.

chuck—A narrow passage or strait swept by
tidal currents, also applied to the tidal current
itself. (2)

ciguatera—An intoxication in humans resultin
from the ingestion of various tropical reef an
inshore fishes and possibly certain invertebrates.
The most common symptoms are tingling and
numbness of the lips, tongue, hands, and feet,
confusion of sensations of heat and cold, nausea,
diarrhea, joint and muscular pain, burning uri-
nation, inability to coordinate voluntary muscu-
lar movements, and difficult breathing. The
fatality rate is about 7 percent. The fishes in-
volved usually are large carnivorous forms such
as barracudas, snappers, groupers, and jacks.
Many other common food fishes have been impli-
cated in sporadic outbreaks of this type of poi-
soning, as well as certain marine snails and sea
urchins.

cilia—Hairlike processes of cells, which beat
rhythmically and cause locomotion of the cells
or produce currents in water.

cinders—See scoria, lapilli.

cinerite—Sedimentary material consisting of vol-
canic cinders. (2)
circle of longitude—Sce parallel of latitude.
circulation—1. The flow or motion of a fluid in
or through a given area or volume. |
9. A general term describing water current
flow within a large area; usually a closed cir-
cular pattern such as in the North Atlantic,.
Mediterranean, etc.
cirripede—Scee barnacle.
cirrus—1. One of the appendages of barnacles;
one of the filamentous respiratory and tactile
appendages of annelids. (26).
9. Also, a principal cloud type.
cladoceran—Scee water flea.
clam—A member of any one of several families
of generally edible bivalves, the majority of
which burrow into mud or sand bottoms.

clamshell snapper—A bottom sampling device
used to collect 2 small amount (less than 1 pint)
of material from the ocean floor.
jaws that snap shut when the device touches the

bottom.

Kingdom: Animal
Subkingdom : Metazoa
Phylum: Chordata

It has metal Subphylum: Gnat-

CLAY

Order: Selachii
Suborder: Galeoidea
Family : Lamnidae
Subfamily : Lamnini

clapotis—The French equivalent for a type of
standing wave. In American usage it is usually
associated with the standing wave phenomenon
caused by the reflection of a wave train from
a breakwater, bulkhead, or steep beach. (73)

Clarke-Bumpus quantitative plankton sam-
pler—A plankton collecting device equipped
with a flowmeter to determine the volume of
water passed through it in a given time interval.

class—See classification of organisms.

classification of marine environments—The
components of this classification commonly are
used with or without the terms division, region,
province, or zone. (40)

classification of organisms—The grouping of
plants and animals according to natural rela-
tionships; the groups range progressively from
those based upon broad and general relation-
ships to those based upon narrow and specific
relationships. One of the large marine sharks
(the white shark) is classified below; the groups
are listed in increasing order of specificity.

hostomata Genus: Carcha-
Class: Chon- rodon
drichthyes Species: car-
Subclass: charias
Elasmo-
branchii

class interval—A range of values of a variable;
an interval used in dividing the scale of the vari-
able for the purpose of tabulating the frequency
distribution ofasample. (5)

clastic—A rock composed principally of detritus
transported mechanically into its place of final
deposition. Sandstones and shales are the com-
monest clastics. Limestones are not clastic rocks
unless formed of particles derived from pre-
existing limestone. (2)

clastic rock—Scee clastic.

clay—As a size term, refers to sediment particles
ranging from 0.0039 to 0.00024 millimeter, in
which case it includes rock flour, calcareous
muds, aragonite, etc. Mineralogically, clay is a
hydrous aluminum silicate material with plastic
properties and a crystal structure. Common
clay minerals are kaolinite, montmorillonite,
and illite. See phigrade scale.

BM OC aS eo

fae — Nar Corer nena rae omer At AA NY I” iC a
SS a | ia s
re, a TT YIN-//>),,7 ns

PELAGIC (Water)
Neritic
Oceanic
Epipelagic
Mesopelagic
Bathypelagic
Abyssopelagic

BENTHIC (Bottom)
Supro-littoral
Littoral (Intertidal)
Sublittoral

Inner

Outer
Bathyal
Abyssal
Hadal

Note:

uncertain.

Question marks indicate that the limits, or
discrete character, of the environment are

Yj; Boundary indefinite.

300
2007 400
Mesopelagic ar)
2 s, ee 1000
MMMM»
< 1500
Bathypelagic bh BCO0
11500:
3000
2000.
Ks. “Mts 4000
48 . Abyssopelagic on
2 5000
® 3000
10000

CLASSIFICATION OF MARINE ENVIRONMENTS

33

(NRC; HEDGPETH, 1957)

CLAY GALL

clay gall—Small pellets of clay which are gen-
erally embedded in a sandy matrix.
clearing—Sce polynya.
cleavage—The splitting of bedded rocks along
definite parallel closely spaced planes which may
be highly inclined to the bedding planes.
cliff—sSee bluff.
climate—The prevalent or characteristic meteor-
ological conditions of a place or region, in con-
trast with weather which is the state of the
atmosphere at any time.
clino—The sloping part of the floor of the sea
which extends from the wave base to the deeper
parts of the sea. The deposit formed in the clino
environment is called a clinoform. The rock
unit of the clinoform is the clinothem. (2)
clinoform—WScee clino.
clinothem—See clino.
clo—A unit of thermal insulation, usually applied
to clothing or bed covers. It is defined as the
amount of insulation necessary to maintaim com-
fort and a mean skin temperature of 92°F for
a person who is producing heat at the standard
metabolic rate (50 kilogram-calories per square
meter of body surface per hour; one met) in an
indoor environment characterized by a tempera-
ture of 70°F, relative humidity of less than 50
percent, and air motion of 20 feet per minute.
5
Se bay—A bay indirectly connected with the
sea through a narrow pass. (2)
close drift ice—Sce close pack ice.
closed sea—1. That part of the ocean enclosed by
headlands, within narrow straits, etc.
2. That part of the ocean within the terri-
torial jurisdiction of a country.
68
aie eae called close pack, packed ice).
Ice that covers from 8-tenths to 10-tenths of
the sea surface. (68) See close pack ice (pre-
ferred WMO term).
close pack—WSee close ice.
close pack ice—(or close drift ice). Sea ice con-
sisting of ice floes that are generally in con-

tact. Their concentration ranges between 7-
tenths and 9-tenths (6-eighths to 7-eighths).
(74)

Cl-ratio—The amount of any ion or substance per
unit weight of chlorinity. It is obtained by di-
viding the concentration of the various ions in
grams per kilogram by the chlorinity. (54)

cnoidal wave—A type of wave profile in shallow
water (depth of water is less than 14 to #5 the
wavelength). The formula is expressed in terms
of the Jacobian elliptic function en wu; hence the
term “cnoidal.” (72)

coast—The general region of indefinite width that
extends from the sea inland to the first major
change in terrain features. (2)

coastal area—The land and sea area bordering
theshoreline. (61)

34

coastal current—A relatively uniform drift
usually flowing parallel to the shore in the
deeper water adjacent to the surf zone. The
current may be related to tides, winds, or dis-
tribution of mass.

Sometimes called a nearshore current or
offshore current. (73)

coastal ice—See fast ice.

coastal plain—A plain which borders the sea
coast, and extends from the sea to the nearest
elevated land.

coastal plain estuary—WSee estuary.

coastal pressure ridge—The ridge formed when
floating sea ice is thrust against fast ice. (59)

coast ice—(or coastal ice). See fast ice.

coastline—The configuration made by the meet-
ing of land and the sea. (68).

Coast Pilot—A book of sailing directions for the
United States or possessions, published by the
U.S. Coast and Geodetic Survey. (5)

cobble—(also called bowlderet, cobblestone). A
rock fragment between 64 and 256 millimeters
in diameter, larger than a pebble and smaller
than a boulder, and rounded or otherwise
abraded. (2) See phi grade scale.

cobblestone—See cobble.

coccolith—Very tiny calcareous plates, generally
oval and perforated, borne on the surface of
some plantonic marine algae (cocolithophores).

coccolithophore—One of a family (Coccolitho-

phoridaceae) of microscopic, often abundant
planktonic algae, the cells of which are sur-
rounded by an evelope on which numerous small
calcareous discs or rings (coccoliths) are em-
bedded. Large concentrations give the water a
milky appearance; this condition is called
“white water” by the herring fishermen of
northern Europe.

cockling sea—See choppy sea.

cocurrent line—A line on a chart passing through
places having the same tidal current hour. (50)

coefficient of absorption—See absorption co-
efficient.

coefficient of compressibility—(or compressi-

bility). The relative decrease of the volume of
a system with increasing pressure in an
isothermal process. This coefficient is

Ses

V\ op a
where V is the volume, p the pressure, and 7’
the temperature. The reciprocal of this
quantity is the bulk modulus. (5)

coefficient of expansion—See coefficient of
thermal expansion.

coefficient of heat conduction—Sce thermal
conductivity.

coefficient of thermal conduction—Scee thermal
conductivity.

coefficient of thermal expansion— (or coefficient
of expansion). The relative increase of the
volume of a system (or substance) with increas-
ing temperature in an isobaric process. In
symbols this coefficient is
1 foV

VNO
where V’ is the volume, 7’ the temperature, and p
the pressure. (5)

coelenterate—One of a phylum (Coelenterata or
Cnidaria) of two-staged (sessile and free-float-
ing) organisms. The sessile stage basically is
cylindrical and is called a polyp; the free-
swimming stage is disc or bell shaped and is
called a medusa or jellyfish. Many coelenter-
ates, particularly the hydrozoans and corals,
are colonial, consisting of many polyps united
in complex or massive structures. AJ] contain
stinging cells or nematocysis, many exhibit
bioluminescence, and some reportedly scatter
sound. See hydrozoan, scyphozoan, antho-
zoan.

col—In meteorology, the point of intersection of a
trough and a ridge in the pressure pattern of a
weather map. It is the point of relatively low-
est pressure between two highs and the point of
relatively highest pressure between two lows.

5)

cold light—Light emitted by any body whose tem-
perature is below that of incandescence.

cold pool—A body of cold water entirely sur-
rounded by warm water.

cold wall—The steep water-temperature gradient
between the Gulf Stream and (a) the slope
water inshore of the Gulf Stream or (b) the
Labrador Current. It is considered part of the
Arctic Convergence by most oceanographers.
(5)

collar ice—See ice foot.

collector—In underwater optics a device required
to fulfill the definition of the quantity being
measured, for instance, a Gershun tube in radi-
ance measurements or a cosine collector in
irradiance measurements. (8)

colligative property—One of four characteristic
properties of solutions, namely the interdepend-
ent changes in vapor pressure, freezing point,
boiling point, and osmotic pressure, with a
change in amount of dissolved matter. If, under
a given set of conditions, the value for any one
property is known, the others may be computed.
In general, with an increase in dissolved matter
(for example, salt in sea water) freezing point
and vapor pressure decrease, and boiling point
and osmotic pressure increase. (5)

colloid—As a size term refers to particles smaller
than 0.00024 millimeter, smaller than clay size.

colonial coral—Coral in which the individuals
are attached together as units, and do not exist as
separateanimals. (2)

35

COMPOUND TIDE

colored filter—WSce selective filter.

comber—(also called roller, beachcomber). 1. A
deepwater wave whose crest is pushed forward
by a strong wind and which is much larger than
awhitecap. (61)

2. A long-period spilling breaker. If there

are many lines of breakers simultaneously on a
shore, they form a surf.

comb jelly—Sce ctenophore.

commensalism—A_ symbiotic relationship be-
tween two species in which one species is bene-
fitted and the other is not harmed. The rela-
tionship between the shark and the remora or
“suckerfish” is an example of commensalism.
See mutualism, inquilinism, symbiosis.

common establishment—Sce establishment of
the port.

community—(also called biocenose, biocenosis).
An integrated, mutually adjusted assemblage of
plants and animals inhabiting a natural area.
The assemblage may or may not be self-sufficient
and is considered to be in a state of dynamic
equilibrium. Although the community concept
is clear, specific communities and their limits,
particularly in the ocean, are often difficult to
recognize. The community usually is character-
ized as having a more or less definite species
composition and may be defined on the basis of
the habitat it occupies or on the basis of the
species present.

compact ice—Sce conglomerated ice.

compaction—The decrease in volume or thickness
of a sediment under load through closer crowd-
ing of constituent particles and accompanied by
decrease in porosity, increase in density, and
squeezing out of interstitial water. (2)

compensation depth—The depth at which photo-
synthesis equals plant respiration during a
24-hour period.

compensation point—Sce compensation depth.

component—Scee constituent.

composite chart—A chart based on data for ex-
tended periods, usually 5 to 10 days, treated as
being synoptic.

composite sample—See compound sample.

compound pancake ice—Ice pancakes which have
frozen together. (68)

compound ripples—Scee ripple marks.

compound sample —(or aggregate sample, com-
posite sample). A mixture of a number of spot
samples to form an aggregate single sample.

compound shoreline—That shoreline whose
essential features combine elements of at least
two of the other shoreline classifications, that is,
emergence, submergence, or neutral shoreline.

compound specific activity—Total radioactivity
of a given isotope per gram of a compound.
(70)

compound tide—A tide constituent with a speed
equal to the sum or difference of the speeds of
two or more basic constituents. Compound tides

COMPOUND VOLCANO

usually occur in shallow water regions. See
shallow water constituent. (50)

compound volcano—A volcano that consists of
a complex of two or more cones, or a volcano
that has an associated volcanic dome, either in
its crater or on its flanks. (2)

3 Ae iol

2

ee cal

vu

Atl
nw an
tat

COMPOUND VOLCANO

oo Primary cone; 4.
7. Magma,

2. Lava flow accumulations;
5. Secondary cone; 6. Lava flow;

1. Vent;
Caldera;

reservoir (AFTER: LEET, L. DON & JUDSON, SHELDON. PHYSICAL

GEOLOGY. NEW YORK: PRENTICE-HALL, INC. 1954. p. 360.)

compressed-air illiness—See decompression

sickness.

compressibility—See coefficient of compressi-
bility.

compressibility fac¢tor—sSee
factor.

compressional wave—A wave in an elastic
medium which causes an element of the medium
to change its volume without undergoing
rotation. (69)

compression factor—(or diving rules, compresst-
bility factor). A coefficient expressing, in
pounds per hundred feet, the combined effect on
submarine buoyancy of the compressions of sea
water and of the ship with increasing depth.
It isalways negative in value.

Compton absorption—The absorption of an
X-ray or gamma ray photon in the Compton
effect. The energy of the electromagnetic
radiation is not completely absorbed since an-
other photon of lower energy is simultaneously
created. (41)

Compton effect—An attenuation process observed
for X- or gamma radiation in which an inci-
dent photon interacts with an orbital electron
of an atom to produce a recoil electron and a
scattered photon of energy less than the incident
photon. (70)

Compton scattering—Scee scattering (sense 3).

concentration—In sea ice reporting, the ratio of
the areal extent of ice present to the total areal
extent of ice and water. Concentration is usu-
ally reported in tenths, and is meaningful in
definitions of open water, very open pack ice,
open pack ice, close pack ice, very close pack
ice.

compression

concentration factor—An expression of the rela-
tive amount of an element in an organism as
compared to its relative amount in sea water.
Concentration factors as high as two million or
higher have been reported for some elements in
some organisms.

concretion—(or concretionary). Nodular or ir-
regular concentrations of material through dep-
osition from solution, usually about a central
nucleus. Examples are clay and manganese
nodules. Seenodules.

concretionary—Scee concretion.

concussion crack—(also called shock crack). A
fracture in sea ice produced by the impact of one
ice cake upon another. (59)

condensation—The physical process by which a
vapor becomes a liquid or solid; the opposite of
evaporation. When water vapor condenses,
heat is released, and the surrounding tempera-
ture is raised.

condensed deposit—Sedimentary material that
accumulated very slowly ; it is thin but not inter-
rupted. (2)

conduction—The transfer of energy within and
through a conductor by means of internal par-
ticle or molecular activity, and without any net
external motion. Conduction is to be distin-
guished from convection (of heat) and radia-
tion (of all electromagnetic energy). (5)

conductivity—See electrical conductivity,
thermal conductivity, thermometric conduc-
tivity.

cone shell—A tropical marine snail of the family
Conidae possessing a venom-injecting apparatus
used to subdue its prey. Several Indo-Pacific
species have been implicated in human fatali-
ties; most species belong to the genus Conus.

conformal projection—A map which preserves
angles; that is, a map such that if two curves
intersect at a given angle, the images of the two
curves on the map also intersect at the same
angles.

On such a map, at each point, the scale is the
same in every direction. Shapes of small regions
are preserved, but areas are only approximately
preserved (the property of area conservation
is peculiar to the equal-area map).

The most commonly used conformal map is
probably the Lambert conformal conic projec-
tion, with standard latitudes at 30° and 60°N.
On the standard latitudes, the scale is exact; be-
tween them, it, is decreased by not more than
about 1 percent; outside them, distortion in-
creases rapidly. The Mercator and_stereo-
graphic projections are also conformal maps.
(5)

confused sea—A rough sea where the direction
and period of the sea and/or swell is indeterm1-
nate, caused by various overriding wave trains.

conglomerate—(or puddingstone). Rock con-
sisting of gravel, pebbles, and sand cemented
together.

conglomerated ice—(or compact ice). All types
of floating ice compacted into one mass; term
refers to the contents of an ice mass, not the
concentration. (65)

conic projection—A map projection in which the
surface of a sphere is conceived as projected, in
the geometrical sense, on a tangent or secant
cone, which is then developed on the plane.

conjunction—The situation of two celestial bodies
with the same celestial longitude (the angular
distance measured east of the vernal equinox
along the ecliptic) ; for example, conjunction
occurs when the moon and the sun are directly
in line with the earth and the moon is between
the earth and the sun. (66) (See figure for
tide cycle.)

Conrad discontinuity—Seismic discontinuity in
the earth’s crust where velocity increases from
6.1 to 6.4-6.7 kilometers per second; occurs at
various depths and is supposed to mark contact
of “granitic” and “basaltic” layers. (2)

consecutive mean— (also called moving average,
running mean, overlapping mean). A smoothed
representation of a time series derived by re-
placing each observed value with a mean value
computed over a selected interval. For example,
if the observations are of daily maximum tem-
perature and the selected interval is five days,
then the value assigned to February 5th is the
mean of the daily maximum from February 3rd
through February 7th, ete.

Consecutive means are used in smoothing
to eliminate unwanted periodicities or minimize
irregular variations. (5)

conservative property—A property whose values
do not change in the course of a particular series
of events. Properties can be judged conserva-
tive only when the events (processes) are speci-
fied; also, properties that are conservative for a
whole system may or may not be conservative
for its parts, and conversely. (5) For ex-
ample, those properties of the ocean, such as
salinity, the concentrations of which are not
affected by the presence or activity of living
organisms but which are affected by diffusion
and advection.

Conshelf Two—Short form for Continental Shelf
Station Number Two. Conshelf Two was a
manned undersea research station consisting of
four prefabricated steel structures, under the
supervision of Capt. Jacques-Yves Cousteau,
located 36 feet beneath the surface of the Red
Sea on a coral ledge which is part of Sha’ob
Rumi (Roman Reef) about 25 miles northeast
of Port Sudan. This underwater research sta-
tion was the second of two successful attempts.
(12) '

37

CONSTITUENTS OF SEA WATER

Consolan—An electronic navigational system pro-
viding a number of rotating equisignal zones
that permit determination of bearings from a
transmitting station.

consolidated ice—(also called consolidated pack).
An area of the sea covered by ice of various
origins compacted by wind and currents into a
firm mass. In sea ice reporting, consolidated
ice 1s a term used to describe an area completely
devoid of open water with a concentration of
10-tenths. It usually includes some of the
heavier forms of ice. See very close pack ice
(preferred WMO term).

consolidated pack—WSce consolidated ice.

consolidated sediments—Sediments which have
been converted into rocks by compaction, deposi-
tion of cement in pore spaces, and/or by physi-
cal and chemical changes in the constituents.

consolidation—The reduction in volume of sedi-
ment and increase in density in response to in-
creased load through decrease in pore space,
void ratio, and water content. (2)

constancy—WSee persistence.

constancy of the current—(or persistency).

The ratio of the magnitude of the resultant
velocity to the mean velocity of the current.
Constancy is dimensionless and may be ex-
pressed as a percentage; it equals 100 percent
if all observations indicate the current setting
exactly in the same direction at the same speed;
it decreases in value with increasing variability
of current direction and speed; it equals zero if
there is an equal number of observations from
all directions and all observations have the same
speed.

constituent—(also called harmonic constituent,
astronomical tidal constituent, component,
tidal constituent, partial tide). One of the
harmonic elements in a mathematical expres-
sion for the tide-producing force and in
corresponding formulas for the tide or tidal
current. Each constituent represents a periodic
change or variation in the relative positions of
the earth, moon,andsun. (50) See harmonic
constant.

constituent day—The duration of the earth’s
daily rotation relative to a fictitious star which
represents one of the periodic tide-producing
forces; it approximates the length of the lunar
or solar day and corresponds to the period of a
diurnal constituent of twice the period of a
semidiurnal constituent. The term is not
applicable to the long-period constituents.
(50)

constituent hour—One twenty-fourth part of a
constituent day. (50)

constituents of sea water—(or chemistry of sea
water). Sea water obeying the Law of Con-

CONTINENT

stancy of Relative Proportions contains the
following constituents:

A. Major constituents

(Chlcrimes= ssa =e 18.980 g/kg (%)
Sodium 2 aaa see 10.561
Majenesium a see 1.272
Sulfurse: 2 2 asses Sena 0.884
Calciumeae= == aaa === 0.40
AQUARIUS eae 0.380
Br OMI e eee 0.065
Carbone] 3eae een 0.028
SHARON = See sees 0.0138
Boronees See eae eee 0.005

B. Minor constituents
Silicon.3-2 = 2 Sees 4x 107-§ to 2« 10-8
BluoTine === ee 1.4 10-5
INGUuRO Ce ee eee 7X 1077 to 6X 1079
PAN arama aaa ee ee S< Ome
IRWMNClWN 4 saeco eascs 21077
ithe eee 1x<1077
IPhosphonlse ees =a =ee= 11077 to 1x10~
Barium eee ese 5x 1078
WoGinee ieee ae eee ase BS< Ore
ATS em Cee eee 2h Om eitoy2><l One
Manganese-_-----_------- 11058 to 1X 105°
Coppers ese e= ea IGlOne
Tin Gees a ae eee Oyen?
UGE KCI te eee es 4x 107°
Selenium =a === nee 4x 107°
@esiuma see see eee DMO
Wiramiginn Soe e se soe sSse 1.5 10-9
Molybdenum-_----------- DyelOme
MeO TUT eee a 5X 107
Genius. eae See nee ae 4% 10710
Silvierseeuee eee eee ce yet = 310-10
Wennnclinm 4 5 2o5eses42 OD LOme
Lanthanum). 2222222222 = 3x 10-10
SVG Grete eee 3107-10
INAGL el ee ee 1x 10719
Scamebivim. 3s ve oessees 410-11
Mie rc uiiy pyar oe ee 3x10
(Giolla ates Bae eee te 6x 10-12
IRevohibo 5 = oe ee oc eee 83x 1058 to 21057
@aduiiiin ae Trace
Cobaltee sae 2 see Trace
ERS ees cout he ae Trace

continent—A large landmass rising abruptly
from the deep ocean floor, including marginal
regions that are shallowly submerged. Con-
tinents constitute about one-third of the earth’s
surface. (2)

continental air—A type of air whose character-
istics are developed over a large land area and
which, therefore, has the basic continental char-
acteristic of relatively low moisture content.
(5)

continental apron—Sce continental rise.

continental borderland— (or borderland). A re-
gion adjacent to a continent, normally occupied
by or bordering a continental shelf, that is
highly irregular with depths well in excess of
those typical of a continental shelf. (62)

continental drift—The concept that the conti-
nents can drift on the surface of the earth be-
cause of the weakness of the suboceanic crust,
such as ice can drift through water. (2)

continental glacier— (also called continental ice).
A continuous sheet of land ice which covers a
very large area and moves outward in many di-

38

rections. This type of ice mass is so thick as to
mask the land surface contours, in contrast to
the smaller and thinner highland ice. The con-
tinental glacier of Greenland often is called
inland ice, that of Antarctica, the ice cap.
Perhaps this term is best used to describe

the great ice masses which characterized the ice
ages. (5)

continental ice—See continental glacier.

continental margin—A zone separating the emer-
gent continents from the deep sea bottom; gen-
erally consists of the continental shelf, slope,
and rise. (2)

continental plateau—A large elevated mass of
the lithosphere coinciding approximately with
‘ ue and including its continental shelf.

48

continental platform—=Scee continental shelf.

continental rise—A gentle slope with a generally
smooth surface, rising toward the foot of the
continental slope. (62)

continental shelf-—(also called continental plat-
form). A zone adjacent to a continent or around
an island, and extending from the low water
line to the depth at which there is usually a
marked increase of slope to greater depth. (62)

continental slope—1. A declivity seaward from a
shelf edge into greater depth. (62)

2. See bathyal.

continental terrace—This term is no longer rec-
ommended by the ACUF for a zone around the
continents, extending from low water line to
the base of the continental slope. It includes
both continental shelf and continental slope.

continuity—The property of a field, such that
neighboring values of a parameter differ only
by an arbitrarily small amount if they are
close enough in space and/or time. (5)

continuity equation—See equation of conti-
nuity.

contour—A line on a chart representing points
of equal value with relation to a datum. It is
called an isobath when connecting points of
equal depth below sea level. See isopleth.

contour interval—The difference in value be-
tween two adjacent contours.

contra solem—Sce cum sole.

contrast—In optics, the ratio of the target reflec-
tance (7) minus the background reflectance
(BR) to the background reflectance, that is,

GAH
Big»
expressed as percentage.
convection—In general, mass motions within a
fluid resulting in transport and mixing of the
properties of that fluid. Convection, along with
conduction and radiation, is a principal means
of energy transfer.
Distinction is made between: free convection
(or gravitational convection), motion caused

only by density differences within the fluid, and
forced convection, motion induced by mechan-
ical forces such as deflection by a large-scale sur-
face irregularity, turbulent flow caused by fric-
tion at the boundary of a fluid, or motion caused
by any applied external force. See thermo-
haline convection. (5)
convection cell—Sce cellular convection.
convective overturn—lIn oceanography, same as
overturn. (5)
convergence—(or front). 1. Situation whereby
waters of different origins come together at a
point or, more commonly, along a line known
as a convergence line. Along such a line the
denser water from one side sinks under the
lighter water from the other side. The recog-
nized convergence lines in the oceans are the
polar, subtropical, tropical, and equatorial con-
vergence lines. Regions of convergence are also
referred to as convergence zones. (25)
2. In refraction phenomena, the decreasing
of the distance between orthogonals in the di-
rection of wave travel. Denotes an area of in-
creasing wave height and energy concentration.
61
oe zone—1. See convergence (sense 1).
2. The region in the deep ocean where sound
rays, refracted from the depths, arrive at the
surface in successive intervals of 30 to 35 nauti-
cal miles. The repeated occurrence of these
zones to several hundred miles from the sound
source depends on the refraction of sound rays
at depth and the reflection of these rays at the
surface.
convergence zone paths—The velocity structure
of permanent deep sound channels which pro-
duces focusing regions at distant intervals from
a Shallow source.
convoy routing—Methods of providing optimal
routes for one or more escorted ships under given
environmental conditions. Routing may be
made to provide minimum time routes, mini-
mum wave routes, minimum submarine detection
routes, etc.
Copenhagen water—WSce normal water.
copepod—One of a subclass (Copepoda) of
minute shrimplike crustaceans, most species of
which range between about 0.5 and 10.0 milli-
meters in length. Many species are biolumi-
nescent, and concentrations can produce bright
sparkling ight. Copepods occur in the surface
layers of temperate and subpolar waters in large
concentrations.
coprolites—Sce fecal pellet.
coquina—(or coqguinoid limestone, biostromal
limestone). A coarse-grained porous friable
variety of limestone made up chiefly of shell,
shell fragments, and coral. (2)
coquinoid limestone—S¢ee coquina.
coral—1. The hard calcareous skeleton of various
anthrozoans and a few hydrozoans (the mil-

39

CORE CUTTER

lepores), or the stony solidified mass of a num-
ber of such skeletons. In warm waters colonial
coral forms extensive reefs of limestone. In
cool or cold water coral usually appears in the
form of isolated solitary individuals. Oc-
casionally, large reefs formed in cold waters by
calcareous algae (Lithothamnion) have been
referred to as a coral. (9)
2. The entire animal; a compound polyp
which produces the skeleton.
coralgal—The carbonate sediment derived from
corals and algae.
coral head—A massive mushroom or pillar-
shaped coral growth. See reef patch. (See
figure for atoll.)
coral knoll—Sce reef patch.
coralline—Pertaining to, composed of, or having
oS structure of corals; as coralline limestone.
2
coralline alga—One of a family (Corallinaceae)
of red algae having either a bushy or encrusting
form and deposits of calcium carbonate either
on the branches or as a crust on the substrate.
Certain genera of the encrusting forms, Zitho-
thamnion and Porolithon, develop massive en-
crustations on coral reefs.
coral patch—See encrusting bryozoans.
coral pillar—Sce reef patch.
coral reef—A ridge or mass of limestone built up
of detrital material deposited around a frame-
work of the skeletal remains of mollusks,
colonial coral, and massive calcareous algae.
Coral may constitute less than half of the reef
material. (55) (See also figure for atoll.)
corange line—A line passing through places of
equal tide range. (50)
cordillera—An entire mountain system, including
all the subordinate ranges, interior plateaus and
basins. (62)
core—1. A vertical, cylindrical sample of the
bottom sediments from which the nature and
stratification of the bottom may be determined.
2. The central zone of the earth (see centro-
sphere). Its upper boundary is defined by a
seismic discontinuity at 2,900 kilometers
(Gutenberg-Wiechert discontinuity). (See fig-
ure for earth structure.)
core barrel—The tubular section of a core sam-
pling device. Bottom sediment samples are
collected either directly in the core barrel or in
a plastic liner placed inside it. Barrel diameter
may vary from 11% inches to several inches.
core catcher—(or core retainer). Any device in
the lower end of a core barrel designed to pre-
vent collected bottom sediments from slipping
out while the coring device is brought up to the
surface. One type consists of an interleaved
metal spring device which slips into the lower
end of a core barrel.
core cutter—(or cutting edge). A device which
fits over the end of the coring tube and holds the

CORER

23 B

ZB
iii

co

3. Island;

SN

ol

CORAL REEF

1. Reef; 2. Lagoon; 4. Islet; 5. Lagoon channel

(MSA, JAPAN, 1952)

core catcher in place. It has a sharpened rim
for penetrating the bottom and is attached with
several steel bolts.

corer—A hollow tube that is driven into the ocean
floor for the purpose of collecting a bottom sedi-
ment sample.

core retainer—Sce core catcher.

core sample—A sample of rock, soil, snow, or ice
obtained by driving a hollow tube into the me-
dium and withdrawing it with its contained sam-
ple or core. In general, the aim of core sam-
pling is to obtain a specimen in its undisturbed
natural state for subsequent analysis. (5)

coriolis force—An apparent force on moving par-
ticles resulting from the earth’s rotation. It
causes the moving particles to be deflected to the
right of motion in the Northern Hemisphere and
to the left in the Southern Hemisphere; the
force is proportional to the speed and latitude of
the moving particle and cannot change the speed
of the particle.

corona discharge—A luminous and often audible,
electric discharge that is intermediate in nature
between a spark discharge and a point discharge.
It occurs from objects, especially pointed ones,
when the electric field strength near their sur-
face attains a value near 1,000 volts per centi-
meter.

40

corposant—Scee St. Elmo’s fire.
corrasion—Mechanical erosion performed by
moving agents such as wear by glacial ice, wind,
running water, etc., but is generally restricted
to basal rather than lateral excavation.
corrected establishment—The mean high water
interval for all stages of the tide.
correction for datum—A conversion factor used
in the prediction of tides to resolve the difference
pees the chart datums of the reference sta-
ion.
corrosion—The gradual deterioration of material
by chemical processes, such as oxidation or at-
tack by acids; if caused by an atmospheric ef-
fect, a form of weathering. (5)
cosine collector—In underwater optics a light
collector which accepts radiant flux in accord-
ance with the cosinlaw. (8)
cosmic rays—Radiation that has its ultimate ori-
gin outside of the earth’s atmosphere, that is
capable of producing ionizing events in passing
through the air or other matter, and that in-
cludes constituents capable of penetrating many
feet of material such as rock. The primary cos-
mic rays probably consist of atomic nuclei,
mainly protons, some of which may have ener-
aS of the order of 10*° to 10*° electron volts.
econdary cosmic rays are produced when the
primary rays interact with nuclei and electrons,
for example, in the earth’s atmosphere; they
consist mainly of mesons, protons, neutrons,
electrons, and photons that have less energy
than the primary rays. Practically all of the
primary cosmic rays are absorbed in the upper
atmosphere, and almost all cosmic radiation
observed at the earth’s surface is of the second-
ary type. (41)
cosmic sediment—Particles of extraterrestrial
origin identified in deep sea sediments as black
magnetic spherules. (2)
cosmogenic radioisotopes—Those radioisotopes
produced in the earth’s gaseous envelope
through the action of cosmic radiation. Exam-
ples of such radioisotopes include Carbon™, Trit-
rum, Beryllium’, and Beryllium”.
cospectrum—1. The spectral decomposition of the
in-phase components of the covariance of two
functions of time.
2. The real part of the cross spectrum of two
functions. (5)
cotidal chart—A chart of cotidal lines that show
approximate locations of high water at hourly
intervals measured from a reference meridian,
usually Greenwich.
cotidal hour—The average interval expressed in
solar or lunar hours between the moon’s passage
over the meridian of Greenwich and the follow-
ing high water at a specified place. (5) (See
figure for cotidal chart.)
cotidal line—A line on a chart passing through all
points where high water occurs at the same time.

COTIDAL CHART

B. Cotidal line; C. Cotidal hour;
E. Degenerate amphidromic system

A. Nodal point;
D. Amphidromic region;

The lines show the lapse of time, usually in
lunar-hour intervals, between the moon’s transit
over a reference meridian (usually Greenwich)
and the occurrence of high water for any point
lying along the line. (See figure for cotidal
chart.)

count—In radiation measurements, the external
indication of a device designed to enumerate
ionizing events. It may refer to a single de-
tected event or to the total registered in a
given period of time. The term often is errone-
ously used to designate a disintegration, ioniz-
ing event, or voltage pulse. (70)

counter—A special gear box that indicates the
amount of oceanographic wire passed over the
sheave of the meter wheel. The counter may be
mounted directly on the meter wheel or con-
nected by a flexible cable.

countercurrent—A current flowing adjacent to
the main current but in the opposite direction.

counterradiation— (also called back radiation).
The downward flux of atmospheric radiation
passing through a given level surface, usually
taken as the earth’s surface and, more specifi-
cally in oceanography, the sea surface. (5)

counter resolving time—The minimum time in-
terval between two distinct events which will
permit both to be counted. It may refer to an
electronic circuit, to a mechanical indicating
device, or toa counter tube. (70)

countertrades—Scee antitrades.

cove—A small bay or baylike recess in the coast,
usually affording anchorage and shelter to small
craft. f

41

CROSSWIND

crack—Any fracture or rift in sea ice not suffi-
tay? wide to be described as a lead (lane).

cream ice—Sce sludge.

creek—A small, narrow bay which extends
farther inland than a cove and is longer than
it is wide. (68)

crest—1. The highest part of a wave.

2. A narrow rise of more or less irregular
longitudinal profile which constitutes the top of
an elevation of the sea bottom. (30)

crest length—Sce crest width.

crest of berm—The seaward margin of the berm.
(See figure for shore profile.)

crest of wave—Sce wave crest.

crest width—(or crest length). The length of a
wave along itscrest. (61)

crinoid—(or sea lily, feather star, sea feather).
One of a class (Crinoidea) of echinoderms most
of which either permanently or when immature
are attached by a long stalk to the bottom; spe-
cles without stalks either creep slowly about or
swim. Crinoids occur in shallow water as well
as at great depths. About 2,000 fossil species
are known.

crinoidal limestone—See limestone.

criquina—See limestone.

critical damping—The minimum viscous damp-
ing that will allow a displaced system to return
to its initial position without oscillation. (6)

critical point—The thermodynamic state in
which liquid and gas phases of a substance
coexist in equilibrium at the highest possible
temperature. At higher temperatures than the
critical no liquid phase can exist. (5)

critical velocity—The speed at which a current
can Scour the bottom enough to maintain the
required depth in a channel.

Cromwell Current—Sce
current.

Cromwell Undercurrent—(or Cromwell Cur-
rent). An eastward-setting subsurface current
that extends about 114 degrees north and south
of the Equator, and from about 150°E to
92°W. It is 300-kilometers wide and 0.2-kil-
ometer thick; at its core the speed is 100 to 150
centimeters per second.

cross sea—The confused, irregular state of the
sea which occurs where waves from two or more
different storms have arrived at a point of ob-
servation. Sometimes the waves appear to be
moving in the same direction as one of the
original waves; sometimes in between. (46)

cross spectrum—The complex vector sum of the
cospectrum and quadrature spectrum.

cross swell—(or intersecting waves). See cross
sea.

cross tide—Sce beam tide.

crosswind—That wind vector component which is
perpendicular to the course of an exposed
moving object.

Cromwell Under-

CRUMBLE

Wind blowing in a direction approximately
90 degrees from the course. One blowing in a
direction approximately 90 degrees from the
heading is called a beam wind. In common
usage these two expressions are usually used
synonymously, crosswind being favored by avi-
ators, and beam wind by marmers. One blow-
ing from ahead is called a headwind. One
blowi ing from astern is called a following wind
by marine navigators and a tailwind by air
navigators.
crumbie—Sce disintegration.
crust—The outer shell of the solid earth the lower
limit of which is taken generally to be the
Mohorovitié discontinuity. The crust varies
in thickness from approximately 5 to 7 kil-
ometers under the ocean basins to 35 kilometers
under the continents. See lithosphere. (See
figure for earth structure.)
crustacean—One of a class (Crustacea) of
arthropods which breathe by means of gills or
branchiae and with the body commonly covered
by a hard shell or crust. The group includes
the barnacles, crabs, shrimps, and lobsters.
crustacean borer—A member of any of three
families (Limnoriidae, Sphaeromidae, and
Cheluridae) of crustaceans, which, in the first
two, resemble pill or sow bugs and in the last,
sand fleas. These crustaceans excavate net-
works of shallow burrows in wood, the roofs of
which are readily eroded by water action.
Progressive burrowing and eroding remove a
considerable thickness of wood. The most
evident and damaging attack is on pilings
within the intertidal zone and near the bottom.
Continued attack results in the characteristic
hourglass shape of severely damaged pilings.
Limnoria usually is the initial and principal at-
tacker. Members of the other two families gen-
erally inhabit and enlarge Limnoria burrows.
The attack by at least one species of Limnoria
is not inhibited by creosote. See marine borer.
eryoclinometer—A device for measuring hori-
zontal dimensions of a sea ice field from an
aircraft.
cryology—1. The study of ice and snow. (5)
2. The study of sea ice. (5)
3. In Europe, a synonym for glaciology. (5)
Note: The term cryology has become almost
meaningless unless it is defined in context.
(59)
erystalline—The term applied to rocks contain-
ing grains of regular polyhedral form bounded
by plain surfaces and having an orderly molecu-
lar structure. Usually applied to igneous and
metamorphic rocks but not to sedimentary
rocks.
ctenophore—(or comb jelly). One of a phylum
(Ctenophora) of spherical, pear-shaped, or
cylindrical animals of jellylike consistency
ranging from less than 1 inch to about 3 feet in

42

length. The outer surface of the body bears
8 rows of comblike structures. Many species
produce glowing-ball luminescence.

cul-de-sac—1. An inlet with a single small
opening.

2. A blind lead.

(68)
cum sole—With the sun; hence anticyclonic or
clockwise; the opposite of contra solem. (5)
curie—(abbreviated c). 1. That quantity of a
radioactive nuclide disintegrating at the rate of
3.700 X 10" atoms per second. Several frac-
tions of the curie are in common usage.

Microcurie—(abbreviated yc). One-mil-
lionth of a curie (3.7X10* disintegrations per
second).

Micro-microcurie—(abbreviated pyc). One-
millionth of a microcurie (3.7 X 10 disintegra-
tions per second or 2.22 disintegrations per
minute). Sometimes called a picocurie.

Millicurie—(abbreviated mc). One-thou-
sandth of a curie (3.7 X10" disintegrations per
second).

(70)

2. An earlier definition of the curie was: The
quantity (grams) of radon in equilibrium with
one gram of radium. (41)

current—A horizontal movement of water. See
ocean current, tidal current, nontidal cur-
rent, flow.
current base—The maximum water depth below
which currents are ineffective in moving sedi-
ment. (2)
current chart—A map of a water area depicting
current speeds and directions by current roses,
vectors, or other means.
current cross section—A graphic presentation
of the current shown as a vertical plane per-
pendicular to the axis of flow; the horizontal
distance between the surface limits is repre-
sented by the abscissa, and the depth is shown
by the ordinate which increases from the sur-
face (zero) down to any depth. See current
profile.
current curve—A graphic presentation of the
speed and duration of the tidal current usually
shown for areas of reversing tidal currents.
The curve is referred to rectangular coordi-
nates; the time is represented by the abscissa
“and the speed by the ordinate. The flood speeds
are positive, and the ebb speeds are negative
values measured from slack (zero speed).
current diagram—A graphic presentation show-
ing the speed of the flood and ebb currents and
the times of slack and strength over a consider-
able stretch of the channel of a tidal waterway,
the times being referred to tide or current phases
at some reference station. (50)
current difference—The difference between the
time of slack water or strength of current in
any locality and the time of the corresponding

HOURS
One per4 Ole Sh TOMe Zeal 4 aS

18 20 22 24

KNOTS

2. Ebb strength;
5. Greater flood;

3. Slack water;
6. Lesser ebb;

1. Flood strength;
4. Greater ebb;
7. Lesser flood

CURRENT CURVE

phase of the current at a reference station for
which predictions are given in current tables.
50

Beene direction—The direction toward which

a current is flowing, called the set of the current.
68

Bent ellipse—A graphic representation of a
rotary current in which the speed and direction
of the current at different hours of the tide cycle
are represented by radius vectors and vectorial
angles. A line joining the extremities of the
radius vectors will form a curve roughly ap-
proximating an ellipse.

current gradient—The rate of increase or de-
crease in the speed of a current relative to a given
distance or period of time. The gradient is
generally represented by a curve.

current hour—The mean interval between the
transit of the moon over a reference meridian
(usually Greenwich) and the time of the
strength of flood current modified by the times
of slack water and strength of ebb current.

current meter—Any one of numerous devices for
the measurement of either speed alone or of both
direction and speed (set and drift) in flowing
water. (5)

current pattern—The horizontal distribution of
the surface or subsurface currents at various
levels in a specified area.

current pole—A pole used in measuring surface
water current, especially from an anchored ship
such as a lightship. The drift of the pole is
timed as it is allowed to carry out a graduated

207-109 O—66——4 43

CURRENT TABLES

line, the azimuth and speed of the line gives the
current velocity. (5)

current profile—A graphic presentation of cur-
rent flow from the surface to a specified depth.
The speed of the current is generally represented
by the abscissa and the depth by the ordinate
which increases from the surface (zero) down-
ward. See current cross section.

current rips—Small waves formed on the sea
surface by the meeting of opposing currents.

current rose—A graphic presentation of currents
for specified areas, utilizing arrows at the cardi-
nal and intercardinal compass points to show
the direction toward which the prevailing cur-
rent flows and the percent frequency of set for
a given period of time. The arrows on some
presentations may be further subdivided (by
thickness or pattern) to designate categories of
current speeds.

current speed—The rate at which the water moves
either horizontally or ‘vertically; usually ex-
pressed in knots, miles per day, feet per second,
or centimeters per second. See current
velocity.

current tables—Tables which give daily predic-
tions of the times, speeds, and directions of the
currents. These predictions are usually supple-
mented by current differences and constants
by means of which additional predictions can be
obtained for numerous other places. (50)

CURRENT ELLIPSE

CURRENT VECTOR

current vector—A geometric presentation show-
ing both current direction and speed, generally
by an arrow whose length is proportional to
the speed and whose direction is resolved into
points of the compass.

current velocity—A rate of motion in which di-
rection as well as speed of flow is considered.
See current speed.

curved path theory—A method for the analysis
and plotting of seismic data which allows for
the curvature of ray paths, resulting from in-
creasing velocities with depth in the earth.
(39)

curve fitting— (also called graduation). The ap-
propriate representation of empirical data by a
mathematical function, typically with arbitrary
constants determined by least squares. (5)

cushion ice—Fine fragmented ice found between
ice floes. It has the effect of cushioning the
impact of floes on each other. (Rare)

cusp—Scee beach cusp.

cuspate bar—A crescent-shaped bar uniting with
the shore at each end. It may be formed by a
single spit growing from shore turning back to
again meet the shore, or by two spits growing
from shore uniting to form a bar of sharply
cuspate form. (61)

cut—A notch, depression, or furrow produced by
erosion or excavation of a slope. Many cuts of
this type occur on the upper portion of a con-
tinental shelf.

cutting edge—See core cutter.

cycle—1. One complete and consecutive set of all
the changes which occur in a recurrent action or
phenomenon, starting from any point in the
action and ending with all conditions as they
were at the start.

2. A unit of wave frequency, actually one cycle

per second.
(5)

cycloidal wave—A very steep, symmetrical wave
whose crest forms an angle of 120 degrees. The
wave form is that of a cycloid. A trochoidal
wave of maximum steepness. (61)

cyclone—An atmospheric cyclonic circulation, a
closed circulation. A cyclone’s direction of ro-

tation (counterclockwise in the Northern Hem-
isphere) is opposite to that of an anticyclone.
Because cyclonic circulation and relatively

low atmospheric pressure usually coexist, the
term cyclone and low are used interchangeably
in common practice. (5)

cyclonic—Having a sense of rotation about the
local vertical the same as that of the earth’s rota-
tion: that is, as viewed from above, counter-
clockwise in the Northern Hemisphere, clock-
wise in the Southern Hemisphere, undefined at
the Equator; the opposite of anticyclonic. (5)

cylindrical projection—A map projection in
which the surface of a sphere is conceived as
projected, in the geometrical sense, on a tangent
cylinder, which is then developed on the plane.

cylindrical spreading—~Sce spreading of sound.

cylindrical wave—A wave in which the instan-
taneous free surface of the fluid takes the shape
of a cylindrical surface with the horizontal gen-
eratrices describing the profile of the wave.

cyphonautes larva—The planktonic triangular-
shaped young of a bryozoan, which is enclosed
in a bivalve shell.

cyprid larva—(or cypris). The stage at which
the young of barnacles attach.

cypris—See cyprid larva.

CUSPATE BAR

(BED, TR-4, 19.54)

daily—See diurnal.

daily inequality—Scee diurnal inequality.

Daily Memorandum—A publication issued by the
U.S. Naval Oceanographic Office and several of
its Branch Offices to disseminate ephemeral nau-
tical information for a specific area, namely East
Coast Edition; West Coast Edition; Pacific
Edition; and Far East Edition.

daily retardation—The amount of time by which
corresponding tidal phases grow later day by
‘a (averages approximately 50 minutes).
(61

daily variation—Sce magnetic diurnal varia-
tion.

damping—tThe dissipation of energy with time or
distance. (6)

dark bottle—Sce black bottle.

date-time group— (abbreviated DTG). The date
and time, expressed in digits and zone suffix, at
which the message was prepared for transmis-
sion. (Expressed as six digits followed by zone
suffix; [generally Z for Greenwich time zone]
first pair of digits denoting the date, second pair
the hour, third pair the minutes.) (63)

datum—1. Any numerical or geometrical quantity
or set of such quantities which may serve as a
reference or base for other quantities.

For a group of statistical references, the plural
form is data; as geographic data for a list of lati-
tudes and longitudes. Where the concept is
geometrical and particular, rather than statisti-
cal and inclusive, the plural form is datums, as,
for example, two geodetic datums have been used
in the U.S. in recent years. (37)

2. See chart datum.

3. See geodetic datum.

datum level—Sce chart datum.

datum plane—Scee chart datum.

datum point—Any reference point of known or
assumed coordinates from which calculations
or measurements may be taken. (63)

daughter—A synonyn for a decay product. (70)

Davidson Current—(also called Davidson In-
shore Current). A coastal countercurrent set-
ting north inshore of the California Current
along the west coast of the United States (from
northern California to Washington to at least
48°N) during the winter months.

Davidson Inshore Current—Sce
Current.

dead reckoning—A method of navigation utiliz-
ing only the speed and heading of the craft,

Davidson

45

without reference to external aids. See fix.
(5)

dead water—The phenomenon which occurs when
a ship of low propulsive power negotiates water
which has a thin layer of fresher water over a
deeper layer of more saline water. As the ship
moves, part of its energy goes into generation
of an internal wave which causes a noticeable
drop in efficiency of propulsion.

debacle—The rush of water or ice in a stream
immediately following the breakup. (59)

debouchure—Sce mouth.

debris—Sce detritus.

debris ice—1. Sea ice which contains soil, stones,
shells, and other materials.

2. Another name for brash ice.
(59).

debris Jine—A line near the limit of storm wave
uprush marking the landward limit of debris
deposits. (61)

decade scaler—A scaler whose scaling factor is
a power of ten. (70)

decapod—1. One of an order (Decapoda) of
crustaceans which includes the shrimps,
lobsters, and crabs.

2. One of an order (Decapoda) of cepha-
lopods which contains the squids.

decapod mollusk—Scee squid.

decay—1. As applied to ocean surface waves: The
gradual decrease of surface wave heights owing
principally to angular spreading, dispersion,
and opposing winds.

2. See disintegration.

decay area—The area of lesser winds through
which ocean waves travel after emerging from
the generating area. (73)

decay constant—Scee attenuation constant.

decay distance—The distance through which
ocean waves travel as swell after leaving the
generating area. (61)

decay of waves—The change that waves undergo
after they leave a generating area (fetch) and
pass through a calm or region of lighter winds.
In the process of decay, the significant wave
height decreases and the significant wavelength
increases. (61)

Decca*—A_ continuous-wave, hyperbolic radio
aid to navigation in which a receiver measures
and indicates the relative phase differences be-
tween signals received from two or more
synchronized ground stations.

DECIBAR

decibar—A unit of pressure used principally in
oceanography. One decibar (10° dynes per
square centimeter) equals 0.1 bar.

In the ocean, hydrostatic pressure in decibars
very nearly equals the corresponding depth in
meters. (5)

decibel—(abbreviated db). A value that ex-
presses the comparison of sound of two different
intensities. This value is defined as 10 times
the common logarithm of the ratio of the two
sound intensities.

declination—(also called variation). 1. At any
given location, the angle between the geographi-
cal meridian and the magnetic meridian; that
is, the angle between true north and magnetic
north. Declination is either “east” or “west”
according as the compass needle points to the
east or west of the geographical meridian. (5)

2. The angle that the sun, moon, planets, or
stars make with the plane of the Equator.

3. See solar declination, lunar declination.

declinational reduction—The processing of high
and low water tide observations or flood and ebb
tidal current observations to obtain quantities
which result from the effect of changes in the
declination of the moon.

decompression sickness—(also called bends,
caisson disease, compressed-air iliness). A con-
dition resulting from the formation of gas
bubbles in the blood or tissues of divers during
ascent. Depending on their number, size, and
location, these bubbles may cause a wide variety
of symptoms including pain, paralysis, un-
consciousness, and occasionally death.

deep—This term is no longer recommended by
the ACUF for a relatively small area of excep-
tional depth found in a depression type of
feature. The term was generally restricted to
depths greater than 3,000 fathoms.

deepening—In meteorology, a decrease in the cen-
tral pressure of a pressure system on a constant-
height chart, or an analogous decrease in height
on a constant-pressure chart; the opposite of
filling. The term is usually applied to a low
rather than to a high, although technically it is
acceptable in either sense. (5)

deep scattering layer—(also called DSL, false
bottom, phantom bottom). The stratified popu-
lation(s) of organisms in most oceanic waters
which scatter sound. The scattered sound is
recorded on echo-sounder records as a uniform,
horizontal band or stripe, and such layers gen-
erally are found during the day at depths from
100 to 400 fathoms. A layer rarely is less than
25 fathoms thick and may be as much as 100
fathoms thick. Several layers often are re-
corded at the same time and may be continuous
horizontally for many miles. Most layers typ-
ically undergo diurnal vertical movements. See
shallow scattering layer, surface scattering
layer, diurnal vertical migration.

46

deep sea anchoring winch—A large size winch
used to anchor an oceanographic/hydrographic
ship in deep water. Ordinarily this type of
winch uses steel wire rope in lengths of about
20,000 to 35,000 feet. Some types use specially
tapered wire particularly when anchoring in
great depths, while others use wire of about
1%-inch diameter.

Deep Underwater Nuclear Counter—(abbre-
viated DUNC). A submersible gamma ray
spectrometer used from ships for in situ detec-
tion of ocean gamma radiation. The DUNC
system was developed by the U. S. Naval Ord-
nance Laboratory for the detection of artificially
introduced radioactive constituents in the ocean.
It represents the first successful application of
gamma spectrometric technique to in situ ocean
radioactivity measurements and has since been
adapted for oceanographic usage by the U. S.
Naval Oceanographic Office.

deep water—In wave forecasting deep water
means that the depth of the water is large com-
pared with the wavelength of the longest wave
generated by the wind. In general, waves may
be considered deepwater waves when the depth
of the water layer is greater than one-half wave-
length. (46)

deepwater wave—(also called short wave). A
surface wave the length of which is less than
twice the depth of the water. The velocity of
deepwater waves is independent of the depth
of the water. (5) Seeshallow water wave.

deflection of the vertical—The angle at a point
on the earth (geoid) between the vertical and
the direction of the normal to the spheroid of ref-
erence through the point.

degaussing—Neutralization of the strength of the
magnetic field of a ship by means of suitably
arranged electric coils permanently installed in
the ship. (68) See deperming.

degenerate amphidromic system—A system of
cotidal lines whose center or nodal (no-tide)
point appears to be located on Jand rather than
in the open ocean. (See figure for cotidal
chart.)

degree—1. A unit of temperature.

2. A unit of angular distance; 469 part of a
circle.
(5)

degree-days of frost—The number of degrees
that the mean daily air temperature fell below
the freezing point of fresh or saline waters.
The total number of degree-days of frost dur-
ing a specific period is determined by adding
the deficiency of the mean air temperature from
the freezing point for each day in the period.
Thus, if the mean air temperature on three
consecutive days is 20°, 10°, and 0°F, the total
number of degree-days of frost, taking the
freezing point of sea water at 30°F, would be
10+20+80=60.

degree of polarization—If a polarized radiance
meter with retardation plate removed is
directed to accept the beam, the polarizer
rotated 180 degrees and maximum and mini-
mum radiances recorded, then the degree of
polarization is the ratio of the difference between
maximum and minimum radiances to the sum
of them, that is, the ratio of the polarized frac-
tion to the totalenergy. (8)

delta—An alluvial deposit, roughly triangular or
digitate in shape, formed at the mouth of a
stream or tidal inlet. See bay delta, bird-foot
delta, tidal delta.

delta moraine—Glacial deposit in deep water
with which delta deposits are associated. (2)

demersal—1. Fishes which live on or near the
bottom.

2. The eggs of certain bony fishes, which have
a hard and smooth or adhensive membrane and
sink tothe bottom. (48)

densitometer—A device for measuring the den-
sity of sea water or of bottom sediments.

density—1. The ratio of the mass of any sub-
stance to the volume occupied by it; the recipro-
cal of specific volume.

2. In oceanography, density is equivalent to
specific gravity and represents the ratio, at
atmospheric pressure, of the weight of a given
volume of sea water to that of an equal volume
of distilled water at 4.0°C (89.2°F). It is
thus dimensionless and expressed in units of
sigma-t.

density current—The flow (caused by density
differences or gravity) of one current through,
under, or over another; it retains its unmixed

DELTA

(AFTER: LOBECK, 1939)”

47

DEPTH FACTOR

identity because of density differences from the
surrounding water. See turbidity current.

density layer—aA layer of water in which density
increases with depth enough to increase the
buoyancy of asubmarine. (Submariner’s term
for pycnocline. )

deperming—The process of changing the mag-
netic condition of a ship by wrapping a large
conductor around it a number of times in a
vertical plane, athwartships, and energizing the
coil thus formed. If a single coil is placed
horizontally around the ship and energized, the
process is called flashing if the coil remains
stationary, and wiping if it is moved up and
down. See degaussing. (68)

deposit—Accumulations of solid material (of
any type or from any source) on the sea bottom
which eventually may become compacted and
consolidated and form sedimentary rock. The
process is deposition.

deposition—Scee deposit.

depression—1. This term is no longer recom-
mended by ACUF for any low place, hollow, or
basin of any size on the sea bed which is sur-
rounded by higher elevations. See basin.
trench, trough, seachannel.

2. In meteorology, an area of low pressure; a
low or a trough. This is usually applied to a
certain stage in the development of a tropical
cyclone, to migratory lows and troughs, and to
upper-level lows and troughs that are only
weakly developed. (5)

depth—1. The vertical distance from a specified
sea level to the sea floor. The charted depth is
the recorded distance from the tidal datum to the
bottom surface at the point, using an assumed
velocity of sound in waters of 800 fathoms per
second (U.S.) and with no velocity or slope
corrections made.

2. Formerly used in combination with a ship
name to designate a record deep sounding, for
example, Milwaukee Depth; no longer recom-
mended by the ACUF.

depth anomaly (AZ) graph—A graph con-
structed to determine the difference between the
computed or thermometric depth and the ideal
or assumed depth of reversal of thermometers
attached to a Nansen bottle.

depth contour—Sce isobath.

depth curve—Scee isobath.

depth excess—The difference between the bottom
depth and the depth at which the sound veloc-
ity is equal to either (1) the surface velocity,
when there is no layer depth, or (2) the maxi-
mum velocity in the surface layer. |

depth factor—The factor by which the apparent
depth of the water measured stereoscopically is
multiplied to give the true depth. This factor is
a ratio of the tangent of the incidence angle to
the tangent of the refraction angle. See shoal-
ing coefficient. (73)

DEPTH FINDER

depth finder—An instrument for determining the
depth of water, particularly an echo sounder.
68
Ae tines See anchor ice.
2. Small particles of ice formed below the
surface of the sea when it is churned by wave
action.

depth of breaking—~Sce breaker depth.

depth of compensation—Sece compensation

depth.

depth of frictional influence—Sce depth of fric-
tional resistance.

depth of frictional resistance— (or depth of fric-
tional influence). The depth at which the wind-
induced current direction is 180 degrees from
that of the wind. (See figure for Ekman
Spiral.)

derelict—Any property abandoned at sea, often
of sufficient size as to constitute a menace to
navigation. See jettison. (68)

desalination of sea water—The process by which
enough dissolved salts are removed from sea
water to render it potable. The most common
method for desalting sea water is distillation,
with the favored form being the “multi-flash”
process whereby sea water is made to evaporate
in low-pressure chambers. See boiling point.

Other methods employed for desalting include

the separation of salts by freezing, the use of
special membranes to extract all salts, and elec-
trodialysis, a method whereby the ions in sea
water are drawn through plastic membranes by
electric fields.

design wave—In the design of harbors, harbor
works, etc., the type or types of wave selected
as having the characteristics against which pro-
tectionis desired. (73)

detritus—(or debris). Any loose material pro-
duced directly from rock disintegration.

deuterium—(symbol H, or D). See heavy
water.

devilfish—See octopus, manta ray.

diadactic structure—Scee graded bedding.

diagenesis—The chemical and physical changes
that sediments undergo after their deposition,
compaction, cementation, recrystallization, and
perhaps replacement, which result in lithifica-
tion.

diastrophism—The process or processes by which
the crust of the earth is deformed and continents
and ocean basins, plateaus and mountains, flex-
ures and folds of strata, and faults are produced.

diatom—One of a class (Bacillariophyceae) of
microscopic phytoplankton organisms, posses-
sing a wall of overlapping halves (valves) im-
pregnated with silica. Diatoms are one of the
most abundant groups of organisms in the sea

and the most important primary food source of
Marineanimals. See diatomaceous ooze.
diatomaceous oo0ze—A pelagic siliceous sediment
composed of more than 30 percent diatom tests,
up to 40 percent calcium carbonate, and up to
25 percent mineral grains. This sediment gen-
erally is restricted to high latitudes or areas of

upwelling such as the Gulf of California. See
00Ze.

diatom film—Sce primary film.

diffracted wave—A wave whose front has been
changed in direction by an obstacle or other non-
homogeneity in the medium other than by
reflection or refraction. (3)

diffraction—The bending of waves (sound, water,
light, etc.) around obstacles. For example,
when a portion of a train of waves is interrupted
by a barrier such as a breakwater, the effect of
diffraction is manifested by propagation of
waves into the sheltered region within the
barrier’s geometric shadow.

diffuse attenuation function—A mathematical
formulation of the relationship between the
illuminance (/,) at the surface, the illumin-
ance (#',) at a depth (X), and the attenuation
coefficient (/).

E,=L,e*

(Strictly this equation relates to monochromatic
light only, but it is a sufficient approximation to
illuminance data for practical purposes.)

diffuser—A device used to alter the angular dis-
tribution of the radiant flux from a source,
depending essentially on the phenomenon of
diffusion. (8)

diffusion—The spreading or scattering of matter
under the influence of a concentration gradient
with movement from the stronger to the weaker
solution.

diffusion coefficient—The constant of propor-
tionality between the rate of diffusion across a
plane area and the concentration gradient
normal to that plane.

diffusivity—A measure of the rate of diffusion
of a property, appearing as the factor A in the
diffusion equation

ey = kK V7q
ot

where g is the property diffused, and V? is the
Laplacian operator. The diffusivity has dimen-
sions of a length times a velocity ; it varies with
the property diffused, and for any given prop-
erty it may be considered a constant or a func-
tion of temperature, space, etc., depending on
the context. (5)

dilatancy—The expansion of granular masses such
as sand when deformed because of rearrange-
ment of the grains. (2)

dilution—The reduction in the concentration of
dissolved or suspended substances by mixing
with water of a lower concentration.

diluvium—A. general term for all glacial and
fluvio-glacial deposits of continental glaciation.

2

disgtagellateOno of a class (Dinophyceae)
of single-celled microscopic or minute organ-
isms. Dinoflagellates may possess both plant
(chlorophyll and cellulose plates) and animal
(ingestion of food) characteristics. Many
marine forms are luminescent and, when in great
numbers, are responsible for sheet-type lumi-
nescence. In addition, dense concentrations
may create a red discoloration, (red tide) and
cause mass mortality of marine life. Other
discolorations due to these organisms may be
yellow, green, or shades of brown, but the ma-
jority of these concentrations are nontoxic to
marine life.

dip—i. The angle at which the rock structure is
inclined with a horizontal plane.

2. The angle formed by the lines of total mag-
netic force and the horizontal plane at the earth’s
surface; reckoned positive if downward. See
inclination.

3. The increase in depth of a moored mine case
(or buoy), due to current force against the case
and cable.

dip equator—Sce magnetic equator.

dipolar spreading—~Sce spreading of sound.

directional hydrophone—A hydrophone the re-
sponse of which varies significantly with the di-
rection of sound incidence. (69)

direction response pattern—(or beam pat-
tern). The directional response pattern of a
transducer used for sound emission or recep-
tion is a description, usually presented graph-
ically, of the response of the transducer as a
function of the direction of the transmitted or
incident sound waves in a specified plane and at a
specified frequency. In general, the beam pat-
tern will change with a change in the operating
frequency. (3)

directional spectrum—The spectral distribution
of wave energy by both frequency and direc-
tion.

directivity—The confining of sound to a beam by
mechanical and/or electronic means.

directivity index—A measure of sound pressure
level in one direction compared to that in all
other directions.

direct path—Scee surface path.

direct tide—A gravitational solar or lunar tide
in the ocean which is in phase with the apparent
motions of the attracting body, and consequently
has its local maximums directly under the tide-
producing body, on the opposite side of the
earth. Seereversed tide. (5)

discharge—The rate of flow of water or ice from
a river, fiord, or harbor at a given instant in

49

DISTRIBUTION

terms of volume per unit time, for example,
cubic feet per second.

discolored water—Sea water having a color other
than the blues and greens normally seen. Varia-
tions of the colors red, yellow, green, and brown,
as well as black and white, have been reported.
Discolorations may appear in patches, streaks, or
large areas and may be caused by concentrations
of inorganic or organic particles or plankton.
See red tide.

discontinuity—The abrupt variation or jump of a
ee at a line or surface. See interface.

4)

discontinuity layer—WScee
nocline.

disintegration— (also called decay, rot, crumble).

break down or decomposition of ice concen-

trations or complete disappearance thereof. See
radioactive decay.

dislocation—(or displacement). Used in a gen-
eral sense to refer to relative movements of rocks
along a fault.

dispersion—1. The separation of a complex sur-
face gravity wave disturbance into its com-
ponent parts. (73)

2. See acoustic dispersion.

disphotic zone—The dimly lighted zone extend-
ing from about 250 to 650 or more feet. Little
plant production can take place in this zone,
and the plants found here have mostly sunk from
the layer above. See aphotic zone, euphotic
zone. (54)

displacement—Sce dislocation.

displacement volume—The volume of fluid dis-
placed by plankton which has been drained of
water and which is a measure of the planktonic
biomass.

displacement weight—See displacement vol-
ume.

display—S¢ce bioluminescent display.

dissected—Cut by erosion into hills, ridges,
valleys, etc. May be applied to a submarine
shelf or slope cut into by submarine canyons or
sea valleys.

dissipation—In thermodynamics, the conversion
of kinetic energy into heat by work done against
the viscous stresses. Sometimes the rate of
conversion per unit volume is meant.

distilled water—Sce pure water.

distortion—An undesired change in waveform.
Noise and certain desired changes in waveform,
such as those resulting from modulation or de-
tection, are not usually classed as distortion.
(6)

distortional wave—See transverse wave.

distribution—Arrangement in time or space, as
the distribution of temperature; or apportion-
ment among various classes, or class intervals,
especially ranges of values of a certain variable.

thermocline, pyc-

DISTRIBUTION GRAPH

distribution graph—In hydrology, a statistically
derived hydrograph for a storm of specified
duration, graphically representing the percent
of total direct runoff passing a point on a stream,
as a function of time. It is usually presented
as a histogram or table of percent runoff within
each of successive short time intervals. In prin-
ciple it is the same as the unit hydrograph;
both are used as tools in river forecasting and
for other purposes such as the comparison of
runoff characteristics of different drainage
areas. (5)

diurnal—(or daily). 1. Daily, especially per-
taining to actions which are completed within
twenty-four hours and which recur every
twenty-four hours; thus, most reference is made
to diurnal cycles, variations, ranges, maximums,
etc. (5)

2. Having a period or cycle of approximately
one lunar day (24.84 solar hours): Certain
tides and tidal currents are said to be diurnal
when one high water and one low water, and
one flood and one ebb current, occur each
lunar day.

diurnal constituent—Any tide constituent
whose period approximates that of a lunar day
(24.84 solar hours). See constituent.

diurnal cooling—Heat lost by the surface of a
body of water during the night. This radia-
tional loss manifests itself in a small and tran-
sient positive gradient of temperature that is
observed near the surface in calm weather. See
diurnal heating.

diurnal current—The type of tidal current hav-
ing only one flood and one ebb period in a tidal
day. (73)

diurnal fluctuations—See diurnal.

diurnal heating—Solar radiation absorbed by a
body of water during the daylight hours. This
short-wave radiation, by heating the upper layer
of the water, creates, in the absence of wind, a
small and transient surface thermocline. See
diurnal cooling.

diurnal inequality—(also called daily in-
equality). The difference in heights and dura-
tions of the two successive high waters or of
the two successive low waters of each day;
also, the difference in speed and direction of the
two flood currents or the two ebb currents of
each day.

diurnal range—1. The amount of variation be-
tween the maximum and minimum of any
element during 24 hours.

2. Contracted form of great diurnal range.

diurnal tide—A tide in which there is only one
high water and one low water each lunar day,

_ (5) (See figure for type of tide.)
diurnal variation—See magnetic diurnal
variation.

diurnal vertical migration—The daily vertical
movement of certain members of the plankton
and nekton. The movement usually is triggered

50

by a change in light intensity, and influenced
by other factors such as temperature and
gravity. The migration generally is upward at
sunset and downward at sunrise. The rhythmic
movements of these organisms are thought to be
responsible for the typical movement of the
deep scattering layer.

divergence—1. A horizontal flow of water, in
different directions, from a common center or
zone; often associated with upwelling.

2. In refraction phenomena, the increasing of
the distance between orthogonals in the direc-
tion of wave travel. Denotes an area of decreas-
ing wave height and energy concentra-
tion. (73)

divergence loss—The part of the transmission
loss which is due to the spreading of sound
rays in accordance with the geometry of the
situation. For example, in the case of spherical
waves emitted by a point source, the sound
pressure at a point 20 yards distant from the
source will be only half as great as the sound
pressure 10 yards from the source.

diving rule—Sce compression factor.

diving saucer—A circular-shaped submersible
for undersea exploration.

diving trim—The condition of a submarine which
is so compensated that completing the flooding
of the main ballast, safety, and bow buoyancy
tanks, will cause it to submerge with neutral
buoyancy and zero fore-and-aft trim. (64)

division—WScee classification of organisms.

doldrums—(also called egwatorial calms). A
nautical term for the equatorial trough, with
special reference to the light and variable
nature of the winds. See equatorial air. (5)

dolomite—A mineral or a rock composed of
the mineral CaMg(CO;).; also called mag-
nesium limestone, which is deposited as dolomite
or produced later by substitution of magnesium
for some of the calcium.

dolphin—1. A member of the cetacean suborder
Odontoceti. The name is used interchangeably
with porpoise by some. More properly it is
given generally to the beaked members of the
family Delphinidae, except the larger members
which have been given the name “whale”, such
as the killer whale and pilot whale.

2. A pelagic fish of the genus Coryphaena
noted for its brilliant colors.

3. Acluster of piles. (66)

dome—(or kuppe). 1. This term is no longer
recommended by the ACUF for an elevation of
small area, rising with a steep angle to a depth
more than 200 meters (109 fathoms) below the
water surface. See seamount, knoll.

2. A (acoustically transparent) transducer
enclosure, usually streamlined, used with echo-
ranging or listening devices to minimize turbu-
lence and cavitation noises arising from the
passage of the transducer through the water.

dome-shaped iceberg—S¢ee ice island iceberg.

Doodson-Lege—A tide-prediction machine, used
at Liverpool (England) Observatory and Tidal
Institution.

Doppler—Sce Doppler effect.

Doppler effect—(also called Doppler shift).
The change in frequency with which energy
reaches a receiver when the receiver and the
energy source are in motion relative to each
other. (5)

Doppler shift—See Doppler effect.

dorsal—Pertaining to or lying near the back;
opposite of ventral. (26)

dosage—See dose.

dose—(or dosage). According to current usage,
the radiation delivered to a specified area or
volume or to the whole body. Units for dose
specification are roentgens for X- or gamma
rays, reps or equivalent roentgens for beta rays.
In radiology the dose may be specified in air,
on the skin, or at some depth beneath the sur-
face; no statement of dose is complete without
specification of location. In recent years there
has been an increasing tendency to regard a
dose of radiation as the amount of energy
absorbed by tissue at the site of interest per unit
mass. See radiation absorbed dose, Roentgen
equivalent physical. (70)

dosimeter—An instrument used to detect and
measure an accumulated dosage of radiation ; in
common usage it is a pencil size ionization
chamber with a built-in self reading electrom-
eter; used for personnel monitoring. (70)

double ebb—An ebb current having two maxi-
mums of speed separated by a smaller ebb
speed. (50)

double flood—A flood current having two maxi-
mums of speed separated by a smaller flood
speed. (50)

double high water—WSce double tide.

double tide—(or agger, double high water,
gulder). A high water consisting of two
maximums of nearly the same height separated
by a relatively small depression, or a low water
consisting of two minimums separated by a
relatively small elevation. (50)

Douglas scale—A: series of numbers from 0 to 9
to indicate the condition of waves and swell.

Replaced by WMO Code 75. (73)

No. State of Sea Swell

0 Calmee eee No swell.

1 Smooth______ Low swell (short or average

length).

2 Sliphite eee Low swell (long).

3 Moderate_____ Moderate swell (short).

4 Roush=sae ss Moderate swell (average length).
5 Very rough__-_ Moderate swell (long).

6 labrede Heavy swell (short).

7 Very high____ Heavy swell (average length).
8 Precipitous___ Heavy swell (long).

9 Confused__-__ Confused swell.

DRIFT BOTTLE

downdrift—The direction of predominant move-
ment of littoral sediment.

downstream—Generally the direction toward
which a fluid is moving, implying the horizontal
component of the mean direction or direction of
the basic current; the opposite of upstream.
(5)

downward irradiance—The radiant flux on an
infinitesimal element of the upper face (0 to 180
degrees) of a horizontal surface containing the
point being considered, divided by the area of
that element.

Unit of measurement is watt per square meter
(W/m?). (8)

downwelling—Scee sinking (sense 1).

dragon’s tail—A towed thermistor chain used to
measure sea temperature.

dredge—1. A simple cylindrical or rectangular
device for collecting samples of bottom sedi-
ment and benthic fauna. These are generally
made of heavy gauge steel plate or pipe and
depend upon a scooping action to obtain the
sample.

2. A ship designed to remove sediment from a
channel or dock region to maintain draft depths.

dried ice—The ice surface from which the water
has disappeared after the formation of cracks
and holes. During the period of drying, the
surface becomes increasingly white. (74)

dried weight—(or dry weight, dry plankton).
The weight of organisms, such as plankton,
fouling, or benthos, from which water has been
driven but which has not been ignited. The
term dry weight is more commonly used in the
study of fouling.

dries—(or wncovers). An area of a reef or other
projection from the bottom of a body of water
which periodically is covered and uncovered by
the water.

drift—1. The effect of the velocity of fluid flow
upon the velocity (relative to a fixed external
point) of an object moving within the fluid;
the vector difference between the velocity of
the object relative to the fluid and its velocity
to the fixed reference. (5)

2. In publications for the mariner, drift is
the speed of a current or ice floe usually given
in nautical miles per day or in knots. For the
oceanographer, drift is a wide, slow-moving cur-
rent principally caused by winds.

3. Any rock material such as boulders, till,
gravel, sand, or clay, transported by a glacier
and deposited by the ice or by the water derived
from melting of theice. (2)

drift bottle—(also called bottle post). A bottle,
of one of various designs, which is released into
the sea for use in studying currents. It con-
tains a card (bottle paper), identifying the date
and place of release, to be returned by the finder
with the date and place of recovery. See drift
card. (5)

DRIFT CARD

drift card—A card such as is used in a drift bottle,
encased in a buoyant, waterproof envelope and
released in the same manner as a drift bottle.

Cheaper and lighter than bottles, drift cards
are especially suited to dropping in large quanti-
ties from aircraft, and it is supposed that the
card, having less freeboard than a bottle, is less
affected by wind. See drift bottle. (5)

drift current—(sometimes called ocean current).
1. A wide, slow-moving ocean current princi-
pally caused by winds. Example are the exten-
sion of the North Atlantic Current (the North
Atlantie Drift) and the West Wind Drift.
See wind-driven current.

2. The current determined from the differ-
ences between dead reckoning and a naviga-
tional fix.

3. A current defined by assuming that the
wind stress is balanced by the sum of the corio-
lis and frictional] forces.

drift ice—(or floating ice). Any sea ice that has
drifted from its place of origin. The term is
used in a wide sense to include any area of sea
ice, other than fast ice, no matter what form it
takes or how disposed. See close pack ice.

(5)
drift ice foot—See ramp.
driftmeter— (or drift sight).
measuring drift angle.
Electrokinetograph. (68)
drift sight—Sce driftmeter.
drift station—A scientific station established on
the ice of the Arctic Ocean. Most drift stations
are based on ice floes, although two American
stations (T-3 and ARLIS IT) have been on ice
islands.

U.S.S.R. stations are numbered consecutively
from NP-1 (NP for North Pole) and are some-
times referred to as “SP” for the Russian
“Severnyy Polyus” (North Pole).

Drift Station Bravo—Scee T-3.

drogue—(or parachute drogue). A current meas-
uring assembly consisting of a weighted para-
chute and an attached surface buoy. The
parachute can be placed at any desired depth
and current speed and direction determined by
tracking and timing of the surface buoy.

drown—To submerge land beneath water either
through a rise in the level of the water or by
sinking of the land. (2)

drowned river mouth—Scee estuary.

drydock iceberg—~Scee valley iceberg.

dry organic matter—Dry plankton less ash after
ignition. The most reliable and the preferred
weighing method in determining the biomass.

dry plankton—Plankton dried to a constant
weight by a specified method. See dried
weight.

dry weight—See dried weight.

duct—A layer in the ocean or atmosphere where
refraction and, probably, reflection result in

An instrument for
See Geomagnetic

52

the trapping of electromagnetic waves, or sound
waves.

ducting—The trapping of sound or electromag-
netic waves within a layer, resulting in extended
ranges.

dugong—An aquatic herbivorous mammal, some-
times referred to as a sea cow, of the order Si-
renia allied to the manatee, but with a bilobate
tail like that of a whale.

duped deposit—The accumulation of sediment
deposited more rapidly than waves and currents
are able to redistribute it. (2)

dumping ground—A sea area within which ma-
terial dredged from other areas is deposited.
See spoil ground.

duration—1. The interval of time of the rising or
falling tide, or the length of time of flood or
ebb tidal currents.

2. In wave forecasting, the length of time the
wind blows in essentially the same direction over
the fetch. (61)

dynamic calculations—The procedure based on
the summation of dynamic depth intervals from
the surface of the ocean to any specified level;
dynamic differences between stations are de-
rived and consequently the relative speed and
direction of currents at different levels.

dynamic depth—WSce dynamic height.

dynamic height—(or geodynamic height). The
amount of work done when a water particle of
unit mass is moved vertically from one level to
another; the dimensions are those of potential
energy per unit mass.

dynamic height anomaly—(also called anomaly
of geopotential difference). In oceanography,
the excess of the actual geopotential difference,
between two given isobaric surfaces, over the
geopotential difference in a homogeneous water
column of salinity 35 per mille (°/,,.) and
temperature 0°C.

The dynamic height anomaly between two
isobaric surfaces is the product of the mean
specific volume anomaly and the difference
in pressure (in decibars) ; the latter is assumed
to equal the difference in depth in meters. (5)
See geostrophic current.

dynamic meter—(or geodynamic meter). The
standard unit of dynamic height expressed as
10 square meters per second per second. Its
inclusion in the hydrostatic equation elimi-
nates the factor of gravity acceleration in
dynamic calculations.

dynamic oceanography—The study of ocean-
ographic motions as solutions of the funda-
mental equations of hydrodynamics or other sys-
tems of equations appropriate to special
situations.

The restrictions of this definition suffice to
distinguish dynamic oceanography from other
fields, for example, physical oceanography or
synoptic oceanography, such distinctions being

a function of the state of the science rather than
of the subject matter itself. hd: ‘
dynamic prediction—Methods of predicting the
future state of the environments by using physi-
cal models—as opposed to empirical or statistical
methods. ;

dynamic theory—A theory considering the hori-
zontal tide-producing forces to be the most im-
portant factor in causing movement of water.
The vertical tide-producing forces are simply
considered small periodical variations in the
acceleration of gravity.

dynamic topography—The configuration formed
by the geopotential difference or dynamic
height (measured in dynamic meters) be-
tween a given isobaric surface and a reference
surface (for example, in the ocean the 2,000-
decibar surface). A topographic chart formed
may be used in determining geostrophic cur-
rents within the oceans. The current along the
isopleths of dynamic height must be considered

53

DYNE

to move relative to the motion of the water at
the reference surface. If the water at the refer-
ence surface has no motion, the current direction
along the isobaric surface is considered
absolute.

dynamometer—(sometimes called strain gauge).
An instrument used in bottom sampling or other
oceanographic operations to indicate that bot-
tom has been reached. The instrument meas-
ures variations on wire tension and is only
effective to depths where the tension due to the
weight of the sampling device is somewhat
greater than the tension caused by the weight
of the lowering cable and the variable loads
produced by ship motion.

dyne—A force which, acting on a mass of one
gram, imparts to that mass an acceleration of
one centimeter per second per second. See gal.

The dyne is the unit of force of the egs sys-

tem. Since 1930, gravity has been reported in
terms of the gal, rather than thedyne. (387)

eager—~See bore.

earbone—See otolith.

earth current—Scee telluric currents.

earthquake—A sudden, transient motion or
trembling of the earth’s crust resulting from
the propagation in the earth of elastic waves
caused by faulting of the rocks or by volcanic
activity.

earthquake intensity—A number describing the
effects of an earthquake on man, on man-made
structures, and on the earth’s surface. The num-
ber is rated on the basis of an “earthquake inten-
sity scale.” The scale in common use in the U.S.
today is the modified Mercalli scale of 1931.

earth radiation—Sce terrestrial radiation.

earth structure—The postulated structure and
composition of the earth by assuming concentric
layering around a core based upon gravity,
density distribution, seismology, and laboratory
determinations of physical and chemical proper-
ties of rocks. See mantle, crust, centrosphere.

earth tide—The periodic movement of the earth’s
crust caused by the tide-producing forces of
the moon and sun. (68)

East Africa Coast Current—(or Somali Cur-
rent). A seasonal current influenced by the
monsoon drifts of the Indian Ocean. It flows
southwestward along the coast of Somalia in

EARTH STRUCTURE

54

the Northern Hemisphere winter and northeast-
ward from about 10°S during the Northern
Hemisphere summer.

East Australia Current—The current which is
formed by part of the South Equatorial Cur-
rent and flows southward along the east coast
of Australia. The East Australia Current turns
and joins the northeast flow through the Tasman
Sea.

In the Southern Hemisphere summer a small
part of this current flows westward along the
south coast of Australia into the Indian Ocean.

East Greenland Current—A current setting
south along the east coast of Greenland and
carrying water of low salinity and low tempera-
ture. The East Greenland Current flows
through Denmark Strait between Iceland and
Greenland and joins the Irminger Current.
The greater part of the current joins the counter-
clockwise circulation south of Greenland; part
curves to the right around the tip of Greenland
and flows northward into Davis Strait as the
West Greenland Current.

The main discharge of the Arctic Ocean is via
the East Greenland Current.

East Ice—1. The sea ice which drifts from the
Arctic Ocean south along the east Greenland
coast, around Kap Farvel, and up the southwest
coast of Greenland. See storis.

2. To Norwegians, “East Ice,” or “Des-isen”
is the ice in the Barents Sea.

(59)

East Wind Drift—A west-setting current close to
the Antarctic Continent caused by the polar
easterlies. (Approved ACUF name.)

ebb axis—The average direction of the tidal cur-
rent at strength of ebb. (59)

ebb current—The tidal current associated with the
decrease in the height of a tide. Ebb currents
generally set seaward, or in an opposite direction
to the tide progression. Erroneously called ebb
tide. (See figure for current curve.)

ebb interval—The interval between the transit of
the moon over the meridian of a place and the
time of the strength of the following ebb tidal
current. (50)

ebb strength—The ebb tidal current at the time
of maximum speed, usually associated with the
lunar tide phases at springs near perigee and/or
maximum river discharge. (See figure for
current curve.)

ebb tide—Scee falling tide, ebb current.

echinoderm—One of a phylum (Echinodermata)
of principally benthic marine animals having
calcareous plates with projecting spines form-
ing a rigid or articulated skeleton or plates and
spicules embedded in the skin; the animals have
radial symmetry, usually is a five-rayed body.
Some echinoderms are the sea stars, sea
urchins, crinoids, and sea cucumbers.

echinopluteus—The planktonic larva of a sea
urchin.

echo—An acoustic signal which has been reflected
or otherwise returned with sufficient magnitude
and time delay to be detected as a signal distinct
from that directly transmitted. (3)

echogram—1. The graphic presentation of echo
soundings recorded as a continuous profile of
the bottom.

2. Often erroneously called a fathogram

when not recorded by a Fathometer*.

echo ranging—The determination of distance by
measuring the time interval between transmis-
sion of a radiant energy signal (sound) and the
return of itsecho. (66)

echo sounder—See echo sounding.

echo sounding—(or acoustic sounding). Deter-
mination of the depth of water by measuring the
time interval between emission of a sonic or
ultrasonic signal and the return of its echo from
the bottom. The instrument used for this pur-
poseiscalled anecho sounder. (68)

ecology— See marine ecology.

eddy—A circular movement of water usually
formed, where currents pass obstructions, be-
tween two adjacent currents flowing counter to
each other, or along the edge of a permanent
current.

eddy-built bar—Sediment deposit believed to be
formed by the rotating action of eddies in a tidal
lagoon. Ridges surrounding some emerged
Carolina bays may have developed in this way.

2

eae conduction—See eddy heat conduction.

eddy conduction coefficient—Sce eddy conduc-
tivity.

eddy conductivity—(also called coefficient of
eddy diffusion, eddy conduction coefficient).
The exchange coefficient for eddy heat con-
duction. (5)

eddy current—See eddy.

eddy diffusion—(or turbulent diffusion). The
transfer of matter by the turbulent eddies in a
fluid.

eddy flux—The rate of transport (or flux) of
fluid properties such as momentum, mass, heat,
or suspended matter by means of eddies in a
turbulent motion; the rate of turbulent ex-
change. (5)

eddy heat conduction—(or eddy heat flux, also
called eddy conduction). The transfer of heat
by means of eddies in turbulent flow, treated
analogously to molecular conduction. (5)

55

EKMAN SPIRAL

eddy heat flux—Sce eddy heat conduction.

eddy viscosity—The turbulent transfer of
momentum by eddies giving rise to an internal
fluid friction, in a manner analogous to the
action of molecular viscosity in laminar flow, but
taking place on a much larger scale.

The value of the coefficient of eddy viscosity
t of the order 10* square centimeters per second.
5)

edge wave—An ocean wave traveling parallel to
a coast, with crests normal to the coastline.
Such a wave has a height that diminishes rapidly
seaward and is negligible at a distance of one
wavelength offshore. (5)

eelgrass—See Seagrass.

effective acoustic center (apparent source)—
The effective acoustic center of an acoustic gen-
erator is the point from which the spherically
divergent sound waves, observable at remote
points, appear to diverge. (67)

effective back radiation—Sce effective terres-
trial radiation.

effective half-life—The time required for a radio-
active element fixed in the tissue of an animal
body to be diminished 50 percent as a result of
the combined action of radioactive decay and
biological elimination. (70)

effective radiation—See effective terrestrial
radiation.

effective sound pressure—The sound pressure
at a point is the root-mean-square value of the
instantaneous sound pressures over a time inter-
val at the point under consideration.

effective terrestrial radiation—(or effective
radiation, effective back radiation). The dif-
ference between the outgoing infrared terres-
trial radiation of the earth’s surface and the
downward infrared counterradiation from the
atmosphere. (5)

ejecta—(or ejectamenta). Material thrown out
by a volcano, such as ash, lapilli, bombs. (2)
See tephra.

ejectamenta—See ejecta.

Ekman current meter—A mechanical device for
measuring ocean current velocity. A sensitive
impeller is turned by current action and the
number of turns recorded on an attached dial.
Speed is measured indirectly from the number of
impeller revolutions by means of conversion
tables. Lead shot are dropped into a compass
box below the meter for a set number of impeller
revolutions. Current direction is determined
from the location of shot dropped in the com-
pass box.

Ekman Spiral—A theoretical representation of
the effect that a wind blowing steadily over an
ocean of unlimited depth and extent and of
uniform viscosity would cause the surface layer
to drift at an angle of 45 degrees to the right of
the wind direction in the Northern Hempishere.

ELASMOBRANCH

Water at successive depths would drift in direc-
tions more to the right until at some depth it
would move in the direction opposite to the wind.
Velocity decreases with depth throughout the
spiral. The depth at which this reversal occurs
is of the order of 100 meters. The net water
transport is 90 degrees to the right of the direc-
tion of the wind in the Northern Hemisphere.

elasmobranch—Any of numerous cartilaginous
fishlike vertebrates belonging to the subclass
Elasmobranchii, which includes the sharks,
skates, and rays.

elbow—1. A change in direction in the contour of
a submerged bank or shoal; not a recognized
term by the ACUF.

2. A sharp change in the direction of a chan-

nel. (80)

electrical conductivity—A unit measure of elec-
trical conduction; the facility with which a sub-
stance conducts electricity, as represented by the
current density per unit electrical-potential
gradient in the direction of flow. Electrical
conductivity is the reciprocal of electrical re-
sistivity and is expressed in units such as mhos
(reciprocal ohms) per centimeter. It is an in-
trinsic property of sea water and varies with
temperature, salinity, and pressure.

EKMAN SPIRAL SHOWING DEPTH
OF FRICTIONAL RESISTANCE (D)

56

electric log—A graphic recording of the various
electrical properties of a sediment or rock
through which a hole has been drilled. Obtained
by lowering electrodes into the hole. (2)

electric ray—Any of the family (Torpedinidae)
of rays possessing a pair of electric organs ca-
pable of delivering a strong shock to humans if
handled. Seeray.

electroacoustic transducer—A transducer for
recelving waves from an electric system and de-
livering waves to an acoustic system, or vice
versa. (69)

electrolyte—A substance which when dissolved
in a suitable liquid, such as water, dissociates into
ions and thus makes the liquid a conductor of
electricity. Sodium chloride (VaC7) is the most
common electrolyte in sea water.

electromagnetic energy—Sece electromagnetic
radiation. :

electromagnetic radiation—(or electromagnetic
energy ; often called, simply radiation). Energy
Beoneeeted through space or through material
media in the form of an advancing disturbance
in electric and magnetic fields existing in space
or in the media. The term radiation, alone, is
used commonly for this type of energy, although
it actually hasa broader meaning. (5)

electromagnetic window—The concept that some
portion of the spectrum, whether radio waves,
ultraviolet rays, infrared (heat), radiant light
or electrical energy of some sort can be made
to penetrate the sea and exploit a “window” in
the opacity of the sea.

electromechanical transducer—A transducer
for receiving waves from an electric system and
delivering waves to a mechanical system, or vice
versa. (69)

electron—An elementary particle of rest mass
me equal to 9.107 X 10-* grams and charge equal
to 4.802X107° statcoulombs. Its charge may
be either positive or negative. The positive elec-
tron is usually called a positron; the negative
electron is sometimes called the negatron. Most
frequently the term electron means negatron.
The negative electron is a constituent of all
atoms. In a neutral atom the number of elec-
trons is equal to the atomic number Z.

electronic bathythermograph (BT)—A bathy-
thermograph which provides temperature read-
ings to 1,350 feet by using a thermistor and

peste element to provide remote readout on
eck.

electron-volt—(abbreviated ev). A unit of
energy equivalent to the amount of energy
gained by an electron in passing through a
potential difference of one volt. Larger multiple
units of the electron-volt are frequently used,
namely; Kev for thousand- or kilo-electron-
volts, Mev for million-electron-volts, and Bev
for billion-electron-volts.

lev=1.6X10~° erg. (70)

electrostatic transducer—A transducer that
consists of a capacitor and depends upon inter-
action between its electric field and the change
of its electrostatic capacitance. (69)

element—1. One of the simpler parts of which a
complex entity is composed; thus a part of an
instrument, as the thermal element of a
bathythermograph or a constituent of the at-
mosphere, such as nitrogen, oxygen, water
vapor, carbon dioxide, ete.

2. In chemistry, a substance which cannot
be broken down by ordinary chemical means
into simpler components (although one element
may be transformed into another by some form
of subatomic bombardment).

5

aes island—An island that rises to a few
feet above high tide level on a reef flat and
consists either of sand and debris or of solid
reef rock. (2)

elevation—A general term for a relief feature of
any size which rises above the surrounding
sea bed.

elk kelp—One of a genus (Pelagophycus) of large
brown algae, which consists of a massive hold-
fast and a long tough stipe terminated by a
large bulbous pneumatocyst from which a
single forked lamina-bearing branch radiates.
The genus occurs only on the Pacific coast of
North America from Point Conception, Cali-
fornia southward along the coast of California
and Baja California and reaches lengths of 100
feet or more.

Elmo’s fire—See St. Elmo’s fire.

El Nifto—A warm current setting south along the
coast of Ecuador. It generally develops just
after Christmas concurrently with a southerly
shift in the tropical rain belt. In exceptional
years the current may extend along the coast of
Peru to 12°S. When this occurs, plankton and
fish are killed in the coastal waters and phenom-
enon somewhat like the red tide of Florida re-
sults. During this time discolored water and
intense displays of bioluminescence are com-
mon. El Nifio is much more widespread and
destructive than the more local phenomenon of
aguaje, which occurs every year. (5)

El Pintor—Scee Callao Painter.

embacle—A term, now rarely used, for the heap-
ing up of ice in a stream following a freeze.
(59)

embayment—An indentation in a shoreline form-
ing an open bay.

embouchure—Scee mouth.

emergence—The fact that part of the ocean floor
has become dry land but does not imply whether
recession of the sea or elevation of the land was
the specific cause. (2)

emissivity—(sometimes called emissive power).
The ratio of the emittance of a given surface at
a specified wavelength and emitting tempera-

57

ENVIRONMENTAL FACTORS

ture to the emittance of an ideal black body
at the same wavelength and temperature. The
greatest value that an emissivity may have is
unity, the least value zero.

It is corollary of Kirchoff’s law that the
emissivity of any surface at a specified tem-
perature and wavelength is exactly equal to the
absorptivity of that surface at the same tem-
perature and wavelength. (5)

encrusting bryozoan—(or coral patch). A
bryozoan which forms hard crusts on under-
water surfaces.

endoergic reaction—A reaction which absorbs
energy. (70)

endothermic reaction—A reaction which absorbs
energy specifically in the form of heat. (70)

energetics—The branch of study dealing with the
systematic description of the energy conversion
and transfer processes which take place within
a physical system. (5)

energy coefficient—The ratio of the energy in a
wave per unit crest length transmitted forward
with the wave at a point in shallow water to the
energy in a wave per unit crest length trans-
mitted forward with the wave in deep water.
On refraction diagrams this is equal to the
ratio of the distance between a pair of orthogo-
nals at a selected point to the distance between
the same pair of orthogonals in deep water.
Also the square of the refraction coefficient.
(61)

English system—A system of physical units
based on the use of the foot, pound, and second
as elementary quantities of length, mass, and
time, respectively. This system, although being
displaced by the egs system, is still in use in
many English-speaking countries.

ensemble average—An average determined over
a finite subset of random time functions for some
particular instant of time.

ensonify—The penetration of sound into any par-
ticular part of the sea.

entrainment—1. The transfer of fluid by friction
from one water mass to another, usually occur-
ring between opposing currents. The turbu-
lence between the water masses results in mixing.

2. The pick-up and movement of sediment as
bed load or in suspension by current flow.

entropy—1. A measure of the unavailable energy
in a system, that is, energy that cannot be con-
verted into another form of energy.

2. A measure of the degree of mixing of dif-
ferent kinds or sizes of sediments; high entropy
approaches an unmixed sediment of one kind.
(2)

environment—The sum total of all the external
conditions which may affect an organism, com-
munity, material, or energy, if brought under
the influence of these external conditions. (2)

environmental factors—In oceanography, the
physical and chemical conditions such as tem-

EOLIAN SANDS

perature, salinity, light conditions, current
velocity, etc., but usually excluding biotic fac-
tors.

eolian sands—(or aeolian sands, blown sands).
Sediments of sand size or smaller which have
been transported by winds. They may be recog-
nized in marine deposits off desert coasts hy the
greater angularity of the grains compared with
waterborne particles.

Eétvés effect—The east-west component of the
movement of the ship, including the effect of
marine currents, modifies the centrifugal force
of the earth’s rotation. It is a vertical force
experienced by a body moving in an east-west
direction on the rotating earth. In gravity
measurements a positive correction is applied if
moving eastward and a negative correction ap-
plied in moving westward.

epeiric seas—Shallow inland seas with restricted
communication with the open ocean and having
depths less than 250 meters (137 fathoms).
Hudson Bay is an example. (2) See inland
seas, epicontinental seas.

epeirogenic movement—Scee epeirogeny.

epeirogeny—(or epeirogenic movement). The
broad uplift and subsidence of the whole or large
portions of continental areas or oceanic basins.
(2)

Ephemeris—A publication giving the computed
places of the celestial bodies for each day of the
year, or for other regular intervals. (63)

epicenter—The point on the earth’s surface di-
rectly above the focus of an earthquake.

epicontinental marginal sea—A _ subdivision of
the ocean, generally less than 7,500 feet deep,
overlying a continental shelf and part of a
continental slope, which is partly enclosed by
extensions of the land, shallow banks, or islands
(such as Laptev Sea).

epicontinental sea(s)—Shallow seas which oc-
cupy wide portions of a continental shelf or he
in the interior of a continent. See epeiric seas,
inland seas, shelf seas.

epilimnion—The layer of water above the thermo-
cline in a fresh water lake or pool; distinguished
from hypolimnion, the layer below the thermo-
cline. In the ocean, the equivalent is the mixed
layer. (5)

epipelagic—The upper portion of the oceanic pro-
vince, extending from the surface to a depth
of about 100 fathoms (200 meters). (See figure
for classification of marine environments.)

epiphytic—Growing attached to another plant.
(13)

epoch—-1. A particular instant for which certain
dataare given. (68)

2. A given period of time during which a
series of related acts or events takes place. (68)
3. (or tidal epoch, phase lag, phase differ-
ence). Angular retardation of the maximum
of a constituent of the observed tide behind the

58

corresponding maximum of the same constitu-
ent of the hypothetical equilibrim tide. (68)

4, A division of geologic time.

equal area projection— (also called authalic pro-
jection). A map projection on which a con-
stant ratio of areas is preserved; that is, any
given part of the map on an equal area pro-
jection bears the same relation to the area on
the reference surface which it represents.

equation of continuity— (or continuity equation).
A hydrodynamical equation which expresses the
principle of the conservation of mass in a fluid.
It equates the increase in mass in a hypothetical
fluid volume to the net flow of mass into the
volume. (5)

equation of motion—The Newtonian law of mo-
tion states that the product of the mass of an
elemental volume of fluid and acceleration equals
the vector sum of the forces acting on the volume.
In meteorological and oceanographic use, both
sides of the equation of motion are divided by
mass to give force per unit mass.

The forces considered in ocean currents are
gravity, coriolis force, pressure gradient force,
and frictional forces.

equatorial air—According to some authors, the
air of the doldrums of the equatorial trough, to
be distinguished somewhat vaguely from the
tropical air of the trade-wind zones. Tropical
air becomes equatorial air when the former en-
ters the equatorial zone and stagnates. There
is no significant distinction between the physical
properties of these two types of air in the lower
troposphere. (5)

equatorial calms—See doldrums.

Equatorial Convergence—The zone along which
waters from the Northern and Southern Hem-
ispheres converge. This zone generally lies in
the Northern Hemisphere, except in the Indian
Ocean.

Equatorial Convergence line—See Equatorial
Convergence.

Equatorial Convergence zone—Sce Equatorial
Convergence.

Equatorial Countercurrent—An ocean current
flowing eastward near the Equator.

In the Atlantic Ocean, it flows east between
the North and South Equatorial Currents across
the full width of the ocean in northern sum-
mer, and across the eastern half of the ocean in
northern winter. It eventually becomes the
Guinea Current.

In the Pacific Ocean, it flows east across the
ocean between 3°N and 10°N. East of the
Philippines it is jomed by the southern part of
the North Equatorial Current.

In the Indian Ocean, it flows to the east be-
tween the monsoon drift and the South Equa-
torial Current; unlike the Equatorial Counter-
currents of the Atlantic and Pacific Oceans, it
is located south of the Equator. In northern

summer, when the southwest monsoon forms a
continuation of the southeast trade winds, the
countercurrent flows with the monsoon drift.

Equatorial Current—See North Equatorial
Current, South Equatorial Current.

equatorial cylindrical orthormorphic projec-
tion—See Mercator projection.

equatorial tidal currents—Tidal currents occur-
ring approximately every two weeks when the
moon is over the Equator. At these times, the
diurnal inequality between successive periods
of flood and ebb is at a minimum and the cur-
rents are most nearly semidiurnal.

equatorial tides—Tides that occur approximately
every two weeks when the moon is over the
Equator. At these times, the moon produces
minimum inequality between two successive
high waters and two successive low waters.

equilibrium—1. In thermodynamics, any state of
a system which would not undergo change if the
system were to be isolated. Processes in an
isolated system not in equilibrium are irrever-
sible and always in the direction of equilibrium.

2. In mechanics, a state in which the vector is

zero. In hydrodynamics, it is usually further
required that a steady state exists throughout
the atmosphere or fluid model. The equilibrium
may be stable or unstable with respect to dis-
placements therefrom. (5)

equilibrium argument—The theoretical phase of
a constituent of the equilibrium tide. See
Greenwich argument.

equilibrium range—The high frequency band of
wind waves whose frequency spectrum satisfies
a minus five power law.

equilibrium spheroid—The shape that the earth
would attain if it were entirely covered by a tide-
less ocean of constant depth. See geoid. (5)

equilibrium theory—A hypothesis which assumes
an ideal earth which has no continental barriers
and is uniformly covered with water of consider-
able depth. It also assumes that the water re-
sponds instantly to the tide-producing forces
of the moon and sun to form a surface in equilib-
rium and moves around the earth without vis-
cosity or friction.

equilibrium tide—(or astronomic tide, astro-
nomical tide, gravitational tide). The hypothet-
ical tide due to the tide-producing forces
under the equilibrium theory; tide relating to
the attractions of celestial bodies, particularly
the sun and moon. (50)

equilibrium vapor pressure—The vapor pres-
sure of a system in which two or more phases
of a substance coexist in equilibrium. In
oceanography the reference is to water substance
unless otherwise specified. If the system con-
sists of moist air in equilibrium with a plane
surface of pure water or ice, the more special-
ized term saturation vapor pressure is usually

207-109 O—66——_5

59

ESTUARY

employed, in which case the vapor pressure is
a function of temperature only. (5)

equinoctial—The celestial equator. (50)

equinoctial spring tides—Those tides occurring
near the equinoxes when the full or new moon
and the sun have little or low declination and
spring tides of greater range than the average
oceur, particularly if the moon is also nearly
in perigee. (30)

equinoctial tide—Tide occurring when the sun
is near equinox. During this period spring tide
ranges are greater thanaverage. (5)

equinoxes—The two points in the celestial sphere
where the celestial equator intersects the eclip-
tic; also the times when the sun crosses the
celestial equator at these points. (50)

eradiation—See terrestrial radiation.

erect bryozoan—(or stolonate bryozoan). A
bryozoan which forms branching upright
growths attached basally to underwater surfaces.

erg—The unit of energy in the centimeter-gram-
second system of physical units; that is, one
dyne centimeter. One erg is equal to 10-7
Joule or to 2.389 10-§ calories. (5)

ergodic—A hypothesis asserting statistical equiv-
alence of ensemble averages and time averages
when steady state conditions occur.

erosion—Any or all processes by which soil or
rock is broken up and transported from one
place to another. It is regarded as including
weathering, corrasion, and transportation. (2)

erosion ramp—A sloping belt of reef rock im-
mediately above the reef flat on an atoll islet
where marine erosion is active. (2)

erratic—A transported rock fragment different
from the bedrock on which it lies, either free
or as part of a sediment. Such fragments are
ice rafted or transported by glacier ice or by
floating ice and are widely distributed on the
sea floor in high latitudes.

eruptive rocks—Rocks which have formed from
molten magma and which have either been in-
truded into older rocks or extruded at the earth’s
surface through volcanic cones or fissures.

escarpment—(or fault scarp, scarp). An elon-
gated and comparatively steep slope of the sea
floor, separating flat or gently sloping areas.
(62)

establishment—See lunitidal interval.

establishment of the port—(or high water full
and change, common establishment, vulgar
establishment). The average interval between
upper and lower lunar transit near time of new
and full moon and the next high water. See
lunitidal internal.

estuarine muds—ASilts, often containing sufficient
clay to impart some plasticity, and containing
a considerable proportion of decomposed organic
matter.

estuary—(or drowned river mouth, branching
bay, firth, frith). A tidal bay formed by sub-

EULERIAN CURRENT MEASUREMENT

mergence or drowning of the lower portion of a
nonglaciated river valley and containing a
measurable quantity of sea salt. See inverse
estuary, neutral estuary, positive estuary,
sound (sense 2), slightly stratified estuary,
vertically mixed estuary, highly stratified
estuary.

Eulerian current measurement—Direct observa-
tion of the current speed and/or direction during
a period of time as it flows past a recording
instrument such as the Ekman or Roberts cur-
rent meter. See Lagrangian current measure-
ment.

eulittoral—According to some authorities a zone
extending from the high tide level to a depth of
about 130 to 195 feet (40 to 60 meters). (54)

euphausiid—One of an order (Euphausiacea) of
shrimplike, planktonic crustaceans, widely dis-
tributed in oceanic and coastal waters, and es-
pecially abundant in colder waters. Euphausi-
ids grow to 8 to 4 inches in length, and nearly
all possess luminous organs. Many of the species
engage in typical diurnal vertical migration
and may contribute to midwater sound scatter-
ing. Some are present near the sea surface at
least during certain periods of the year, where
they form the principal food for many of the
baleen (whalebone) whales. See krill.

euphotic zone—The layer of a body of water
which receives ample sunlight for the photo-
synthetic processes of plants. The depth of this
layer varies with the water’s extinction coeffici-
ent, the angle of incidence of the sunlight, length
of day, and cloudiness; but it is usually 260 feet
(80 meters) or more. The compensation depth
is the lower boundary of the euphotic zone. (5)

euryhaline—Normally inhabiting salt water, but
adaptable to a wide range of salinity. (58)

eurythermic—Tolerant of a wide range of tem-
perature. (58)

eustatic—Pertaining to a simultaneous, world-
wide change in sea level such as from melting of
continental glaciers, but not a relative change
in level resulting from local coastal subsidence
orelevation. (2)

eutrophic—Pertaining to bodies of water contain-
ing abundant nutrient matter.

euxinic deposition—Deposition in a nearly iso-
lated sea basin where for lack of circulation
and mixing, the deep waters are deficient in oxy-
gen and toxic to all life, but anaerobic bacteria
and hydrogen sulfide muds rich in organic mat-
ter are produced. Examples are the Black Sea,
Carioco Basin, and some fiords.

evaporation—(also called vaporization). The
physical process by which a liquid or solid is
transformed to the gaseous state; the opposite
of condensation.

Energy is lost by an evaporating liquid; and
when no heat is added externally the liquid al-
ways cools. The heat thus moved is termed the
latent heat of vaporization. (5)

60

evaporite—One of the sediments which are de-
posited from aqueous solution as a result of ex-
tensive or total evaporation of the solvent. (2)

Ewing corer—A piston-type coring device used
to obtain 21%-inch diameter core samples. The
sampler consists of a weight stand on which re-
movable weights can be placed, a core barrel
(generally of 20-foot length), a core cutter, and
a core catcher.

expendable bathythermograph—Scee airborne
expendable bathythermograph, shipborne ex-
pendable bathythermograph.

explosives anchorage—Scee anchorage.

exposed anchorage—WS¢ee anchorage.

exposure—See outcrop.

extinction coefficient—A measure of the space
rate of diminution, or extinction, of any trans-
mitted light; thus, it is the attenuation co-
efficient applied to visible radiation.

In oceanography, it isa measure of the attenu-
ation of downward-directed radiation in the
sea. (5)

extracellular bioluminescence—Light produc-
tion outside the organism resulting from the
secretion of photogenic material from special
secretory glands. Cypridina, an _ ostracod,
extrudes yellow granules of luciferin and small
colorless granules of luciferase into the sea
water. These granules dissolve and react to pro-
duce light. The deep sea squid, Heteroteuthis
dispar, emits a luminous cloud much like other
squid emit an ink cloud. See photogenic
granules.

extrapolation—The extension of a relationship be-
tween two or more variables beyond the range
covered by knowledge, or the calculation of a
value outside that range. (5)

extratropical cyclone—(sometimes called exétra-
tropical low, extratropical storm). Any cyclon-
ic-scale storm that is not a tropical cyclone,
usually referring only to the migratory frontal
cyclones of middle and high latitudes. (5)

extratropical low—Scee extratropical cyclone.

extratropical storm—WSee extratropical cyclone.

extrusive rocks—Igneous material which has
forced its way through other rocks and flowed
out upon the surface of the earth or the sea bot-
tom before solidifying. The material may
emerge as volcanic ash or as lava flows from
fissures or cones. See eruptive rocks. (48)

eye—In meteorology, usually the “eye of the
storm” (hurricane, typhoon); that is, the
roughly circular area of comparatively light
winds and fair weather found at the center of a
severe tropical cyclone. The winds are gen-
erally 10 knots or less; no rain occurs; some-
times blue sky may beseen. Eye diameters vary
from 4 miles to more than 40 miles; common
magnitudes seem to be 12 to 25 miles. Modern
observations indicate that the eye does not re-
main in steady state but is continuously under-
going changes in shape and size. (5)

fabric—The relative size, shape, and spatial
arrangement of grains or crystals in a sediment
deposit or arock. (2)

facies—A really segregated parts of a sedimentary
deposit which differ in mineral composition,
bedding, fossils, etc. but belong to any geneti-
cally related body of sedimentary deposits. (2)

Fahrenheit temperature scale—(abbreviated
F). A temperature scale with the freezing
point at 82 degrees and the boiling point of water
at 212 degrees at standard atmosphere pressure.

fair tide—See beam tide.

Falkland Current—A current flowing northward
along the Argentine coast. The Falkland Cur-
rent originates from part of the West Wind
Drift. At about 35°S it is joined by the Brazil
Current where both turn to flow east across the
South Atlantic.

falling tide—(sometimes called ebb tide). The
portion of the tide cycle between high water and
the following low water. (5)

falloff—In underwater sound, the decrease in
acoustic energy as it travels away from the sound
source.

fallout—The radioactive debris, usually from a
nuclear detonation, which has been deposited on
the earth after being airborne. Special forms
of fallout are “dry fallout”, “rainout”, and
“snowout”. (70)

false anticline—A structure resembling an anti-
cline produced by compaction of sediment over
a resistant mass such as a buried hill or reef.

(2)

false bottom—Scee deep scattering layer.

false ice foot—tIce formed along a beach terrace
just above high water mark, derived from snow
melting above the beach terrace. (59) Rare.
See ice foot, quar ice.

family—See classification of organisms.

fan—A gently sloping, fan-shaped feature nor-
mally located near the lower termination of a
canyon. (62)

fan shooting—See are shooting.

faro—A small atoll-shaped reef or coral knoll with
lagoons a few to about 100 feet (30 meters) deep,
forming part of a barrier or atoll rim. (2)

fast ice—1. Sea ice that generally remains in the
position where originally formed and may attain
a considerable thickness. It is formed along
coasts where it is attached to the shore or over
shoals where: it may be held in position by is-
lands, grounded icebergs, or grounded polar ice.

61

(Preferred definition) (74)

2. (also called landfast ice). Any type of
sea ice attached to the shore (ice foot, ice shelf),
beached (shore ice), stranded in shallow water,
or frozen to the bottom of shallow waters (an-
chor ice). (5)

fast ice belt—Scee ice foot.

Fata Morgana—A complex mirage that is charac-
terized by multiple distortions of images, gen-
erally in the vertical, so that such objects as
cliffs and cottages are distorted and magnified
into fantastic castles.

An unusual density stratification is required to
produce this mirage, namely the joint occur-
rence, in vertically adjacent layers, of density
gradients that would give an inferior mirage
and asuperior mirage. A strong inversion over
a relatively warm sea may satisfy this require-
ment. The instability of the air layer lying
immediately over the sea in the mirage charac-
teristics, a circumstance that suggests the fairy-
like features of the mirage forms. (5)

fathogram—1. The graphic presentation of the
bottom profile determined by a Fathometer*.

2. Often erroneously applied to any echo-
gram.

fathom—The common unit of depth in the ocean
for countries using the English system of units,
equal to 6 feet (1.83 meters). It is also some-
times used in expressing horizontal distances, in
which case 120 fathoms make one cable or very
nearly 1-tenth nautical mile.

fathom curve—See isobath.

Fathometer*— Copyrighted trade name for a
type of echo sounder. Often incorrectly used
for any sonic submarine depth measuring
system.

fault—A fracture or fracture zone in rock along
which one side has been displaced relative to
the other side. The intersection of the fault
surface with any designated surface, such as the
sea bottom, is called a fault line. Ifa fault is
not a single clean fracture but a wide zone
(hundreds or thousands of feet) with small
interlacing faults and filled with breccia, it is
called a fault zone.

fault blockK—A rock body bounded on at least two
opposite sides by faults. It usually is longer
than it is wide; when it is depressed relative to
the adjacent regions it is called a graben, fault
embayment, fault trough, or rift valley, and
when it is elevated it is called a horst. Mozam-

FAULT COAST

bique Channel and the Red Sea are examples of
graben, fault embayment, fault trough, or rift
valley fault blocks.

fault coast—(or fault scarp coast). A straight
coast formed by a fault, consisting of a sea-
ward facing escarpment and a downthrown
block below sea level. (2

fault embayment—See fault block.

fault line—See fault.

fault-line coast—See wave-straightened coast.

fault scarp—See escarpment.

fault scarp coast—Scee fault coast.

fault trough—See fault block.

fault zone—Scee fault.

fauna—The animal population of a particular lo-
cation, region, or period.

feather star—See crinoid.

fecal pellet—(or castings). EExcrement of ma-
rine animals frequently found in sediments.
When fossilized they are often called coprolites,
which may also connotea larger size. (2)

feeder beach—An artifically widened beach
serving to nourish downdrift beaches by natural
littoral currents or forces. (61)

feeder channels—Channels parallel to shore
along which feeder currents flow before con-
verging to form the neck of a rip current. See
also feeder current.

feeder current—(or rip feeder current). ‘The
current which flows parallel to shore before
converging and forming the neck of a rip cur-
rent. (73) (See figure for nearshore cur-
rent system.)

feeling bottom—The action of a deepwater wave
on running into shoal water and beginning to
be influenced by the bottom. (5)

Fermat’s principle—The principle which states
that the path along which electromagnetic ra-
diation travels between any two points will be
that path for which the elapse time for the
travel is a minimum. (5) See multipath
transmission.

fetch—1. (also called generating area). An area
of the sea surface over which seas are generated
by a wind having a constant direction and speed.

2. The length of the fetch area, measured in
the direction of the wind in which the seas are
generated.

fetch length—The horizontal distance (in the di-
rection of the wind) over which a wind having
a constant direction and speed, generates a sea.

fiard—A Swedish term for a glacially formed
drowned valley with low glaciated sides which
occurs in lowland regions. Fiards are shorter
and shallower than fiords. (2)

fibrous ice—Scee acicular ice.

fibrous sponge—A sponge in which the internal
skeletal elements are composed of spongin fibers.
The commercial sponges are of this type.

fiducial point—A point (or line) on a scale used
for reference or comparison purposes. In the

62

calibration of oceanographic thermometers, for
example, the fiducial points are 100°C (212°F)
and 0°C (32°F), which correspond to the boil-
ing point and ice point at standard pressure (760
millimeters of mercury). (5)

field ice—1. A general term used for all types of
sea ice except newly-formed ice.

2. An obsolescent term for consolidated ice.

field of ice—See ice field.

figure of merit—The allowable transmission loss
between a sonar and a target.

filling—In meteorology, an increase in the central
pressure of a pressure system on a constant-
height chart, or an analogus increase in height
on a constant-pressure chart; the opposite of
deepening. The term is commonly applied toa
low ratherthantoahigh. (5)

film badge—A pack of photographic film used for
approximate measurements of radiation expo-
sure for personnel monitoring purposes. The
badge may contain two or three films of differ-
ing sensitivity, and it may contain a filter which
shields part of the film from certain types of
radiation. (70)

filter—In ocean-wave forecasting, a set of formu-
las that define the particular wave frequencies
and directions in the fetch area which are of
significance at the point of forecast. (5)

filtering effect—In wave hydrodynamics, the dif-
ferential damping of pressures or of vertical
oscillation of water particles with increasing
depth, depending upon the wave period. At any
given depth longer waves are damped less than
shorter waves.

filtration method—A technique used in the
quantitative estimation and identification of
planktonic organisms. Organisms, usually
phytoplankton, are removed from water by fil-
tration and retained on the surface of the filter.
The organisms can then be counted or identified
by microscope after suitable preservation and
staining of the organisms and subsequent clear-
ing (making transparent) of the filter.

fines—The silt and clay fraction of a sediment.

fiord—(also spelled fjord). A narrow, deep,
steep-walled inlet of the sea, formed either by
the submergence of a mountainous coast or by
entrance of the sea into a deeply excavated gla-
cial trough after the melting away of the gla-
cier. A fiord may be several hundred fathoms
deep and often has a relatively shallow sill of

rock or gravel across its entrance. (2) See
fiard.
fiord ice—Winter ice formed in a fiord. (59)

fire body—Sce pyrosome.

fire cylinder—See pyrosome.

fireworm—A luminescent marine worm mainly in
the Bermuda area. The swarming of this worm
during certain phases of the moon creates
luminescent displays. (28)

firn—(also called névé, firn snow). 1. See firn
snow (sense 1).

2. Old snow that has become granular and
compacted (dense) as the result of various sur-
face metamorphoses, mainly melting and_re-
freezing but also including sublimation. The
resulting particles are generally spherical and
rather uniform. Firnification is the first step
in the transformation of snow into land ice
(usually glacier ice). Some authorities restrict
the use of firn to snow that has lasted through
one summer, thereby distinguishing it from
spring snow. (5)

firnification—The process of firn formation. (5)
firn snow—(also called névé). 1. According to
the adopted WMO definition, a snow which has
become coarse grained and compact through tem-
perature change, forming the transition stage

to glacier ice. (74)

2. See firn.
First Approximation chart—WScee historical
chart.

first ice—1. The first appearance of ice in the
water at any particular location, whether locally
formed (grease ice, young ice) or formed else-
where (drift ice).

2. Sometimes, the first appearance of locally
formed ice only.

first reduction—A name formerly given to a high
and low water reduction in which the quantities
sought were the mean high and low water in-
tervals, the mean high and low water heights,
and the mean range of tide. (50)

firth—(or frith). A long, narrow arm of the sea.
(68) See estuary.

fish—1. Any towed sensing device.

2. A member of the class Pisces, which in-
cludes the true fishes (elasmobranchs excluded)
having a bony endoskeleton, paired fins, and an
operculum covering the gills.

fission—The splitting of a nucleus into two more-
or-less equal fragments. Fission may occur
spontaneously or may be induced by capture of
bombarding particles. In addition to the fission
fragments, neutrons and gamma rays are usually
produced during fission. (41)

fissionable—Having the property of certain
atomic nuclei, such as some isotopes of uranium
and plutonium, of capturing neutrons and there-
upon splitting imto two particles with great
kinetic energy. The term properly is applicable
to nuclei that undergo fission by neutrons of
thermal energies; but it sometimes is applied
lcosely to cases where the neutron must be of
high energy, as in saying that U** is fissionable
by fast neutrons. (41)

fission fragments—The nuclear species which are
first produced when an atom such as U2* or
Pu’ undergoes fission. In slow neutron fission
the fragments are seldom equal in mass but gen-
erally fall into a heavier group with masses

63

FLOEBERG

around 140 and a lighter group with masses
around 95. The fragments are abnormally rich
in neutrons and decay to stability by successive
B- emissions, in decay chains, averaging 3 to 4
members. (41)
fission neutrons—Neutrons that are emitted as a
result of nuclear fission. Prompt fission neu-
trons are those that are emitted during fissions.
Delayed fission neutrons are those emitted by
fission products. (41)
fission products—The nuclides produced by the
fission of a heavy element nuclide such as
U** or Pu**. Thirty-five fission product ele-
ments from zinc through gadolinium have been
identified from slow neutron fission. (41)
fix—A relatively accurate position determined
without reference to any former position. It
may be classed as visual, sonic, celestial, elec-
tronic, radio, hyperbolic, Loran, radar, etc.,
depending upon the means of establishing it. A
pinpoint is a very accurate fix, usually estab-
lished by passing directly over or near an aid
to navigation or a landmark of small area.
(68) See dead reckoning.
f jord—See fiord.
flagellum—A_ whiplike process of protoplasm
hee provides locomotion for a motile cell.
13)
flashing—The process of reducing the amount of
permanent magnetism in a ship by placing a
single coil horizontally around the ship and
energizing it. Ifthe energized coil is moved up
and down along the sides of the ship, the process
is called wiping. (68) See deperming.
flaw—A lead between fractured offshore ice and
landfast ice.
flaw ice—See fast ice.
Fletcher’s Ice Island—See T-3.
float—1. An air sac or other light structure con-
taining air or gas serving to buoy up the body of
a pelagic animal (as the Portuguese man-of-
war) ;a pneumatophore.
2. A hollow vesicle found in certain algae
(as of the genus Fucus) containing gases (as
carbon dioxide) and serving to buoy up the
plant.
float gage—Scee box gage.
floating ice—Sce driftice.
nea: aggregate of tiny sedimentary grains.
flocculate—To aggregate into lumps, as when fine
or colloidal clay particles in suspension in fresh
water clump together upon contact with salt
water and settle out of suspension; a common
depositional process in estuaries.
floe—See ice floe.
floe belt—A belt consisting of ice floes.
floeberg—1. See bergy bit.
2. A mass of thick, heavily hummocked sea
ice resembling an iceberg or bergy bit. Floe-
bergs have been reported to be as high as 50

(68)

FLOOD AXIS

feet, and are considered to be the result of ex-
treme pressure ice formation.

flood axis—The average direction of the tidal
current at strength of flood.

flood current—The tidal current associated with
the increase in the height of a tide. Flood cur-
rents generally set toward the shore, or in the
direction of the tide progression. Erroneously
called flood tide. (See figure for current
curve.)

flood interval—The interval between the transit
of the moon over the meridian of a place and
the time of the strength of the following flood
tidalcurrent. (50)

flood strength—The flood tidal current at time
of maximum speed, usually associated with the
lunar tide phase and/or minimum river dis-
charge at springs near perigee. (See figure for
current curve.)

flood tide—WSee rising tide, flood current.

flora—The plant population of a particular loca-
tion, region, or period.

florescence—The rapid reproduction of plankton.
See plankton bloom.

Florida Current—A fast current with speeds of
2 to 5 knots that sets through the Straits of
Florida to a point north of Grand Bahama
Island where it joins the Antilles Current to
form the Gulf Stream.

The Florida Current is traced to the Yucatan
Channel where the greater part of the water
flowing through that channel turns clockwise
into the Straits of Florida.

flotsam—WSee jettison.

flow—The combination of tidal and nontidal cur-
rent which represents the actual water move-
ment.

flowmeter—1. A device employing propellers,
savonious rotors and/or pressure sensors to
measure water movement, such as currents,
stream flow, etc.

2. A special type device employing a pro-
peller-counting mechanism (which must be prop-
erly calibrated) is used to measure the amount
of water passing through a plankton net or
other sampling device.

flow noise—The noise produced by water move-
ment past the transducer or hydrophone array
housing, and the noise produced by breaking
waves against the hull of a moving ship.

fluctuation—1. The variations of water level
height from mean sea level that are not due to
tide-producing forces and are not included in
the predicted heights of the tide.

2. The change in average amplitudes of suc-
cessive pulses; sound pulses that are projected
with the same amplitude at intervals of a few
seconds will, after transmission, differ from each
other in amplitude.

fluorescence—1. The emission of electromag-
netic radiation by a substance as the result of an

absorption of energy from some other radiation,
either electromagnetic or corpuscular, and char-
acterized by the fact that it occurs only so long
as the stimulus responsible for it is maintained.
The continued emission of light after the absorp-
tion of radiation has ceased is called phosphor-
escence.

2. The electromagnetic X-radiation so pro-
duced.

3. In X-rays, characteristic X-radiation emit-
ted as a result of absorption of X-rays of higher
frequency.

4. See phosphorescence.

(41)

flushing time—The time required to remove or
reduce to a permissible concentration any dis-
solved or suspended contaminant in an estuary
or harbor.

fluviomarine—Deposits carried into the sea from
the land, re-sorted and redistributed by waves
and currents, and mixed with the remains of
marine animals.

flux—(or transport). The rate of flow of a
quantity, as for example, heat flux.

flux-gate magnetometer—An instrument de-
signed to measure the earth’s magnetic field.

The flux-gate magnetometer, also known as
the saturable reactor, makes use of a ferromagnet
element of such high permeability that the
earth’s field can induce a magnetization that is
a substantial proportion of the saturation value.
If this field is superimposed upon a cyclic field
induced by sufficiently large alternating current
in a coil around the magnet, the resulting field
will saturate the core. The phase of each en-
ergizing cycle at which saturation is reached
gives a measure of the earth’s ambient field.
(35)

fluxmeter—An instrument for measuring the in-
tensity of a magnetic field. (68)

fluxoturbidite—Strata deposited from turbidity
currents later disturbed by sliding or
slumping. (2)

flying bar—A looped bank or spit formed on the
landward side of an island which remains after
the island itself has been eroded to below sea
level by wave attack. (2)

flying squid—See sea arrow.

foam line—The front of a wave as it advances
shoreward after it has broken. (61) (See
figure for breaker.)

focus—In seismology, the source of a given set
of elastic waves. The true center of an earth-
quake, within which the strain energy is first
converted to elastic wave energy. (2)

fog—A hydrometer consists of a visible aggregate
of minute water droplets suspended in the at-
mosphere near the earth’s surface. According
to international definition, fog reduces visibility
below one kilometer (0.62 statute mile). (5)

fog bank—Generally, a fairly well-defined mass
of fog observed in the distance, most commonly
at sea. This is not applied to “patches” of
shallow fog. (5)

following sea—See beam sea.

following wind—Generally, same as _ tailwind;
specifically, a wind blowing in the direction of
ocean-wave advance; the opposite of opposing
wind.

fondo—The sea floor exclusive of the continental
shelf and slope. The sedimentary deposit is
the fondoform, and the rock unit of the fondo-
form is the fondothem. (2)

fondoform—Sce fondo.

fondothem—Sce fondo.

food chain—The sequence of organisms in which
each is food for a higher member of the
sequence. (26)

food cycle—The production, consumption, and
decomposition of food in the sea, and the en-
ergy relationships involved in this cycle. De-
composition products are transformed by
bacteria into inorganic nutrients suitable for
use by the producers (marine plants) which,
directly or indirectly, are the food source for all
animals in the sea.

food web—A group of interrelated food chains.

foot-pound—A unit of energy equal to 1.356
Joules. (5)

foram—Scee foraminiferan.

foraminifer—Sce foraminiferan.

foraminifera—Sce foraminiferan.

foraminiferal ooze—A pelagic sediment consist-
ing of more than 30 percent calcium carbonate
in the form of foraminiferal tests. See also
ooze.

foraminiferan—(or foraminifera, foraminifer,
foram). One of an order (Foraminifera) of
benthic and planktonic protozoa possessing var-
iously formed shells of calcium carbonate, silica,
chitin, or an agglomerate of materials. Shells
of an abundant planktonic genus, Globigerina,
form an important part of a marine sediment
called globigerina ooze.

forced wave—A wave generated and maintained
by a continuous force, in contrast a free wave
that continues to exist after the generating force
has ceased to act. (68)

foredeep—A long, narrow, crustal depression, or
furrow, bordering the convex or ocean side of a
folded orogenic belt or island are. See trench.
(2)

foreland—A promontory or cape; a point of land
extending into the water from the shoreline.
(2)

Forel scale—1. A scale of yellows, greens, and
blues for recording the color of sea water, as seen
against the white background of a Secchi disk.
(5)

2. As used in the U.S. Naval Oceanographic
Office:

65

FOUL GROUND

Description Code

Deep) (blues = eee eee 00

Wetec ees So eee Ee ee eee 10
Greenish, blues 2) 2.; = 2-2-5455 s52 52 20
Bluish green. -— => == 22-seceec= 30
Greene = eh ee eee 40
Light green =). - 22222225 255 Soe 50
Wellowish jsreent22e= sa. ees 60
Wellowiereen+-2-22222.025 3.2522 s=55 70
Greentoyellow == -= hs ee 80
Greenishvyellow=- =. 2-2-2 o ses oe 90
SWellow? = 22 oe eee aa ee Se ee 99

fore reef—The steeply dipping talus slope com-
monly found on the seaward side of an organic
reef. (2)

forerunner—Low, long-period, ocean swell which
commonly precedes the main swell from a dis-
tant storm, especially a tropical cyclone. (5)

foreset beds—The series of inclined layers of sedi-
ment deposited on the relatively steep frontal
slope of a delta. (2) (See figure for bottom-
set beds.)

foreshore—The zone that les between the or-
dinary high and low water marks and is daily
traversed by the oscillating water line as the
tides rise and fall. (2) (See figure for shore
profile.)

formation—A lithologically distinctive product of
essentially continuous sedimentation selected
from a local succession of strata as a convenient
unit for mapping, description, and reference.

2

form of floating ice—A categorical form used by
WMO to denote the size type of the pack ice
fragments; that is, ice crystal, small ice floes,
vast ice floes, etc.

forward scatterance—The ratio of the radiant
flux scattered through angles 0 to 90 degrees
from a beam, to the incident flux. (8)

forward scattering coefficient—The coefficient
which relates to forward scatterance. Unit of
measurementism-?. (8)

fossil—The remains or traces of animals or plants
which have been preserved by natural causes in
the earth’s crust, exclusive of organisms which
have been buried since the beginning of historic
time. (2)

foul—1. To attach to or come to lie on the surface
of submerged manmade or introduced objects,
usually in large numbers or amounts, as barna-
cles on the hull of a ship or silt on a stationary
object.

2. To entangle or become entangled, as a pro-

peller, cables, nets, or seaweed.

foul area—See rocky area.

foul bottom—A hard, uneven, rocky, or obstructed
bottom having poor holding qualities for an-
chors, or one having rocks or wreckage that
would endanger an anchored ship. (68)

fouler—See fouling organism.

foul ground—An area where the holding qualities
for an anchor are poor, or where danger of strik-

FOULING

ing or fouling the ground or other obstructions
exists. Seefoulbottom. (68)

fouling—The mass of living and nonliving bodies
and particles attached to or lying on the surface
of a submerged manmade or introduced object;
more commonly considered to be only the living
or attached bodies. See foul.

fouling community—(or fouling complex). 1.
The assemblage of plants and animals growing
on a specific artificial surface or a specific type
of surface.

2. An assemblage of plants and animals on an
artificial surface dominated by one or more or-
ganisms, such as the A/yti/us (mussel) commu-
nity.

fouling complex—WScee fouling community.

fouling organism—(or fowler). A plant or ani-
mal that attaches to the surface of submerged
manmade or introduced objects.

fouling panel—(or fouling plate, test panel, test
plate, test board). An object of wood, metal,

glass, or other solid material placed in water to
determine various physical and/or biological
aspects of fouling; the objects may be flat,
curved, or bent plates or boards and square or
rectangular blocks.

fouling plate—Sce fouling panel.

fracture—Breaks in rocks due to intense folding
or faulting. (2)

fracture zone—An extensive linear zone of un-
usually irregular topography of the sea floor
characterized by large seamounts, steep-sided
or asymmetrical ridges, troughs, or escarp-
ments. (62)

frazil—(or frazil crystals, also called needle ice).
Ice crystals which form in supercooled water
that is too turbulent to permit coagulation into
sheet ice. This is most common in swiftly flow-
ing streams, but also is found in a turbulent sea
(where it is called lolly ice). It may accumulate
as anchor ice on submerged objects and obstruct
the water flow. (5)

frazil crystals—Scee frazil, ice crystals.

frazil ice—(or needle ice, lolly ice, underwater
ice). An accumulation of frazil in a body of
water. (5)

free-air anomaly—The difference between ob-
served gravity and theoretical gravity which
has been computed for latitude and corrected for
elevation of the station above the geoid, by
application of the normal rate of change of
gravity for change of elevation, as in free air.

The elevation correction is for height above
the geoid. No correction is applied for the effect
of topography and isostatic compensation.

9
Oo
free-air correction—A correction factor, usually
expressed as milligals per meter, which is ap-
plied to observed gravity to reduce the value to
sea level.

66

free sound field—A field in a homogeneous, iso-
tropic medium free from boundaries. In
practice it is a field in which the effects of the
boundaries are negligible over the region of
interest. (3)

free wave—Any wave not acted upon by any
external force except for the initial force that
created it; a wave solution satisfying a homo-
geneous equation of motion and homogeneous
boundary conditions.

A free wave on a water surface is one created
by a sudden impulse, thereafter influenced only
by friction, the dimensions of the basin, and the
dispersive character of the water medium it
moves in. Most ocean surface waves except
tidal waves are free waves. (5) See oscilla-
tion.

freezeup—The formation of a continuous ice
cover. Generally, freezeup is restricted to the
hardening of locally formed young ice, although
the freezing together of pieces of drift ice also
can be called freezeup.

freezing point—(also called apparent freezing
point). The temperature at which a liquid
solidifies under any given set of conditions.
Pure water under atmospheric pressure freezes
at 32°F (0°C). However, the freezing point
of water is depressed with increasing salinity;
thus sea water with a salinity of 35 per mille
will freeze at about —1.9°C or 28.6°F. Both
freezing point and melting point can be defined
as the temperature at which both the solid and
liquid forms of a substance can coexist.

frequency—The frequency of a function periodic
in time is the reciprocal of the primitive period.
The unit is the cycle per unit time and must be
specified.

frequency distribution—A tabulation of fre-
quency or relative frequency of occurrence of a

36°

w w w
fo) nN ~
° ° °

TEMPERATURE (°F)
Ld
ao

26°

SALINITY (PARTS PER THOUSAND)

RELATIONSHIP BETWEEN FREEZING POINT AND TEMPERATURE
OF MAXIMUM DENSITY FOR WATER OF VARYING SALINITY

variable. It may be presented as a histogram,
frequency curve, rose, or other graphic form.
frequency of set—The number of observations
showing a current set in a particular direction.
It is expressed as a percentage of the total ob-
servations in a specific area or location.
frequency of sound—The number of sound waves
passing a point in a given time; usually meas-
ured as cycles per second.
freshet—An area of comparatively fresh water
at or near the mouth of a stream flowing into the
sea. (68)
fresh ice—1. Ice formed on fresh water.
2. Young ice of any kind.
3. Ice that has been salty but is now free of
salt.
(59)
fresh water—Water containing no significant
amounts of salts, such as in rivers and lakes,
as contrasted with sea water.
frictional drag—See intrainment force.
frictional layer—The layer of the ocean which
is affected by wind action.
friction factor—The wave height reduction factor
due to friction (along the bottom) alone. (10)
friendly ice—From the point of view of the sub-
mariner, an ice canopy containing many large
ice skylights or other features which permit
the submarine to surface. (7)
fringing reef—A reef attached directly to the
shore of an island or continental landmass. Its
outer margin is submerged and often consists
of algal limestone, coral rock, and living coral.
frith—See firth, also estuary.
frond—Sce lamina.
front—1. In meteorology, generally, the interface
or transition zone between two air masses of
different density. Since the temperature dis-
tribution is the most important regulator of
atmospheric density, a front almost invariably
separates air masses of different temperature.
2. See ice front, convergence.

(5)

67

FUNNEL SEA

front bay—A large irregular bay connected with
o sea through passes between barrier islands.

front of the fetch—The end of the generating
area toward which the wind is blowing. (61)

frost columns of ice—Scee candle ice.

frost smoke—1. (sometimes called barber). Fog-
like clouds, due to the contact of cold air with
relatively warm sea water, which appear over
newly-formed leads (lanes) and pools or lee-
ward of the ice-edge. These clouds may persist
while slush or sludge and young ice are
forming. (74)

2. See steam fog.

frustule—The siliceous shell of a diatom, con-
sisting of two valves, one overlapping the
other. It is the principal constituent of marine
diatomaceous ooze. (2)

fulls—See beach ridge.

fully-arisen sea—Sce fully-developed sea.

fully-developed sea—(also called fully-arisen
sea). The maximum height to which ocean
waves can be generated by a given wind force
blowing over sufficient fetch, regardless of
duration, as a result of all possible wave com-
ponents in the spectrum being present with their
maximum amount of spectral energy.

fundamental unit—A unit measure of basic phys-
ical quantity such as mass, length, time; for
example, one gram, one centimeter, one second,
respectively. Other quantities such as force,
temperature, etc., may be considered funda-
mental and each assigned a fundamental unit.
(5)

fungus—(or mold). <A thallophyte lacking
chlorophyll. Many marine fungi have been
identified. Some are believed to add to the
damage caused by marine borers by penetrating
the wood around burrows of the borers.

funnel sea—A gulf or bay, narrow at its head
and wide at its mouth and deepening rapidly
from head to mouth. (2)

G

gabbro—See igneous rock.

gal—A unit of acceleration equal to one centi-
meter per second per second (1 cm/sec?) or 1,000
milligals. A milligal is 0.001 gal. The term
gal is not an abbreviation. It was invented to
honor the memory of Galileo. (37)

Galofaro—A whirlpool in the Strait of Messina.
Formerly called Charybdis. (68)

galvanometer—An instrument for measuring a
small electric current, or for detecting its pres-
ence or direction by means of the movement of a
magnetic needle or of a wire, or coil, in a mag-
netic field. String (wire) or mirror galvanom-
eters are used in oscillographs and other instru-
ments of applied geophysics. (35)

gam—(or school). A large school of whales
(sperm whales travel about in small parties
which sometimes join up to form schools, or
gams, of considerable size).

gametophyte—In the sexual generation of an
alga, the male or female plant which produces
motile or nonmotile gametes.

gamma—A small unit of magnetic field intensity
generally used in describing the earth’s mag-
netic field. It is defined as being equal to 10-°
oersted.

gamma ray—A quantum of electromagnetic
radiation emitted by a nucleus, each such pho-
ton being emitted as the result of a quantum
transition between two energy levels of the
nucleus. Gamma rays have energies usually be-
tween 10 thousand-electron-volts and 10 million-
electron-volts, with correspondingly short wave-
lengths and high frequencies. They are often as-
sociated with alpha and beta radioactivity, fol-
lowing transitions that leave the product nuclei
in excited states; in general, they are more pen-
etrating than alpha or beta particles. They also
occur in isomeric transitions and in many in-
duced nuclear reactions. A gamma ray spectrum
consists of one or more sharp lines, each corre-
sponding to an energy and intensity that are
characteristic of the source. (41)

gamma ray spectrometer—An electronic device
which counts and measures the energy of in-
cident gamma rays. These data are presented
as the number of gamma ray counts in small
energy increments over a selected energy range;
usually 0 to 3 million-electron-volts. Thus the
spectra of emitted gamma ray energy from a
radioactive substance (such as sea water) can
be determined. Since each gamma ray emitting

68

radioisotope gives off one or more gamma rays
of characteristic energy such measurements per-
mit radioisotope identification and quantitative
assessment. Techniques such as spectrum
stripping are used to separate the spectrum con-
tribution of individual radioisotopes in mixtures
such as sea water. Some types of spectrometers
are the shipboard gamma ray spectrometer and
deep underwater nuclear counter (DUNC).

gamma scintillation spectrometer—Sce gamma
ray spectrometer.

gap—A _ steep-sided depression cutting trans-
versely acrossaridgeorrise. (62)

gas—aA state of matter in which the molecules are
practically unrestricted by cohesive forces, A
gas hasneither shape nor volume. (27)

gas bladder—See air bladder.

gas chromatography—aA separation technique
involving passage of a gaseous moving phase
through a column containing a fixed phase. It
includes (1) gas-liquid chromatography (GLC),
or more precisely, gas-liquid partition chroma-
tography, in which the fixed phase (column
packing) is a liquid solvent distributed on an
inert solid support; and (2) gas-solid chroma-
tography (GSC), in which the fixed phase is a
surface-active sorbent (charcoal, silica gel, acti-
vated alumina). Gas chromatography is used
principally as an analytical technique for the
determination of volatile compounds (gases and
liquids) with boiling points up to 400°C or even
higher. However, it is useful also as a research
method for determining certain physical quanti-
ties such as distribution or partition coefficients
and adsorption isotherms, and as a preparative
technique for isolating pure components or cer-
tain fractions from complex mixtures.

gastroliths—Stones which have been transported
in the stomach of marine animals such as
walruses.

gastropod—(or snazl). One of a class (Gastro-
poda) of mollusks in which the animals possess
a distinct head, generally with eyes and tentacles,
and a broad flat foot and usually are enclosed in
a spiral sheli.

gat—A natural or artificial passage or channel
extending inland through shoals or steep banks.

68

Pan unit of magnetic induction (or magnetic
flux density) equal to one dyne per unit cgs
magnetic pole. Prior to 1932, the gauss was
used both as a unit of magnetic induction and as

a unit of magnetic field intensity, but the latter
quantity is now measured in oersteds. (5)

Gaussian wave packet—An isolated group of
waves, with infinitely long crests in the direction
perpendicular to the direction of propagation
and with a constant wavelength in the direction
of propagation, of the sine wave form, which is
modulated mathematically according to the
normal probability curve (or Gaussian curve).

73

Geiner counter—Historically, a “point counter.”
By popular usage, a Geiger-Miller counter
tube or such a tube together with its associated
electronic equipment. (41)

Geiger-Mueller Counter (or tube)—Sce Geiger-
Miller counter tube.

Geiger-Miiller counter tube— (or Geiger-Mueller
tube). A gas-filled chamber usually consisting
of a hollow cylindrical cathode and a fine wire
anode along its axis. It is operated with a volt-
age high enough such that a discharge triggered
by a primary ionizing event will spread over the
entire anode until stopped by the reduction of
the field by space charge. (41)

generating area—See fetch.

generation of waves—1. The creation of waves
by natural or mechanical means. (61)

2. The creation and growth of waves caused
by a wind blowing over a water surface for a
certain period of time. The area involved is
called the generating area or fetch.

genus—See classification of organisms.

geo—An Icelandic term for a narrow inlet walled
in by steep clifts. (2)

geodesic—A geodesic line. (37)

geodesic line—A line of shortest distance between
any two points on any mathematically defined
surface. Also termed a geodesic. (37)

geodesy—The investigation of any scientific ques-
tion connected with the shape and dimensions of
theearth. The term geodesy is often used to in-
clude both the science which must depend upon
determinations of the figure and size of the earth
from direct measurements made on its surface
(triangulation, leveling, astronomic, and gravity
determinations), and the art which utilizes the
scientific determinations in a practical way.
(37)

geodetic datum—A datum consisting of five quan-
tities: the latitude and longitude of an initial
point, the azimuth of a line from this point, and
two constants necessary to define the terrestrial
spheroid.

It forms the basis for the computation of
horizontal control surveys in which the curva-
ture of the earth isconsidered. (37)

geodetic line—A geodesic on the reference
spheroid.

geodynamic height—Scee dynamic height.

geodynamic meter—See dynamic meter.

69

GEOMORPHOLOGY

geoid—The figure of the earth considered as a
mean sea level surface extended continuously
through the continents. The actual geoid is an
equipotential surface to which, at every point,
the plumb line (direction in which gravity
acts) is perpendicular. It is the geoid which is
obtained from observed deflections of the verti-
cal, and is the surface of reference for astronom-
ical observations and for geodetic leveling.
Theoretical geoids obtained with computed
values of deflections of the vertical include the
Pepeleatcd geoid and the isostatic geoid.
(37)

geological oceanography—The study of the floors
and margins of the oceans, including descrip-
tion of submarine relief features, chemical and
physical composition of bottom materials, inter-
action of sediments and rocks with air and sea
water, and action of various forms of wave
energy in the submarine crust of the earth.

geologic time scale—The divisions of time, from
the formation of the earth to the present, into
eras, periods, and epochs based primarily upon
fossil evidence. See table on next page.

Geomagnetic Electrokinetograph— (abbreviated
and also commonly called GEK). A shipboard
current measuring device used in depths greater
than 100 fathoms. It is dependent upon the
principle that an electrolyte moving through a
magnetic field (the earth’s) will generate an
electric current.

geomagnetic equator—A great circle on the
earth’s surface that is everywhere equidistant
from the geomagnetic poles; that is, the equa-
tor in the system of geomagnetic coordinates.

geomagnetic pole—The point where the axis of a
centered dipole that most nearly duplicates the
earth’s magnetic field would intersect the sur-
face of the earth. The earth’s geomagnetic
poles are located approximately 78.5°N, 69.0°
W and 78.5°S, 111.0°K. (36)

geomagnetism—(or terrestrial magnetism). 1.
The magnetic phenomenon, collectively con-
sidered, exhibited by the earth and its atmos-
phere.

2. The study of the magnetic field of the
earth.

geometric shadow—In wave diffraction theory,
the area outlined by drawing straight lines par-
alleling the direction of wave approach through
the extremities of a coastal protective structure.
It differs from the actual protected area to the
extent that the diffraction and refraction effects
modify the wave pattern. (61)

geomorphology—That branch of both geography
and geology which deals with the form of the
earth, the general configuration of its surface,
and the changes that take place in the evolution
of land forms.

GEOPHYSICS

PERIOD

EPOCH
QUATERNARY RECENT
PLEISTOCENE

PLIOCENE
MIOCENE
OLIGOCENE
EOCENE
PALEOCENE

MILLIONS
OF YEARS

CENOZOIC

TERTIARY

CRETACEOUS

JURASSIC MIDDLE

LOWER

TIME

MESOZOIC TRIASSIC

PROVINCIAL
SERIES

5
PENNSYLVANIAN| NO FORMAL 55
MISSISSIPPIAN SUBDIVISION

UPPER
DEVONIAN 5

PERMIAN

GEOLOGIC

MIDDLE 5

LOWER
UPPER
SILURIAN MIDDLE 40
PALEOZOIC COMER
UPPER
ORDOVICIAN MIDDLE 80
LOWER
UPPER
CAMBRIAN MIDDLE 80
LOWER

PRE-CAMBRIAN a 1600 +

THE DIVISIONS OF GEOLOGIC TIME

geophysics—The physics or nature of the earth.
It deals with the composition and physical
phenomena of the earth and its liquid and
gaseous envelopes; it embraces the study of ter-
restrial magnetism, atmospheric electricity, and
gravity; and it includes seismology, volea-
nology, oceanography, meteorology, and related
sciences. (24)

geosphere—The “solid” portion of the earth, in-
cluding water masses; the lithosphere plus
the hydrosphere.

Above the geosphere lies the atmosphere
and at the interface between these two regions
is found almost all of the biosphere, or zone
of life. (5)

geostrophic current—A current defined by as-
suming that an exact balance exists between the
horizontal pressure gradient and the coriolis
force. The usual manner of deriving geo-
strophic currents is to prepare a dynamic
topography chart which is based on observations

of temperature and salinity at various depths
for a network or a line of oceanographic sta-
tions. The direction of the current is indicated
by the contours of dynamic topography and its
speed by the spacing of the contours.
geostrophic equation—An equation which repre-
sents a balance between the horizontal pressure
gradient and the coriolis force. The equation
used to compute the speed of the current, is:

=i C(Di—Dr) n

yy L

1
2o sin p: 10°
D,—D»= difference in dynamic height anom-

alies at stations A and B in dy-
namic meters,

n= unit conversion factor,

L=distanee between stations (in kilo-
meters or nautical miles),

V=speed in knots,

o=angular velocity of the earth,

$= latitude.

geosyncline—A large generally linear subsident
trough in which many thousands of feet of sedi-
ments are accumulating or have accumulated.
Deep oceanic trenches paralleling island ares
are considered to be developing geosynclines.

2)

Benen gradient—The change in tempera-
ture of the earth with depth, expressed either in
degrees per unit depth, or in units of depth per
degree. (35)

giant clam—One of a genus (7 ridacna) of large
bivalves inhabiting coral reefs in the Indo-Pa-
cific region. The shells may attain weights of
several hundred pounds and lengths to four or
more feet. Although said to have caused fatal-
ities by trapping divers and waders, documenta-
tion of such incidents is lacking.

giant floe—An obsolete term since adoption of
WMO code; term now used is big ice floe.

giant kelp—One of a genus (J/acrocystis) of large
vinelike brown algae, which grow attached to
the sea bottom by a massive holdfast and reach
lengths to 150 feet. Members of this genus are
the largest algae in existence.

giant squid—One of a genus (Architeuthis), par-
ticularly Architeuthis princeps, of large cephal-
opods. These animals inhabit the middepths in
oceanic regions but may come to the surface at
night normally or by accident. The body of one
measured 10 feet long and the tentacles 42 feet
long. It is food for the sperm whale but often
may give battle. The fabulous sea monster,
kraken, as-originally drawn, resembles the giant
squid. See squid.

gill—A platelike or filamentous outgrowth; res-
piratory organ of aquatic animals.

gill cover—Scee operculum.

glacial—Pertaining to the presence, size, composi-
tion, or activity of extensive masses of land ice.
(59)

glacial deposit—Scee glacial drift..

glacial drift—(or glacial deposits). Sediments
and rock fragments transported by glaciers or
icebergs and deposited on land or in the sea.

glacial epoch—The Pleistocene epoch, the earlier
of the two divisions of geologic time included in
the Quaternary period; characterized by conti-
nental glaciers which covered extensive regions
now free from ice. (2) See geologic time
scale.

glacial trough—A U-shaped valley, excavated by
a glacier either on land or sea bottom.

glaciated coast—A coast whose features indicate
that it has been covered by continental glaciers
of the Pleistocene epoch or a coast covered by
glaciers at the present time. (2)

glacier—(or land ice). A mass of land ice, formed
by the further recrystallization of firn, flowing
slowly (at present or in the past) from an ac-
cumulation area to an area of ablation.

This term covers all such ice accumulations
from the extensive continental glaciers of pre-
historic ice ages to tiny snowdrift glaciers. (5)

glacier berg—A mass of glacier ice that has
broken away from its parent formation on the
coast, and either floats, generally at least 5
meters (16.4 feet) above sea level, or is stranded
onashoal. (74)

glacier ice—(or land ice). Any ice floating on the
sea, such as an iceberg, which originated from a
glacier. (74)

glacier iceberg—An iceberg derived from a
glacier as distinguished from tabular icebergs
derived from shelfice. (59)

glacier tongue—Projecting seaward extension of
a glacier, usually afloat. In the Antarctic,
glacier tongues may extend over many tens of
kilometers. (74)

glaciology—The study of snow and ice on the
earth’s surface, with specific concentration on the
regime of active glaciers. See cryology (sense
3). (B

Bey fragment of sea ice ranging in size
from brash ice to a medium ice floe. (59)

glade—See polynya.

glare ice—Any highly reflective sheet of ice on
water, land, or glacier. (5)

glass ice—Rare. See ice rind.

glass sponge—A sponge in which the internal
skeletal elements (spicules) are composed of
silicic acid. These sponges are principally in-
habitants of deep water to depths as great as
about 16,400 feet (5,000 meters) .

glass worm—See arrow worm.

glauconite—A green mineral, closely related to
the micas and essentially a hydrous potassium
iron silicate. Occurs in sediments of marine

71

GRADED SEDIMENT

origin and is produced by the alteration of var-
lous other minerals in a marine reducing or
anaerobic environment.

glauconitic sand—Sce green sand.

glaze—A smooth, transparent or translucent coat-
ing of ice deposited by a heavy fall of freezing
rain. Sometimes popularly called sleet. Called
“glaze ice” in British terminology. (68)

glimmer ice—Ice newly formed in cracks, holes,
or puddles on the surface of old ice. (59)
Rare.

glitter—The spots of light reflected from a point
source by the surface of the sea.

Statistical analysis of glitter patterns has
revealed relationships from which the roughness
of the sea can be determined by the study of
photographs of the glitter. (5)

globe-type luminescence—Scee
luminescence.

Globigerina—A common form of sediment-pro-
ducing foraminiferan.

globigerina ooze—A pelagic sediment consisting
of more than 30 percent calcium carbonate in the
form of foraminiferal tests of which Globiger-
ina is the dominant genus. See ooze.

glowing-ball luminescence—(or globe-type lu-
minescence). A display of biological light ap-
pearing as distinct and separate flashes or blobs
of light of various diameters, commonly having
a disc or globual shape, and originating either at
or below the surface of the sea. The organisms
responsible for this type of display include jelly-
fishes, ctenophores, and tunicates. Glowing-
ball type displays are seen more frequently in
warmer waters. See bioluminescence.

gnomonic projection—A perspective map projec-
tion upon a tangent plane, with the point from
which the projecting lines are drawn situated at
the center of the sphere. The projection is
neither conformal nor equal area. It is the only
projection on which great circles on the sphere
are represented as straight lines. (37)

goe—A Scottish term for a small sea-cut gorge
eroded into a cliffed coast. (48)

goose barnacle—Scee stalked barnacle.

gooseneck barnacle—Sce stalked barnacle.

grab—An instrument in which jaws enclose a por-
tion of the bottom for retrieval and study. The
sample may be unrepresentative in coarse sedi-
ments where the jaws may be propped open by
gravel or stones permitting part of the sample
to wash out.

graben—See fault block.

graded bedding—(or diadactic structure). A
type of stratification in which each stratum dis-
plays a gradation in grain size from coarse below
to fineabove. (2)

graded sediment—In geology, a sediment con-
sisting principally of grains of the same size
range. In engineering, a sediment having a

glowing-ball

GRADED SHORELINE

uniform distribution of particles from coarse to
fine. (2)

graded shoreline—A shoreline that has been
straightened by the building of bars across
embayments and by the cutting back of head-
lands. (2)

grade scale—A subdivision of an essentially con-
tinuous scale of particle size into a series of
size classes. (2) See Atterberg grade scale,
phi grade scale, Tyler standard grade scale,
Udden grade scale, Wentworth grade scale.

gradient—The rate of decrease of one quantity
with respect to another, for example, the rate of
decrease of temperature with depth. See
ascendant.

gradient current—A current defined by assuming
that the horizontal pressure gradient in the sea
is balanced by the sum of the coriolis and bot-
tom frictional forces. At some distance from
the bottom the effect of friction becomes negligi-
ble, and above this the gradient and geostrophic
currents are equivalent.

-graduation—Scee curve fitting.

Graf sea gravimeter—A_ balance-type gravity
meter (heavily overdamped to attenuate ship-
board vertical accelerations) which consists of a
mass at the end of a horizontal arm that is sup-
ported by a torsion spring rotational axis. The
mass rises and falls with gravity variation, but
is restored to near its null position by a horizon-
tal reading spring, tensioned with a micrometer
screw. The difference between actual beam
position and null position gives indication of
gravity value after the micrometer screw posi-
tion has been taken into account. (35)

grail—Coarse or medium sized sediment particles,
that is, gravel or sand.

grains—(or particle). The individual particles
which form a sediment which range in size from
smaller than 0.0039 millimeter (clay particles)
to larger than 256.0 millimeters (boulders).
See phi grade scale.

gram—A cgs unit of mass; originally defined as
the mass of 1 cubic centimeter of water at 4°C;
but now taken as the one-thousandth part of the
standard kilogram, a mass preserved by the
International Bureau of Weights and Measures
at Sevrés, France. (5)

gram atom—Scee gram atomic weight.

gram atomic weight—The mass of an element in
grams, numerically equal to its atomic weight.
Thus, the gram atomic weight of carbon is 12
grams (one gram atom of carbon weighs 12
grams).

Dissolved elements in a unit volume of sea
water are usually measured in milligram (or
microgram) atoms per liter.

gram calorie—WSee calorie.

gram mole—See gram molecular weight.

gram molecular weight—The mass of a molecule
in grams, numerically equal to its molecular

weight. Thus, the gram molecular weight of
molecular oxygen is 382 grams (one mole of
O. weighs 32 grams).

granite—A crystalline plutonic rock consisting es-
sentially of alkali feldspar and quartz. In seis-
mology, a rock in which the compressional wave
velocity varies approximately between 5.5 and
6.2 kilometers per second. Granitic is a textural
term applied to coarse and medium-grained
granularigneousrocks. (2)

granitic—Scee granite.

granular ice—Ice composed of many tiny, opaque,
white or milky pellets or grains frozen together
and presenting a rough surface. This is the
type of ice deposited as rime and compacted as
névé. (68)

granule—Rock fragments of overall gravel size
larger than very coarse sand (2.0 millimeters)
but smaller than pebbles (4.0 millimeters). See
phi grade scale.

granulometric facies—Cumulative curves rep-
resenting sedimentary grain size analyses; sub-
divided into linear, parabolic, logarithmic, and
hyperbolic facies depending upon the shape of
thecurve. (2)

grapestone—A cluster of small calcareous pellets,
resembling grapes, stuck together by incipient
cementation shortly after deposition. (2)

grass—See seagrass.

graticule—The network of lines representing
parallels and meridians on a map, chart, or plot-
ting sheet. (68)

gravel—Loose detrital material ranging in size
from 2 to 256 millimeters. See stone, phi
grade scale.

gravimeter—A weighing device or instrument of
sufficient sensitivity to register variations in the
weight of a constant mass when the mass is
moved from place to place on the earth and
thereby subjected to the influence of gravity at
those places.

Gravimeters are employed in determining dif-
ferences in the intensity of gravity between an
initial or base station at which the value of
gravity is known or assumed and at nearby
points for which values of gravity are desired.
Gravimeters are also termed gravity meters.
(37)

gravitation—In general, the mutual attraction be-
tween masses of matter (bodies). In geodesy,
the mutual attraction between the earth and
bodies on or near its surface. Gravitation is the
component of gravity which acts toward the
earth. (87)

gravitational tide—Scee equilibrium tide.

gravity—That force which tends to pull bodies
towards the earth: that is, to give bodies weight.

Gravity is the resultant of two opposing
forces: gravitation and the centrifugal force
due to the rotation of theearth. (87)

gravity corer—Any type of corer that achieves
bottom penetration solely as a result of gravita-
tional force acting upon its mass.

gravity instruments—Devices for measuring the
differences in the gravity force or acceleration at
two or more points. They are of three principal
types: (1) A static type in which a linear or
angular displacement 1s observed or nulled by an
opposing force. (2) A dynamic type in which
the period of oscillation is a function of gravity
and is the quantity directly observed. (3) A
gradient measuring type, for example, Eotvés
torsion balance.

gravity meter—Sce gravimeter.

gravity wave—A wave whose velocity of propa-
gation is controlled primarily by gravity.
Water waves of length greater than 2 inches are
considered gravity waves. (61)

gravity wind—WScee katabatic wind.

gray ice—A Russian term for sea ice 10 to 30
centimeters (4 to 12 inches) in thickness. It is
roughly comparable to medium winter ice.

gray mud—(or gray ooze). A deep sea deposit
of grayish color which is intermediate in com-
position between red clay and globigerina ooze.
(2)

gray ooze—See gray mud.

grazing—The feeding of zooplanktonic organisms
upon phytoplanktonic organisms. Generally in
reference to the feeding of copepods upon
diatoms.

grazing angle—The angle that the sound ray
path forms with the reflecting surface; usually
applies to sound rays reflected from the bottom.
Conventionally, the angle is measured from the
horizontal.

grease ice—(also called ice fat, lard ice). A
sludge of ice crystals in the sea that gives the
sea surface a greasy appearance. (5)

great circle—The curve on the surface of a sphere
traced by the intersection of the sphere and a
plane containing the center of the sphere.

great diurnal range— (also called diurnal range).
The average difference in height between all
mean higher high waters and all mean lower
low waters measured over a 19-year period,
or its computed equivalent.

greater ebb—The stronger of two ebb currents
occurring during a tidal day, usually associated
with tidal currents of mixed characteristics.
(66) See mixed current. (See figure for
current curve.)

greater flood—The stronger of two flood tidal
currents occurring during a tidal day, usually
associated with tidal currents of mixed char-
acteristics. (66) See mixed current. (See
figure for current curve.)

great tropic range—(also called tropic range).
The average difference in height between all
tropic higher high waters and all tropic lower
low waters which occur twice monthly when

73

GROSS PRIMARY PRODUCTION
the moon’s north and south declination is
greatest. See lunar declination.

green alga—One of a division or phylum (Chloro-
phyta) (the Chlorophyceae of another scheme)
of grass-green, single-celled, filamentous, mem-
branous, or branching plants in which the color,
imparted by chlorophylls a and 4, is not masked
by the accessory pigments. Green algae are
cosmopolitan in the upper littoral zone but are
most abundant in warmer waters.

greenhouse effect—In the ocean where a layer
of low salinity water overlies a layer of more
dense water the short wavelength radiation of
the sun is absorbed in the deeper layers. The
radiation given off by the water is in the far
infrared, and since this cannot radiate through
the low salinity layer, a temperature rise results
in the deeper layers.

In the atmosphere the same effect is produced
by a layer of clouds and the long wave radiation
is trapped between the clouds and the earth.

Greenland currents—See East Greenland Cur-
rent, West Greenland Current.

green mud—1. A fine-grained terrigenous mud or
oceanic ooze found near the edge of a continen-
tal shelf, and similar to other terrigenous muds
except for the greenish color and, in some cases,
less organic matter. It occurs at depths of 300
to 7,500 feet (91 to 2,286 meters).

2. A deep sea terrigenous deposit character-
ized by the presence of a considerable proportion
of glauconite and CaCO, in variable amounts
up to 50 percent.

(2)

green sand—(or glauconitic sand). A sand con-
taining a considerable quantity of glauconite
which gives ita green color. (2)

Greenwich argument—The equilibrium argu-
ment computed for the meridian of Greenwich.
(50) See equilibrium argument.

Greenwich epoch—The phase difference between
a tidal constituent and its equilibrium argu-
ment referenced to the corresponding Greenwich
equilibrium argument.

Greenwich interval—An interval referred to the
transit of the moon over the meridian of Green-
wich as distinguished from the local interval
which is referred to the moon’s transit over the
local meridian. (50)

Greenwich mean time—(abbreviated GMT).
Local mean time at the Greenwich meridian.
(68)

gribble—See Limnoria.

grit—Coarse sand or coarse-grained sandstone.

groin—A low artificial wall-like structure of dur-
able material extending from the land to sea-
ward for a particular purpose, such as to protect
the coast or to force a current to scour a channel.
(30)

gross primary production—See
production.

primary

GROUNDED HUMMOCK

grounded hummock—A hummock which has
stranded on the bottom, either during its forma-
tion or later upon drifting into shallow water.
Grounded hummocks appear either singly or in
lines (or chains).

grounded ice—Scee shore ice.

ground ice—1. See anchor ice for preferred
definition.

2. Glacial or sea ice that has been covered
with soil.

ground motion—The displacement of the ground
caused by the passage of elastic waves, arising
from earthquakes, explosions, seismic shots,
machinery, wind, traffic, and other causes. (85)

ground swell—A long high ocean swell; also, this
swell as it rises to prominent height in shallow
water, although usually not as high or dangerous
as blind rollers. (61)

ground wave—The sound (seismic) wave whose
path is partially through water and partially
within the sediments, or rocks, beneath the ocean
bottom. (35)

group velocity—The velocity of a wave disturb-
ance as a whole, that is, of an entire group of
component simple harmonic waves.

For water surface waves, the group velocity
of deepwater waves is equal to one-half the
velocity of individual waves in the group; for
shallow water waves, it is the same as their
velocity. (5)

growler—A piece of ice smaller than a bergy bit,
which often appears greenish in color and barely
shows above water. It may originate from sea
ice and glacierice. (74)

growler ice—An ice pack of growlers.
Rare.

Guiana Current—A current flowing northwest-
ward along the northeast coast of South America
(the Guianas).

The Guiana Current is an extension of the
South Equatorial Current. Eventually, it

(59)

74

joins the North Equatorial Current and sets
through the Lesser Antilles to become the Carib-
bean Current.

Guinea Current—A current flowing eastward
along the south coast of northwest Africa into
the Gulf of Guinea.

The Guinea Current originates from the
Equatorial Countercurrent which flows east
across the equatorial Atlantic.

gulder—A double low water occurring on the
south coast of England. See double tide. (68)

gulf—A large embayment in the coast in which
the entrance generally is wider than the length.

gulf ice—Winter ice formed in a gulf or bay.
(59) Rare.

Gulf Stream—A warm, well-defined, swift, and
relatively narrow ocean current which originates
north of Grand Bahama Island where the Flor-
ida Current and the Antilles Current meet.
The Gulf Stream extends to the Grand Banks at
about 40°N, 50°W where it meets the cold
Labrador Current, and the two flow eastward
as the North Atlantic Current.

The Florida Current, Gulf Stream, and North
Atlantic Current together form the Gulf Stream
system. Sometimes the entire system is referred
to as the Gulf Stream. See wind-driven
current.

Gulf Stream system—The Florida Current,
Gulf Stream, and North Atlantic Current,
collectively.

gulfweed—See Sargassum.

gully—This term is not recommended by the
ACUF for a relatively narrow ravine in the
ocean bed. See seachannel, trench.

gut—A narrow channel orstrait. (68)

guyot—This term is not recommended by the
ACUF foraseamount. See tablemount.

gyre—A closed circulatory system, but larger than
a whirlpool or eddy.

H

haar—A wet sea fog which sometimes invades
eastern Scotland and parts of eastern England,
especially duringsummer. (68)

hachures—1. Short lines on topographic or
nautical charts to indicate the slope of the
ground or submarine bottom. They usually
follow the direction of the slope. (68) See
contour.

2. Inward pointing short lines or “ticks”
around the circumference of a closed contour
indicating a depression or a minimum. (60)

hadal—(also called swperoceanic deep). Pertain-
ing to the greatest depths of the ocean. (See
figure for ¢lassification of marine environ-
ments.)

half-life—The average time, ¢:,, required for the
decay of one-half the atoms of a sample of a
radioactive substance. Each radionuclide has
an unique half-life, which is related to its dis-
integration constant, A, and mean life, 7, as
follows:

t= 1n2/A=0.693/A= 0.698 +.

See radioactive half-life. (41)

half-meter plankton net—A qualitative type
filtering net with a half-meter opening tapering
to a detachable bucket of a few inches diameter.
The net is usually some grade of silk bolting
cloth numbered 0000 to 25 depending upon the
number of meshes per linear inch.
half tide—The condition or time of the tide when

~ at the level midway between any given high tide
and the following or preceding low tide. (68)

half-tide level—Sce mean tide level.

halmyrolysis—Chemical rearrangement and re-
placement, and weathering which occurs in sedi-
ment or rocks on the sea floor. (2)

halobolite—Sce nodules.

halocline—A_ well-defined vertical gradient of
salinity which is usually positive.

halogen—Any of four elements (chlorine, bro-
mine, iodine, and fluorine) found as ions in sea
water.

halogenic deposits—Marine salt deposits. (2)

Halosphaera—A_ genus of green, single-celled
marine phytoplankton of the class Xantho-
phyceae. The genus occurs in both warm and
temperate waters and also has been reported to
be very abundant at times in antarctic waters.

harbor—An area of water affording natural or
artificial protection for ships.

Harbor Analog System—See Nearshore Envi-
ronmental Analog Prediction System.

207-109 O—66——6

75

harbor area—The area of the water surface in a
harbor or port, measured at a given datum.

harbor oscillation—(or harbor surging). The
nontidal vertical water movement in a harbor or
bay. Usually the vertical motions are low, but
when oscillations are excited by a tsunami or
storm surge they may be quite large. Variable
winds, air oscillations, or surf beat -also may
cause oscillations. See seiche.

harbor surging—Sce harbor oscillation.

harbor volume—The volumetric water content of
a harbor or port measured at a given datum.

hard bottom—The sea floor not covered by uncon-
solidated sediment. (2)

Hardy continuous plankton recorder—(or
Hardy recorder). A plankton sampler de-
signed to collect specimens of plankton during
normal passage of a ship. The device consists
of a towed container enclosing a continuously
moving strip of silk gauze (about 60 meshes per
inch) which filters and stores the plankton pass-
ing into the orifice of the container. Knowing
the speed of travel of the gauze and the course
and speed of the ship, it is then possible to deter-
mine the distribution of plankton along the
ship’s route.

Hardy recorder—Sce Hardy continuous plank-
ton recorder.

harmonic—A sinusoidal quantity having a fre-
quency that is an integral multiple of the fre-
quency of a periodic quantity to which it is
related. (6)

harmonic analysis—(or harmonic reduction).
1. A statistical method for determining the
amplitude and period of certain harmonic or
wave components in a set of data with the aid of
Fourier series. (5)

2. The method by which the observed tide or
tidal current at any place is separated into
elementary harmonic constituents. (50)

harmonic analyzer—A machine designed to re-
solve a periodic curve into its harmonic con-
stituents. (50)

harmonic constant—The amplitude and epoch of
any harmonic constituent of the tide or tidal
current at any locality. (50) See constituent.

harmonic constituent—Sce constituent.

harmonic function—1. Any solution of the La-
placeequation. (5)

2. In tide and tidal current predictions, a
quantity that varies as the cosine of an angle that
increases uniformly with time. (68)

HARMONIC PREDICTION

harmonic prediction—The method of predicting
tides and tidal currents by combining the
harmonic constituents into a single tide curve.

50

Ree anie reduction—See harmonic analysis.

harmonic synthesizer—A machine, such as the
tide-predicting machine, which combines the
elementary harmonic constituents into a single
periodic function. See tide-predicting ma-
chine. (50)

harmonic tide plane—Indian spring low water.

haul— (ortow). A single tow of a net.

haycock—An isolated conical pile of ice thrown
up above the surface of land ice or shelf ice,
resulting from pressure or ice movement. (68)
Rare. .

haze—Fine dust or salt particles dispersed through
a portion of the atmosphere; a type of litho-
meteor. The particles are so small that they
cannot be felt or individually seen with the
naked eye, but they diminish horizontal visibil-
ity and give the atmosphere a characteristic
opalescent appearance that subdues all colors.
5

head—1. In hydraulics, the vertica] distance be-
tween the surface of a liquid and another point
in the column; thus, a measure of the force
exerted at the lower point by the weight of the
column.

2. That part of a rip current that has
widened out seaward of the breakers. (61)
(See figure for nearshore current system.)

3. A precipitous cape or promontory extend-
ing into a large body of water. See headland.
(30)

heading—The direction toward which a ship is
oriented. A heading is often designated as true,
magnetic, compass, or grid north, respectively.

headland—(or head, promontory, naze, ness). A
high, steep-faced promontory extending into
the sea. Usually called head when coupled with
a specific name.

head sea—See beam sea.

head tide—Sce beam tide.

head wind—See crosswind.

heart urchin—See sea urchin.

heat—(sometimes called thermal energy). A
form of energy transferred between systems by
virtue of a difference in temperature, and exist-
ing only in the process of energy transformation.
By the first law of thermodynamics, the heat
absorbed by a system may be used by the system
to do work or to raise its internal energy. (5)

heat balance—1. The equilibrium which exists on
the average between the radiation received by
the earth and atmosphere from the sun and that
emitted by the earth and atmosphere.

That the equilibrium does exist in the mean
is demonstrated by the observed long term con-
stancy of the earth’s surface temperature. On

76

the average, regions of the earth nearer the
Equator than about 35° latitude receive more
energy from the sun than they are able to radi-
ate, while latitudes higher than 35° receive less.
The excess of heat is carried from low latitudes
to higher latitudes by atmospheric and oceanic
circulations, and is reradiated there.

2. The equilibrium which is known to exist
when all sources of heat gain and loss for a
given region or body are accounted for. In
general this balance includes advection, evap-
oration, etc., as well as radiation.

(5)

heat budget—The accounting for the total
amount of the sun’s heat received on the earth
during any one year as being exactly equal the
total amount which is lost from the earth by
reflection and radiation into space. The por-
tion reflected by the atmosphere does not affect
the earth’s heat budget. The portion absorbed
must balance the long-range radiation into space
from the earth’s entire system. That portion
absorbed into the oceans causes the surface
warming critical to the phenomenon of layer
depth. Transport by currents further extends
the distribution of heat. See heat transport.

heat capacity—(also called thermal capacity).
The ratio of the heat absorbed (or released) by
a system to the corresponding temperature rise
(or fall). Ifthis ratio varies with temperature,
it must be defined as a differential d@Q/dT where
d@Q is the infinitesimal increment of heat and d7
the infinitesimal increment of temperature. (5)

heat conduction—The transfer of heat from
one part of a body to another, or from one body
to another in physical contact with it without
displacement of the particles of the body, for ex-
ample, the transfer of heat by conduction
through the sea bottom. Since the amount is
very small, 50 to 80 gram calories per square
centimeter per year, it is neglected when con-
sidering the heat budget.

heat conductivity—See thermal conductivity.

heat equivalent of fusion—Scee latent heat.

heat transport—The process by which heat is car-
ried past a fixed point or across a fixed plane;
thus, a warm current such as the Gulf Stream
represents a poleward flux of heat.

heat trap—A temperature increase just above the

thermocline. A winter phenomenon due to
surface cooling in areas of warm water
advection.

heave—1. The motion imparted to a floating body
by wave action. It includes both the vertical rise
and fall, and the horizontal transport.

2. The up and down motion of the center of

gravity ofaship. See ship motion.
(5)

heaving—See heave.

heavy floe—An ice floe more than 10 feet thick.
(59) Obsolete.

heavy ice—Any mass of sea ice more than 10 feet
thick. (59) Obsolete.

heavy minerals—<Accessory detrital minerals of
high specific gravity, 2.8 or more, in rock or
sediments. Examples are magnetite, ilmenite.

heavy sea—A sea in which the waves run high.

73

rae water—1. Water in which the hydrogen of
the water molecule consists entirely of the heavy
hydrogen isotope of mass 2 (deuterium).

2. Written D.O. Density, 1.1076 at 20°C.
It is used as a moderator in certain types of
nuclear reactors.

3. The term is sometimes applied to water
whose deuterium content is greater than natural
water.

(41)

heeling—Causing a ship to roll by mechanical
means so as to enable it to gain headway when
working inice. (65)

height—Scee wave height.

height of the tide—The vertical distance from
chart datum to the surface water level at any
stage of the tide usually measured in feet; a pre-
determined reference plane.

height-period combination—Waves with speci-
fied height and period.
height ratio—Sce ratio of ranges.

hekistoplankton—See mu flagellates.

hemipelagic-abyssal sediments—Deep sea de-
posits which contain terrestrial material. (2)

herd—A congregation of gregarious wild animals
or of marine mammals. The term is most often
applied to pinnipeds (herds of seal coming
ashore to bear young), but is also used in refer-
ence to cetaceans (the dolphin herd playing
through the swell).

hermatobiolith—See hermatolith.

hermatolith—Reef rock, also called hermatobio-
lith to indicate organic origin. (2)

hermatrypic—Reef building. (2)

herringbone cross-lamination—Thin layers of
sand cross-laminated in opposite directions in
alternating layers by frequently shifting cur-
rents in shallow water.

hertz—(abbreviated Hz). A unit of wave fre-
quency, equal to one cycle per second.

hervidero—Sce mud volcano.

heteropod—One of a division (Heteropoda) of
pelagic, free-swimming gastropods in which the
foot is modified into a swimming organ con-
sisting of a flattened fin and a posterior tail.
The shell and body are transparent.

heterotrophic nutrition—That process by which
an organism utilizes only preformed organic
compounds for its nutrition. See holozoic
nutrition, saprophytic nutrition, parasitic
nutrition, autotrophic nutrition, mixotrophic
nutrition.

high—1. In meteorology, elliptical for “area of
high pressure” referring to a maximum of

HIGH WATER INTERVAL

atmospheric pressure in two dimensions (closed
isobars) in the synoptic surface chart, or a maxi-
mum of height (closed contours) in the con-
stant-pressure chart.

Since a high is, on the synoptic chart, always
associated with anticyclonic circulation, the
a is used interchangeably with anticyclone.

5

2. No longer commonly used in combination
form and not recommended by the ACUF for
the least depth of a general use type of feature
of any size, shape, or height.

high energy environment—A region character-
ized by considerable wave and current action
which prevents the settling and accumulation
of fine-grained sediment smaller than sand size.
(2)

higher high water—(abbreviated HHW). The
higher of two high waters occurring during a
tidal day where the tide exhibits mixed charac-
teristics. See mixed tide.

higher high water interval—(abbreviated
HHWI1). The interval of time between the
transit (upper or lower) of the moon over the
local or Greenwich meridian and the next higher
high water. This expression is used when there
is considerable diurnal inequality. See luni-
tidal interval. (68)

higher low water—(abbreviated HLW). The
higher of two low waters of a tidal day where
the tide exhibits mixed characteristics. See
mixed tide.

higher low water interva1—(abbreviated
HLWI1). The interval of time between the
transit (upper or lower) of the moon over the
local or Greenwich meridian and the next higher
low water. This expression is used when there
is considerable diurnal inequality. See luni-
tidalinterval. (68)

highly stratified estuary—An estuary in which
salinity increases significantly from head to
mouth and surface to bottom; characterized by a
density discontinuity separating surface river
flow and bottom sea water.

high seas—Scee oceanic.

high-speed layer—A layer in which the compres-
sional wave velocity is greater than in at least
one adjacent layer. (2)

high tide—See high water. _

high water—(abbreviated HW;; also called high
tide). The highest limit of the surface water
level reached by the rising tide. High water is
caused by the astronomic tide-producing forces
and/or the effects of meteorological conditions.

high water full and change—(abbreviated
HWF&C). See establishment of the port.

high water inequality—WSce diurnal inequality.

high water interval—(abbreviated HWI). See
lunitidal interval.

HIGH WATER LINE

high water line—The intersection of the plane
of high water with the shore; it varies daily
with changing lunar phases and meteorological
conditions.

high water lunitidal interval—See lunitidal
interval.

high water mark—An established reference mark
on a structure or natural object which indicates
the maximum observed stage of tide. (73)

high water neaps—See mean high water neaps.

high water of ordinary spring tides—(abbrevi-
ated HWOST). A tidal datum appearing in
some British publications, based on high water
of ordinary spring tides. (61)

high water quadrature—Scee mean high water
neaps.

high-water rock platform—A coastal terrace a
little below high tide level and coinciding with
the ground-water table resulting from wave ero-
sion of rocks which are relatively softer or more
decomposed above the ground-water table than
below.

high water springs—See mean high water
springs.

high water stand—The condition at high tide
when there is no change in the height of the
water level. A similar condition at low tide is
called low water stand. (68)

hindeasting—The determining of a predictand or
predictands for some past situation using a
known predictor or predictors. For example, a
wave hindcast would be based upon wind direc-
tion, speed, duration, and perhaps fetch for
some past situation. These data could be
utilized in wave forecasting techniques to esti-
mate the wave direction, height, and period.

hinge crack—(or weight crack). A crack in sea
ice running parallel and adjacent to a pressure
ridge. Hinge cracks are believed to be caused
by the weight of the pressure ridge. (59)

hinter deep—A deep sea trough on the convex
side of an island are. (2) See deep, trench.

hinter surf beds—Littoral, lagoonal, deltaic, and
tidal flat deposits which form the continental
shelf. (2)

histogram—A graphical representation of a fre-
quency distribution. The range of the variable
is divided into class intervals for which the
frequency of occurrence is represented by a rec-
tangular column; the height of the column is
proportional to the frequency of observations

within the interval. (5)
historical chart—(or First Approximation
chart). A chart based on data from previous

years to determine probable oceanographic pat-
terns for a specified time.

hodograph—In general (mathematics), the locus
of one end of a variable vector as the other end
remains fixed. A common hodograph in ocean-
ography represents a tidal current or a compo-
nent of a tidal current for a complete tide cycle.
The current speed is shown by the length of the

arrow ; the change in time is shown by the differ-
ent directions of the arrow from a common
center. See Ekman Spiral, current ellipse.

hogback coast—Sce wave-straightened coast.

holdfast—A basal attachment structure of algae,
ranging in complexity from the simple or modi-
fied cells of filamentous algae to the massive root-
like structures of the kelp.

holding ground—The sea bottom of an anchor-
age designated as good or poor, depending upon
whether an anchor holds, catches, or drags.
Mud or silt usually is good holding ground.
Rock, gravel, or hard packed sand often is poor
holding ground, since an anchor often will drag,
snag, or become fouled.

hole—1. An abrupt hollow in the ground or ocean
floor.

2. An opening through a piece of sea ice, or
an open space between ice cakes. Such an
opening made to permit observation of the height
of the tide is called a tide hole.

3. A small bay, particularly in New England.
(68)

holophytic nutrition—(or photoautotrophic
nutrition, phototrophic nutrition). That proc-
ess by which an organism manufactures its food
by using the energy of the sun. See auto-
trophic nutrition.

holoplankton—(or permanent plankton). Or-
ganisms living their complete life cycle in the
floating state.

holosteric barometer—Rare.
rometer.

holothurian—See sea cucumber.

holozoic nutrition—That process by which an
organism ingests solid food and digests it inter-
nally; typical of free living animals.
See heterotrophic nutrition.

homogeneous fluid—A fluid within which the
density isuniform. (5)

homopyenal (equally dense) inflow—A sediment-
laden stream enters a basin filled with a water
of comparable density, as when a stream enters
a fresh-water lake. The resulting delta is the
classical type with top-, fore-, and bottom-set
beds. (2)

homothermal—See isothermal.

honeycombing—During the final disintegration
of floating ice, the process of partial melting that
leaves the piece of ice filled with pockets of
water. Honeycombed ice is generally soft and
spongy, and floats low in the water. Usually
only small pieces of ice are found in a honey-
combed state (such as growlers or brash ice),
although occasionally in a calm sea icebergs or
big ice floes may become honeycombed without
breaking up.

hook—1. A spit or narrow cape of sand or gravel
whose outer end bends sharply landward. (68)

9. See recurved spit.

hooked bay—An open bay or bight having only

oneheadland. (2)

See aneroid ba-

hooked spit—Sce recurved spit.

horizon—One of several lines or planes used as
reference for observation and measurement rela-
tive toa given location. (5)

horizontal haul—(or horizontal tow). The tow-
ing of one or more nets for predetermined
periods at a selected depth or depths. In this
type of haul, attempts are made to minimize
sampling from other levels. See oblique haul,
vertical haul.

horizontal intensity—The intensity of the hori-
zontal component of the magnetic field in the
plane of the magnetic meridian.

horizontal tow—wSee horizontal haul.

horse latitudes—The belts of latitude over the
oceans at approximately 30° to 35°N and S
where winds are predominantly calm or very
light and weather is hot and dry.

These latitudes mark the normal axis of the
subtropical highs, and move north and south
by about 5 degrees following the sun. The two
calm belts are known as the calms of Cancer
and calms of Capricorn in the Northern and
Southern Hemispheres, respectively; and in
the North Atlantic Ocean, these are the latitudes
of the Sargasso Sea. (5)

horst—Sce fault block.

hostile ice—From the point of view of the sub-
mariner, an ice canopy containing no large ice
skylights or other features which permit a sub-
marine to surface. (7)

hove-to—The condition in which a ship is kept
headed into the wind with no headway or by
working engines as necessary.

Humboldt Current—Sce Peru Current.

hummock—1. A mound or hill in pressure ice;
the corresponding submerged portion is called
a bummock.

2. Occasionally, any form of pressure ice
which has been smoothed and weathered is
called a hummock.

3. Ice pieces piled one over another on a
rather smooth icesurface. (74)

hummocked ice—Pressure ice, characterized by
haphazardly arranged mounds or _hillocks
(“hummocks”). This has less definite form, and
shows the effects of greater pressure than either
rafted ice or tented ice, but in fact may de-
velop from either of those. When hummocked
ice has been weathered and snow-covered it re-
sembles similarly metamorphosed rafted ice, the
term “hummocked ice” is then applied to both
formations. (5)

ar floe—An ice floe of hummocked ice.

68

hummocky ice field—An ice field composed of
hummocked ice. (68)

hurricane—A severe tropical cyclone in the
North Atlantic Ocean, Caribbean Sea, Gulf of
Mexico, and the eastern North Pacific off the
west coast of Mexico. (5)

79

HYDRODYNAMIC EQUATIONS OF MOTION

hurricane delta—A deposit formed in a lagoon
by sand carried by storm waves washing across
a reef.

hurricane surge—Sce
storm surge.

hurricane tide—Sce hurricane wave.

hurricane wave—(also called hwrricane surge,
hurricane tide). As experienced on islands and
along a shore, a sudden rise in the level of the
sea associated with a hurricane.

In low latitudes, the hurricane wave appears
to occur in the proximity of the storm’s center.
As the hurricane moves into higher latitudes,
however, the maximum wave appears to become
associated more and more with only the dan-
gerous semicircle. See storm surge, tsunami.
(5)

Huygen’s principle—A very general principle
applying to all forms of wave motion which
states that every point on the instantaneous posi-
tion of an advancing phase front (wave front)
may be regarded as a source of secondary
spherical “wavelets”. The position of the phase
front a moment later is then determined as the
envelope of all of the secondary wavelets (ad
infinitium) .

This principle, stated by the Dutch physicist
Christian Huygens (1629-1695), is extremely
useful in understanding effects due to refrac-
tion, reflection, diffraction, and scattering, of
all types of radiation, including sonic radiation
as well as electromagnetic radiation and ap-
plying even to ocean wave propagation. (5)

hydraulic current—Gravity flow through a
channel that results from a difference between
water levels at the two ends of the channel
because of a difference in phase and/or range
of the tide. (50) See head.

hydraulic gradient—The slope of the profile of
the static level for a hydraulic system. In open
channel flow the hydraulic gradient is the slope
of the water surface taken parallel to the flow.
(5)

hydraulic jump—aA steady-state, finite-ampli-
tude disturbance in a channel, in which water
passes turbulently from a region of (uniform)
low depth and high velocity to a region of
(uniform) high depth and low velocity. When
applied to hydraulic jumps, the usual hydraulic
formulas governing the relations of velocity and
depth do not conserve energy. See also bore.
(5)

hydraulic radius—The quotient of the cross-
sectional area of a channel (below the water
surface) divided by the wetted perimeter. (5)

hydrodynamic equations of motion—Three
equations which express the net acceleration of
a unit water particle as the sum of the five
partial accelerations due to pressure gradient
force, earth’s deflecting force, frictional force,
geostrophic and hydrostatic equations are

hurricane wave, also

HYDRODYNAMIC NOISE

simplified versions of the hydrodynamic equa-
tions.

hydrodynamic noise—Noise produced by the mo-
tion of the ship or sonar housing through the
water.

hydrodynamics—The study of fluid motion.
“Fluid” here refers ambiguously to liquids and
gases. (5)

hydrofoil—Any surface, such as a wing or rudder,
designed to obtain reaction upon it from the
water through which it moves. In recent usage,
it connotes a ship equipped with planes which
provide lift when the ship is propelled forward.

hydrogen sulfide mud—Scee black mud.

hydrograph—A graphical representation of stage
or discharge at a point on a stream as a function
of time. The most common type, the observed
hydrograph, represents river gage readings
plotted at time of observation. Other types of
hydrograph which are statistically derived from
observed data include the distribution graph
and the unit hydrograph. The possible hydro-
graph varieties are numerous, representing aver-
ages, storm units, seasonal characteristics, etc.,
in cumulative or differential form, and utilizing
different graphing or tabulating methods. (5)

hydrographic datum—Scee chart datum.

hydrographic station—See serial station.

hydrographic survey—A survey of a water area,
with particular reference to submarine relief,
and any adjacent land. See oceanographic
survey. (68)

hydrography—That science which deals with the
measurement and description of the physical
features of the oceans, seas, lakes, rivers, and
their adjoining coastal areas, with particular
reference to their use for navigational purposes.

66)

hydroid—The polyp form of a hydrozoan, as dis-
tinguished from the medusa or jellyfish form.

hydrologic cycle—The composite picture, includ-
ing change of state and vertical and horizontal
transport, of the interchange of water substance
between the earth, the atmosphere, and the sea.

(5)

hydrology—The scientific study of the waters of
the earth, especially with relation to the effects
of precipitation and evaporation upon the oc-
currence and character of water in streams, lakes,
and on or below the land surface. (5)

hydromedusa—Scee hydrozoan.

hydrometeor—Sce meteor.

hydrometer—An instrument used for measuring
the specific gravity ofa liquid. (5)

hydromica—See illite.

hydrophone—An electroacoustic transducer
that responds to water-borne sound waves and
oo essentially equivalent electric waves.

1

hydrophone effect—See machinery noise, pro-

peller noise.

80

hydrophone loss—A pplied to a sonar transducer
used for the reception of acoustic energy at a
specified frequency; it may be defined as the
transmission loss measured by the ratio of
(1) the source power of the free-field acoustic
energy available as plane sinusoidal waves from
a water surface having an area of one square
centimeter and lying perpendicular to the direc-
tion of the maximum response reference axis of
the transducer at the point to be occupied by its
effective center to (2) the resulting output power
of the electric energy available from the trans-
ducer. (28)

hydrophotometer—An instrument used to meas-
ure the extinction coefficient or transmission of
light in water. It consists of a constant light
source placed at a specific distance from a photo-
cell. When placed in the water, the electrical
output of the photocell is proportional to the
amount of light striking the cell which, in turn,
depends upon the transparency of the water.
The instrument is calibrated to read 100 per-
cent light transmission in air.

Hydroplastic corer—(or polyvinyl (PVC)
corer). A deep sea coring device, developed at
the U.S. Naval Oceanographic Office, to obtain
31-inch diameter cores up to 12 feet in length.
The barrel is constructed of high-impact grade
polyvinyl chloride plastic without an inner liner.

hydropsis—That part of oceanography concerned
with continuous observations and data collecting
and the reporting of oceanographic phenomena
on a regular and prompt basis with the aim of
supplying those that use the seas, particularly in
commercial fishing, current information.
Oceanographic counterpart to synopsis, or
synoptic meteorology. (25)

hydrosphere—The water portion of the earth as
distinguished from the solid part, called the
lithosphere, and from the gaseous outer enve-
lope, called the atmosphere. (5) See bio-
sphere, geosphere.

hydrostatic equation—The form assumed by the
vertical component of the vector equation of
motion when all coriolis force, earth curvature,
frictional, and vertical acceleration terms are
considered negligible compared with those in-
volving the vertical pressure force and the
force of gravity. Thus

Op _

ae

where p is the pressure, p the density, g the accel-
ae of gravity, and z the geometric height.

5

hydrostatic equilibrium—The state of a fluid
whose surfaces of constant pressure and constant
mass (or density) coincide and are horizontal
throughout. Complete balance exists between
the force of gravity and the pressure force.
The relation between the pressure and the geo-

—PIs

metric height is given by the hydrostatic
equation. (5)

hydrostatic instability—Sce instability. ;

hydrostatic pressure—The pressure at a given
depth due to the weight of the water column
above that depth. :

hydrotroilite—A black, finely divided colloidal
material (MeS) reported in many muds and
clays.

fein char (or hydromedusa). One of a class
(Hydrozoa or Hydromedusae) of coelenter-
ates. The highly branched polyp or hydroid
stage of many members is an important compo-
nent of fouling.

hyperpycnal (more dense) inflow—Sediment-
laden water flowing down the side of a basin and
then along the bottom as a turbidity current,
with vertical mixing inhibited because the dense
water seeks to remain at the lowest possible level.
Delta formation by such flow is most frequent at
the mouth of submarine canyons. (2)

hypolimnion—The layer of water below the
thermocline in a fresh water lake or pool;

81

HYPSOMETRY

distinguished from epilimnion, the layer above
the thermocline.

hypopycnal (less dense) inflow—Sediment-laden
fresh water discharging into denser saline water
of the ocean. The fresh water spreads over the
surface of the sea water forming a lunate bar if
discharge is small or cuspate, arcuate, or bird-
foot deltasif dischargeislarge. (2)

hypothermia—A fall in the temperature of an
animal body below the usual level. This state
is brought about when the homeostatic mecha-
nisms fail to maintain adequate production of
heat under conditions of extreme cold. (5)

hypsographic chart—A chart or part of a chart
showing land or submarine bottom relief in
terms of height above datum; also a hypsomet-
ric chart which is a chart showing gradients by
means of tints. Hypsography or hypsometry
is the science of measuring or describing eleva-
tions above a datum.

hypsography—See hypsographic chart.

hypsometric chart—Sce hypsographic chart.

hypsometry—Scee hypsographic chart.

Ice A—The indicator group in the WMO Ice code
which denotes an aircraft ice observation.

ice age—Scee glacial epoch.

Ice B—The indicator group in the WMO Ice code
which denotes a ship ice observation.

ice bar—An ice edge consisting of ice floes com-
pacted by wind, sea, and swell, and difficult to
penetrate. (7 4)

ice barrier—See ice shelf.

ice-basin lake—A lake, pond, or pool on sea or
glacier ice. (59)

ice bay—(also called ice bight). 1. A_bay-like
recess in the edge of a large ice floe or ice shelf.
(5)

2. An inward bend of the edge or limit of
pack ice, formed either by wind or current.
(65)

ice belt—Sce belt.

iceberg—(or berg). A large mass of detached
land ice floating in the sea or stranded in shallow
water. Irregular icebergs generally calve from
glaciers, whereas tabular icebergs and ice is-
lands are usually formed from shelf ice. Ice-
bergs are the largest form of floating glacier ice,
berg bits and growlers being generally the
fragments of broken icebergs.

An iceberg is usually defined as being the size
of a ship or larger, although any piece of glacier
ice greater than 15 feet in r height is often called
an iceberg. The WMO code defines an iceberg
as any piece of glacier ice more than 5 meters
(16.4 feet) above sea level.

ice bight—WSee ice bay.

ice blink—A relatively bright, usually yellowish-
white glare on the underside of a low cloud layer,
produced by light reflected from a distant ice-
covered surface such as pack ice. This term is
used in polar regions with reference to the sky
map; ice blink is not as bright as snow blink,
but much brighter than water sky or land sky.
(5)

ice boulder—A large fragment of sea ice stranded
on shore, which has been shaped by ice and wave
action into nearly spherical form. (59)

icebound—Surrounded so closely by ice as to be
incapable of proceeding. If steering control is
lost, the ship is beset. If pressure is involved,
the ship i issaid tobe nipped. (68)

icebreaker—A ship specially designed for break-
ing channels through floating ice. (59)

ice breccia—( or ice mosaic). “Ice pieces of differ-
ent age frozen together. (74)

82

Ice C—The indicator group in the WMO Ice code
which denotes a shore ice observation.

ice cake—(or cake, block). An ice floe smaller
than 10 meters (32.8 feet) across. (74)

ice canopy—Pack ice and its enclosed water
areas from the point of view of the submariner.

ice cap—A perennial cover of ice and snow over
an extensive portion of the earth’s land surface.
The most important of the existing ice caps are
those on Antarctica and Greenland (the latter
often called inland ice). (5)

ice clearing—Scee polynya.

ice cliffi—See ice front.

ice cluster—A concentration of sea ice covering
hundreds of square miles which is found in the
same region every summer. (7)

ice crust—See ice rind.

ice crystals—(or frazil crystals). 1. Fine ( e
ules or plates of ice suspended in water.

2. See frazil ice.

ice day—In climatology, a day on which the maxt-
mum air temperature in a thermometer shelter
does not rise above 32°F, and ice on the sur-
face of water does not thaw.

This term is not used in the United States,
but is used in Great Britain, throughout most
of Europe, and probably in many other parts of
the world. (5)

ice edge—The boundary at any given time be-
tween the open sea and sea ice of any kind,
whether drifting or fast. (74)

ice face—Scee ice ‘front.

ice eke grease ice.

ice field— (or field of ice). 1. Any area of Sea ice
of any size and of such extent that its limit
cannot be seen from the crow’s nest. (74)

2. An area of sea ice more than 5 n. miles
across; the largest areal subdivision of sea ice.
(59)

ice floe—(or floe). A single piece of sea ice,
other than fast ice, large ¢ or small, described if
possible as “light” or “heavy” according to
thickness.

Vast—over 10 kilometers (5.4 n. miles) across.

Big—1 to 10 kilometers (3,281 feet to 5.4 n.
miles) across.

Medium—200 to 1,000 meters (656 to 3,281
feet) across.

Small—10 to 200 meters (32.8 to 656 feet)
across.

(74)

ice flowers—1. Formations of ice crystals on the
surface of a quiet, slowly freezing body of water.

2. (also called frost flowers). Delicate tufts
of hoarfrost that occasionally form in great
abundance on an ice or snow surface (surface
hoar) ; it also forms as a type of crevasse hoar
or window frost.

3. See Tyndall flowers.

ice fog—A type of fog, composed of suspended
particles of ice, partly ice crystals 20 to 100
microns in diameter but chiefly, especially when
dense, droxtals (crystals) 12 to 20 microns in
diameter. It occurs at very low temperatures,
and usually in clear, calm weather in high lati-
tudes. The sun is usually visible and may cause
halo phenomena.

Ice fog is rare at temperatures warmer than
—30°C or —20°F, and increases in frequency
with decreasing temperature until it is almost
always present at air temperatures of —45°C
or —50°F in the vicinity of a source of water
vapor. Such sources are the open water of
fast-flowing streams or of the sea, herds of
animals, voleanoes, and especially products of
combustion from heating or propulsion. At
temperatures warmer than — 20°F, these sources
can cause Steam fog of liquid water droplets,
which may turn into ice fog when cooled. See
frost smoke. (5)

ice foot—(also called bellicatter, ballycadder,
catter, cadder, collar ice, fast ice belt). Sea ice
firmly frozen to the shore at the high tide line,
and unaffected by tide. There are several
varieties of ice foot. (74)

Ice foot is formed by the freezing of sea water
during ebb tide, and of spray. It is separated
from the floating sea ice by a tide crack; in
many areas it offers a fairly level, continuous
route for surface travel. (5)

ice pace er surface completely free of ice.
(74)

ice fringe—A belt of sea ice extending a short
distance from the shore. (68)

ice front—(also called front, ice cliff, ice face, ice
wall). 1. The seaward facing, cliff-like edge
of an ice shelf (so called by the British Ant-
arctic Place-names Committee).
y Any vertical wall of ice.

5

ice gang—~Scee debacle.

ice gruel—A type of slush formed by the irregular
freezing together of ice crystals. (68)

ice hummock—Sce hummock.

ice island—1. A large tabular fragment of shelf
ice found in the Arctic Ocean. Nearly one hun-
dred have been identified since the first one was
discovered on aircraft radar in 1946. All have
level, slightly undulating surfaces 10 to 25 feet
above water, and most appear to have calved
from the Ward Hunt ice shelf off the northern
coast of Ellesmere Island. Ice islands are
smaller than the largest tabular icebergs of the

83

ICE PILLAR

antarctic, the largest one known being about 300
square miles in area. They are up to 175 feet
thick and unlike the surrounding pack ice, they
are influenced more by currents than by wind.
Several ice islands have been occupied as drift
stations.

2. Any tabular iceberg. (59)

3. A giant floe. (59) Rare.

4. An island completely covered by ice and
snow. (59) Rare.

ice island iceberg—(also called dome-shaped ice-
berg). An iceberg having a conical or dome-
shaped summit. Such icebergs are often mis-
taken by mariners for ice-covered islands. Also
called ice island. (68) Obsolete term.

ice jam—Fields of lake or sea ice thawed loose
from the shores in early spring, and blown
against the shore, sometimes exerting great
pressures. (5)

ice keel—From the point of view of the sub-
mariner, a downward projecting ridge on the
underside of the ice canopy; the submerged
counterpart of a pressure ridge. Ice keels may
extend as much as 50 meters (164 feet) below
sea level. (7)

Icelandic low—The low pressure center located
near Iceland (mainly between Iceland and south-
ern Greenland) on mean charts of sea-level
pressure. It is a principal center of action in
the atmospheric circulation of the Northern
Hemisphere. (5)

ice ledge—WSee ice foot.

ice limit—The average position of the ice edge in
any given month or period, based on observa-
tions over a number of years. (74)

ice mosaic—Scee ice breccia.

ice pack—1. See pack ice.

2. See arctic pack.
3. See ice cluster.

ice pan—(alsocalleda pan). A large flat piece of
sea ice protruding from a few inches to 3 feet
above the water, usually composed of winter ice.
(59) Rare.

ice pedestal—(or mushroom ice, ice pillar). A
pillar of ice with a round, expanded top formed
when a portion of an ice-covered area is pro-
tected from the melting effect of sunlight by
some surface object. (59)

ice period—The time between first appearance and
final clearance of ice during any year.

ice piedmont—Ice covering a coast strip of low-
lying land backed by mountains. The surface
of an ice piedmont slopes gently seaward, may
range from a width of about 50 meters (164
feet) to 50 kilometers (27 n. miles) and fringes
long stretches of coastline with ice cliffs. Ice
piedmonts frequently merge into ice shelves.
(7)

ice pillar—1. See ice pedestal.

2. Any ice formation of columnar shape.
(59)

Rare.

ICE POINT

ice point—The true freezing point of water; the
temperature at which a mixture of air-saturated
pure water and pure ice may exist in equilibrium
at a pressure of one standard atmosphere.

The ice point is often used as one fiducial
point (0°C or 32°F) in establishing a thermo-
metric scale because it is reproduced relatively
easily under laboratory conditions.

The ice point is frequently called the freezing
point, but the latter term should be reserved for
the much broader reference to the solidification
of any kind of liquid under various conditions.
(5)

ice pole—(or pole of inaccessibility). The area
round which the more consolidated part of the
arctic ice pack is located and therefore the most
difficult point to reach by surface travel. At
present its location is about 84°N and 160°W.
(59)

ice port—An embayment in an ice front, often
of a temporary nature, where ships can tie up
and unload directly onto the ice shelf or thick
sea ice.

ice potential—The potential amount of ice that
would be formed in a given water mass if sur-
face heat loss provided the thermohaline cir-
culation.

icequake—The concussion attending the breaking
up of masses of ice. (68)

ice rafting—The transportation of sediments and
rock fragments of all sizes by floating ice. Such
material is widely distributed in marine sedi-
ments along the paths of melting icebergs and
is identified by glacial abrasion marks, composi-
tion, angularity (in contrast to rounded, water-
worn alluvial-marine sediments), and size too
large for any but ice-rafting method of trans-
portation.

ice rind—(or glass ice, ice crust). A thin, elastic,
shining crust of ice, formed by the freezing of
ice slush or sludge on a quiet sea surface. It
has varying degrees of whiteness depending on
its age, thickness, and the rapidity of freezing.
It is easily broken by wind or swell, and is gen-
erally less than 5 centimeters (2 inches) in thick-
ness. (74)

ice routing—Optimal routes for ships in ice-in-
fested water provided through forecasting fu-
ture ice conditions.

ice run—See debacle.

ice Sheet—Any large area of continuous ice overly-
inga land surface. (65)

ice shelf—(also called shelf ice; formerly barrier
ice). 1. A thick ice formation with a fairly level
surface, formed along a polar coast and in shal-
low bays and inlets, where it is fastened to the
shore and often reaches bottom. It may grow
hundreds of miles out to sea. It is usually an
extension of land ice, and the seaward edge
floats freely in deep water.

The calving of an ice shelf forms tabular ice-
bergsandiceislands. (5)

2. More specifically, a level ice formation
over 2 meters (6.6 feet) above the sea surface
which originates from annual accumulations
of firn snow layers on bay ice or on the seaward
extension of a glacier. (74)

ice skylight—From the point of view of the sub-
mariner, thin places of the ice canopy, usually
less than 1 meter thick and appearing from be-
low as relatively light translucent patches in
dark surroundings. The undersurface of an ice
skylight is normally flat. Ice skylights are
called large if big enough for a submarine to
attempt to surface through them (120 meters or
393.7 feet) or small if not. (7) See lead.

ice Slush—An accumulation on the water surface
of ice needles that are frozen together; it forms
patches or a thin compact layer of a grayish or
leaden-tinted color. The surface of the area
covered with ice slush has a dim tint. (74)

ice stream—1. A glacier, usually an_ outlet
glacier, located on the periphery of an ice cap.

2. See strip.

ice strip—See strip.

ice table—A mass of levelice. (68)

ice tongue—Any narrow extension of a glacier or
ice shelf, such as a projection floating in the sea
or an outlet glacier of anice cap. (5)

ice tongue afloat—A terminal extension of a
glacier which extends so far into the sea that its
end is buoyed. This is primarily an antarctic
phenomenon but occurs occasionally in the
arctic. (59)

ice wall—See ice front.

ice yowling—A long, high-pitched sound accom-
panying the formation of contraction cracks in
ice.) (59)

icing—1. The formation of ice on aircraft sur-
faces, within aircraft engines, or on ships.

2. Glaze.

(59)

ideal sea level—The theoretical sea surface which
is everywhere normal to the plumb line. Refer-
ence of all depth soundings to this level would
make them all comparable.

ideal transducer—A hypothetical passive trans-
ducer that transfers the maximum possible
power from the source to the load, in regard to
connecting a specified source to a specified load.

igneous rock—Rock formed by solidification of
molten matertal or magma. (2)

illite—(or hydromical). A group of clay minerals
composed of interlayered mica and montmoril-
lonite and intermediate between muscovite and
montmorillonite.

illuminance—The total luminous flux received on
a unit area of a given real or imaginary surface,
expressed in such units as the foot-candle, lux,
or phot.

The only difference between this term and illu-
mination is that the latter always refers to light
incident upon a material surface.

A distinction should be drawn, as well, be-
tween illumination and luminance. The latter
is a measure of the light coming from a surface;
thus, for a surface which is not self-luminous,
luminance is entirely dependent upon the illumi-
nance upon that surface and its reflection
properties. (5) f

ilmenite—A mineral, /e7%0,, the principal ore of
titanium. Sometimes mined from beach and
shallow water sand deposits.

immobile ice—A Russian term for fast ice.

impedance—The total opposition (in ohms)
offered to the flow of an alternating current. It
may consist of any combination of resistance,
inductive reactance, or capacitive reactance.

incised—Pertaining to a steep-sided trench or
notch cut into a plane surface or slope by cur-
rent erosion, as a sea valley or submarine can-
yon cut into a continental shelf or slope.

inclination—(also called dip). In terrestrial
magnetism, the angle which the total magnetic
field vector makes with its horizontal component.
(15)

incoming solar radiation—S¢e insolation.

index contours—Certain contour lines (usually
every fifth) accentuated by use of a line heavier
than the intervening ones. (2)

index of refraction—(or refractive index, also
called absolute index of refraction, absolute re-
fractive index, refractivity). 1. A measure of
the amount of refraction (a property of a di-
electric substance). It is the ratio of the wave-
length or phase velocity of an electromagnetic
wave in a vacuum to that in the substance. It
can be a function of wavelength, temperature,
and pressure. (5)

2. (or refractive index, also called relative
index of refraction). A measure of the amount
of refraction experienced by a ray as it passes
through a refractive interface, that is, a surface
separating two media of different densities. It
is the ratio of the absolute indices of refraction
of the two media (see definition 1 above). (5)

3. As related to ocean waves, it is the measure-
ment of the amount of refraction (or turning) of
an ocean wave front as the wave passes from
deeper into shallower water. It is a function
of wavelength, water depth, and the angle that
the approaching wave makes with the depth con-
tour. See wave refraction.

Indian Ocean—That ocean area bounded on the
north by the southern limits of the Arabian Sea,
Laccadive Sea, Bay of Bengal, the limits of the
East Indian Archipelago and the Great Aus-
tralian Bight ; on the east from South East Cape
(the southern point of Tasmania) down the
meridian to the Antarctic Continent; and on
the west from Cape Agulhas southward to the
Antarctic Continent.

The limits of the Indian Ocean exclude the
seas lying within it.

85

INJECTION PROBE

Indian spring low water—The approximate mean
water level determined from all lower low
waters at spring tides. It is also the computed
plane located below mean sea level by an amount
equal to the sum of the amplitudes of the har-
monic constants J/,, S,, K,, and 0.

Indian tide plane—The datum of Indian spring
low water. (73)

indicator species—A species of marine plankton
that is characteristic of a certain water mass to
which it is restricted, so that, with proper pre-
cautions, its presence can be taken as an indica-
tion of the presence of water of that origin.
Species of medusae, chaetognaths, euphausiids,
pteropods and tunicates, among others have been
shown to be indicator species.

induced magnetism—The field produced in a
magnetic material when it is placed in an ambi-
ent magnetic field. In the earth’s field, the in-
duced magnetism is in the direction of the field
and the strength is proportional to it.

induced radioactivity—That radioactivity pro-
duced in a substance after bombardment with
neutrons or other particles. The resulting
activity is natural radioactivity if formed b
nuclear reactions occurring in nature and arti-
ficial radioactivity if the reactions are caused
by man. See nuclear reaction. (70)

induration—The hardening of sediments through
cementation, pressure, heat, or other processes.
(2)

inertia currents—Currents resulting after the
cessation of wind in a generating area or after
the water movement has left the generating area.
See swell.

infralittoral—Below the region of littoral
deposits. (2)

infraneritic—According to some authorities,
this term refers to the marine environment in
a zone between 120 and 600 feet (36 and 183
meters) below sea level.

infrared—Scee infrared radiation.

infrared radiation— (abbreviated IR; also called
long-wave radiation or infrared). “Electro-
magnetic radiation lying in the wavelength
interval from about 0.8 micron to an indefinite
upper boundary sometimes arbitrarily set at
1,000 microns (0.01 centimeter). At the lower
limit of this interval, the infrared radiation
spectrum is bounded by visible radiation, while
on its upper limit it is bounded by microwave
radiation of the type important in radar
technology. (5)

initial angle—The angle that a sound ray leaving
a sound source makes with a horizontal plane.

initial range—The horizontal distance between
the source and the closest point of the reswept
(convergence) zone.

injection probe—A thermistor that is installed
in the ship’s sea water injection intake pipe
(engine room).

INJECTION TEMPERATURE

injection temperature—The temperature of the
sea water as measured at the sea-water intakes
in the engine room of a ship.

Because the injectors are commonly located
well below the surface, and because the tem-
perature may be influenced by the heat of engines
or boilers, injection temperature is not con-
sidered as reliable as bucket temperature for
sea surface temperature. (5)

Electronic temperature probes have been de-
veloped (surtems) to improve the procedure
mentioned above.

inland ice—See continental glacier.

inland sea(s)—A sea surrounded by land which
connects with an ocean or another sea by one or
more narrow straits. Examples are the Medi-
terranean and Baltic Seas. See also epeiric
sea(s), epicontinental sea(s).

inlet—A short, narrow waterway connecting a
bay or lagoon with the sea. When it is a natural
inlet maintained by tidal currents, the name
tidal inlet or tidal outlet is applied.

inner space—A nickname given to an area in-
volved in modern marine research, especially in
regard to underwater exploration. (35)

inquilinism—A special kind of commensalism in
which one organism lives within another, usually
in the digestive tract or respiratory chamber,
without being harmful to its host. Some au-
thorties consider that relationship where one
species lives in the burrow or nest of another
is a form of inquilinism. See commensalism,
mutualism, symbiosis.

insertion loss—Applied to a transducer connect-
ing an energy source and an energy load it is the
transmission loss measured by the ratio of
(1) the load power which would be measured
if the load were connected directly to the source,
to (2) the actual load power when source and
load are connected by the transducer in question.

inshore—In beach terminology, the zone of vari-
able width between the shoreface and the sea-
ward limit of the breaker zone. (2) (See
figure for shore profile.)

inshore current—The horizontal movement of
water inside the surf zone, including longshore
and rip currents. (See figure for nearshore
current system.)

inshore water—Water contiguous to land in
which the physical properties are considerably
influenced by continental conditions.

in situ—A Latin term meaning “in place”; in the
natural or original position.

insolation—(contracted from incoming solar
radiation). 1. In general, solar radiation re-
ceived at the earth’s surface.

2. The rate at which direct solar radiation is
incident upon a unit horizontal surface at any
point on or above the surface of the earth.
(9)

insonification—The penetration of sound into any
particular part of the sea.

86

instability—(or static instability, hydrostatic in-
stability). A property of the steady state of a
system such that certain disturbances or pertur-
bations introduced into the steady state will in-
crease in magnitude, the maximum perturbation
amplitude always remaining larger than the
initial amplitude. In oceanography, usually
refers to the vertical displacements of a parcel in
hydrostatic equilibrium.

insular shelf—See continental (or island) shelf.

insular slope—See continental (or island) slope.

intake temperature—Sce injection temperature.

intensity—In general, the. degree or amount,
usually expressed by the elemental time rate or
spatial distribution, of some condition or physi-
cal quantity, such as rainfall, electric field,
sound, ete. (5)

intensity level—The intensity level, in decibels,
of a sound is 10 times the logarithm to the base
of 10 of the ratio of the intensity of this sound
to the reference intensity. The reference in-
tensity shall be stated explicitly. (6)

interbedded—(or interlaminated, interstratified,
intercalated). Occurring between beds or in
beds parallel to other beds of a different material.

5)

a

intercalated—Scee interbedded.
interdeep—This term is not recommended by the
ACUF for a trench or trough lying between

inner and outer island ares. See trench,
trough.
interface—(also called internal boundary, surface

of discontinuity, or boundary surface). A sur-
face separating two media, across which there is
a discontinuity of some property, such as density,
velocity, etc., or of some derivative of one of
these properties in a direction normal to the
interface. (5)

interfacial tension—Sce surface tension.

interference filter—An optical filter which
transmits, at normal incidence, only a narrow
band of wavelengths, other wavelengths being
suppressed by the destructive interference of
waves transmitted directly through the filter and
those reflected 2n times, where 7 is an integer
(from back and front faces of the filter). (8)

interfinger—Interlocking or overlapping wedge-
shaped sediment or rock layers.

interlaminated—Sce interbedded.

intermediate water—Sce water mass.

intermediate waves—Waves under conditions
where the relative depth (or the ratio of water
depth to wavelength) lies between 0.5 and 0.04.

intermittent current—An unidirectional current
interrupted at intervals. (68)

internal boundary—NScee interface.

internal friction—See viscosity.

internal wave—A wave that occurs within a fluid
whose density changes with depth, either
abruptly at a sharp surface of discontinuity (an
interface) or gradually. Its amplitude is great-
est at the density discontinuity or, in the case of

a gradual density change, somewhere in the in-
terior of the fluid and not at the free upper
surface where the surface waves have their maxi-
mumamplitude. (61)
Because of the small density gradient in-
volved, compared to that at the surface, a rel-
atively small amount of energy is required to set
up and maintain an internal wave. Wave
heights, periods, and lengths are usually large as
compared to surface waves.
International Gravity Formula—A development
of the formula for theoretical gravity, based
on the assumptions that the spheroid of reference
is an exact ellipsoid of revolution having the
dimensions of the International Ellipsoid of
Reference, rotating about its minor axis once
in asidereal day ; that the surface of the ellipsoid
is a level surface; and that gravity at the Equa-
tor equals 978.049 gals.
international low water—(abbreviated ILW).
A plane of reference below mean sea level by
the following amount; half the range between
mean lower low water and mean higher high
water multiplied by 1.5.
International Synoptic Code—A synoptic code
approved by the World Meteorological Orga-
nization in which the observable meteorological
elements are encoded and transmitted in “words”
of five numerical digits length. (5)
intersecting waves—(or sugarloaf sea, pyramidal
sea). One of the component waves which, when
superimposed on others, produces cross swells.
interstitial water—Water contained in the pore

spaces between the grains in rock and sediments.
interstratified—wSce interbedded.
intertidal—See littoral.

intertidal zone—(also called ittoral zone). Gen-
erally considered to be the zone between mean
high water and mean low water levels. (See
figure for classification of marine environ-
ments.)

intracellular bioluminescence—A widespread
form of biological light production usually as-
sociated with special luminous organs (photo-
phores) or luminous cells which contain photo-
genic granules. In some organisms intracel-
lular hight may be produced by luminous bacteria
living within special sacs or organs. In all orga-
nisms, the light emitted is internal, below the
body surface.

intrainment force—(or frictional drag). Motion
induced in water in physical contact with a re-
gion of relatively high velocity. (20)

intrusive rocks—(or irrwptive rocks). Igneous
rocks which while molten, have penetrated into
and between other rocks but which have solidi-
fied before reaching the surface of the earth or
the sea floor/water interface. They may either
have penetrated fissures in the original rocks or
absorbed and replaced the original rocks.

IRRADIANCE

inverse cylindrical orthomorphic projection—
See transverse Mercator projection.

inverse estuary—An estuary in which evapora-
tion exceeds land drainage plus precipitation,
with resulting mixture of high salinity estuarine
water and sea water.

inverse law—WSce spreading of sound.

inverse Mercator projection—Sce transverse
Mercator projection.

inversion layer—A layer of water in which tem-
perature increases with depth. (25)

invertebrate—Any animal without a backbone or
spinal column.

inverted tide—Sce reversed tide.

ion—An electrically charged group of atoms either
negative or positive. ‘The dissolved salts in sea
water dissociate into ions.

ion exchange—A chemical process involving the
reversible interchange of ions between a solution
and a particular solid material such as an ion ex-
change resin consisting of a matrix of insoluble
material interspersed with fixed ions of opposite
charge. (70)

ionization—Any process by which a neutral atom
or molecule loses or gains electrons, thereby
acquiring a net charge; the process of producing
ions. (41)

ionizing particle—A particle that directly pro-
duces ion pairs in its passage through a sub-
stance. In practice it is a charged particle
having considerably greater kinetic energy than
the ionizing energy appropriate to the medium.
(41)

ionizing radiation—Any electromagnetic or par-
ticulate radiation capable of producing ions,
directly or indirectly, in its passage through
matter. (70)

ion pair—A positive ion (cation) and a negative
ion (anion) (usually, an electron) that have
charges of the same magnitude and are formed
from a neutral atom or molecule by the action of
radiation. A primary ion pair is an ion pair
produced by a primary particle or photon.
(41)

Irish moss— (or carrageen, carragheen). One of
several species of red algae, but particularly
Chondrus crispus, having a short bushy form
and often forming a carpet on rocks in the
lower intertidal zone. Carrageenin, or carra-
gheenin is prepared irom this alga.

Irminger Current—An ocean current that is one
of the terminal branches of the Gulf Stream
system (part of the northern branch of the
North Atlantic Current) ; it flows west off the
south coast of Iceland.

A small part of the Irminger Current turns
clockwise around the west coast of Iceland but
the greater amount turns southwest, and joins
the East Greenland Current.

irradiance—(or zrradiation). The total radiant
flux received on a unit area of a given real or
imaginary surface. This is a general term for

IRRADIANCE

the flux density of electromagnetic radiation,
and is to be distinguished from illuminance.
5

pees a (at a point of the surface)—The radi-
ant flux incident on an infinitesimal element of
surface containing the point under considera-
tion, divided by the area of that element. Unit
of measurement is watt per square meter
(W/m?). (8)

irradiance meter—A radiant flux meter with
plane (usually circular) cosine collecting sur-
face (usually an opal glass) of effective area A.
If / is the radiant flux recorded by the meter,
then the associated irradiance is by definition
H=F/A. (8)

irradiance (on a vertical plane)—The radiant
flux on an infinitesimal element of a vertical
surface (90 degrees) containing the point under
consideration, divided by the area of that ele-
ment. Unit of measurement is watt per square
meter (W/m?). (8)

irradiance ratio (reflectance)—The ratio of the
upward to the downward irradiance at a depth
in thesea. (8)

irradiation (at a point of a surface)—The prod-
uct of an irradiance and its duration. Unit
of measure is Joule per square meter (J/m?).
(8)

irrotational wave—A wave in which the particles
have an irrotational movement, that is, the rota-
tion vector is nil and consequently the speeds
are derived from potential energy.

Tn a rotational movement the rotation vector
is not nil, there is no velocity potential; any in-
finitely small element of the liquid is moved
not only by translation along three axis (pro-
ducing a change in form) but also by a rotation.

irruptive rocks—Scee intrusive rocks.

Isaac-Kidd midwater trawl—A device designed
to collect actively swimming marine organisms
from subsurface ocean layers. The midwater
trawl consists essentially of a towing bridle, a
net, and an inclined-plane surface placed in
front of the net to act as a depressor. When
streamed, the trawl shape is that of an asym-
metrical cone with a large pentagonal mouth
opening on one end and a small perforated col-
lecting can on the other.

isabnormal—See isanomal.

isallotherm—Lines connecting points in which
an equal temperature variation is observed
within a definite interval.

isanomal—A line connecting points of equal
variations from a normal value.

isaurore—See isochasm.

isentropic—Of equal or constant entropy with
respect to either space or time. (5)

island—A_ body of land surrounded by water;
relatively smaller than a continent. (30)

island are—A term used for a group of islands
usually having a curving archlike pattern, gen-
erally convex toward the open ocean, with a

88

deep trench or trough on the convex side and
usually enclosing a deep sea basin on the con-
cave side; not considered a recommended term
by the ACUF.

island ice—An ice sheet covering an island. See
ice island. (68)

island shelf—(or insular shelf). See conti-
nental shelf.
island slope—(or insular slope). See conti-

nental slope.

islet—A small island. (380)

isoanomal—See isanomal.

isoballast lines—A set of lines, on the submarine
bathythermograph chart, starting from a set of
selected points on the temperature scale and
passing through all points for which the net
change in buoyancy resulting from changes in
water temperature and depth, is zero for a
submarine of given compression.

isobar—1. A line on a chart connecting all points
of equal or constant pressure; an isopleth of
pressure. (5)

2. One of several nuclides having the same
number of nucleons in their nuclei and hence
having approximately the same atomic mass.
For example, P?? and S* are isobars. Com-
monly, one of several nuclides of the same mass
number but different atomic numbers. Origi-
nally called isobares but the name isobars is
now general employed. (41, 70)

isobaric surface—A surface where the pressure
is everywhere the same. This is not necessarily
a horizontal surface. If several parallel equally
spaced plane surfaces are used to cut an isobaric
surface into horizontal sections a pattern of
isobaric lines is formed. If the lines are closely
spaced, the pressure gradient is strong, less close
spacing indicates a weaker gradient.

isobath—(sometimes called fathom curve, depth
contour, and depth curve). A contour line con-
necting points of equal water depths on a chart.

isobathytherm—A line or surface showing the
depths in oceans or lakes at which points have
the same temperature. Isobathytherms are
usually drawn to show cross sections of the
water mass. (5)

isochasm— (also called zsawrore). A line connect-
ing points having the same average frequency
of auroras. (68)

isochrone—A line on a chart connecting all points
having the same time of occurrence of particular
phenomenon or of a particular value of a quan-
tity, for example, a line representing all points
having the same time difference in the reception
of signals from two radio stations such as the
master and slave stations of a Loran rate.

isoclinic line—A line drawn through all points on
the earth’s surface having the same magnetic
inclination. The particular isoclinic line drawn
through points of zero inclination is given the
special name of aclinic line. (5)

isodynamic—A line connecting points of equal
magnitude of any force. (5)

isogal—A contour line of equal gravity values on
the surface of the earth.

isogonic line—In the study of terrestrial mag-
netism, a line drawn through all points on the
earth’s surface having the same magnetic
declination; not to be confused with magnetic
meridian. The particular isogonic line drawn
through all points having zero declination is
called the agonic line. (5)

isogram—(or isoline). Seeisopleth.

isohaline—1. Of equal or constant salinity.

2. A line on a chart connecting all points of

equal salinity; an isopleth of salinity.

5)
ie A line drawn through geographical
oints recording equal amounts of precipitation
uring a given time period or for a particular
storm. (5)

2. A line which connects places with equal

average total preciptation.

isoline—See isopleth.

isomegathy—A chart showing the distribution of
sediments in terms of median grain size.
Isomegathies are lines connecting points of
equal median grain size. (2)

isomer—1. An element, compound, or atomic
nucleus having the same atomic number and
mass number but differing in one or more prop-
erties, as is the rate of radioactive decay.

One of several nuclides having the same num-
ber of neutrons and protons but capable of
existing, for a measurable time, in different
quantum states with different energies and
radioactive properties. Commonly, the isomer
of higher energy decays to one with lower
enerey by the process of isomeric transition.

0
2 Literally, equal parts. A British term for
a line on a chart along which an equal percent-
age of the annual precipitation falls in a given
month or season.

isopach—(or tsopachous, tsopachyte). A con-
tour line on a chart drawn through points of
equal thickness of a sedimentary layer.
isopachous—See isopach.
isopachyte—A British term for isopach.
isopag—A line connecting points where ice is
a for the same number of days per year.
68
isopectic—A line connecting points at which ice
begins to form at the same time of the winter.
A line connecting points at which ice melts at the
ce time of the spring is called an isotac.
68
isopiestic—A term denoting equal or constant
pressure.
isopleth—A line of equal or constant value of a
given quantity, with respect to either space or
time. ;

89

ISOSTATIC CORRECTION

oints of
density.

isopod—One of an order (Isopoda) of generally
flattened crustaceans. They are mostly scaven-
gers. Several members burrow into wood. See
marine borers.

isopor—A line sometimes found on magnetic
joan showing points of equal annual change.

28)

isopycnic—1. Of equal or constant density, with
respect to either space or time; equivalent to an
isostere.

2. A line on a chart connecting all
equal or constant density ; an isopleth of

3. Short form for isopyenic line.

isopycnic line—A line of equal or constant den-
sity. It is equivalent to an isostere. (5)

isopycnic surface—A surface of constant density.
A particle of water of a certain density moves
along an isopycnic surface or, if forced away
from this surface, will seek to return to it.

isostasy—A condition of approximate equilibrium
in the outer part of the earth, such that
the gravitational effect of masses extendin
above the surface of the geoid in continenta
areas 1s approximately counterbalanced by a
deficiency of density in the material beneath
those masses, while the effect of deficiency of
density in ocean waters is counterbalanced by an
excess of density of the material under the
oceans.

isostatic adjustment—The process of restoring
and maintaining that condition of equilibrium
in the so-called crust of the earth which is known
as isostasy.

The distribution of material in the outer part
of the earth is undergoing continual change by
the operation of erosion, sedimentation, and
other natural forces. The unbalanced condition
which would naturally result from such disturb-
ing processes is offset by the movement of ma-
terial at considerable depths below the surface
of the earth. (87)

isostatic anomaly—The difference between an
observed value of gravity and a theoretical
value at the point of observation which has been
corrected for elevation of the station above the
geoid and for the effect of topography over the
whole earth and for its isostatic compensation.
(37)

isostatic compensation—The departure from
normal density of material in the lower part of a
column of the earth’s crust which balances (com-
pensates) landmasses (topography) above sea
level and deficiency of mass in ocean waters, and
produces the condition of approximate equilib-
rium of the earth’s crust known as isostasy.
(37)

isostatic correction—The adjustment made to
values of gravity or to deflections of the ver-
tical observed at a point to take account of the
assumed mass deficiency under topographic fea-
Beas for which a topographic correction is also
made.

ISOSTATIC EQUILIBRIUM

isostatic equilibrium—Sce isostasy.

isostere—A line of equal or constant specific
volume. Itisequivalent toanisopyenic. (5)

isotac—A line connecting points at which ice
melts at the same time of the spring. A line con-
necting points at which ice begins to form at the
same time of the winter is called an isopectic.
(68)

isotach—A line connecting points of equal rates
of speed; for example, the flow of currents.

isotherm—A line on a chart connecting all points
of equal or constant temperature; an isopleth
of temperature. (5)

isothermal—Of equal or constant temperature,
with respect to either space or time. (5)

isothermal layer—Sce mixed layer.

isothermal layer depth—See layer depth.

isotherm follower—1. A device which plots the
time change in depth of an isotherm on a chart.

9. An instrument used to study the movement

of subsurface layers of oceanic water.

isotope—1. One of several nuclides having the
same number of protons in their nuclei, and
hence belonging to the same element, but differ-
ing in the number of neutrons and therefore in
mass number A, or in energy content (isomers).
Small quantitative differences in chemical prop-
erties exist between isotopes.

90

2. A synonym for isotopic tracer.

3. A radionuclide or a preparation of an ele-
ment with special isotopic composition (allobar)
as an article of commerce, so called because of
the principal use of such materials as isotopic
tracers.

4. In common usage, synonym for nuclide
(not recommended).

(41)

isotopic tracer—The isotope or non-natural mix-
ture of isotopes of an element which may be in-
corporated into a sample to make possible obser-
vation of the course of that element, alone or in
combination, through a chemical, biological, or
physical process. The observations may be
made by measurement of radioactivity or of
isotopicabundance. (70)

isotropic—Having the same physical properties in
all directions. (68)

isovelocity—Having equal values of sound
velocity in all parts of a given water column;
no change in sound velocity with depth.

isovelocity conditions—Those conditions which
occur when the sound velocity within a layer is
constant, that is, the temperature gradient is
<0.2°C per 30 meters.

isthmus—A narrow strip of land, bordered on
both sides by water, that connects two larger
bodiesofland. (2)

Japan Current—See Kuroshio.

jellyfish—(or medusa). 1. Any of various free-
swimming coelenterates having a disc- or bell-
shaped body of jellylike consistency. Many have
long tentacles with nematocysts (stinging
cells). Some are capable of producing glowing
ball luminescence.

2. Any jellylike free-floating organism. The
term jellyfish often is applied to the cteno-
phores and may be to certain tunicates.

jetsam—WSee jettison.

jettison—The throwing overboard of objects, es-
pecially to lighten a craft in distress. Jettisoned
objects that float are termed flotsam; those that
sink, jetsam; and heavy articles that are buoyed
for future recovery, lagan. Seederelict. (68)

jetty—1. In United States terminology a struc-
ture, such as a wharf or pier, so located as to in-
fluence current or protect the entrance to a har-
bor or river. A jetty extending into the sea to
protect the coast from erosion is called a groin.
A jetty which breaks the force of the sea at any
place is called a breakwater. A jetty, wall, or
bank, often submerged, built to direct or confine
the flow of a river or tidal current is called a
training wall. A wall or embankment along a
waterfront, to resist encroachments of the sea,
is called a sea wall.

207-109 O— 66-7 91

2. In British terminology a pier, usually
of solid construction, intended as a berthing
place for ships.

(68)

jingle shell—One of a family (Anomiidae) of
rounded bivalves with asymmetrical, thin al-
most transparent valves. The individuals are
attached to firm surfaces by a calcified byssus
projecting through a hole in the lower smaller
valve. These organisms are abundant foulers
in some regions.

Jog-Log—A towed electrode that can detect ocean
electric current induced by magnetic disturb-
ances.

joint—A fracture in a rock, generally vertical or
transverse.to bedding, along which no appre-
ciable movement has occurred. (2)

Joule—A unit of energy equal to 10% ergs or to
0.2389 calories. (5)

juvenile water—Water that enters for the first
time into the hydrologic cycle. It is released
from igneous rocks through volcanic activity
at a rate probably not exceeding 0.1 cubic kilo-
meter per year. (32)

juvenile wave platform—A shoal nearshore bot-
tom consisting of rock, jagged reefs, cobbles, and
boulders and having little material easily mov-
able by waves. It represents the stage before
planation by wave erosion.

K

kalema—A very heavy surf breaking on the
Guinea coast of Africa during the winter. (5)

kaolin—See kaolinite.

kaolinite—A common clay mineral, hydrous
aluminum silicate, formed by the replacement
or alteration of feldspars or other minerals.
Kaolin is rock composed principally of
kaolinite.

katabatie wind—(or gravity wind). Any wind
blowing down an incline. If the wind is warm,
it is called a foehn; if cold, it may be a fall wind
ora gravity wind.

kay—See cay.

kelp—1. One of an order (Laminariales) of
usually large, blade-shaped, or vinelike brown
algae (principally American usage). Repre-
sentative species are the giant kelp (J/acrocys-
tis pyrifera), bull kelp (Nereocystis luetkeana
or Durvillea antarctica), elk kelp (Pelagophy-
cus porra), and laminarians (species of
Laminaria).

2. The burnt ash of rockweeds or laminarians
produced by Europeans since the 17th century
and still used around the world as a source of
sodium carbonate, potash, and iodine.

Kelvin temperature scale—(abbreviated K;
also called absolute temperature scale). An
absolute temperature scale independent of the
thermometric properties of the working sub-
stance. For convenience the Kelvin degree is
identified with the Celsius degree (O°K=
—273.16°C). Therefore, the ice point in the
Kelvin scale is 273.16°K. (5)

Kelvin wave—A type of tide progression in rela-
tively confined water bodies (such as the North
Sea) where because of coriolis force the tide
wave is higher to the right of direction of ad-
vance (in the Northern Hemisphere). How-
ever, upon reflection from a landmass the pro-
gression reverses direction and consequently the
tide wave is higher on the opposite coast.

key—A low island ora reef. See cay. (68)

killer whale—The largest member (Orcinus
orca) of the dolphin family (Delphinidae),
having worldwide distribution. Although this
animal has been implicated in several attacks
upon boats containing men and in bumping sea
ice bearing men, no documented fatality is
known.

Kilogram-calorie—(abbreviated K: cal, kg-cal,
Cal). See calorie.

92

kilometer—(abbreviated km). The unit of dis-
tance measurement in the metric system equal
to 0.62 statute mile or 0.54 nautical mile. A
statute mile equals 1.61 kilometers; a nautical
mile equals 1.85 kilometers. (4)

kinetic energy—The energy which a body pos-
sesses aS a consequence of its motion, defined as
one-half the product of its mass and the square
of its speed, 14 mv*. The kinetic energy per unit
volume of a fluid parcel is thus 14pv*, where p is
the density and v the speed of the parcel. (5)

In a progressive oscillatory wave, a summa-
tion of the energy of motion of the particles
within the wave. This energy does not advance
with the wave form.

kingdom—VSee classification of organisms.

Kirchoff’s law—The radiation law which states
that at a given temperature the ratio of the emis-
sivity to the absorptivity for a given wave-
length is the same for all bodies and is equal to
the emissivity of an ideal black body at that tem-
perature and wavelength. (5)

kneaded gravel—Gravel or conglomerate trans-
ported by mud flows. (2)

knoll—An elevation rising less than 500 fathoms
(1,000 meters) from the sea floor, and of limited
extent across the summit. (62)

knot—A speed unit of one nautical mile (6,076.12
feet) per hour. It is equivalent to a speed of
1.688 feet per second or 51.4 centimeters per
second.

Knudsen’s Tables—Tables published by Martin
Knudsen in 1901 (““Hydrographical Tables”), to
facilitate the computation of results of sea water
chlorinity titrations and hydrometer readings,
and their conversion to salinity, density, and
sigma-t. (5)

K, constituent—The lunisolar diurnal constitu-
ent of the theoretical tide-producing forces.
(See figure for partial tide.)

kraken—See giant squid.

krill— (Norwegian kril). A term used by whalers
and fishermen for euphausiids.

K, constituent—The lunisolar semidiurnal con-
stituent of the theoretical tide-producing
forces. (See figure for partial tide.)

Kullenberg corer—A coring device (piston or
gravity fall) used to obtain 2-inch diameter core
samples. The sampler consists of a weight
stand on which removable weights can be placed,

KYMATOLOGY

a core barrel (generally of 12-foot length),core Kuroshio extension—A general term for the

cutter, core catcher, and a tripping arm if used warm, eastward-transitional flow that connects
with piston. the Kuroshio and the North Pacific Current.
kuppe—The German term for dome. Kuroshio system—A system of ocean currents
Kuroshio— (also called Japan Current). A fast which includes part of the North Equatorial
ocean current (2 to 4 knots) flowing northeast- Current, the Tsushima Current, the Kuroshio,
ward from Taiwan to Ryukyu Islands and close and the Kuroshio extension.
to the coast of Japan to about 150°E. K value—The reciprocal of the difference bet ween
The Kuroshio originates from the greater part the coefficient of the thermal expansion of
of the North Equatorial Current, which mercury and that of the type glass used in a

divides east of the Philippines. Beyond 150°E thermometer. (67)
it widens to form the slower moving North kymatology—The science of waves and wave
Pacific Current. motion.

93

Labrador Current—A current that flows south-
ward from Baffin Bay, through the Davis Strait,
and southeastward along the Labrador and New-
foundland coasts. East of the Grand Banks of
Newfoundland the Labrador Current meets the
Gulf Stream, and the two flow eastward as the
North Atlantic Current.

LaCoste-Romberg (zero length spring) gravi-
meter—A long-period vertical seismograph su-
spended system adapted to the measurement of
gravity differences.

LaFond’s Tables—A set of tables and associated
information for correcting reversing thermom-
eters and computing dynamic height
anomalies, compiled by E. C. LaFond and pub-
lished by the U.S. Naval Oceanographic Office
as H.O. Publication 614.

lagan—Scee jettison.

lag coefficient—Scee time constant.

lagging of the tide—(also called daily retarda-
tion, retardation). he periodic retardation in
the time of occurrence of high and low water
due to changes in the relative positions of the
moon and the sun. The opposite effect is called
priming of the tides.

lag gravel—Residual accumulations of coarse
particles from which the fine material has been
winnowed by currents unable to move the coarse
material.

lagoon—A shallow sound, pond, or lake generally
separated from the open sea. (See figures for
atoll and coral reef.)

lagoon beach—The lagoonward facing beach of
reef islands. (56) See figure for atoll.)

lagoon channel—Properly refers to a naviga-
tional channel or pass through a reef and into
and through the lagoon. It has been applied
to the lagoon itself. (See figure for coral reef.)

lagoon cycle—The time required and sequence of
events involved in the filling of a lagoon by
sediments followed by their erosion by wave
action and eventual refilling by deposition.

lagoon floor—The undulating to nearly level floor
of the lagoon. (56) (See figure for atoll.)

lagoon reef margin—The lagoonward margin of
the reef or island in anatoll. (56) (See figure
for atoll.)

lagoon slope—The border zone of the lagoon that
slopes downward from the lagoon reef margin
or lagoon beach to the lagoon floor. (56)
(See figure for atoll.)

94

Lagrangian current measurement—Direct ob-
servation of the current speed and/or direction
by a recording device such as a parachute
drogue, which follows the movement of a water
mass through the ocean. See Eulerian current
measurement. (73)

laguna—A shallow coastal sound, channel, or lake
connected with thesea. (48)

Lambert conformal conic projection—A con-
formal projection in which all materials are
represented by straight lines that meet in a com--
mon point beyond the limits of the map, and
the parallels, are concentric circles whose center
is at the point of intersection of the meridians.
Meridians and parallels intersect in right angles,
and angles on the earth are correctly represented
on the projection. This projection may have
one standard parallel] along which the scale is
held exact; or there may be two such standard
parallels, both maintaining exact scale. (37)

Lambert’s formula—A formula for computing
the mean wind direction from a series of observa-
tions. It mayybe written: pe oT:

E—[W{NE+SE—NW—SW) cos 45°]

N—[S{NE+NW—SE—SW) cos 45°] _
where « is the mean wind direction, and each
point of the compass replaced by the number of
observations of wind from that direction. (5)

lamellibranch—See bivalve.

lamina—1. A sediment or sedimentary rock layer
less than one centimeter thick visually separable
from the material above and below. Lamina-
tion refers to the alternation of such layers
which differ in grain size or composition. (2)

2. (or blade, frond). The expanded and/or
elongate portion of the thallus of an alga.
laminar flow—(also called sheet flow, streamline
flow). <A flow in which the fluid moves smooth-
ly in streamlines in parallel layers or sheets; a
nonturbulent flow. See turbulent flow. (5)
lamination—See lamina.

lamp shell—Sce brachiopod.

land and sea breeze—The combination of a land
breeze and a sea breeze as a diurnal
phenomenon. (61)

land breeze—A light wind blowing from the land
caused by unequal cooling of land and water
masses. (61)

landfast ice—Sce fast ice.

land floe—An unusually thick fragment of fast
ice which has become detached from the parent
formation and isafloat. (59)

tan a=

land ice—Scee glacier, glacier ice.

landlocked—A body of water enclosed or nearly
enclosed by land, thus protected from the sea.
San Francisco Bay is a classic example.

land sky—The relatively dark appearance of the
underside of a cloud layer when it is over land
that is not snow covered. This term is used
largely in polar regions with reference to the
sky map; land sky is brighter than water sky,
but is much darker than ice blink or snow
blink. (5)

lane—1. See lead.

2. A narrow, not necessarily navigable, crack
in pack ice. It may widen into a lead. (5)
Obsolete.

3. An electronically defined area and system
of measurement used in certain electronic con-
trolled systems, such as Decca survey and
LORAC. A proportional reading of the dis-
tance between the two rates which define a lane
are taken and define a line of position.

langley—A unit of energy per unit area commonly
employed in radiation theory ; equal to one gram

calorie per square centimeter. (5)
lanternfish—Sce myctophid.
lanthanides—The rare-earth elements from
atomic numbers 58 to 71 inclusive. They have
chemical properties similar to lanthanum. (41)

lapilli— Volcanic ejecta ranging from 4 to 32
millimeters in diameter. (2)
lappered ice—See anchor ice.
lard ice—Rare. See grease ice.
large calorie—(abbreviated Cal).
large field of ice—See large ice field.
large ice field—(or large field of ice). 1. Anice
field over 20 kilometers (10.8 n. miles) across.
74
5) A Russian term for an ice field of 2 to 10
kilometers (1.1 to 5.4 n. miles) in width. All
large ice fields would fall into the current WMO
definition of big ice floe.
large ice skylight—See ice skylight.
large scale—Scee scale.
larva—An embryo which becomes self-sustaining
and independent before it has assumed the char-
acteristic features of its parents. (26)
last ice—The last appearance of ice in the waters
of a particular location, whether it melts locally
or is carried off by winds or currents.
latent heat—The heat released or absorbed per
unit mass by a system in a reversible, isobaric-
isothermal change of phase. At 0°C, the latent
heats of vaporization (or condensation), fusion,
and sublimation of water substance are, re-
spectively,
L,=597.3 cal/gm
L;=79.7 cal/gm
L;=677.0 cal/gm
latent heat of evaporation—That amount of heat
required to change one gram of water into water
vapor without a change in temperature. For

See calorie.

95

LEAD SMOKE

example, 536 calories are required to change one
gram of water to water vapor at 100°C at stand-
ard atmospheric pressure.

lateral line—A system of sense organs possessed
by fishes, usually arranged in a single series
along the side of the body, and functioning in
part to detect low frequency vibrations such as
those produced by local disturbances in the
water.

lateral shift—The offset of the position of the
peak of an anomaly with the mass of magnetiza-
tion (or gravitation).

latitude correction—The amount of the adjust-
ment of observed gravity values to an arbitrar-
ily chosen base latitude.

lava—Molten rock which issues from a volcano or
a fissure in the earth’s surface and solidifies upon
cooling. (See figure for compound volcano.)

lava delta—A delta like body of lava formed
where a lava flow enters the sea. A coast con-
sisting of such deltas formed by recent lava flows
has a convex shoreline and is called a lava-flow
coast.

lava-flow coast—Scee lava delta.

Law of Constancy of Relative Proportions—
Regardless of the absolute concentration of total
dissolved solids in sea water, the ratios between
the more abundant substances are virtually con-
stant in the world’s oceans.

Law of Universal Gravitation—Newton’s law of
gravitation. Gravitation is directly propor-
tional to the product of the masses of the two
bodies and inversely proportional to the square
of the distance between them. (387)

layer—See stratum.

layer depth—(or ¢sothermal layer depth, mixed
layer depth). In oceanography, the thickness
of the mixed layer; or the depth to the top of
the thermocline. (5)

layer depth effect—The weakening of the sound

- beam owing to abnormal spreading as it passes
from an isothermal or a positive gradient layer
to an underlying negative layer.

layer of no motion—A layer, assumed to be at
rest, at some depth in the ocean. This implies
that the isobaric surfaces within the layer are
level, and hence they may be used as reference
surfaces for the computation of absolute gradi-
ent currents. '

This same concept can define a level of no mo-
tion or a surface of no motion. (5)

lead—(or channel, lane). A navigable passage
through pack ice. (74)

A lead may be covered by young ice. From
the point of view of the submariner it becomes
an ice skylight.

lead line—(or sounding line). <A line, wire, or
cord used in sounding. It is weighted at one
end with a plummet (sounding lead). (61)

lead smoke—Sce frost smoke.

LEAST SQUARES

least squares—Any procedure that involves min-
imizing the sum of squared differences. For
example, the deviation of the mean from the
population is less, in the squared sense, than any
other linear combination of the population
values. (5)

lee—Shelter, or the part or side sheltered or
turned away from the wind or waves. (61)

lee tide—Sce leeward tidal current.

leeward—The direction toward which the wind
is blowing; the direction toward which waves
are travelling. (61)

leeward tidal current—A tidal current setting
in the same direction as that in which the wind
is blowing. (68)

leeward tide—Obsolete form. See leeward tidal
current.

lenticular—In the shape of a double convex lens.
Applied to commonly occurring lens-shaped
sediment or rock bodies of all sizes. Also ap-
plied to clouds that attain this shape in the proc-
ess of dissipation.

leptocephalus—The small, elongate, transparent,
planktonic larva of the eel (Anguilla).

lesser ebb—The weaker of two ebb tidal currents
occurring during a tidal day, usually associated
with tidal currents of mixed characteristics.
(66) See mixed current. (See figure for
current curve.)

lesser flood—The weaker of two flood tidal cur-
rents occurring during a tidal day, usually asso-
ciated with tidal currents of mixed character-
istics. (66) See mixed current. (See figure
for current curve.)

levee—An embankment bordering one or both
sides of a seachannel or the low-gradient sea-
ward part of a canyon or valley.

level ice—Ice with a flat surface, which has never
been hummocked; typical with regard to bays,
gulfs, straits, archipelagoes, and shallow waters,
where the ice formation occurs in undisturbed
conditions. (74)

level of no motion—See layer of no motion.

level surface—A surface which at every point is
perpendicular to the plumb line of the direction
im which gravity acts.

light absorption—Sce absorption.

light and dark bottle technique—Sce oxygen
technique.

light bottle—A container used for measuring
photosynthetic activity of primary producers.

light floe—In sea ice reporting, an ice floe gen-
erally less than 2 feet thick. (59)

light ice—Sea ice less than 2 feet thick.

light ice floe—See light floe.

light intensity—Sce luminous intensity.

light minerals—Detrital minerals in rock or sedi-
ments that have a specific gravity of less than
2.8 and usually are light in color. Examples
are quartz, feldspar, calcite. (2)

(68)

96

lightship—(or light vessel). A distinctively-
marked ship, anchored or moored at a charted
point, to serve as an aid to navigation. (66)

light vessel—See lightship.

lily-pad ice—Pancake ice when the cakes are not
more than about 18 inches in diameter. (68)

liman—Shallow coastal lagoon or embayment
with a muddy bottom; also a region of mud or
slime deposited nearastream mouth. (2)

lima coast—An alluvial coast usually character-
ized by many lagoons.

limestone—A general term for a class of rocks
which contain at least 80 percent of the carbo-
nates of calcium or magnesium. Varieties of
limestone take their names from the source ma-
terial, for example, algal limestone, reef lime-
stone, coquina, crinoidal limestone, etc.

limited form wave—Deformation of the wave by
the formation of a sharp crest followed by a
propagation with bubbling of water on the front
face until the final breaking into a roller.

limiting ray—The sound ray which becomes tan-
gent at the depth where the sound velocity is at
maximum.

limnology—The physics and chemistry of fresh
water bodies and of the classification, biology,
By ecology of the organisms living in them.

5)

Limnoria—(or gribble).
cean borers.

2. The common name of this group. Mem-
bers of this group are the most destructive of
the crustacean borers.

3. See crustacean borer and marine borer.

limpet—One of several suborders (Docoglossa,
Patellacea, Fissurellidae, or Zygobranchia) of
flattened cone-shaped gastropods in which the
spiral of the shell is absent or not apparent.

linear amplifier—A pulse amplifier in which the
output pulse height is proportional to an input
pulse height for a given pulse shape up to a point
at which the amplifier overloads. (70)

linear transducer—A transducer for which the
pertinent measures of all sound waves concerned
are linearly related. (69)

line hydrophone—A directional hydrophone
consisting of a single, straightline element, or
any array of contiguous or spaced electroacous-
tic transducing elements, disposed on a straight
line, or the acoustic equivalent of such an array.
(69)

line spectrum—aA spectrum whose components
occur at a number of discrete frequencies.

liquid—A state of matter in which the molecules
are relatively free to change their positions with
respect to each other but restricted by cohesive
forces so as to maintain a relatively fixed
volume. (27)

liquid limit—See Atterberg limits.

lithifaction—Scee lithification.

1. A genus of crusta-

lithification—(or Jithifaction). The processes of
induration, cementation, petrification, consoli-
dation, and crystallization which convert mag-
ma and newly deposited sediments into rock.

lithofraction—Fragmentation of rocks by wave
action on beaches.

lithoid tufa—Gray algal reeflike material form-
ing beds and the core of reef domes.

lithology—The study and description of rocks
based upon magascopic and microscopic exami-
nation of samples.

lithometeor—Sce meteor.

lithosphere—The outer, solid portion of the
earth; the crust of the earth; usually used in
contexts wherein the lithosphere is said to make
contact with the atmosphere and the hydro-
sphere. See also biosphere, geosphere. (5)
(See figure for earth structure.)

lithostrome—See lithotope.

Lithothamnion ridge—A ridge, composed of the
calcium carbonate secretions of Lithothamnion
and other red calcareous algae, which rises about
3 feet above sea level at the seaward edge of a
reef flat. The secretions of Lithothammnion and
related genera may compromise 50 percent or
more of a coral reef.

lithotope—An area and environment of uniform
sedimentation. The layer or deposit of uniform
or uniformly heterogeneous composition and tex-
ture produced in a lithotope is called a litho-
strome.

littoral—(or intertidal). The benthic zone be-
tween high and low water marks. According
to some authorities the benthonic zone between
the shore and water depths of approximately
100 fathoms (200 meters). It is also called the
littoral benthal which is subdivided into the
eulittoral and the sublittoral. The usage and
interpretation of this term varies widely in the
literature. (See figure for classification of ma-
rine environments. )

littoral benthal—See littoral.

littoral current—A current, caused by wave ac-
tion, that sets parallel to the shore; usually in
the nearshore region within the breaker zone.
See longshore current.

littoral deposits—Deposits of littoral drift, that
is, sand, gravel, and other material which moves
along the shore between high and low water
marks. Littoral drift also refers to the long-
shore movement or littoral transport of such
material by longshore currents.

littoral drift—The material moved in the littoral
zone under the influence of waves and currents.
(61) See littoral deposits.

littoral transport—The movement of material
along the shore in the littoral zone by waves and

‘currents. (61) See littoral deposits.
littoral zone—Scee intertidal zone.

live weight—See biomass.

97

LONGSHORE CURRENT

load—The quantity of sediment transported by a
current. It includes the suspended load of
small particles, which float in suspension distrib-
uted through the whole body of the current, and
the traction load, bottom load, or bed load of
large particles which move along the bottom by
traction, that is, saltation, rolling, and sliding.

loam—A soil composed of clay, silt, sand, and
organic matter. The term occasionally is used
to describe a marine sediment. (2)

lobes—If a three-dimensional representation of a
transducer directivity is made by rotating the
two-dimensional directivity pattern these sec-
tors generate zones, or regions, on the constant
distance surface. These regions are known as
lobes. The term is also used with reference to
the corresponding portions of the directivity
pattern. The region, or sector, which includes
the reference axis is known as the primary lobe;
the remaining regions, or sectors, are known as
the secondary lobes. (28)

local winds—Winds which, over a small area, dif-
fer from those which would be appropriate to
the general pressure distribution, or which po-
sess some other peculiarity. (5)

loch—(or dough). An inlet or arm of the sea,
often nearly landlocked. (68)

log line—A graduated line used to measure the
speed of a ship through the water, or to measure
a a of the current from a ship at anchor.

59

lolly ice—See frazil ice.

longerested wave—A wave, the crest width of
ay, is long compared to the wavelength.

3

longitudinal wave—(also called pressure wave,
compressional wave, irrotational wave). A
wave in which the direction of displacement of
each particle in the medium is perpendicular to
the wave front.

long-period constituent—A tide or tidal current
constituent with a period that is independent
of the rotation of the earth but which depends
upon the orbital movement of the moon or of
the earth. The period is usually longer than a
day and in general a half month or larger. See
constituent.

longshore bar—(or ball). See ball, bar.

longshore current— (also called littoral current).
The resultant current produced by waves being
deflected at an angle by the shore. In this
case the current runs roughly parallel to the
shoreline. (See figure for nearshore current
system.)

The longshore current is capable of carrying
a certain amount of material depending upon its
velocity and the particle size of the material;
however, any obstruction, such as a submarine
rock ridge or a land point cutting across the
path of the current will cause loss of velocity
and consequent loss of carrying power.

LONG WAVE

long wave—In oceanography, same as shallow
water wave. (5)

long-wave radiation—See infrared radiation.

looming—An apparent elevation of distant ter-
restrial objects caused by abnormal atmospheric
refraction. Because of looming, objects below
the horizon are sometimes visible. The opposite
is Sinking. (68)

loop—1. That part of a standing wave or
clapotis where the vertical motion is greatest
and the horizontal velocities are least. Loops
(sometimes called antinodes) are associated with
elapotis and with seiche action resulting from
resonant wave reflections in a harbor or bay.

61
a A pattern of field observations. Such a
pattern is useful in correcting for drift in grav-
ity meter observations.

loop bar—A bar formed by the junction of the
ends of two spits on the mainland side of an
offshore island undergoing wave erosion.

loose ice—Sce broken ice.

loose pack ice—Broken ice which is easily nav-
igable. (59)

Loran—A long-range electronic navigation sys-
tem which uses the time divergence of pulse-
type transmission from two or more fixed sta-
tions. (This term is derived from the words
“Jong-range navigation.”) (63)

lough—See loch.

love wave—(or Q@ wave). A transverse wave
propagated along the boundary or two elastic
media, both of which have rigidity; that is,
both media must be capable of propagating
transverse waves. A surface seismic wave in
which the particles of an elastic medium, vibrate
transverse to the direction of the wave’s travel,
with no vertical component. (35)

low—1. A cyclone, or area of low atmospheric
pressure. (68)

2. A submarine depression of any size or
shape; also called a bathymetric low.

low energy environment—A region character-
ized by a general lack of wave or current motion,
permitting the settling and accumulation of very
fine-grained sediment (silt and clay). (2)

lower high water—(abbreviated LHW). The
lower of two high waters of any tidal day where
the tide exhibits mixed characteristics. See
mixed tide.

lower high water interval—(abbreviated
LHWI). The interval of time between the
transit (upper or lower) of the moon over the
local or Greenwich meridian and the next lower
high water. This expression is used when there
is considerable diurnal inequality. See luni-
tidal interval. (68)

lower low water—(abbreviated LUW). The
lower of two low waters of any tidal day where
the tide exhibits mixed characteristics. See
mixed tide.

98

lower low water datum—An approximation of
mean lower low water that has been adopted
as a standard datum for a specific area although
it may differ slightly from a later determination.

lower low water interval— (abbreviated LLW1).
The interval of time between the transit (upper
or lower) of the moon over the local or Green-
wich meridian and the next lower low water.
This expression is used when there is consider-
able diurnal inequality. See lunitidal inter-
val. (68)

lower transit—Scee transit.

lowest low water—(or lowest normal low water).
A plane of reference whose distance below mean
sea level corresponds with the mean level of
lowest low water of any normal tide.

lowest low water springs—A plane of reference
approximating the mean level of lowest low
water during syzygy (spring tides).

lowest normal low water—Sce lowest low water.

low tide—Scee low water.

low velocity layer—Any layer in which the veloc-
ity of compressional wave propagation is lower
than in the adjacent layers. Such a layer can
act as an efficient channel for the propagation
of elastic waves for great distances. (2)

low water— (abbreviated LW;; or low tide). The
lowest limit of the surface water level reached
by the lowering tide. Low water is caused by
the astronomic tide-producing forces and/or
the effects of meteorological conditions.

low water datum—An approximation of mean
low water which has been adopted as a standard
datum for a specific area although it may differ
slightly from a later determination.

low water equinoctial springs—Low water
springs near the times of the equinoxes.

low water full and change—The average inter-
val of time between the transit (upper or lower)
of the full or new moon and the next low water.
(68)

low water inequality—See diurnal inequality.

low water interval—(abbreviated LWI). See
lunitidal interval.

low water line—The intersection of the plane of
low water with the shore; it varies daily with
changing lunar phases and meteorological con-
ditions.

low water lunitidal interval—Sce lunitidal in-
terval.

low water neaps—See mean low water neaps.

low water of ordinary spring tides—(abbrevi-
ated LWOST). A tidal datum appearing in
some British publications, based on low water
of ordinary spring tides. (61)

low water quadrature—See mean low water
neaps. 3

low water springs—See mean low water springs.

low water stand—The condition at low tide when
there is no change in the height of the water
level. A similar condition at high tide is called
high water stand. (68)

loxodrome—Sce rhumb line.

luciferase—An enzyme which is heat labile, has
protein characteristics, and catalyzes the oxida-
tion of luciferin in bioluminescence.

luciferin—A group of heat-stable compounds con-
taining amino acids and showing properties of
polypeptides. Bioluminescence is produced
when these compounds are oxidized by the cata-
lytic action of luciferase. See also oxylucif-
erin.

lumachelle—Shell conglomerate formed of mol-
lusk shells which have been consolidated into
cemented aggregates. (2)

luminance—(also called brightness). In _pho-
tometry, a measure of the intrinsic luminous
intensity emitted by a source in a given direc-
tion. It may be defined as the illuminance pro-
duced by light from the source upon a unit
surface area oriented normal to the line of sight
at any distance from the source, divided by the
solid angle subtended by the source at the re-
ceiving surface. It is assumed that the medium
between source and receiver is perfectly trans-
parent; therefore, luminance is independent of
extinction between source and receiver. The
source may or may not be self-luminous.

Luminance is a measure only of light; the

comparable term for electromagnetic radia-
tion in general is radiance. (5)

luminescence—(or biolwminescence, phosphores-
cence). Any emission of light at temperatures
below that required for incandescence. (5)

luminous intensity—(or candle power, light in-
tensity). The intensity (flux per unit solid
angle) of visible radiation weighted to take into
account the variable response of the human eye
as a function of the wavelength of radiation.
The basic unit for luminous flux is the lumen.

(5)

lunar day—(or tidal day). The interval between
two successive upper transits of the moon over a
local meridian. The period of the mean lunar
day, approximately 24.84 solar hours, is de-
rived from the rotation of the earth on its axis
relative to the movement of the moon about the
earth.

lunar declination—The angular distance of the
moon expressed in degrees north or south of the
celestial equator ; 1t is indicated as positive when
north, and negative when south of the equator.

99

L-Z GRAPH

Maximum declination is about 2814 degrees
and minimum declination about 1814 degrees,
depending on the longitude of the moon’s node.
Tides or tidal currents occurring near times of
maximum north or south declination are called
tropic tides or tidal currents. The moon’s dec-
linational cycle of 271% days is called a tropical
month. (50)

lunar interval—The time difference between the
moon’s transit of the Greenwich meridian and
a local meridian. (50)

lunar tide—That part of the tide caused solely
by the tide-producing forces of the moon as
distinguished from that part caused by the forces
of the sun. (50)

lunar transit—Scee transit.

lunate bar—Sce bar.

lunation—The period during which the moon
completes all its phases from one new moon to
the next new moon; approximately 29.5 days.

lunicurrent interval—l. The interval between
the moon’s transit (upper or lower) over a local
or the Greenwich meridian and a specified phase
of the tidal current following the transit, such
as Strength of flood and ebb or slack water.
The interval is described as local or Greenwich
according to whether the reference is to the
moon’s transit over the local or Greenwich me-
ridian. (50)

2. See strength of flood interval, strength

of ebb interval.

lunitidal interval—The interval between the
moon’s transit (upper or lower) over the local
or Greenwich meridian and the following high
or low water. The average of all high water
intervals for all phases of the moon, the mean
high water lunitidal interval, is abbreviated to
high water interval. Similarly, the mean low
water lunitidal interval is abbreviated to low
water interval. The high water or low water
interval is described as local or Greenwich ac-
cording to whether the reference is to the transit
over the local or the Greenwich meridian. (50)

lutaceous—Scee lutite.

lutite— (sometimes spelled lutyte). Sediments or
sedimentary rock composed of mud (silts and/
orclays). (2)

L-Z graph—A graph used to determine in situ
depths of oceanographic observations by the
wire depth minus thermometric depth method.

M

machinery noise—Noise produced by the main
propulsion plant, reduction gears, propeller
shafts, auxiliary machinery, and the under-
water discharges from the ship.

macroplankton—Plankton organisms within the
size range 1 millimeter to 1 centimeter. Some-
times referred to as mesoplankton. Formerly
the term included megaloplanktonic forms. See
megaloplankton, mesoplankton.

madrepore—A branching or stag-horn coral, also
any perforated stone coral. (2)

maelstrom—A confused and often destructive
current usually caused by the combined effects of
high, wind-generated waves and a strong oppos-
ing tidal current: the rapid flows may follow
eddying patterns or circular paths with whirl-
pool characteristics. Named after the fre-
quently cited phenomenon along the south shore
of Moskenesoy Island in the Lofoten Islands off
the Norway coast; here, the maelstrom reaches
its strength when the tidal current ebbs west-
ward with spéeds up to 9 knots at springs during
a strong opposing westerly wind. Similar
phenomena occur in Pentland Firth, Scotland
and off Cape de la Hague, Normandy.

magma—Mobile rock material generated within
the earth from which igneous rock is derived by
solidification. When extruded it is called lava.
(See figure for compound volcano. )

magnetic anomaly—A distortion of the regular
pattern of the earth’s magnetic field due to local
concentrations of ferromagnetic minerals.

magnetic declination—At any point, the angle
between the direction of the horizontal com-
ponent of the earth’s magnetic field and true
north.

magnetic deviation—The angle between the mag-
netic meridian and the axis of a compass card,
expressed in degrees east or west to indicate the
deviation in which the northern end of the com-
pass card is offset from magnetic north. Devia-
tion is caused by disturbing magnetic influences
in the immediate vicinity of the compass, as
within the craft. (68)

magnetic dip—(also called dip, inclination). The
angle which the magnetic lines of force make
with the plane of the horizon. (42)

magnetic disturbance—(also called magnetic
storm). Irregular, large amplitude, rapid time
changes of the earth’s magnetic field which oc-
cur at approximately the same time all over the
earth. (24)

magnetic diurnal variation— (also called diwrnal
variation, daily variation). Oscillations of the
earth’s magnetic field which have a periodicity
of about a day and that depend to a close ap-
proximation only on local time and geographic
latitude. (15)

magnetic elements—The declination (J), the
horizontal intensity (47), the vertical inten-
sity (Z), the total magnetic intensity (/), the
inclination or dip (/), the strength of the force
toward geographic north (XY), and the strength
of the force toward geographic east (Y).

magnetic equator—(also called aclinic line, dip
equator). The imaginary line on the earth’s
surface where the magnetic inclination is zero
degrees, that is, the magnetic field is horizontal.

magnetic field—A region in which a magnetic
influence exists. See magnetic field intensity.

magnetic field intensity—(also called magnetic
intensity, magnetic field, magnetic field
strength). The magnetic force exerted on an
imaginary unit magnetic pole placed at any
specified point of space. It is a vector quantity.
Its direction is taken as the direction toward
which a north magnetic pole would tend to move
under the influence of the field. If the force is
measured in dynes and the unit pole is a cgs
unit pole, the field intensity is given in oersteds.

Prior to 1932 the oersted was called the

gauss: but the latter term is now used to meas-
ure magnetic induction (within magnetic ma-
terials), while oersted is reserved for magnetic
force. By definition, one magnetic line of force
per square centimeter (in air) represents the
field intensity of one oersted. (5)

magnetic field strength—See magnetic field
intensity.

magnetic inclination— (or dip).
dip.

magnetic intensity—See magnetic field inten-
sity.

magnetic latitude—At any point on the earth’s
surface the angle whose tangent is one-half the
tangent of the magnetic dip at that point. (36)

magnetic meridian—<At any point, the direction
of the horizontal component of the earth’s
magnetic field.

magnetic pole—1. (also called dip pole). A place
where the actual earth’s magnetic pole is vertical.

2. In magnetic theory, a fictitious entity anal-

ogous to a unit electric charge of electrostatic

See magnetic

100

theory. In nature only dipoles, not isolated
magnetic poles, exist. (5)

magnetic secular change—The slow change over
many years of either intensity or direction of
the earth’s magnetic field due to causes lying
deep within the earth.

magnetic storm—Sce magnetic disturbance.

magnetic variation—1. Changes in the magnetic
field with time or space.

2. Magnetic declination.

magnetometer—An instrument for measuring
the intensity and/or direction of the earth’s
magnetic field.

magnetostriction transducer—A _ transducer
that depends for its operation on the interaction
between the magnetization and the deformation
of a material having magnetostrictive proper-
ties.

magnitude—1. In mathematics, a number as-
signed to a quantity, by which the quantity may
be compared with other quantities of the same
class.

2. A quantity which represents the total
energy released by an earthquake, as contrasted
to “intensity,” which describes its effects at a
particular place. In 1935 C. F. Richter de-
vised the magnitude scale in current use. The
Richter magnitude scale ranges numerically
from near 0 to about 8.5. The smallest shocks
felt have a magnitude of 1.5, which represents
an energy release of about 10% ergs. A magni-
tude 5 shock represents the release of 10°' ergs of
energy, which is equivalent to the energy re-
leased by 20,000 tons of TNT.

3. The intensity of a short- period magnetic
fluctuation, usually expressed in milligausses or

gammas.

major constituents—Those chemical elements
present in sea water which together make up over
99.9 percent of the known dissolved solid con-
stituents of sea water. These include the follow-
ing ions: chloride, sulfate, bicarbonate, bro-
mide, fluoride, boric acid, sodium, magnesium,
calcium, potassium, and strontium.

makatea—The raised fin of a coral reef.

manatee—Any of the three species of sea cow
which constitute the genus 7richechus. All
three are confined to shallow tropical marine
waters, estuaries, and rivers on both sides of the
Atlantic Ocean. The tail is broad and rounded,
not whalelike as in the dugong.

manateegrass—Sce seagrass.

manganese nodules—S¢ee nodules.

mangrove—One of several genera of tropical
trees or shrubs which produce many prop roots
and grow along low-lying coasts into shallow
water.

manta ray—(or devilfish). One of a family
(Mobulidae) of large rays. This is the largest
of the rays, with widths over 20 feet and w eights
over 3,000 pounds having been recorded. “See
ray.

101

MARINE BENCH

mantle—(also called asthenosphere). The rela-
tively plastic region between the crust and core
of the earth. (See figure for earth structure.)

mantle rock—Scee regolith.

many-year ice—See artic pack (sense 2).

map—A representation on a plane surface, at an
established scale, of the physical features (nat-
ural, artificial, or both) of a part or the whole of
the earth’s surface, by means of signs and sym-
bols, and with the means of orientation indi-
cated. (37)

marginal basin—This term is not recommended
by the ACUF for a basin at the foot of a con-
tinental slope bounded by an outer ridge. See
basin.

marginal conglomerate—Coarse pebble deposits
along the shore which form the landward mar-
gins or facies of other types of sediments into
which they grade. (2)

marginal crushing—The destruction of the outer
edges of ice cakes because of collision of the
cakes. (65)

marginal deep—This term is not recommended
by the ACUF for a narrow linear zone of deep
water adjacent to an island are. See trench,
trough.

marginal platform—This term is not recom-
mended by the ACUF for a shelf adjacent to a
continent and similar topographically to a con-
tinental shelf but located at a greater depth
that may reach 1,250 fathoms. See terrace,
plateau.

marginal seas—(or adjacent seas). Semienclosed
seas adjacent to, widely open to, and connected
with the oceans at the water surface but bounded
at depth by submarine ridges; for example,
Yellow Sea. When shallow (less than about 150
fathoms) they are called shelf seas; for exam-
ple, Hudson Bay.

marginal trench—This term is not recommended
by the ACUF for a trench which parallels the
continental trend between the base of the con-
tinental slope and abyssal plain. See trench,
trough.

marginal zone—The outer (seaward) ridge and
generally the highest portion of a coral reef.
(2)

marigram—A graphic record of the rise and fall
of the tide in the form of a curve which shows
the time of any stage of the tide represented by
abscissas and the height in feet by ordinates.
(50) (See figure for tide curve.)

marigraph—Sec tide gage.

marine abrasion— The erosion of a bedrock sur-
face by wave movement of sand and gravel.

marine alluvium—A contradiction in terms which
is best avoided. Use marine sediment.

marine arch—Sce sea arch.

marine bench—A small wave eroded terrace
along the shore which is level or gently inclined
seaward.

MARINE BIOGEOGRAPHY

marine biogeography—The description of the dis-
tribution of marine animals and plants, and
analyses of those factors which determine the
distribution and abundance of a given species.
(25)

marine biology—The study of the plants and ani-
mals living in the sea. See biological oceanog-
raphy.

marine borer—Any marine invertebrate that ex-
cavates tunnels, holes, or depressions in one or
more of a variety of materials by abrasive, chew-
ing, or chemical action. Marine borers exist in
several phyla, including the sponges, annelids,
arthropods, mollusks, and echinoderms. The
most destructive of the borers on a worldwide
basis are the shipworms, crustacean borers,
and rock borers.

marine bridge—Sce sea arch.

marine-built terrace—A terrace seaward of a
marine-cut terrace, shore platform, or plain of
marine abrasion which consists of materials
eroded from the marine-cut terrace. (2)

marine cave—See sea cave.

marine cliff—A cliff or slope marking the inshore
limit of beach erosion. It may vary from an in-
conspicuous slope to an escarpment hundreds
of feet high. (68)

marine climate—(also called maritime climate,
oceanic climate). A regional climate which is
under the predominant influence of the sea, that
is, a climate characterized by oceanicity; the
antithesis of a continental climate.

Such a climate is found where the prevailing
winds blow onshore as on oceanic islands and
on the western coasts of the continents in middle
latitudes. It extends inland either until it meets
a climatic divide or, in level country, until it
becomes modified and gradually attains greater
continentality. A marine climate is character-
ized by small diurnal and annual ranges of tem-
perature, with retardation of the annual ex:
tremes until one or two months after each
solstice. (5)

marine-cut terrace—(or wave-cut terrace). The
level or gently sloping submerged shelf formed
along a sea coast by the erosive action of waves
and currents.

marine ecology—The science which embraces all
aspects of the interrelations of marine organisms
and their environment and the interrelations be-
tween the organisms themselves. (38)

marine environments—Sce classification of
marine environments.

marine geology—Sce geological oceanography.

marine meteorology—That part of meteorology
which deals mainly with oceanic areas, includ-
ing island and coastal regions. In particular
it serves the practical needs of surface and air
navigation over the oceans.

Since there is a close interaction between
ocean and atmosphere, and oceanic influences
upon weather and climate can be traced far

102

inland over the continents, modern meteorology
uses this name mainly for making regional or
administrative distinctions. (5)

marine salina—A body of salt water separated
from the sea by a sand or gravel barrier through
which sea water percolates. Marine salinas are
found along arid coasts where little or no inflow
of fresh water occurs. (2)

marine snow—Sce sea snow.

marining—The submergence of low-lying land by
an epicontinental sea. (2) [

maritime air—A type of air whose characteris-
tics are developed over an extensive water sur-
face and which, therefore, has the basic maritime
quality of high moisture content in at least its
lower levels. (5)

maritime climate—Sce marine climate.

marl—A calcareous clay, or a mixture of clay and
particles of calcite or dolomite and shell frag-
ments. Often applied to calcareous sediments
ranging in size from clay through sand. See
tosca.

marl ball—See algal biscuits.

marlite—Sce marlstone.

marlstone—(or marlite). An indurated mixture
of calcium carbonate and clay of which clay
comprises 25 to 75 percent. (2)

Marsden chart—A system introduced by Marsden
early in the nineteenth century for showing the
distribution of meteorological data on a chart
especially over the oceans. A Mercator map
projection is used; the world between 90°N and
80° S being divided into Marsden “squares” each
of 10 degrees latitude by 10 degrees longitude.
These squares are systematically numbered to
indicate position. Each square may be divided
into quarter squares, or into 100 one-degree sub-
squares numbered from 00 to 99 to give the posi-
tion to the nearest degree. (5)

marsh—An area of soft wet land. Flat land
periodically flooded by salt water is called a salt
marsh. Sometimes called slough. (68)

marsh bar—A narrow ridge of sand at the edge
of a marsh undergoing wave attack.

mascaret—WSce bore.

mass movement—Unit movement or slippage of
a mass of sediment down a slope, such as in a
submarine canyon, which often initiates a tur-
bidity current.

mass transport—The transfer of water from one
region to another originating from the orbital
motion of waves. (Nee figure for nearshore
current system.)

mass transport speed—The speed of the current
originating from waves.

matrix—Rock or sediment in which larger grains
are imbedded in a mass of smaller grains.

mature wave platform—A platform of marine
ubrasion which has an abundance of rocky debris
not yet reduced to pebble size by wave action.

maximum—tThe greatest value attained (or at-
tainable) by a function; the opposite of mini-
mum.

maximum ebb—The greatest speed of an ebb tidal
current. (66)

maximum flood—The greatest speed of a flood
tidalcurrent. (66)

maximum sound pressure—For any given cycle
of a periodic wave, the maximum absolute value
of the instantaneous sound pressure occurring
during that cycle.

mean—WScee arithmetic mean.

mean chart—(or mean map). Any chart on
which isopleths of the mean value of a given
oceanographic element are drawn.

mean current— (or average current, scalar mean).
The current speed and direction determined to
be the average of a total number of observations
for a specified area.

meander—A deviation of the flow pattern of a
current.

mean diurnal high water inequality— (abbrev-
lated DHQ). Half the average difference be-
tween the heights of the two high waters of each
tidal day over a 19-year period, obtained by sub-
tracting the mean of all high waters from the
mean of the higher high waters. (68)

mean diurnal low water inequality— (abbrevi-
ated DLQ). Half the average difference be-
tween the heights of the two low waters of each
tidal day over a 19-year period, obtained by sub-
tracting the mean of the lower low waters from
the mean of all low waters. (68)

mean higher high water—(abbreviated
MHHW). The average height of all the daily
higher high waters recorded over a 19-year pe-
riod, or a computed equivalent period. It is
usually associated with a tide exhibiting mixed
characteristics. See mixed tide.

mean higher high water springs— (abbreviated
MHHWS). The average height of all higher
high waters recorded during syzygy over a 19-
year period, or a computed equivalent period.

mean high water—(abbreviated MHW). The
average height of all the high waters recorded
over a 19-year period, or a computed equivalent
period. (See figure for tide range.)

mean high water lunitidal interval—See luni-
tidal interval.

mean high water neaps—(abbreviated MHWN).
The average height of all high waters recorded
during quadrature over a 19-year period, or a
computed equivalent period. (See figure for
tide range.)

mean high water springs—(abbreviated
MHWS). The average height of all high
waters recorded during syzygy over a 19-year
period, or a computed equivalent period. (See
figure for tide range.)

mean horizontal sound speed—The mean veloc-
ity along the horizontal for one cycle of a sound
ray path.

103

MEAN SEA LEVEL

mean lower low water—(abbreviated MLLW).
The average height of all the lower low waters
recorded over a 19-year period, or a computed
equivalent period. It is usually associated with
a tide exhibiting mixed characteristics. See
mixed tide. (See figure for surf zone.)

mean lower low water springs—(abbreviated
MLLWS). The average height of all lower
low waters recorded during syzygy over a 19-
year period, or a computed equivalent period.

mean low water—(abbreviated MLW). ‘The
average height of all the low waters recorded
over a 19-year period, or a computed equivalent
period. (See figure for tide range.)

mean low water lunitidal interval
tidal interval.

mean low water neaps—(abbreviated MLWN).
The average height of all low waters recorded
during quadrature over a 19-year period, or a
computed equivalent period. (See figure for
tide range.)

mean low water springs— (abbreviated MLWS).
The average height of all low waters recorded
during syzygy over a 19-year period, or a com-
puted equivalent period. (See figure for tide
range.)

mean map—Scee mean chart.

mean neap range—(abbreviated Np). The aver-
age semidiurnal range occurring at the time of
quadrature. It issmaller than the mean range
where the type of tide is either semidiurnal or
mixed and is of no practical significance where
the type of tide is diurnal. (See figure for tide
range. )

mean neap rise—The height of mean high water
neaps above the chart datum. (68) (See
figure for tide range.)

mean range—(abbreviated Mn). The difference
in height between mean high water and mean
low water, measured in feet or meters. (See
figure for tide range.)

mean rise—The height of mean high water above
chart datum. (50) (See figure for tide
range.)

mean rise interval—(abbreviated MRI). The
time interval in hours and minutes between the
transit of the moon and the height of the tide
measured above chart datum. The mean rise
interval may be referred either to the local or
Greenwich meridian.

mean river level—The average height of the sur-
face of a river at any point for all stages of the
tide over a 19-year period, usually determined
from hourly height readings. Unusual varia-
tions of river level due to discharge or runoff
may be excluded in computation.

mean sea level—(abbreviated MSL; or sea level
datum). The mean surface water level deter-
mined by averaging heights at all stages of the
tide over a 19-year period. Mean sea level is
usually determined from hourly height readings

See luni-

MEAN SOUNDING VELOCITY

measured from a fixed predetermined reference
level (chart datum).

mean sounding velocity—Mean values for veloc-
ity of sound through the vertical water column
of specific depths based on different velocities of
sound in different sections of the column. These
values yield more nearly correct depths when
sonic depth finding machines are used. The
velocity of sound at any specific depth may dif-
fer considerably from the mean.

mean sphere depth—The uniform depth to which
the water would cover the earth if the solid sur-
face were smoothed off and were parallel to the
surface of the geoid. This depth would be
about 8,000 feet (2,440 meters). (5)

mean spring range—(or spring range). The
average semidiurnal range of tide at time of
syzygy. It is greater than the mean range
where the type of tide is either semidiurnal or
mixed and is of no practical significance where
the type of tide is diurnal. (See figure for tide
range.)

mean spring rise—(or spring rise). The surface
water level height of mean high water springs
measured above the basic reference plane (chart
datum). (See figure for tide range.)

mean tide level— (abbreviated MTL; or half-tide
level, ordinary tide level). The reference plane
midway between mean high water and mean
low water. (See figure for tide range.)

mean tropic range—The mean of the great tropic
range and the small tropic range. (68) See
lunar declination.

mean water level—(abbreviated MWL). The
mean surface level determined by averaging the
height of the water at equal intervals of time,
usually at hourly intervals, over a considerable
period of time.

mechanical analysis—Measurement of the par-
ticle size distribution of asediment. (2)

mechanical mixing—Action of waves in mixing
the surface layer of the ocean.

median—Pertaining to a series of numbers, the
median is the middle term when the numbers are
arranged in algebraic order. If the number of
terms is even, the median is taken halfway be-
tween the two middle terms. (5)

medimarimeter—An instrument for measuring
mean sea level. The term is not generally used
in the United States. (68)

mediterranean—A large body of salt water or
inland sea surrounded by land, which:may have
one or more narrow openings to the ocean or an-
other sea.

medium field of ice—See medium ice field.

medium floe—Sce medium ice floe.

medium ice field—(or medium field of ice). An
ice field 15 to 20 kilometers (8.1 to 10.8 nautical
miles) across. (74).

medium ice floe—1. An ice floe of sea ice 600 to
3,000 feet across. (59)

2. See ice floe.

medium scale—See scale.

medium winter ice—1. Winter ice thicker than
15 to 80 centimeters (6 to 12 inches). (74)

2. See winter ice.

medusa—See jellyfish.

megaloplankton—Plankton larger than 1 centi-
meter; includes the larger forms of the plank-
ton, such as salps and large jellyfishes.

megaripple—(or sand wave). A large wavelike
sediment feature in very shallow water composed
of sand. The wavelength may reach 100 meters,
and amplitude is about 0.5 meter.

meizoseismal—Refers to the maximum destruc-
tive effects of an earthquake. A line or curve
connecting points of maximum destruction
around an earthquake epicenter is a meizoseis-
malcurve. (48).

meizoseismal curve—Sce meizoseismal.

melting point—The temperature at which a solid
substance changes from the solid to the liquid
form. Although sea ice melts at a specific tem-
perature, it actually begins to disintegrate and
weaken when its temperature approaches the
melting point.

membrane filter—aA strainer used for the quan-
titative extraction of phytoplankton and bac-
teria from water samples by vacuum filtration
and usually consisting of a collodion membrane
with fine pores of uniform size.

Mercator projection—(also called equatorial
cylindrical orthomorphic projection). A con-
formal projection derived by mathematical
analysis in which the meridians and parallels
are portrayed as parallel straight lines at right
angles to one another. The scale is chosen to be
true along the Equator. This projection can be
equivalently described as the development of a
rhumb line on the earth, being portrayed as a
straight line on the projection.

meridian—A north-south reference line, through
the geographical poles of the earth from which
longitudes and azimuths are measured. (68)

meridional flow—The current moving along a
meridian. (32)

mermaid’s hair—See blue-green alga.

mermaid’s purse—See sailor’s purse.

meroplankton—Chiefly the floating develop-
mental stages (eggs and larvae) of the benthos
and nekton. ‘These forms are especially abun-
dant in neritic waters.

mesopelagic—That portion of the oceanic provy-
ince extending from about 100 fathoms (200
meters) down to a depth of about 500 fathoms
(1,000 meters). (See figure for classification
of marine environments.)

mesoplankton—Plankton within the size range
0.5 to 1.0 millimeter. Rarely used in this mean-
ing since it is also used to designate all plankton
living in middepths. !

messenger—A cylindrical metal weight approxi-
mately 3 inches long and 1 inch in diameter; it
is usually hinged and with a latch and 1s at-

104

tached around an oceanographic wire and sent
down to actuate the tripping mechanism on
oceanographic devices such as Nansen bottles
and current meters after they have been
lowered to the desired depth.

metamorphic rock—Rocks which have undergone
structural and mineralogical changes, such as
recrystallization, in response to marked changes
of temperature, pressure, and chemical environ-
ment. (2)

metaripples—S¢ee ripple marks.

metasediments—Scee quick.

meteor—A general term for any atmospheric
phenomenon including hydrometeors (such as
rain, cloud, fog, and mist) and lithometers
(atmospheric dust or salt particles). The term
now is usually restricted to astronomical meteors
which are bodies travelling through interplan-
etary space whose remnants occasionally reach
the earth’s surface as meteorites.

meteorological tide—The change in water level
due to meteorological conditions, such as wind
and barometric pressure. (66)

meter—The basic unit of length of the metric
system, equal to 1,650,763.73 wavelengths of Kr
orange-red radiation. On October 14, 1960 the
11th General Conference on Weights and Meas-
ures adopted this standard to replace the plati-
num-irridium meter bar which had been kept
in Paris as the international standard of lengths
since 1889 under the 7'reaty of the Meter.

9. A device for measuring, and usually indi-
cating, some quantity. (68)

meter wheel—A special block used to support the
oceanographic wire payed out over the side of a
ship. Attached to or connected by means of a
speedometer cable is a gear box to measure the
length of wire. On some meter wheels the gear
box or counter is an integral part of the wheel.

Metonic cycle—A period of approximately 19
years, during which all phase relationships be-
tween moon, sun, and earth occur.

During any cycle, new and full moon will re-
cur on approximately the same day of the same
year. (68)

microatoll—A circular growth of coral with a
central depression and a breadth of only a few
feet. (2

microcoquina—Partially cemented sand-size (2
millimeters and smaller) shell fragments. (2)

microcurie— (abbreviated pc). One-millionth of
acurie (10-‘curie). (41)

micron—(abbreviated »). A unit of length equal
to one-millionth of a meter or one-thousandth
of a millimeter. The micron is a convenient
length unit for measuring wavelengths of in-
frared radiation, diameters of atmospheric par-
ticles, ete. (5)

microplankton—Plankton within the size range
60 microns to 1 millimeter. Most phytoplank-
ton forms are included in this group and the
nannoplankton.

MILITARY OCEANOGRAPHY

microseism—A feeble oscillatory disturbance of
the earth’s crust, detectable only by very sensi-
tive seismographs.

Certain types of microseisms seem to be
closely correlated with atmospheric disturbances
and can be used to locate such disturbances,
especially in the case of tropical cyclones. In
addition, traffic, industrial activities, and wind
flexure of trees and tall structures can create
microseisms. (5)

middle ground—Bar deposits formed by ebb and
flood tides in the middle of the channel at the
entrance and exit of a strait. They result from
the decrease in current velocity and deposition
of suspended material with the widening of the
channel at either end of the constriction.

middle pack—See Baffin Bay pack.

Middle Passage—The route across Melville Pug
(made possible by the breaking up of the pac
ice in the center of Melville Bugt) which is a
direct course from Upernavik to Kap York,
Greenland. (21)

mid-extreme tide—A level midway between the
extreme high water and extreme low water oc-
curring ata place. See mean tide level. (68)

Midocean Canyon—This term is not recom-
mended by the ACUF for an Atlantic Ocean
seachannel.

midocean canyon—This term is not recommended
by the ACUF for a steep-walled, flat-floored
continuous depression up to 5 miles wide and
100 fathoms in relief that crosses a plain and
eae leads into or out of a gap. See seachan-
nel.

midoceanic islands—lIsolated volcanic islands
rising from the deep sea floor, composed of
basaltic lava or limestone reefs on a base of vol-
canicrock. (2)

midocean ridge—A great median arch or sea bot-
tom swell extending the length of an ocean basin
and roughly paralleling the continental mar-
gins. See cordillera. (2)

midocean rift—This term is not recommended
by the ACUF for a deep, narrow-notched, cleft
valley, or graben, which is reportedly found
almost continuously along the crest of a cordil-
leraorridge. See cordillera.

midwater trawl—A bag-type net generally towed
laterally at depths ranging from just above the
bottom to the surface. Two types are:

(1) Rigid—with a metal frame to form the
shape of the open end of bag.

(2) Nonrigid—depends on floats, paravanes,
weights and/or depressors to form the shape of
the open end.

migrating inlet—A tidal inlet, such as one con-
necting a coastal lagoon with the open sea, which
shifts its position in the direction of the long-
shore current flow. (2)

military oceanography—The study of those spe-
cific characteristics and phenomena of the deep
sea environment which may influence the design

105

MILKY SEA

and performance of ships, equipment, or weap-
ons. (39)

milky sea—S¢ee sheet-type luminescence.

milky weather—S¢ee whiteout.

Millepore * filter—A copyrighted trade name for
a membrane filter.

millicurie—(abbreviated mc).
of acurie. (41)

milligauss—A unit of magnetic force equal to
0.001 gauss (oersted) or 100 gammas.

million-electron-volt—(abbreviated Mev). <A
common unit of energy in nuclear science, equiv-
alent to 10° electron-volts. (41)

milliroentgen—One-thousandth of a roentgen.

One-thousandth

minimum—The least value attained (or attain-
able) by a function; the opposite of maximum.
5)

minimum current—The phase of the tidal cur-
rent when the speed is least; usually referenced
in knots and in hours before or after low and
high water. (See figure for current ellipse.)

minimum duration—The time necessary for
steady state wave conditions to develop for a
given wind velocity over a given fetch length.
(61)

minimum ebb—The lowest speed of a continuously
outflowing current during the period of ebb tidal
current, usually in a river or estuary; where
currents are solely tidal, the lowest speed of an
ebb current is at or near slack water. See
river discharge.

minimum flood—Where currents are solely tidal,
the lowest speed of a flood current is at or near
slack water.

minor constituents—Those chemical elements
present in sea water which together comprise
approximately 0.1 percent of the total known
dissolved solid constituents. Nearly all of the
elements occur in sea water, although most are
present in extremely small amounts. See con-
stituents of sea water.

mixed current—The type of tidal current char-
acterized by a conspicuous difference in speed
and duration between the two successive flood
or two successive ebb currents occurring during
any tidal day. (50)

mixed layer—The layer of the water which is
mixed through wave action or thermohaline
convection.

mixed layer depth—The depth of the bottom of
the mixed layer.

mixed tide—The type of tide in which a diurnal
wave produces large inequalities in heights and/
or durations of successive high BARS low
waters. This term applies to the tides inter-
mediate to those predominantly semidiurnal and
those predominantly diurnal. (See figure for
types of tide).

mixotrophic nutrition—The process by which an
organism obtains its food by both autotrophic

and heterotrophic modes. See autotrophic nu-
trition, heterotrophic nutrition.

mixture—Mixtures consist of two or more sub-
stances intermingled with no constant percent-
age composition, and with each component re-
taining its essential original properties. (27)

moat—An annular depression that may not be
continuous, located at the base of many sea-
mounts orislands. (62)

mode—tThe item, in a series of statistical data,
which occurs most often.

modified Mercalli scale—Sce earthquake inten-
sity.

Mohole—A proposed deep borehole to penetrate
the earth’s crust and into the earth’s mantle
below the Mohorovi¢i¢ discontinuity. (2)

Mohorovitié discontinuity—(abbreviated Mo-
ho). The sharp discontinuity in composition
between the outer layer of the earth (the crust)
and the next inner layer (the mantle). This
was discovered by Mohorovicié from seismo-
grams. The thickness of the crust has been de-
termined by the refraction of seismic waves at
this discontinuity which is situated about 35
kilometers below the continents and about 10
kilometers below the ocean basins and defines
the top of the mantle. (See figure for earth
structure.)

Mohr-Knudsen method—A chemical method
for estimating the chlorinity of sea water. In
this method, the volume of silver nitrate neces-
sary to precipitate the sample in relation to the
volume of silver nitrate necessary to precipitate
normal water is determined by titration using
potassium chromate as an indicator.

The chlorinity is calculated by Knudsen’s
Tables.

moisture flux—wSee eddy flux.

mold—See fungus.

mole—1. See gram-molecular weight.

2. A massive structure of masonry or large
stones serving as a pier or breakwater, or both.
68

molecule—The smallest unit quantity of matter
which can exist by itself and retain all the prop-
erties of the original substance. (27)

mollusk— (also spelled mollusc). One of a phy-
lum (Mollusca) of soft unsegmented animals,
most of which are protected by a calcareous
shell. The phylum is second only to the insects
in number of species. Some members are an
important food source, some are dangerous to
man, some are notable fouling organisms, and
others are destructive to wood, concrete, and oth-
er submerged materials. The group includes
the snails, bivalves, chitons, squid, and octo-
pus.

momentum—That property of a particle which
is given by the product of its mass with its
velocity.

momentum flux—Scee eddy flux.

106

monitoring—Periodic or continuous determina-
tion of the amount of ionizing radiation or
radioactive contamination present in an occu-
pied region as a safety measure for purposes of
health protection. (70)

monsoon—A name for seasonal winds (derived
from Arabic “mausim,” a season). It was first
applied to the winds over the Arabian Sea,
which flow for six months from northeast and
for six months from southwest, but it has been
extended to similar winds in other parts of the
world. (5)

monsoon current—A seasonal wind-driven cur-
rent occurring in the northern part of the In-
dian Ocean and the northwest Pacific Ocean.

montmorillonite—A group of clay minerals char-
acterized by swelling in water.

moraine—Rock debris, deposited chiefly by direct
glacial action, and having various constructional
topographic features independent of control by
the underlying preglacial surface. Where
glaciers float upon or discharge into the sea,
or glaciated regions are drowned by the sea,
moraines form marine deposits.

moraine bar—A bar, rising from deep water on
both sides, which is composed of glacial detritus
including large boulders. It is deposited as a
terminal moraine by a valley glacier and extends
across a fiord.

moss animal—WScee bryozoan.

mouth—The place of discharge of a stream into
the ocean or entrance to a bay from the ocean.

moving average—Sce consecutive mean.

Mozambique Current—The part of the South
Equatorial Current that turns and flows along
the African coast in the Mozambique Channel.
It is considered part of the Agulhas Current.

M. constituent—The principal lunar semi-
diurnal constituent of the theoretical tide-pro-
ducing forces. (See figure for partial tide.)

mud—Pelagic or terrigenous detrital material
consisting mostly of silt and clay-sized particles
(less than 0.06 millimeter) but often containing
varying amounts of sand and/or organic mate-
rials. It isa general term applied to any sticky
fine-grained sediment whose exact size classifi-
cation has not been determined.

muddy ice—Scee debris ice.

mud flat—A muddy or sandy coastal strip usually
submerged by high tide. (2)

mud flow—See turbidity current.

mud lumps—Small transient sigmoidal islands of
bluish-gray clay squeezed up by the pressure of
surface sediments or buried clays off the Missis-
sippi River delta. They rise to 5 or 10 feet
above sea level and are an acre or more in extent.

mudstone—A rock consisting of an indefinite m1x-
ture of clay, silt, and sand particles, the propor-

207-109 O—66——S

107

MYSTICETE

tions varying from place to place. May also be
applied to shales. See pelite.

mud volcano—(or hervidero). A cone-shaped

clay mound composed of clay and usually

formed by the eruption of sulfurous and bitumi-

nous mud from a central orifice or vent. There
are both land and submarine forms.
mu (.) flagellates—(or hekistoplankton). The

extremely tiny phytoplankters measured in mi-
crons and bearing one or more whiplike hairs
(flagella).

multichannel analyzer—Sce pulse height ana-
lyzer.

multipath transmission—The process, or condi-
tion, in which radiation travels between source
and receiver via more than one path. Since
there can be only one “direct” path, some process
of reflection, refraction, or scattering must be
involved. (5)

multiple tide staff—aA succession of tide staffs
placed on a sloping shore, so that the vertical
graduations on the several staffs from a contin-
uous scale with reference to the same datum.
(68)

mush—Rare. See brash ice.

mushroom ice—Sece ice pedestal.

mussel—One of a family (Mytilidae) of elongate,
tapering bivalves, usually dark colored, grow-
ing in masses on stationary and floating objects,
underwater structures, rocks and rocky cliffs, or
ships’ hulls, covering mud flats in the intertidal
zone, and boring into rock. Mussels attach by
means of a mass of threads called the byssus.
They are one of the most notable groups of foul-
ing organisms.

mutualism—A symbiotic relationship between
two species in which both are benefitted. An
example of mutualism is the attachment of cer-
tain sponges and coelenterates to the shells of
crabs. The attached animal is carried about to
fresh feeding areas, and the crab is camouflaged
by the animal on its back and may be thus pro-
tected from enemies. See commensalism, in-
quilinism, symbiosis.

myctophid—(or lanternfish). One of a family
(Myctophidae) of small oceanic fishes which
normally live at depths between about 100 and
2,000 fathoms (200 and 4,000 meters). They
characteristically have numerous small photo-
phores on the sides of the body. Many species
undergo extensive diurnal vertical migrations
and are thought to contribute to sound scattering
layers in the sea.

mysid—One of an order (Mysidacea) of elongate
crustaceans which usually are transparent (or
nearly so) and benthic or deep living.

mysticete—See baleen whale.

N

nadir—The point on the celestial sphere vertically
below the observer, or 180 degrees from zenith.
(66)

nannoplankton — (or centrifuge plankton).
Plankton within the size range 5 to 60 microns.
Includes many dinoflagellates and smaller
diatoms. Individuals will pass through most
nets and usually are collected by centrifuging
water samples. This spelling is as originally
coined; the spelling nanoplankton used by some
authorities is etymologically correct.

nanocurie—EKquals 10-° curie.

Nansen bottle—A device used by oceanographers
to obtain subsurface samples of sea water.

The “bottle” is lowered by wire; its valves are
open at both ends. It is then closed in sttu by
allowing a weight (called a messenger) to slide
down the wire and strike the reversing mech-
anism. This causes the bottle to turn upside
down, closing the valves and reversing the re-
versing thermometers which are mounted in a
special thermometer case on it. If, as is usually
done, a series of bottles is lowered, then the re-
versal of each bottle releases another messenger
to actuate the bottle beneath it. (5)

Nansen cast—See oceanographic cast.

narrows—A narrow passage or strait. (2)

natural arch—Scee sea arch.

natural. frequency—The characteristic frequen-
cy, that is, the number of vibrations or oscilla-
tions per unit time of a body controlled by its
physical characteristics (dimensions, density,
etc.). Ina harbor, the natural frequency gives
rise to waves, called seiches, which have periods
and amplitudes dependent on the physical char-
acteristics of the harbor.

natural radioactivity—1. The property of radio-
activity exhibited by more than fifty naturally
occurring radionuclides.

2. The natural radioactive constituents of sea
water include Potassium*, Rubidium’, Ura-
nium, Uranium’, Thorium???, Radium:*s,
Carbon™, and Hydrogen? (Tritium). Of these
Potassium*? is by far the largest contributor to
(ie oceans natural radioactivity.

0)

natural scale—The ratio between the linear di-
mensions of a chart, drawing, etc., and the actual
dimensions represented, expressed as & propor-
tion. (68)

nature of the bottom—Sce character of the
bottom.

nauplius—A_ limb-bearing early larval stage of
many crustaceans.

nautical almanac—A periodical publication (us-
ually annual) of astronomical statistics useful
to and designed primarily for marine naviga-
tion. (68)

nautical mile—(abbreviated n. mile). In general
a unit used in marine navigation equal to a
minute of are of a great circle on a sphere.
Depending upon the radius of the sphere, vari-
ous lengths of nautical miles have been defined.
The adopted value in the United States since
July 1, 1959 is one international nautical mile
equals 6,076.11549 U.S. feet (approximately).

nautilus—1. Any of a genus (Wautilus) of
cephalopods of the South Pacific and Indian
Oceans having a spiral chambered shell, pearly
on ae inside, whence the name Pearly Nautilus,

An eight-armed cephalopod (Argonauta)

eel to the octopus, the female having a
fragile, papery, unchambered shell, called also
Paper Nautilus.

navigation season—The average statistical dates
for commencement and ending of shipping with-
in or through a port or given area and controlled
generally by ice and weather conditions.

Naval Oceanographic and Meteorological
Automatic Device—(abbreviated NOMAD).
A deep sea moored buoy which provides auto-
matic radio transmission of surface weather
and subsurface temperature.

naze—Scee headland.

neap high water—Scee mean high water neaps.

neap low water—Sce mean low water neaps.

neap range—Sce mean neap range.

neap rise—See mean neap rise.

neaps—See neap tide.

neap tidal currents—Tidal currents of decreased
speed occurring at the time of neap tides. (68)

neap tide—(or neaps) . Tide of decreased range
which occurs about every two weeks when the
moon is in quadrature. (50) (See figure for
tide cycle.)

nearshore circulation—The ocean circulation
composed of the nearshore currents and coastal
curents. (61)

nearshore current system—The current system
caused by wave action in and near the surf
zone. The nearshore current system consists of
four parts: the shoreward mass transport of
water, longshore currents, rip currents, and
longshore movement of expanding heads of rip

108

Yee heh

2
ve MASS TRANSPORT OF WAVES
io"

SSS
—— —
—P
— FEEDER CURRENT~
SHORE LINE

a | | I

LONGSHORE
<—

CURRENT

CURRENT OFFSHORE CURRENT

INSHORE

NEARSHORE CURRENT SYSTEM
(AFTER WIEGEL, 1953)

currents. Sometimes called inshore currents.

(73)

Nearshore Environmental Analog Prediction
System— (formerly called Harbor Analog Sys-
tem). A technique used at the U.S. Naval
Oceanographic Office to classify nearshore areas
(shore to 30 fathoms) so that characteristics of
unsurveyed locations can be inferred from sur-
veyed locations in a similar class.

nearshore water—Sce inshore water.

nearshore zone—Pertaining to the zone extend-
ing seaward from the shore to an indefinite dis-
tance beyond the surf zone.

near surface path—Sce surface path.

neck—The narrow band of water flowing swiftly
seaward through the surf. See rip current.
ee (See figure for nearshore current sys-

em.

nectochaeta larva—A stage of the young of cer-
tain annelids, more advanced than the polytroc-
ular larva, in which muscle-powered para-
podia provide the swimming power.

needle ice—Scee candle ice, frazil ice.

negative gradient—A layer of water where tem-
perature decreases with depth.

negative pressure duration—The length of time
the bottom pressure is affected by the passage
of the trough of a wave. It is approximately
equal to one-half the wave period.

hegative pressure response—The maximum
amount (in inches or feet of water) the bottom
pressure is reduced by the passage of the trough
of a wave.

nekton—Those animals of the pelagic division
that are active swimmers, such as most of the
adult squids, fishes, and marine mammals.

nematocyst—The stinging mechanism of coe-
lenterates, consisting of a chitinous sac filled
with venom and elongated at one end into a long

NEUTRON

narrow pointed hollow thread, which normally
lies inverted and coiled up within the sac but
can be everted by mechanical or chemical stimuli.

nepheloid zone—A suspension of fine organic
matter and clay-sized sediment particles in sea
water which forms a zone about 200 to 1,000
meters thick near the bottom of the continental
slope and rise in the western North Atlantic.
One theory holds that it results from the stirring
up of sea floor sediments by the turbulent flow of
bottom water. (16)

neritic—That portion of the pelagic division ex-
tending from low water level to the approximate
edge of a continental shelf. Some writers have
used this term in describing bottom organisms
of a continental shelf, but its recommended
usage is restricted to the waters overlying a
shelf. (See figure for classification of marine
environments.)

neritic province—Scee pelagic division.

neritic zone—Scee neritic.

ness—Scee headland.

net plankton—Sce microplankton.

net primary production—The total amount of
organic matter produced by photosynthetic
organisms, minus the amount consumed by
these organisms in their own respiratory proc-
esses. See primary production.

net radiometer—A device which measures the net
radiation by subtracting the outgoing long-wave
energy total from the incoming or reradiated
short-wave energy.

network—In surveying and gravity prospecting,
a pattern or configuration of stations, often ar-
ranged as to provide a check on the consistency
of the measured values, that is, a level network,
a gravity network based on the integration of
torsion balance gradients.

neuston—The group of organisms living in asso-
ciation avith the surface film; the majority are
fresh water forms, since the ocean surface gen-
erally is too rough to support such a group.
The marine strider Halobates and surface float-
ers, such as the Portuguese man-of-war, may be
considered to be neuston forms.

neutral estuary—An estuary in which neither
fresh water inflow nor evaporation dominates.

neutral filter—An optical filter which reduces
the magnitude of the radiant energy without
changing its relative spectral distribution. (8)

neutral shoreline—That shoreline whose essential
features do not depend on either submergence of
a former land surface or the emergence of a
former subaqueous surface.

neutron—An elementary nuclear particle with a
mass approximately the same as that of a hydro-
gen atom and electrically neutral; its mass is
1.008982 mass units. Neutrons are commonly
divided into sub-classifications according to their
energies as follows: thermal, around 0.025 elec-
tron-volts; epithermal, 0.1 to 100 electron-volts ;
slow, less than 100 electron-volts; intermediate,

109

NEVE

10° to 10° electron-volts; fast, greater than 0.1
million-electron-volts. (70)

névé—See firn, firn snow.

névé iceberg—An iceberg similar in appearance
and color to a iceberg, but composed of névé
(firn). (68)

new ice—A general term which includes frazil
ice, sludge, medium winter ice, pancake ice,
and ice rind. (74)

newly formed ice—(also called fresh ice). Ice in
the first stage of formation and development.
See youngice. (68)

newly frozen ice—See newly formed ice.

niggerhead—1. Large blocks of coral torn loose
from the outer face of a reef and tossed on to the
reef flat by storm waves or tsunamis. The
blocks are blackened by a crust of lichens after
detachment from the reef.

2. See reef patch.

night-sky light—See airglow.

nilas—A Russian term for gray or dark-colored
ice that forms in a sheet on a calm sea.

nip—The cut made by waves in a shoreline of
emergence. (61)

nipped—Pertaining to a ship which is icebound
and subjected to pressure from ice, sometimes to
the extent that the ship is damaged and even
sunk. (59) See beset.

nipping—(or pinching). The closing of ice
around a ship so that the ship is beset and sub-
jected to pressure from the ice. (59)

nitrate nitrogen—The most abundant and readily
assimilable form of nitrogen for marine orga-
nisms. Like phosphate, it is an essential nutri-
ent. Estimates of primary productivity have
been made by determining the concentrations of
nitrates in a water sample.

nitrogen cycle—The series of chemical changes
that nitrogen undergoes in its use by plants and
animals. Inorganic nitrogenous compounds
(nitrates, nitrites, and ammonium) and, to a
small extent, organic nitrogenous compounds
in the sea are utilized by marine plants, which
form other nitrogenous compounds, such as
amino acids. More complex amino acids and
proteins are synthesized from these by the ma-
rine animals, which feed on the plants. Final-
ly, these compounds, in the waste products and
the dead bodies of the animals, are broken down
by bacteria into inorganic compounds and sim-
ple organic compounds, completing the cycle.

nitrogen narcosis—(or rapture of the deep). An
intoxicating or narcotic effect of gaseous nitro-
gen, produced in divers breathing air at depth.
Usually the effect first becomes noticeable at a
depth of 100 feet or more, although individuals
vary in their susceptibility.

no-bottom—A notation appearing on nautical
charts indicating that the sounding did not reach
the bottom.

Noctiluca—A_ genus of usually pale pink lumi-
nescent dinoflagellates large enough to be seen
by the unaided eye. This particular organism
is responsible for much of the sheet-type lumi-
nescence noted in coastal waters of various parts
of the world ocean. A green form occurring in
coastal regions of the Far East is not lumi-
nescent.

nocturnal radiation—Long-wave back radiation
from the sea surface. A misnomer since back
radiation is a continuous process.

nodal line—In a tide area, the line about which
the tide oscillates and where there is little or no
rise and fallofthetide. (59)

nodal point—See amphidromic point.

nodal zone—An area at which the predominant
direction of the littoral transport changes.
(61)

node—That part of a standing wave or clapotis
where the vertical motion is least and the hori-
zontal velocities are greatest. Nodes are associ-
ated with clapotis, and with seich action re-
sulting from resonant wave reflections in a har-
bor or bay. (61)

node cycle—The time required for the regression
of the moon’s nodes (the points where the plane
of the moon’s orbit intersects the ecliptic) to
complete a circuit of 360 degrees of longitude;
a period of approximately 18.6 years. It is ac-
companied by a corresponding cycle of chang-
ing inclination of the moon’s orbit relative to
the plane of the earth’s Equator, with resulting
inequalities in the rise and fall of the tide and
speed of the tidal current. (50)

nodules—(or halobolite, pelagite). Concretion-
ary lumps of manganese, cobalt, iron, and nickel
found widely scattered on the ocean floor.
Rocks of various sizes and shapes often are en-
crusted with these metals.

noise—Any undesired sound. By extension, noise
is any unwanted disturbance within a useful fre-
quency band, such as undesired electric waves
in a transmission channel or device. (69)

noise level—The comparison of sound intensity,
usually measured in decibels, to a reference
level. Underwater sound pressures are com-
monly expressed in decibels or dynes per square
centimeter.

noise spectrum—The relative amplitude of the
several frequencies present in a complex tone
(sound).

nomogram—(or «lignment chart, also called
nomograph, nomographie chart). The graph-
ical representation of an equation of three
variables f(u, v, #)=O, by means of three
graphical scales (not necessarily straight), ar-
ranged in such a manner that any straight line,
called an index line, cuts the scales in values of
uw, v, and w satisfying the equation. By in-
troducing auxiliary variables and constructing
auxiliary scales, equations containing more than

110

three variables may also be represented by nomo-
grams. (5)

nomograph—See nomogram.

nomographic chart—See nomogram.

nonastacin carotenoid—Any of a group of plant
pigments, such as carotenes and xanthophylls,
exclusive of astacin carotenoids, which are also
animal pigments. The measurement of the con-
centration of these pigments in addition to vari-
ous chlorophylls is useful in estimating the rate
of photosynthesis (primary production) or as
an index of the standing crop (biomass) of
plant forms.

nonharmonic constant—A tidal constant such
as a lunitidal interval, range, or inequality
which may be derived directly from high and
low water observations without regard to the
harmonic constituents of the tide. The term
is also applicable to tidal currents. (59)

nonlinear waves—Waves in relatively shallow
water, with no superimposition of motion. (35)

nontidal current—Any current that is caused by
other than tide-producing forces. This in-
cludes all permanently established oceanic cur-
rents as well as all temporary ocean currents
caused by winds. (59)

normal gravity—The value of gravity at sea level
according to a theoretical formula which as-
sumes the earth to be a spherical or of some
similar regular shape.

normal ripples—Simple asymmetrical ridges
made in sediments by water currents.

normal stresses—The components of the stress
tensor which are normal to the faces of the
fluid element.

normal temperature and pressure—(abbrevi-
ated N.T.P.). See standard temperature
pressure.

normal water—(also called Copenhagen water,
standard sea water). A standard sea water
preparation, the chlorinity of which lies be-
tween 19.30 and 19.50 per mille and has been
determined to within =0.001 per mille.

Normal water is used as a convenient compari-

son standard for chlorinity measurements of sea
water samples by titration. It is prepared by
the Hydrographical Laboratories, Copenhagen,
Denmark. (5)

normal winter—Refers to normal ice season, that
is, the average ice conditions based on a num-
ber of recorded winters in a given area.

North-About Route—The coastal route through
Melville Bugt from Upernavik to Kap York,
Greenland, by going along the Greenland coastal
fast ice or floe leads. This passage usually
offers the earliest route to Thule and the “North
Open Water,” and can generally be effected be-
fore the end of August, even in the worst season.

North Atlantic Current—A wide slow-moving
continuation of the Gulf Stream originating in
the region east of the Grand Banks of New-

111

Nz CONSTITUENT

foundland at about 40°N and 50°W. The
North Atlantic Current is often masked by shal-
low and variable wind-driven surface move-
ments. Branches of the North Atlantic Current
form the Norway Current and the Irminger
Current.

North Atlantic Drift—The weak, sluggish, north-
east part of the North Atlantic Current that is
easily influenced by winds; currents have been
observed to change speeds and directions fre-
quently, and at times reverse directions.

North Cape Current—A warm current flowing
northeastward and eastward around northern
Norway, and curving into the Barents Sea. The
North Cape Current is a continuation of the
Norway Current.

North Equatorial Current—Ocean currents
driven by the northeast trade winds blowing
over the tropical oceans of the Northern Hemi-
sphere. In the Atlantic Ocean it is known as
the Atlantic North Equatorial Current and flows
west between the Atlantic Equatorial Counter-
current and the Sargasso Sea.

In the Pacific Ocean it is known as the Pacific
North Equatorial Current and flows westward
between 10° and 20°N. East of the Philippines
it divides, part turning south to join the Equa-
torial Countercurrent, and part going north to
form the Kuroshio.

In the North Indian Ocean there is no equa-
torial current; monsoon drifts dominate.

northern lights—See aurora borealis.

North Open Water—(or North Water). A con-
siderable area of open navigable water in north-
ern Baffin Bay roughly oval in shape, with its
major axis orientated north to south. It is
bounded by the fast ice of Smith Sound to the
north and by the Baffin Bay pack to the south.
Its southern boundary is usually a little north
of the 75th parallel. North Open Water usually
appears during April and May. (21)

North Pacific Current—The warm branch of the
Kuroshio extension flowing eastward across
the Pacific Ocean.

North Pole 1—(abbreviated NP-1). See drift
station.

North Water—Sce North Open Water.

Norway Current—(sometimes called Vorwegian
Current). A continuation of the North At-
lantie Drift, which flows northward along the
coast of Norway.

Norwegian Current—Sce Norway Current.

notch—A deep narrow cut in the base of a sea cliff
made by breaking waves. See nip.

Notice to Mariners—<A periodic publication con-
taining information affecting the safety of
navigation.

N. constituent—The larger lunar elliptic semi-
diurnal constituent of the theoretical tide-
Bes forces. (See figure for partial
tide.)

NUCLEAR FISSION

nuclear fission—The division of a heavy nucleus
into two epee equal parts. For the
heaviest nuclei the reaction is highly exothermic,
the release of energy being about 170 million-
electron-volts per fission. A well-known exam-
ple is the fission of the compound nucleus formed
when U**> captures a slow neutron. The ap-
proximate equality of the fission fragments dis-
tinguishes fission from such processes as spalla-
tion, in which, relatively small fragments are
ejected, leaving only one large residual nucleus.
Fission has been induced by neutrons, charged
particles, and photons. When induced by pho-
tons, it is called photofission. (41)

nuclear fusion—The act of coalescing two or more
atomic nuclei. See thermonuclear reaction.
(70)

nuclear isomer—One of two or more nuclides
having the same mass number A and atomic
number Z, but existing for measurable times in
different quantum states with different energies
and radioactive properties. (41)

nuclear oceanography—The study of the nuclear
properties of the marine environment and the
nuclear phenomena occurring therein. This is
a broad oceanographic discipline which includes
radioisotopic oceanography and the applica-
tion of nuclear science and technology to ocean-
ographic investigations.

nuclear precession magnetometer—A magne-
tometer that utilizes the precessional character-
istics of hydrogen nuclei when in an ambient
magnetic field. The data output of this instru-
ment is in the form of a frequency measurement,
which in turn is proportional to the magnetic
field intensity.

nuclear reaction—An induced nuclear disintegra-
tion, that is, a process occurring when a nucleus
comes into contact with a photon, an elementary
particle, or another nucleus. In many cases the
reaction can be represented by the symbolic
equation: Y+a—->Y+6 or, in abbreviated form,
X (a,b) ¥, in which X is the target nucleus, a
is the incident particle or photon, 6 is an emitted
Hons or photon, and ¥ is the product nucleus.

10

nuclear reactor—An apparatus in which nuclear
fission may be sustained in a self-supporting
chain reaction. It includes fissionable material
(fuel) such as uranium or plutonium, and mod-
erating material (unless it is a fast reactor) and
usually includes a reflector to conserve escaping
neutrons, provision for heat removal, and meas-
uring and control elements. The terms pile and
reactor have been used interchangeably, with

reactor now becoming more common. They
usually are applied only to systems in which the
reaction proceeds at a controlled rate, but they
also have been applied to bombs. (70)

nuclear sediment density meter—An oceano-
graphic instrument which employs the back-
scattered radiation from a small sealed radioac-
tive source for the in situ measurement of sedi-
ment densities in the upper 5 meters of the ocean
floor. The instrument is a tubelike device, about
25 feet in length overall, which is lowered to the
ocean floor and projected vertically in the bot-
tom sediment for measurement. The radioac-
tive source with a G—M detector rides up and
down in the tube stopping at 2-foot itervals
for measurement of backscattered radiation.
Such counts are inversely proportional to sedi-
ment density. Recording is accomplished photo-
graphically in the upper enlarged barrel of the
probe.

nuclear species—1. A kind of atom characterized
by the charge, mass number, and quantum state
of its nucleus; a nuclide.

2. A nucleus of a given charge, mass number,
and quantum state. Also a collection of such
nuclei.

(41)

nucleon—A constituent particle of the atomic nu-
cleus; therefore, according to present theory, a
proton ora neutron. (41)

nuclide—A species of atom characterized by the
constitution of its nucleus. The nuclear con-
stitution is specified by the number of protons,
number of neutrons, and energy content, or
alternatively, by the atomic number, mass num-
ber, and atomic mass. To be regarded as a dis-
tinct nuclide, the atom must be capable of
existing for a measurable lifetime (generally
greater than 107° second). Thus nuclear
isomers are separate nuclides, but promptly de-
caying excited nuclear states and unstable inter-
mediates in nuclear reactions are not so con-
sidered. (41)

nudibranch—(or sea slug). One of the order
(Nudibranchia) of gastropods in which the
shell is entirely absent in the adult. The body
bears projections which vary in color and com-
plexity among the species.

nutrient—In the ocean any one of a number of
inorganic or organic compounds or ions used
primarily in the nutrition of primary producers.
Nitrogen and phosphorus compounds are essen-
tial nutrients. Silicates are essential for the
growth and development of diatoms. Vitamins
such as B,. are essential to many algae.

112

O

oarweed—The British term for a blade-shaped
brown alga. See kelp.

oblique haul— (or oblique tow). The retrieval of
an open plankton net from a certain depth at a
certain rate while the ship is underway. See
horizontal haul, vertical haul.

oblique tow—See oblique haul.

observed depth—WSee accepted depth.

observed gravity—The uncorrected value ofgrav-
ity at a station as determined from the gravity
meter.

ocean—(or sea). 1. The intercommunicating
body of salt water occupying the depressions of
the earth’s surface.

2. One of the major primary subdivisions of
the above, bounded by continents, the Equator,
and other imaginary lines.

(5)

ocean basin—That part of the floor of the ocean
that is more than about 100 fathoms below sea
level. (2)

ocean current—A movement of ocean water char-
acterized by regularity, either of a cyclic nature
or more commonly as a continuous stream flow-
ing along a definable path.

Three general classes, by cause, may be dis-
tinguished: (1) currents related to sea water
density gradients, comprising the various types
of gradient currents; (2) wind-driven cur-
rents, which are those directly produced by the
stress exerted by the wind upon the surface and;
(3) currents produced by long-wave motions.
The last is principally the tidal currents, but
may include currents associated with internal
waves, tsunamis, and seiches. The major
ocean currents are of continuous, stream-flow
character, and are of first-order importance in
the maintenance of the earth’s thermodynamic
balance. (5)

oceanic—(or high seas, open ocean). That por-
tion of the pelagic division seaward from the
approximate edge of a continental shelf. (See
figure for classification of marine environ-
ments.)

oceanic anticyclone—Scee subtropical high.

oceanic climate—Sce marine climate.

oceanic crust—A mass of gabbroic material ap-
proximately 5-kilometers thick which lies under
the ocean bottom and may be more or less con-
timuous beneath the continental crust. (35)

oceanic high—Sce subtropical high.

oceanicity—(or oceanity). The degree to which
a point on the earth’s surface is in all respects
subject to the influence of the sea; the opposite
of continentality. Oceanicity usually refers to
climate and its effects. One measure for this
characteristic is the ratio of the frequencies of
maritime to continental types of air masses.
(5)

oceanic polar’ front—See Antarctic Conver-
gence, Arctic Convergence.

oceanic province—Scee pelagic division.

oceanity—Scee oceanicity.

oceanogenic sedimentation—Sediments exclu-
sively marine, siliceous, chemical, or organic in
origin which accumulate in abyssal depths far
from land.

oceanographic cast—A single lowering of a series
of Nansen bottles at an oceanographic station.

oceanographic analysis—The science of manual
or automatic production of charts of oceano-
graphic parameters in which isopleths are
drawn to indicated data by some rational theory.

oceanographic equator—(or thermal equator).
The zone of maximum sea surface temperature
located near the geographic equator. It gen-
erally lies north of this line; but crosses during
the southern summer in the Indian Ocean, west-
ern Pacific Ocean, and western Atlantic Ocean.
Some oceanographers define the oceanographic
equator more specifically as the zone within
which the sea surface temperature exceeds 28°C
(82.4°F).

oceanographic forecasting—The production by
automatic or manual means of charts showing
forecasted values of oceanographic parameters,
similar to weather charts.

oceanographic model—A theoretical representa-
tion of the marine environment. Generally, a
pattern or expression which relates known with
derived oceanographic properties. These ocean-
ographic properties may be physical, chemical,
geological, and/or biological.

oceanographic slide rule—A specially designed
slide rule used for calculating the correction of
thermal expansion of a deep sea reversing
thermometer.

oceanographic station—A term used to designate
oceanographic observations taken at a geo-
graphic location from a ship that is lying to or
anchored at sea.

113

OCEANOGRAPHIC STATION LOCATION

oceanographic station location—The accepted
geographical position at which an oceano-
graphic station was taken.

oceanographic survey—A study or examination
of conditions in the ocean or any part of it, with
reference to animal or plant life, chemical ele-
ments present, temperature gradients, etc. See
hydrographic survey. (68)

oceanographic tracer—A foreign substance in-
troduced into the ocean by natural or artificial
means which enables determination of the ocean
water movement through measurement of the
distribution or location of the substance at some
later time. Such oceanographic tracers include
Tritium (H*), Carbon", other radioisotopes, as
well as non-radioactive tracers such as fluores-
cent dyes and various chemical substances.

oceanographic winch—A medium size winch used
for most oceanographic instrument lowering and
raising. This winch is a high-speed type hold-
ing about 20,000 to 30,000 feet of wire rope.

oceanography—1. The study of the sea, embrac-
ing and integrating all knowledge pertaining to
the sea’s physical boundaries, the chemistry and
physics of sea water, and marine biology.

2. In strict usage oceanography is the descrip-
tion of the marine environment, whereas ocean-
ology is the study of the oceans and related
sciences.

oceanology—See oceanography.

ocean station—(or station). As defined by the
Internation Civil Aviation Organization, a spe-
cifically located area of ocean surface, roughly
square and 200 nautical miles on a side. An
ocean station vessel on patrol is said to be “on
station” when it is within the perimeter of the
area. (5) s

ocean station vessel—(abreviated OSV; also
called ocean weather ship, weather patrol ship,
weather ship). An ocean-going ship assigned
to patrol an ocean station.

These ships are specially equipped to take
comprehensive meteorological and some oceano-
graphic observations of conditions both at the
surface, subsurface, and aloft. The United
States ships are provided by the U.S. Coast
Guard, and the meteorological personnel and
equipment are provided by the U.S. Weather
Bureau. (5)

ocean water—Water having the physical-chemi-
cal characteristics of the open sea, where con-
tinental influences are at a minimum.

ocean weather ship—See ocean station vessel.

ocean weather station—As defined by the World
Meteorological Organization, a specific mari-
time location occupied by a ship equipped and
staffed to observe weather and sea conditions and
report the observations by international ex-
change. (5

octopus—(or devilfish). One of a family (Octo-
podidae) of cephalopods with round or saclike
bodies, eight arms, no shell, and generally with-

out fins. Although there are no known docu-
mented fatalities from attacks by these animals,
many documented attacks on humans are re-
corded.

odontocete—Sce toothed whale.

oersted—The basic unit of magnetic field inten-
sity. A magnetic field with an intensity of one
oersted will exert a force of one dyne upon a
unit magnetic pole. See gauss.

off-reef facies—Sce reef talus.

offshore—The comparatively flat zone of variable
width which extends from the outer margin of
the rather steeply sloping shoreface to the edge
of the continental shelf. (2) (See figure for
shore profile.)

offshore bar—See bar.

offshore barrier—Sce barrier beach.

offshore current—1. A prevailing nontidal cur-
rent usually setting parallel to the shore out-
side the surf zone. See coastal current. (See
figure for nearshore current system.)

2. Any current flowing away from shore.

offshore water—Water adjacent to land in which
the physical properties are slightly influenced
by continental conditions.

offshore wind—A wind blowing seaward from
the land in a coastal area; a land breeze. (61

old ice—Any sea ice more than one year old.

oligotrophic—Pertaining to water bodies contain-
ing nutrient matter.

olistostrome—A deposit produced by sliding or
slumping of a submarine sediment mass.

omnidirectional hydrophone—A hydrophone
whose response is essentially independent of
angle of arrival of the incident sound wave.

69

oS aes ice—1. Sea ice formed the previous sea-
son, not yet one year old.

2. A Russian term for ‘sea ice thicker than
white ice. By the end of spring it reaches a
thickness of 1.5 to 2.0 meters (4.9 to 6.6 feet)
or more. Usually during the summer this ice
does not entirely disappear and becomes two-
year ice or young polar ice.

(59)

onshore—A direction landward from the sea.
(61)

onshore wind—A wind blowing landward from
the sea in a coastal area; a Sea breeze. (61)

on station—Sce ocean station.

odid—See oodlite.

oblite—(or odlith, oid). A spherical or ellipsoi-
dal particle of sand or granule size (0.25 to 2.00
millimeters in diameter) with concentric or
radial structure, which usually is calcareous but
may be siliceous or hematic. It is formed by
replacement or by accretion of concentric layers
of lime around a quartz grain nucleus in shallow,
wave agitated, limy water.

oodlith—See odlite.

114

O, constituent—The lunar diurnal constituent
of the theoretical tide-producing forces. (See
figure for partial tide.)

ooze—1. A soft mud or slime.

2. A fine-grained pelagic sediment containing
undissolved sand- or silt-sized, calcareous or sili-
ceous skeletal remains of small marine organisms
in proportion of 30 percent or more, the re-
mainder being amorphous clay-sized material.
Deep sea oozes often are characterized by mark-
edly bi-modal grain-size distributions, one mode
being in the sand or silt range, the other in the
clay range. See also diatomaceous, formi-
niferal, globigerina, pteropod, and radio-
larian oozes.

open drift ice—See open pack ice.

open ice—See broken ice.

open ice edge—Unsteady and not sharply defined
ice edge limiting an area of open ice, usually
located to the leeward. (74)

opening—Any break in sea ice which reveals the
water.

ree (an lead that is not covered with ice.

68

open ocean—Scee oceanic.

open pack ice—(or open drift ice). Ice floes of
sea ice that are seldom in contact with each
other; generally covermg between 4- and 6-
or (or 3- to 5-eighths) of the sea surface.

4

open port—A port which is not icebound during
winter.

open sound—A bay similar to a lagoon but with
large openings between the protecting islands.

2

open water—1. A relatively large area of free
navigable water in an ice filled region. (68)

2. More specifically, water which has less than
one-tenth of its surface covered with floating
ice. (59)

operculum—(or gil/ cover). In fishes, a bony or
membranous flap covering the external openings
of the gill slits.

ophiopluteus—The planktonic larva of a brittle
star.

opposing wind—Generally, same as headwind;
specifically, a wind blowing in the direction
opposite to ocean-wave advance; the opposite of
following wind. (5) See crosswind.

opposition—The situation of two celestial bodies
with their celestial longitudes (the angular dis-
tance measured east of the vernal equinox along
the ecliptic) differing by 180 degrees; for exam-
ple, opposition occurs when the moon and the
sun are directly in line with the earth and on
opposite sides of the earth. (66) (See figure
for tide cycle.)

optical filter—A device which changes, by absorp-
tion or interference, the magnitude or the spec-
tral distribution of the radiant energy passing
through it. (8)

ORTHOGONAL

optical length—The geometrical length of a path
multiplied with the total attenuation coefficient
associated with the path. (8)

optimum ship routing—A technique for routing
ships, based on knowledge of sea currents,
weather, and wave conditions to get a ship to
its destination in the quickest time and with
least damage to cargo or discomfort to passen-
gers.

orange peel sampler—A bottom sediment sam-
pling device capable of obtaining as much as
1% cubic foot of sample from the ocean floor.
Named for its likeness to an orange that has its
peel quartered.

orbit—In water waves, the path of a water particle
affected by the wave motion. In deepwater
waves the orbit is nearly circular, and in shal-
low water waves the orbit is nearly elliptical.
In general, the orbits are slightly open in di-
rection of wave motion, giving rise to Mass
transport. (61) See figure on next page.

orbital current—The flow of water accompany-
ing the orbital movement of the water particles
in a wave. Not to be confused with wave-gen-
erated littoral currents. (6) See mass trans-
port.

orbital energy—The total energy associated with
the orbital motion of all water particles.

orbital energy difference—The excess of orbital
energy of water particles in orbital motion at
any depth over that at any lower depth of the
same water column.

orbital motion—Sce orbit.

orbital period—The time required for a water
particle in orbitalsmotion to complete one or-
bit.

orbital speed—The speed of water particles in
orbital motion along their orbits.

order—Scee classification of organisms.

ordinary tide level—Sce mean tide level.

ordinary tides—The word “ordinary” may be
used in tides as the equivalent of the word
“mean.” (50)

organic bank—See organic reef.

organic reef—A sedimentary rock aggregate com-
posed of living and dead colonial organisms
such as algae, coral, crinoids, and bryozoa.
When it is covered by more than 6 fathoms of
water, it isan organic bank.

orogeny—Large scale regional mountain form-
ing processes by folding, faulting, and thrust-
ing.

orthogonal—(or wave ray). A member of a
family of curves everywhere perpendicular to
the family of curves representing wave crests
on a refraction diagram; analogous to rays in
the theory of geometrical optics. (73) (See
figure for refraction diagram.)

115

PERIOD
t—T t — 5/6T t = 2/3T t= 1/2T t= 1/3T t — 1/6T t=O

WAVE DIRECTION

WAVE LENGTH (L)

~<— DEPTH

i MAJOR AXIS >
|

Qa
°

qd,

I MAJOR AXIS 34

a ee ee =<

ae AXIS

bs Sy —

rm MAJOR >

| 8 | Fa
d, gd MINOR —=——
AXIS

BOTTOM .

ELLIPTICAL ORBITS, SHALLOW WATER (BOTTOM DEPTH 500 FEET)

PERIOD
t—T t = 5/6T t = 2/3T t= 1/2T t= 1/3T t= 1/6T t=O

WAVE DIRECTION

WAVE LENGTH (L)

<—DEPTH

‘ Senet ee ae Hema

AO OO Oe mn en
aT nO: Sy Tat TO Oe a Qn eo — OOM
d, TOT TS sO Gs 2s Qe Bee) = —O—— OM

CIRCULAR ORBITS, DEEP WATER (BOTTOM DEPTH 500 FEET)

116

oscillation—The variation, usually with time, or
the magnitude of a quantity with respect to a
specified reference when the magnitude is alter-
nately greater and smaller than the reference.

(6

we etion ripple—Tiny sediment waves with
sharp, narrow, symmetrical crests and broader,
more rounded troughs formed by the action of
currents of equal speed alternating in opposite
directions. (2)

oscillatory wave—A wave in which each ‘indi-
vidual particle oscillates about a point with little
or no permanent change in position. The term
is commonly applied to progressive oscillatory
waves in which only the form advances, the in-
dividual particles moving in closed orbits. Dis-
tinguished from a wave of translation. See
also orbit. (61)

ostracod—One of a subclass (Ostracoda) of
minute crustaceans, the individuals of which
are unsegmented, laterally compressed, and en-
closed in a bivalve shell (carapace). Some
members are benthic; others are planktonic.
Many species are luminescent, and the dried
bodies of one genus often are used to demon-
strate bioluminescence.

otolith—(or carbone). An earbone of a fish or
marine mammal (such asa whale). Such bones
are more resistant to decomposition, digestion, or
solution than other bones and frequently occur
in marine sediment samples.

otter trawl—A large commercial fishing trawl
using kitelike wooden boards at the corners of
the mouth of the net. The boards are attached
to long cables and so angled that water pressure
drives them apart and keeps the net well spread
as it drags along the sea floor. (35)

outcrop—(or exposure). Naturally protruding,
or erosionally exposed or uncovered part of a
rock, bed, or formation, most of which is covered
by overlying material.

outer ridge—WSee ridge, rise.

outer slope—The steeply descending outer slope
of the reef below the dwindle point of abundant
living coral and coralline algae, which is or-
dinarily at about 10 fathoms. (56) (See fig-
ure for atoll.)

outflow—1. The flow of water from the river or its
estuary to the sea.

2. Total volume for any given period of time.

outlet glacier—A stream of ice from an ice cap
tothe sea. (68)

overfalls—Breaking waves caused by opposing
currents or by the wind moving against the
current. (73) —

overlapping mean—See consecutive mean.

overtide—A_ shallow water harmonic tide con-
stituent with a speed that is a multiple of the
speed of one of the basic constituents of the tide-
producing force. (49) See shallow water
constituent. .

OXYLUCIFERIN

overtopping—The amount of water passing over
the top of a structure as a result of wave run-up
orsurge action. (61)

overturn—(also called convective overturn).
The renewal of bottom water that occurs an-
nually in lakes and ponds in regions wherever
winter temperatures are cold enough. As the
surface waters are cooled in the autumn and
early winter, they become denser and therefore
sink, until the whole body of water is at 4°C, the
temperature of maximum density. Further
cooling is restricted to the surface layers, since
both ice and water colder than 4°C are less dense
than the underlying waters at 4°C.

This phenomenon does not take place over
most areas in the ocean because of the salinity
stratification, and usually the resulting brine is
dense enough to sink to the bottom only in the
extreme polar regions, where extensive freezing
occurs. (5)

overwash—That portion of the uprush that car-
ries over the crest of a berm or of a structure.
(61)

own-ship’s noise—(or self noise). Often the
limiting noise registered by a sonar receiver
produced by the ship (or equipment) itself or as
aresult of itsmotion. (28)

oxygen—The element occurring as a free gas in
the atmosphere and as a dissolved gas in sea
water, where it is usually measured in milliliter
per liter. The concentration of dissolved oxygen
in the sea generally at N.T.P. ranges between
0 and 8 milliliters per liter. Its saturation con-
centration decreases with increasing temperature
and salinity.

The oxygen content of sea water generally de-
creases from a maximum at and near the surface
to a minimum between 500 and 1,500 meters
(1,640 and 4,921 feet) , then increases with depth.

oxygen minimum layer—A subsurface layer in
which the dissolved oxygen content is very low
ornil. (25)

oxygen technique— (or light and dark bottle tech-
nique). A method of measuring gross photo-
synthesis by following the changes in dissolved
oxygen in a water sample containing phyto-
plankton. The method involves the use of
light bottles for indicating net photosynthesis
(oxygen evolution) and the use of dark bottles
to indicate loss of oxygen due to respiration.
Gross photosynthesis then equals the amount of
oxygen gained in the light bottle plus the amount
of oxygen lost through respiration in the dark
bottle.

oxyluciferin—An end product. of oxidized lucif-
erin compounds. In a generalized reaction
oxyluciferin, water, and energy released as a
form of visible light are produced during a
chemiluminescent reaction involving a luciferin
compound and luciferase, a biological catalyst.

117

OYASHIO

Oyashio—A cold current flowing from the Bering oyster—A member of one of several families, but

Sea southwest along the coast of Kamchatka, better known as one of the families Ostreidae
past the Kuril Islands, continuing close to the and Spondylidae, of irregularly shaped bi-
northeast coast of Japan and reaching nearly valves, which are cemented to a firm surface by
35°N. The Oyashio turns east into the the larger valve. They are notable fouling
Kuroshio extension. organisms in some regions.

118

Pacific anticyclone—Scee Pacific high.

Pacific high— (or Pacific anticyclone). The near-
ly permanent subtropical high of the North
Pacific Ocean, centered in the mean, at 30° to
40°N and 140° to 150°W.

On mean charts of sea level pressure, this
high is a principal center of action. (5)
Pacific Ocean—The ocean area bounded on the
east by the western limits of the coastal waters
of southwest Alaska and British Columbia, the
southern limits of the Gulf of California, and
from the Atlantic Ocean by the meridian of
Cape Horn to Antarctica; on the north by the
southern limits of Bering Strait and the Gulf
of Alaska; on the west by the easternly limits
of the Sea of Okhotsk, Japan Sea, Philippine
Sea, the East Indian Archipelago from Luzon
Island to New Guinea, Bismarck Sea, Solomon
Sea, Coral Sea, Tasman Sea, and from the In-
dian Ocean by a line from Southeast Cape (the
southern point of Tasmania) down the meridian
to the Antarctic Continent. The Equator sepa-
rates the Pacific Ocean into the North and South

Pacific Oceans.

The limits of the Pacific Ocean exclude the
seas lying within it.

ae short term for ice pack or pack ice.

65

packed ice—See close ice.

pack ice—(also called drift ice, ice pack, pack).
1. The term used to denote any area of sea ice
other than fast ice, no matter what form it takes
or how disposed. (74

The WMO Code defines very open pack ice
as ice of 1- to 3-tenths concentration, open pack
ice as 4- to 6-tenths concentration, close pack
ice as ice of 7- to 9-tenths concentration, and
very close pack ice as ice of 10-tenths concen-
tration.

2. A large area of floating ice which has been
driven together. The concentration can gen-
erally vary between 1- and 10-tenths. Other
terms that can be applied to pack ice include:
broken, loose, consolidated, and unbroken. The
terms pack ice and ice pack have been used in-
discriminately for both the sea area containing
floating ice and the ice itself.

packing—The spacing or density pattern of the
mineral grains in a rock or sediment. (2)

painter—(also called Callao painter, El Pintor).
A fog frequently experienced on the coast. of
Peru. The brownish deposit which it often

leaves upon exposed surfaces is sometimes called
Peruvian paint. (5)

pair production—An absorption process for X-
and gamma radiation in which the incident pho-
ton is annihilated in the vicinity of the nucleus
of the absorbing atom with subsequent produc-
tion of an electron and positron pair. This reac-
tion only occurs for incident photon energies ex-
ceeding 1.02 million-electron-volts. (70)

paleocrystic ice—Old sea ice, generally consid-
ered to be at least ten years old; it is nearly al-
ways a form of pressure ice, and often is found
in floebergs and in the pack ice of the central
Arctic Ocean. (5)

paleomagnetism—Remanent magnetism pro-
duced by the earth’s field when a material was
initially formed.

Palolo worm—A species (Hunice viridis) of poly-
chaete worms which spawns in vast, freeswim-
ming swarms over the reefs of the Samoan and
Fiji Islands during the last quarter of the moon
at the lowest tides during October and
November.

pan—An individual piece of pancake ice. (68)

pancake ice—(also called lly-pad ice, plate ice).
1. Pieces of newly-formed ice, usually approxi-
mately circular, about 30 centimeters (12 inches)
to 3 meters (10 feet) across, and with raised rims
caused by the striking together of the pieces as
a result of wind and swell. (74)

2. One or more pieces of newly-formed filoat-
ing ice, usually between 1 and 6 feet in diameter,
with raised rims and circular outline caused by
rotation and collision with other ice fragments.
(59)

Paper Nautilus—Scee nautilus.

parachute drogue—Scee drogue.

parallax—i. A tide term referring to the angle
at the center of a celestial body between a line
to the center of the earth and a line tangent to
the earth’s surface; the ratio of the mean radius
of the earth to the distance of the tide-producing
body. The term is usually applied to inequali-
ties in the tide which result from the continually
changing distance of the principal tide-produc-
ing body, the moon. See parallax inequality.

50
eM The change in apparent position of a nearby
object compared with more remote reference
objects when the nearby object is viewed from
two different points in space.

119

PARALLAX INEQUALITY

In reading several different-types of oceano-
graphic instruments, errors of parallax are
easily introduced if the line of sight is not care-
fully maintained perpendicular to the reading
scale. Parallax errors are of particular concern
in reading liquid-in-glass thermometers.

parallax inequality—The variation in the range
of tide or in the speed of tidal currents because
of the continual change in the distance of the
moon from the earth. The range of tide and
speed of tidal currents tend to increase as the
moon approached perigee and to decrease as it
approached apogee. (50)

parallel—See parallel of latitude (sense 1).

parallel of latitude—1. (also called parallel). A
circle (or approximation of a circle) on the sur-
face of the earth, parallel to the Equator, and
connecting points of equal latitude.

2. (also called circle of longitude). A circle
of the celestial sphere, parallel to the ecliptic,
and connecting points of equal celestial latitude.
(68)

paralytic shellfish poisoning—An intoxication in
humans resulting from the ingestion of marine
mollusks, usually mussels or soft clams, that
become toxic during periods of high concentra-
tions of certain dinoflagellates. The effects
range from mild discomfort to fatal respiratory
paralysis, with symptoms including tingling or
burning of the lips, gums, tongue, and face fol-
lowed by numbness of the extremities, a general
feeling of weakness and dizziness, inability to
coordinate muscular movements, and respira-
tory distress.

parameter—1!. In general, any quantity of a
problem that is not an independent variable.
More specifically, the term is often used to dis-
tinguish, from dependent variables, quantities
which may be more or less arbitrarily assigned
values for purposes of the problem at hand.

(Vote. Carelessly used by many oceanogra-
phers for almost any oceanographic quantity or
element.)

2. In statistical terminology, any numerical
constant derived from a population or a prob-
ability distribution. Specifically, it is an arbi-
trary constant in the mathematical expression
of a probability distribution.

(5)

parapodium—A paired lateral locomotive struc-
ture on body segments of polychaetes.

parasitic nutrition—That process by which an
organism absorbs organic food directly from
the body of its host. See hetereotrophic nutri-
tion.

parasitism—A relationship between two species
in which one lives on or in the body of its host,
and obtains food from its tissues. Some au-
thorities distinguish between a “commensal
parasite,” which obtains nourishment from its
host without causing harm, and a “pathogenic

120

parasite,” which benefits at the expense of its
host.

parent—A_ radionuclide that upon distintegra-
tion yields a specified nuclide, either directly or
as a later member of a radioactive series. (70)

partial node—The point, line, or surface, in a

standing wave system where some characteristic
of the wave field has a minimum amplitude dif-
fering from zero. (6)

partial tide—(also called tidal component, tidal

constitutent). One of the harmonic components
comprising the tide at any point. The periods
of the partial tides are derived from various
combinations of the angular velocities of earth,
sun, moon, and stars relative to each other. See
constituent. (5)

ANGULAR
NAME OF PARTIAL TIDE VELOCITY
’ | (DEGREES/HR.)

SEMIDIURNAL
PRINCIPAL LUNAR K 28.9841
PRINCIPAL SOLAR d 30.0000
LARGER LUNAR ELLIPTIC E 28.4397
LUNI-SOLAR d 30.0821

DIURNAL
LUNI-SOLAR d 15.0411
PRINCIPAL LUNAR J 13.9430
PRINCIPAL SOLAR : 14.9589

THE BASIC COMPONENTS OF THE TIDE-PRODUCING FORCES

(AFTER SVERDRUP, ET. AL., 1949)

particles—Scee grains.

particle velocity—In ocean wave studies, the in-
stantaneous velocity of a water particle under-
going orbital motion. At the crest, its direc-
tion is the same as the direction of progress of
the wave, and at the trough it is in the opposite
direction. (5)

parts per thousand—NSee per mille.

Pascal’s law—Pressure exerted at any point upon
a confined liquid is transmitted undiminished in
all directions.

pass—A narrow connecting channel between two
bodies of water; also the inlet through a bar-
rier reef atoll or sand bar or a navigable chan-
nel atariver’s mouth. (2)

passage—A narrow navigable pass or channel
between two landmasses or shoals. (68)

passive sonar—A method or equipment by which
information concerning a distant object under-
water is obtained by evaluating the sound gen-
erated by the object itself. (3)

patch—1. A collection of pack ice, less than 10

kilometers (5.4 nautical miles) across. (74)
2. An irregular cluster of floating sea ice frag-
ments of any concentration. (59)

path function—The radiance per unit length in
the direction of the line of sight, generated by
the scattered light of a beam.

peak—(or seapeak). See seamount.

peak sound pressure—The peak sound pressure
for any specified time interval is the maximum
absolute value of the instanteous sound pres-
sure in that interval. (6)

peak-to-peak value—For an oscillating quantity,
the algebraic difference between the extremes of
the quantity. (6)

Pearly Nautilus—S¢ee nautilus.

pebbles—Usually smooth and rounded stones
ranging in diameter between 4 and 64 millime-
ters. (2) See phi grade scale.

pedicellaria—One of the minute pincerlike ap-
pendages of sea urchins (and some starfishes),
borne abundantly on the test between the spines,
and consisting of three movable jaws (rarely
two, four, or five) mounted on a stalk. In some
species these organs are provided with poison
glands.

pelagic—See pelagic division.

pelagic-abyssal sediments—Deep sea sediments
that are free of terrestrial material except for a
small proportion of very fine clay.

pelagic division—A primary division of the sea
which includes the whole mass of water. The
division is made up of the neritic province which
includes the water shallower than 100 fathoms
(200 meters), and the oceanic province which
includes that water deeper than 100 fathoms.
(See figure for classification of marine
environments. )

pelagic limestone—A rock formed principally of
the calcareous tests of pelagic forminifera. It
usually is deposited in deep water.

pelagite—Sce nodules.

pelecypod—See bivalve.

pelite—(or mudstone, pelyte). Clastic sediments
composed of clay, minute particles of quartz,
rock flour, or volcanic ash (pelitic tuff) and
which may be calcareous.

peltic tuff—wSee pelite.

pelyte—See pelite.

pendulum—1. A body so suspended from a fixed
point as to swing freely to and fro under the
combined action of gravity and momentum.

2. A vertical bar so supported from below
by a stiff spring as to vibrate to and fro under
the combined action of gravity and the restoring
force of the spring.

peninsula—A body of land nearly surrounded by
water and connected with a large body by a neck
or isthmus; also any piece of land jutting out
into the water. (2)

penknife ice—See candle ice.

percolation—The process by which water is forced
by wave action through the interstices of the
bottom sediment and has a tendency to reduce
wave heights..-

PER MILLE

percolation factor—A quantity by which the
wave heights are reduced through percolation
alone.

perennial ice—Sea ice more than two years old.

59

Be ace figure—A numerical value (in deci-
bels) given to illustrate the operational effective-
ness of a sonar device, that is, the source level
minus the background noise level.

perigean range—(abbreviated Pn). The average
of all monthly tide ranges occurring at the time
of perigee. It is larger than the mean range,
where the type of tide is either semidiurnal or
mixed, and is of no practical significance where
the type of tide is diurnal. (73)

perigean tidal currents—Tidal currents of in-
creased speed occurring at the time of perigean
tides. (68)

perigean tide—Tides of increased range occurring
monthly near the time of the moon’s perigee.

perigee—The point in the orbit of the moon (or
any other earth satellite) nearest to the earth;
opposed to apogee. (50)

perihelion—The point in the earth’s orbit nearest
to the sun. (50)

periodic current—Sce tidal current, reversing
current.

periscope depth range—(abbreviated PDR).
The maximum range at which active sonar echo
ranging contact can be made with a submarine
operating at periscope depth.

permafrost—1. A layer of soil or bedrock at a
variable depth beneath the surface of the earth
in which the temperature has been below freez-
ing continuously from a few to several thou-
sands of years. Permafrost exists where the
summer heating fails to descend to the base of
the layer of frozen ground. A continuous
stratum of permafrost is found where the annual
mean temperature is below about 23°F.

2. As limited in application by P. F. Svetsov :
soil which is known to have been frozen for at
least a century.

(5)

permanent aurora—See airglow.

permanent current—A current such as the Kuro-
shio, which flows continuously and whose speed
and direction is little changed by the tide and
meteorological factors. A permanent current
also includes the continuous outflow of fresh
river water discharge. (50). See also ocean
current.

permanent ice foot—An ice foot that does not
melt completely insummer. (68)

permanent plankton—Sce holoplankton.

per mille—(symbol °/,,). Per thousand or 10%:
used in the same way as percent (%, per hun-
dred or 10-?). Per mille (by weight) as com-
monly used in oceanography for salinity and
chlorinity; for example, a salinity of 0.03452
(or 3.452 percent) 1s commonly stated as 34.52
per mille (parts per thousand). (5)

121

PERSISTENCE

persistence—1. In general, the tendency for the
occurrence of a specific event to be more proba-
ble, at a given time, if that same event has oc-
curred in the immediately preceding time period.
2. (also called constancy, steadiness). With
respect to the long term nature of the wind at
a given location, the ratio of the magnitude of
the mean wind vector to the average speed of
is wind without regard to direction.
5)
persistency—= See constancy of the current.
Peru Current— (also called Humboldt Current).
The cold ocean current flowing north along the
coasts of Chile and Peru. The Peru Current
originates from the West Wind Drift in the
subantarctic Pacific Ocean. The northern limit
of the current can be placed a little south of the
Equator, where the flow turns toward the west,
joining the South Equatorial Current.
Petersen grab—A type of bottom sampler con-
sisting of two hinged semicylindrical buckets
held apart by a cocking device. On striking
the bottom the locking device is released so that,
on hauling, the buckets revolve and come to-
gether, enclosing a sample of the bottom.
Phaeocystis—A genus of brown, unicellular, and
colonial, marine phytoplankton of the class
Chrysophyceae. Colonies are surrounded by
large gelatinous sheaths. This alga appears in
vast concentrations at times, especially in neritic
parts of the North Atlantic, coloring the water
brown and imparting an offensive odor to it.
Plankton nets towed through such masses are
clogged rapidly. Herring reportedly avoid
these concentrations.
plantom bottom—Scee ‘deep scattering layer.
pharyngeal teeth—Specialized dentition on vari-
ous gill arch elements in fishes; in some species
these teeth are used in sound production.
phase—The state of aggregation of a substance,
for example, solid (ice), liquid (water), or gas
(vapor). (5)
phase angle—The angular measure along a simple
harmonic wave. (5)
phase difference—Sce epoch.
phase inequality—1. Variations in the tide or
tidal currents associated with changes in the
phase of the moon. At new and full moon
(springs) the tide-producing forces of the sun
and moon act in conjunction, resulting in greater
than average tide and tidal currents. At first
and last quarters of the moon (neaps) the tide-
producing forces oppose each other result in
smaller than average tide and tidal currents.
(See ae for tide cycle.)
2. See spring tide, neap tides, tidal cur-
rents.
(50)
phase lag—~See epoch.
phase reduction—A processing of high and low
water observations to obtain quantities such as
spring and neap tide ranges and tidal currents,

which are associated with the changing phase
of the moon.

phase speed—See wave velocity.

phase velocity—Velocity, measured over a short
time period, at which a particular wave crest
is propagated through water or rock media.
(35)

phasor—The complex quantity measuring an
impedance. It may be computed as the quotient
of two other complex quantities, which are also
called phasors, and which are derived from
sinusoidally varying magnitudes of the stimu-
lus and the response in question. (28)

phi grade scale—A logarithmic transformation
of the Wentworth grade scale for size classifica-
tions of sediment grains based on the negative
logarithm to the base 2 of the particle diameter.

Phi Modified
Grade Grades Wentworth
Scale (Millimeters) Sediment Class
—8 >256. 0 Boulders, Rock______
—7 128. 0
me a a Cobblesu =e aaa
—5 32. 0 fe :
—4 16. 0 rave
9 80 Pebbles22))
—2 4.0
—1 2.0 Granuless== ===
0 1.0 Very Coarse_—+-----
+1 0. 5 Coarse___-_-__---
sae 0. 25 Medium === === Sand
+3 0. 125 Fines =. 02.5
+4 00625 ‘Very Pine == 22222 2=
a) 0. 03138
+6 0. 0156 ;
+7 0. 0078 Sue
+8 0. 0039
=p) 0 eae
+10 0. 0009
+11 0. 00049 Clay
+12 0. 00024
>+12 <0; 00024 Colloids= 2222-222)"

Phleger corer—A gravity sampling tube used to
obtain 114-inch diameter samples up to 4 feet
long. The sampler consists of a tailfin assembly
with attached weight, a core barrel with a
plastic liner inside it, a core cutter, and a core
catcher. When fully rigged, the corer weighs
about 100 pounds.

pholad—Scee rock borer.

phosphate phosphorus—An ionic form of phos-
phorus occurring in nature; an essential nutrient
for marine organisms. Estimates of primary
productivity have been made by determining
phosphate concentrations in a water column dur-
ing different seasons.

phosphor—See scintillator.

phosphorescence—1. The production of lght
without sensible heat.

2. Emission of electromagnetic radiation by
a substance as a result of previous absorption of
radiation of shorter wavelength. In contrast
to fluorescence, the emission may continue for
a considerable time after cessation of the exist-
ing irradiation.

122

3. Often erroneously used for biolumines-

cence, which is a chemiluminescence.

phosphorescent wheel—A phenomenon which
when fully developed gives the appearance of a
wheel of light revolving around a point source
on or just beneath the sea surface. Various
stages of development and sizes of wheels have
been reported. The vast majority of wheels
have been observed in oceans bordering southern
Asia and in the Indonesian Archipelago.

photic zone—Scee euphotic zone. (See figure for
classification of marine environments.)

photoautotrophic nutrition—See holophytic
nutrition.

photoconductive cell—A_ photocell whose elec-
trical conductance changes under irradiation.
“i oe supply is required in the cell circuit.

8

photoelectric effect—aA_ process by which a pho-
ton ejects an electron from an atom. All the
energy of the photon is absorbed in ejecting the
con and in imparting kinetic energy to it.

0

photoemissive cell—A_ photocell whose working
depends upon the photoemissive effect, that is,
the capacity of certain surfaces to release elec-
on under the influence of radiant energy.

8

photogenic granules—Chemical substances in the
form of granules associated with biolumines-
cence. The granules may be within luminous
organs (photophores) or scattered within the
surface layer of the body, or they may be se-
creted into the environment where they create
extracellular bioluminescence.

photomultiplier cell—A tube (valve) in which
secondary emission multiplication is used to in-
crease the output for a given incident radiant
energy. (8

photomultiplier tube—An electronic device which
converts photon interactions at the photocathode
into measurable electrical pulses.

It is utilized for measuring light intensity in
the ocean and in gamma ray detection
instrumentation.

photon—A quantity of electromagnetic energy
whose value in ergs is the product of its fre-
quency (v) in cycles per second and Planck’s
constant (h). The equation is: H=Av. (70)

photophore—A luminous organ, resembling an
eye, within which hght is produced either by
chemical reactions controlled by the organism or
by luminous bacteria living within the cells.
Photophores occur most commonly in marine
organisms inhibiting the middepths.

photosynthesis—The manufacture of carbohy-
drate food from carbon dioxide and water in the
presence of chlorophyll, by utilizing light ener-
gy and releasing oxygen.

See nutrition—See holophytic nutri-
ion. ;

207-109 O—66—_9

PIEZOELECTRIC EFFECT

<— ALUMINUM FOIL

Y
PHOSPHOR

3

DIAGRAMMATIC REPRESENTATION
OF A SCINTILLATION COUNTER

PHOTOCATHODE

PHOTOMULTIPLIER
TUBE

photovoltaic cell—A photocell which sets up a po-
tential difference between its terminals when ex-
posed to radiant energy. It is a self contained
current and voltage generator.

Note: The term “barrier-layer” cell is depre-

cated. (8)

phyllosoma larva—A modified schizopod stage
of the spiny lobsters; it is planktonic, paper
thin, and transparent.

phyllum—WSee classification of organisms.

physical oceanography—The study of the physi-
cal aspects of the ocean, such as its density, tem-
perature, ability to transmit light and sound,
and sea ice; the movements of the sea, such as
tides, currents, and waves; and the variability of
these factors both geographically and temporal-
ly in relationship to the adjoining domains,
namely, the atmosphere and the ocean bottom.

physical properties—The physical characteristics
of sea water; for example, temperature, salinity,
density, velocity, sound, electrical conductivity,
and transparency. (35)

phytoplankton—The plant forms of plankton.
They are the basic synthesizers of organic mat-
ter (by photosynthesis) in the pelagic division.
The most abundant of the phytoplankton are
the diatoms.

phytoplankton bottle—1. A container for taking
up a sample of water at a desired depth in order
to obtain a quantitative sample of phytoplank-
ton by filtration in the laboratory.

9. See vacuum filtration, Millepore* filter.

phytoplankton equivalent—S¢ee plankton equiv-
alent.

picocurie—One micro-microcurie or 107% curie.

piezoelectric effect—The phenomenon, exhibited
by certain crystals, in which mechanical com-
pression produces a potential difference between
opposite crystal faces, or, an applied electric

123

PILOT CHART

field produces corresponding changes in dimen-
sions.

Pilot Chart—A chart of a major ocean area pub-
lished, for the benefit of mariners, by the U.S.
Naval Oceanographic Office in cooperation with
the U.S. Weather Bureau. These charts con-
tain information required for safe navigation,
including ocean currents, ice at sea, wind roses,
storm tracks, isotherms, magnetic variation,
great circle routes, limits of trade winds, etc.
See sailing directions.

pilot whale—(or blackfish). Any of several spe-
cies of a genus (Globicephala) of large dolphins,
having worldwide distribution. These animals
commonly travel in schools, and many strand-
ings of them have been reported.

pinching—Scee nipping.

ping—An acoustic pulse signal projected by an
underwater transducer.

pinger—A battery powered acoustic device
equipped with a transducer that transmits
sound waves. When the pinger is attached to a
wire and lowered into the water, the direct and
bottom reflected sound can be menitored with
a listening device. The difference between the
arrival time of the direct and reflected waves
is used to compute the distance of the pinger
from the ocean bottom.

pingo—A hill or mountain completely covered by
an ice sheet, but revealing its presence by sur-
face indications. (2)

pinnacle—A sharp pyramidal or cone-shaped rock
partly or completely covered by water. Also a
small coral spire which lies near the water sur-
face in a lagoon..:

pinnacled iceberg—An iceberg formed and
weathered in such manner as to produce spires
or pinnacles. (68)

pinniped—A marine mammal of the order Pinni-
pedia, which comprises the seals, sea lions, and
walruses.

pinpoint—WSee fix.

pip—An echo trace on an electronic indicator
screen.

pisolites—Rounded granule-sized concretions
larger than o@lites, found in land and marine
deposits. They form pisolitic limestone when
cemented together.

pistol shrimp—Sce snapping shrimp.

piston-type corer—A corer equipped with a pis-
ton inside the core tube that is connected to the
lowering cable. When the corer penetrates the
ocean bottom, the piston, in effect, provides a
suction which overcomes the frictional forces
acting between the sediment sample and the in-
side wall of the coring tube. See Kullenberg,
Ewing, and Hydroplastic corers.

pitch—Scee ship motion.

Pit log—Short form for Pitometer long.

Pitometer log—A log consisting essentially of a
Pitot tube projecting into the water, and suit:
able registering devices. (68)

124

plain—A flat, gently sloping or nearly level
region of the sea floor. (62)

Planck’s constant—A natural constant of propor-
tionality (A) relating the frequency (v) of a
quantum of energy to the total energy (/) of
the quantum :

h= cs =6.624 x 10-°" erg-sec.

Vv

(70)

plane of reference—Sce chart datum.

planform—The outline or shape of a body of
water as determined by the still water level.
(61)

plankter—A single organism in the plankton.

plankton—The passively drifting or weakly swim-
ming organisms in marine and fresh waters.
Members of this group range in size from micro-
scopic plants to jellyfishes measuring up to 6
feet across the bell, and included the eggs and
larval stages of the nekton and benthos. See
phytoplankton, zooplankton.

plankton bloom—(or sea bloom). An enormous
concentration of plankton (usually phyto-
plankton) in an area, caused either by an ex-
plosive or a gradual multiplication of organisms
(sometimes of a single species)! and usually pro-
ducing an obvious change in the physical appear-
ance of the sea surface, such as discoloration.
Blooms consisting of millions of cells per liter
often have been reported. See red tide.

plankton centrifuge—A device for separating
plankton from water samples by centrifugal
force.

plankton equivalent—A _ relationship between
various chemical constituents or characteristics
of plankton whereby the measurement of one
characteristic can be used to derive the quantity
of other characteristics. In phytoplankton
studies, 1.0 milligram (mg) of carbon is equiva-
lent to 2.3 milligrams of dry organic matter,
42.0 milligrams of biomass, and 3.3 milligrams
of dry plankton. In zooplankton studies, 1.000
milligram of carbon is equivalent to 0.170 milli-
gram of nitrogen, 0.013 milligram of phos-
phorus, 8.300 milligrams of plankton biomass,
and 1.700 milligrams of dry plankton.

plankton haul—(or plankton tow, haul, tow). A
single tow of a plankton net.

plankton indicator—Sce plankton sampler.

plankton net—A net for collecting plankton. A
great variety of plankton nets have been con-
structed in attempts to fulfill specific require-
ments. Typically, the nets are cone shaped, but
several modifications of this shape as well as
completely different shapes exist. Variations in
design involve: mouth diameter, net length,
mesh aperture size, material, type of collecting
bucket, and opening or closing capability. Many
nets are used without any attachment (except
the necessary collecting bucket and mouth ring).
Others are attached to hollow cylinders bearing

flowmeters and closing devices, or are enclosed
within devices that may permit one or more of
the following: high-speed towing, quantitative
sampling, multiple sampling, and _ strip
sampling.

plankton pump—A device to raise water from de-
sired depths in order to collect plankton exist-
ing at those depths; the water is filtered at the
surface.

plankton recorder—See plankton sampler.

plankton sampler— (or plankton recorder, plank-
ton indicator). A device for collecting plank-
ton, usually designed to take quantitative sam-
ples. See plankton net.

plankton snow—Scee sea snow.

plankton tow—Scee plankton haul.

planula—A young ovoid planktonic larva of a
coelenterate.

plastic flow—A phenomenon in which bottom
sediments under pressure of a weight may flow
out from under the weight allowing partial or
complete burial.

plastic limit—Scee Atterberg limits.

plateau—A comparatively flat-topped elevation
of the sea floor of considerable extent across the
summit and usually rising more than 100 fath-
oms (200 meters) onallsides. (62)

plate ice—See pancake ice.

platform—Any manmade structure (aircraft,
ship, buoy, or tower) from or on which oceano-
graphic instruments are suspended or installed.

platform reef—An organic reef with a flat upper
surface. (2) See table reef.

pleuston—A community of macroorganisms float-
ing on the surface of the sea, for example
siphonophores, barnacles, isopods, gastro-
pods, etc. Seeneuston. (44)

plunge point—1. For a plunging wave, the point at
which the wave curls over and falls. (See fig-
ure for surf zone.)

2. The final breaking point of the waves just
ae they rush up on the beach.
61

plunging breaker—Scee breaker.

pluteus—A free-swimming larva of the sea ur-
chins and brittle stars, from supposed resem-
blance to an upturned easel.

plutonic rock—Igneous rock which has cooled
some distance below the surface and usually is
ae by a coarse grained structure.

5

pneumatocyst—(or vesicle, air bladder, float).
An air or gas bladder or float; structures so
called in siphonophores and in several species
of brown algae.

pneumatophore—In certain organisms, a gas-
filled, saclike structure, such as the float of the
Portuguese man-of-war, which generally serves
as a buoyant mechanism.

pocket—See blind lead.

pod—(or school). A number of animals (as seals
or whales) closely clustered together. (“We

POLYNYA

lowered for a pod of four or five whales.”—
Herman Melville): School (pod is usually used
for groups smaller than a school, as, “pods of
15 to 25 seals detached from the main group.”—
M. E. Stansby).
point—The extreme end of a cape; or the other
end of any area protruding into the water, us-
ually less prominent than a cape. (61)
polar air—A type of air whose characteristics are
developed over high latitudes, especially within
the subpolar highs. Continental polar air (cP)
has low surface temperature, low moisture con-
tent, and, especially in its source regions, has
great stability in the lower layers. It is shallow
im comparison with arctic air. Maritime polar
air (mP) initally possesses similar properties to
those of continental polar air, but in passing
over warmer water it becomes unstable with a
higher moisture content. (5)
polar anticyclone—Scee arctic high.
polar cap ice—See polar ice.
polar convergence—A line along which cold polar
intermediate water sinks under the warmer
subpolar water in its movement toward lower
latitudes. It is marked by a sharp change in
surface temperatures, particularly in the South-
ern Hemisphere. See Arctic Convergence,
Antarctic Convergence.
polar drift ice—Drift ice composed exclusively
of polar ice.
polar fast ice—1. Fast ice formed by the ground-
ing and cementing together of polar ice. (74)
2. Fast ice of more than one winter’s growth
polar high—See arctic high.
polar ice—(or polar-cap ice). 1. Seaice that is
more than one year old (in contrast to winter
ice). It is usually the thickest form of sea ice,
occasionally exceeding a thickness of ten feet.
The WMO Code defines it as any sea ice more
than one year old and more than 3 meters (9.8
feet) thick.
9. See arctic pack (sense 3).
3. A Russian term for any sea ice more than
two years old.
pole of inaccessibility—WSee ice pole.
pollutants—Waste products from industry or in
sewage. (35)
polychaete—One of an order (Polychaeta) of
annelids which includes most of the marine seg-
mented worms, some of which are the tube-
worms of fouling. Some of these worms are
luminescent during spawning. See tubeworm.
polyconic projection—A projection where the
latitude curves are developed as a series of tan-
gent cones. The scale is chosen to be true along
a selected central meridian. This projection is
neither conformal nor equal area.
polynya—(or clearing, ice clearing). 1. A water
area enclosed in ice, generally fast; this water
area remains constant and usually has an oblong
shape; sometimes limited to one side by the
coast. (74)

125

POLYNYA OFF EDGE OF SHORE ICE

2. Any enclosed sea water area in pack ice
other than a lead, not large enough to be called
open water. Ifa polynya is found in the same
region every year, for example, off the mouths
of big rivers, it is called a recurring polynya. A
temporary small clearing in pack ice which con-
sists of small ice floes and brash ice in con-
tinuous local movement is called an unstable
polynya; an opening which is flanked by large
floes and therefore appears to be relatively
stable is called a stable polynya. When frozen
over, a polynya becomes an ice skylight from
the point of view of the submariner. (7)

polynya off edge of shore ice—A polynya be-
tween shore ice and drift ice formed by squeez-
ing winds and currents. (74)

polyp—An individual sessile coelenterate.

polytrocular larva—An advanced stage of the
planktonic young of certain annelids, in which
several segments, each bearing a ring of cilia,
are present.

Polyvinyl (PVC)
corer.

polyzoa—See bryozoan.

polyzoan—See bryozoan.

P, constituent—The principal solar diurnal con-
stituent of the theoretical tide-producing
forces. (See figure for partial tide.)

pool—Any enclosed relatively small sea area in
pack ice, drift ice other than a lead or lane.
(74) See polynya, puddle.

population—The total collection of units being
considered statistically. (22)

porosity—The ratio of the aggregate volume of
pore space in a rock or sediment to its total vol-
ume, usually expressed as a percentage. (2)

porpoise—A small to moderate sized member of
the cetacean suborder Odontoceti. The name is
used interchangeably with dolphin by some.
More properly it is given to the small and beak-
less members of the family Delphinidae, which
have a triangular dorsal fin and spade-shaped
teeth.

port plan—A geographical outline of a port area
showing piers, railroad extensions, repair facili-
ties, pilot office, customhouse, and other applica-
ble non-navigational features.

positive estuary—An estuary in which there is
a measurable dilution of sea water by land
drainage.

positive gradient—A positive rate of change with
depth.

potential density—The density that a parcel of
water would have if raised adiabatically to the
surface, that is, if determined from the parcel’s
in situ salinity and potential temperature.

potential energy—The energy resulting from the
elevation or depression of the water surface
from the undisturbed level. This energy ad-
vances with the wave form. (61)

potential temperature—In oceanography, the
temperature that a water sample would attain

corer—See Hydroplastic

if raised adiabatically to the sea surface. For
the deepest points of the ocean, which are just
over 10,000 meters, the adiabatic cooling would
be lessthan1.5°C. (5)

potrero—An accretionary ridge separated from
the coast by a lagoon and barrier island, as
along the Texas coast. (2)

potted—Instruments, connections, or fittings en-
capsulated in a waterproof plastic material.

power gain—The amount (in decibels) by which
the output power level exceeds the input power
level. Thus, if the output power of a device
is 10 times that of the input, the power gain
is 10 decibels. On the other hand, if the out-
put is one hundred times that of the input, the
gain is 20 decibels. (8)

power level—Power level, in decibels, is 10 times
the logarithm to the base 10 of the ratio of a
given power to a reference power. The refer-
ence power must be indicated. (6)

power spectrum—The decomposition of the vari-
ance of a random process over frequency inter-
vals.

precision—See accuracy.

pressure fluctuation—Sce
fluctuation.

pressure force—(or pressure gradient force).
The force due to differences of pressure within a
fluid mass. The force per unit volume is equal
to the pressure gradient, and the force per unit
mass is equal to the product of the volume force
and the specific volume. (5)

pressure gage—A tide gage that is operated at
the bottom of a body of water and which records
tide heights by the change in pressure due to the
rise and fall of the tide. (50)

pressure gradient—The rate of decrease (gradi-
ent) of pressure in space at a fixed time. The
term is sometimes loosely used to denote simply
the magnitude of the gradient of the pressure
field. (5)

pressure gradient force—Sce pressure force.

pressure gradient hydrophone—A. hydrophone
in which the electric output substantially corre-
sponds to a component of the gradient (space
derivative) of the sound pressure. (69)

pressure hydrophone—A hydrophone in which
the electric output substantially corresponds to
the instantaneous sound pressure of the im-
pressed sound wave. (69)

pressure ice—(or screw ice). Sea ice (or river or
lake ice) which has been deformed or altered by
the lateral stresses of any combination of wind,
water currents, tides, waves, and surf. This
may include ice pressed against the shore or over
another piece of ice. Rafted ice, tented ice,
pressure ridges, and hummocks are forms of
pressure ice.

pressure ice foot—An ice foot formed along a
shore by the freezing together of stranded pres-
sure ice. (68)

bottom pressure

126

pressure level—The sound intensity, as measured
in decibels relative to units of dynes per square
centimenter, such as 0.0002 dyne per square
centimeter, 20 times the common logarithm of
the acoustic pressure.

pressure ridge—A ridge or wall of hummocks
where one ice floe has been pressed against an-
other. (74)

Ridges may be several miles long and up to 100
feet high. A corresponding ridge may also oc-
cur on the underside of the ice canopy and is
called anice keel. (7)

pressure wave—A _ short-period oscillation of
pressure such as that associated with the propa-
gation of sound through the atmosphere; a type
of longitudinal wave. (5)

prevailing current—The flow most frequently
observed during a given period, usually a month,
season, or year.

Price-Gurley current meter—A battery powered
electromechanical current meter which measures
current speed only.

primary bench mark—See bench mark.

primary film—(or slime film, diatom film, bac-
terial film). he thin slimy layer that usually
forms initially on a surface placed in sea water ;
it is composed of bacteria, diatoms, or both, and
is believed by some to be a necessary precursor
to attachment of larger fouling organisms.

primary production—(or gross primary produc-
tion, primary productivity). The amount of or-
ganic matter synthesized by organisms from in-
organic substances in unit time in a unit volume
of water or in a column of water of unit area
cross section and extending from the surface to
the bottom. (40)

primary productivity—Sce primary production.

primary tide station—A place at which contin-
uous tide observations are made over a number
of years. (68) See reference station.

prime meridian—The meridian of longitude 0
degrees, used as the origin for measurements of
longitude. The meridian of Greenwich, Eng-
land is the internationally accepted prime merid-
lan on most charts. However, local or national
prime meridians are occasionally used.

priming of the tides—The periodic acceleration
in the time of occurrence of high and low wa-
ter because of changes in the relative positions
of the moon and the.sun. The opposite effect
is called lagging of the tides.

primitive period—The primitive period of a peri-
odic quantity is the smallest increment of the
independent variable for which the function re-
peats itself. (6)

principal axis—In a transducer used for sound
emission or reception, a reference direction for
angular coordinates used in describing the di-
rectional characteristics of the transducer. It
is usually an axis of structural symmetry or the
direction of maximum response, but if these do

PROTON

not coincide, the reference direction must be de-
scribed explicitly. (69)

probability—The chances that a prescribed event
will occur, represented as a pure number p in the
range 0SpS/. The probability of an impossi-
ble event is zero and that of an inevitable event
is unity.

Probability is estimated empirically by rela-
tive frequency, that is, the number of times the
particular event occurs divided by the total
count of all events in the class considered. (5)

probability theory—Sce probability.

probe—A measuring device or sensor inserted into
the environment to be measured. As applied to
oceanography the term is used for devices which
are lowered into the sea for in situ measure-
ments.

production—The sum of the organic matter pro-

duced by living organisms in a given area or
volume in a given time, inclusive of such orga-
nisms which might have developed and disap-
peared in the given time.

productivity—An inexact term, indicating the
fertility of an ocean area. Most authorities have
abandoned the term and use primary produc-
tion or production instead to which specific
definitions have been assigned.

profile—1. A drawing showing a vertical section
along a surveyed line.

2, A graph showing as ordinate the variation
of some oceanographic quantity along a straight
line against horizontal distance on this line as
abscissa.

3. See trace.

progressive wave—A wave which is manifested
by the progressive movement of the wave form.
(61) (See figure for standing wave.)

prohibited anchorage—Sce anchorage.

promontory—A high point of land extending into
a body of water. (30) See cape, headland,
bluff.

propagation—The
through a medium.

propagation anomaly—In underwater acoustics
the difference between the actual propagation
loss for a given length of water path and the
nominal value of propagation loss identified
with the distance covered by that path. (28)

propagation loss—The transmission loss asso-
ciated with any given length of ray path in the
water. (28)

propeller noise—Noise produced by cavitation at
the propellers.

protected thermometer—A reversing thermom-
eter which is encased in a strong glass outer shell
that protects it against hydrostatic pressure.
(5)

proton—An elementary nuclear particle with a
positive electric charge equal numerically to the
charge of the electron and a mass of 1.007594
mass units. It is one of the constituents of every
nucleus. (70)

transmission of energy

127

PROTOZOA

Protozoa—l. A phylum of mostly microscopic,
one-celled animals. This group constitutes one
of the largest populations in the sea, including
some bioluminescent genera.

2. An often used common name for the mem-
bers of the phylum.

protozoan—One of a phylum (Protozoa) of
single-celled animals. See Protozoa.

proud of the bottom—Resting on the surface of
the bottom, that is, not imbedded in the bottom.

province—A region composed of a group of simi-
lar bathymetric features whose characteristics
iG Hak: in contrast with surrounding areas.

62

psammite—(or spelled psammyte).
stone.

psephite—A coarse fragmental rock (conglom-
on or deposit composed of rounded pebbles.

2

pteropod—(or sea butterfly). One of an order
(Pteropoda) of pelagic, free-swimming gastro-
pods in which the foot is modified into fins; both
shelled and nonshelled forms exist. The accum-
ulated shells of these organisms form a type of
bottom sediment called pteropod ooze in some
ocean areas. See ooze.

pteropod ooze—A pelagic sediment containing
at least 30 percent calcium carbonate in the form
of tests of marine animals, the dominant form
being pteropods. See ooze.

puddingstone—Sce conglomerate.

puddle—(also called pool, snow puddle on the
ice). 1. See snow water on the ice.

2. A small body of water, usually fresh melt
water, in a depression or hollow on ice. (68)
pulse height analyzer—An electronic circuit
which sorts and records pulses according to

height (energy).

Such electronic devices are used for sorting of
pulses from gamma ray interactions in the de-
tector of a gamma ray spectrometer. Ob-
served pulses are sorted into adjacent energy

See sand-

channels enabling determination of the energy
spectra or energy frequency distribution of ob-
served gamma rays in a selected energy range
(usually 0 to 3 million-electron-volts for gamma
ray emitting radioisotopes). Pulse height
analyzers may be single or multichannel devices.
All multichannel analyzers consist of (1) an
analog-to-digital converter which assigns a
channel to each input pulse according to its
amplitude (energy), (2) a memory which re-
cords the number of counts falling into each
channel and, (3) a display or readout device
indicating the number of counts in each channel.
(70)

pumice—An excessively cellular, glassy lava. It
is very light and can float on water until it be-
comes waterlogged and sinks.

pure water—(or distilled water). Water that
contains no impurities. Compare with fresh
water.

purse seine—A large net, used in commercial fish-
eries, placed in a circle around a school of fish
and drawn together. (35)

pycnocline—The vertical gradient of density.

pycnogonid—See sea spider.

pyramidal iceberg—A pinnacled iceberg of
pyramidal shape. (59)

pyramidal sea—Scee intersecting waves.

pyrheliometer—A general term for the class of ac-
tinometers which measure the intensity of direct
solar radiation. In oceanography, this instru-
ment measures the total sun and sky radiation
received on a horizontal surface.

pyrosome— (or jire body, fire cylinder). One of a
genus (Pyrosoma) of luminescent, pelagic, co-
lonial tunicates. Individuals form thimble-
shaped colonies commonly 3 or 4 inches long but
reaching a length of at least 2 feet. They occur
only in warm waters and produce brilliant
luminescence resembling long incandescent gas
mantles.

128

Q

Q factor—1. The pressure coefficient of the un-

protected thermometer expressed in °C. (67)
2. See quality factor.

quadrature—The position in the phase cycle when
the two principal tide producing bodies (moon
and sun) are nearly at a right angle to the earth;
the moon is then in quadrature in its first quarter
or last quarter. (See figure for tide cycle.)

quadrature spectrum—tThe spectral decomposi-
tion of the 90-degree out-of-phase components of
the covariance of two functions of time.

qualitative plankton sampler—A sampler that
sieves out organisms from the water but does not
measure the volume of water filtered.

quality factor—(also called @ factor). The
quantity, @, 1s a measure of the sharpness of
resonance of frequency selectivity of a resonant
vibrator system having a single degree of free-
dom, either mechanical or electrical. A high
value for @ means that the resonance is sharp,
that is, any small change in the frequency of the
excitation causes a large drop in the response of
the system. (38)

quantitative plankton sampler—A sampler that
sieves out organisms from the water and meas-
ures the volume of water filtered.

quantity of radiant energy—The quantity of
energy transferred by radiation. Unit of
measurement isin Joules orergs. (8)

quar ice—A Labrador term for ice formed in
spring from melt water draining on to a beach,
ice foot, or fast ice, where it refreezes. (8)
Rare.

quarter-diurnal tide—The tide resultmg from
the distortion of the normal tide in shallow wa-

ter, with four high water and four low wa-
ters during oneday. (32)

quartering sea—Sce beam sea.

quartz—A form of silicon dioxide. The most
common inorganic constituent of marine sedi-
ments. (9)

quasi-synoptic—Nearly
mental] measurements.

quenching—The great reduction in underwater
sound transmission or reception resulting from
absorption and scattering of sound energy by
air bubbles entrapped around the sonar dome.
Roll and pitch of the ship in relatively rough
water is the primary cause of air bubble
entrapment.

quench/ping ratio—In sound ranging, a meas-
ure of the sound lost from quenching. Based
on the ratio of the number of echoes received
oe to the number of pulses emitted
ping)

quick—Sediment of clay to sand size which by
absorption or admixture of water becomes loose,
incoherent, unstable, liquid or semiliquid, and
capable of flowing easily under load or by force
of gravity. Quick clay of glacial or marine
origin becames metastable or “quick” as a result
of the leaching out of salts and their replace-
ment by water. Any shock may cause a re-
orientation of the grain structure with squeezing
out of the interstitial water and conversion of
the clay into a plastic or semiliquid state in
which the clay will flow and fail under load.

quick clay—See quick.

quicksand—~See quick.

Q wave—See Love wave.

simultaneous environ-

129

R

race—A very fast current flowing through a
relatively narrow channel. (50)

radiance—In radiometery, a measure of the in-
trinsic radiant intensity emitted by a radiator
in a given direction. It is the irradiance
(radiant flux density) produced by radiation
from the source upon a unit surface area oriented
normal to the line between source and receiver,
divided by the solid angle subtended by the
source at the receiving surface. It is assumed
that the medium between the radiator and re-
ceiver is perfectly transparent; therefore, radi-
ance is independent of attenuation between
source and receiver. (5)

radiance meter—An irradiance meter which
collects radiant energy from a set of directions
and which has its field of view limited to a cir-
cular solid angle of © magnitude (defined, for
example, by a cylindrical tube) whose axis is
fixed normal to the plane of the collecting area
of the meter. If # is the reading of the meter,
the associated radiance is L=ZH'/Q. (8)

radiant emittance (at a point on a surface)—The
radiant flux emitted by an infinitesimal element
of surface containing the point under considera-
tion, divided by the area of that element. Unit

of measurement is watt per square meter
(W/m?). (8) sis
radient energy—(also called radiation). 1. The

energy of
radiation.

2. Infrequently, any energy that may be
radiated, as, for example, sonic energy.

radiant flux—The time rate of flow of radiant
energy. Unit of measurement is watts. (8)

radiant intensity (of a source in a given direc-
tion)—The radiant flux emitted by a source,
or by an element of a source, in an infinitesimal
cone containing the given direction, divided by
the solid angle of that cone.

Note: For a source which is not a point
source; the quotient of the radiant flux received
on an elementary surface by the solid angle
which this surface subtends at any point of the
source, when this quotient is taken to the limit
as the distance between the surface and the
source 1s increased.

Unit of measurement is watt per steradian
(W/sr). (8)

radiated noise—The underwater sound energy
emitted by ships, submarines, and torpedoes.

any type of electromagnetic

radiation—1. The emission and propagation of
energy through space or through a material
medium in the form of waves; for instance, the
emission and propagation of electromagnetic
waves, or of sound and elastic waves.

2. The energy propagated through space or
through a material medium as waves; for
example, energy in the form of electromagnetic
waves or of elastic waves. The term radiation
or radiant energy, when unqualified, usually
refers to electromagnetic radiation; such
radiation commonly is classified according to
frequency, as Hertzian, infrared, visible (light),
ultra-violet, X-ray, and gamma ray. (See
photon).

3. By extension, corpuscular emissions, such
as alpha and beta radiation, or rays of mixed or
unknown type, as cosmic radiation.

(70)

radiation absorbed dose—(abbreviated rad). A
measure of the dose of any ionizing radiation to
body tissues in terms of the energy absorbed per
unit mass of the tissue. One rad is the dose cor-
responding to the absorbtion of 100 ergs per
gram of tissue. One millirad (mrad) equals
0.001 rad. (As defined by the Atomic Energy
Commission.)

radiation detector—Any device for converting
radiant energy to a form more suitable for
observation. (Reactor engineering) An instru-
ment used to determine the presence and some-
times the amount of radiation or neutron flux.
(70)

radioactive age determination—The determina-
tion of the age of a rock or sediment by measur-
ing the proportion of the radioisotope Carbon™*
in the organic material it contains. A method
(radiocarbon dating) is based upon the known
rate of conversion of carbon to its isotope and is
accurate to a maximum age of about 30,000
years. Other chemical elements can be used
similarly for age determination.

radioactive decay—The disintegration of the
nucleus of an unstable nuclide by the sponta-
neous emission of charged particles and/or
photons. (70)

radioactive equilibrium—A condition which may
occur in the course of the decay of a radioactive
parent having shorter-lived descendants, in
which the ratio of the activity of the parent to
that of a descendant is independent of time.

130

This condition can exist only when no activity
longer-lived than that of the parent is interposed
in the decay chain. (41)
radioactive half-life—The time required for a
radioactive substance to lose 50 percent of its
activity by decay. Each radionuclide has an
unique half-life. (70)
radioactive series—A succession of nuclides, each
of which transforms by radioactive disintegra-
tion into the next until a stable nuclide results.
The first member is called the parent, the inter-
mediate members are called daughters, and the
final stable member is called the end product.
Three such series are encountered in natural
radioactivity, and many others are encountered
in induced radioactivity, particularly among
the heavy elements and fission products. (41)
radioactive tracer—A radionuclide used as an
oceanographic tracer having radioactivity as
its distmguishmg property. Radioactive
oceanographic tracers include Tritium (H*),
Carbon™, and fallout radioisotopes (fission
products).
radioactivity—1. The process whereby certain nu-
clides undergo spontaneous disintegration in
which energy is liberated, generally resulting in
the formation of new nuclides. The process is
accompained by the emission of one or more
types of radiation, such as alpha particles, and
gamma photons.
2. A particular radiation component from a
radioactive source, such as gamma radioactivity.
3. A radionuclide, such as a radioactivity
produced in a bombardment.
(70)
radiobiology—That branch of biology which deals
with the effects of radiation on biological sys-
tems. (41)
radiocarbon age—This age is calculated from the
specific activity, due to Carbon", of the carbon
in a once-living object; such radiocarbon dating
is possible because Carbon" is produced in the
atmosphere by cosmic rays and is incorporated
into all living objects; after death the Carbon**
activity decays exponentially with a half-life of
5,568 years. (41)
radiocarbon dating—WSce
determination.
radiochemistry—The aspects of chemistry con-
nected with radionuclides and their properties,
with the behavior of minute quantities of radio-
active materials by means of their radioactivity
and with the use of radionuclides in the study
of chemical problems. (70)
radioisotope—1. Any radioactive isotope of an
element.
2. A word loosely used as a synonym for
radionuclide.
(41)
radioisotopic oceanography—That _ oceano-
graphic disclipline dealing with the measure-

radioactive age

RATE OF DECAY

ment and distributional analysis of ocean-borne
radioisotopes.

Radiolaria—Sce radiolarian.

radiolarian—One of an order (Radiolaria) of
single-celled planktonic protozoa possessing a
skeleton of siliceous spicules and radiating
threadlike pseudopodia. Most members are
pelagic, and many are luminescent.

radiolarian 00ze—Deposits of siliceous sediments
distinguished by large proportions of minute
opaline silica shells (es) of radiolarians.
Water depths between about 13,000 and 25,000
feet are most favorable for the preservation of
radiolarian tests. See ooze.

radionuclide—A synonym for radioactive nu-
clide. (41) See radioisotope.

rafted ice—(also called telescoped ice). Pres-
sure ice in which one ice floe overrides
another. (74)

rafting—1. The process by which rafted ice is
formed. (65)

2. The transporting of sediment, rocks, silt,

and other matter of land origin out to sea by
ice, logs, etc., with subsequent deposition of the

rafted matter when the carrying agent
disintegrates. (68)
ram—1. (also called spur or apron). An under-

water ice projection from an iceberg or a
hummocked ice floe. Its formation is usually
due to a more intensive melting of the unsub-
merged part of the floe. (47)

2. In ice navigation, to charge obstructing
ice withaship. (59)

ramp—(also called drift ice foot). An accumula-
tion of snow that forms an inclined plane be-
tween land or land ice elements and sea ice or
shelf ice. See bridge. (65)

random noise—An oscillation whose instanta-
neous magnitude is not specified for any given
instant of time. The instantaneous magnitudes
of a random noise are specified only by proba-
bility distribution functions giving the fraction
of the total time that the magnitude, or some
sequence of magnitudes, lie within a specified
range. (6)

range—1. The difference between the maximum
and minimum of a given set of numbers; in a
periodic process it is twice the amplitude, that
is, the wave height.

2. The distance between two objects, usually
an observation point and an object under
observation.

3. A maximum distance attributable to some
process, as in visual range or the range of an
aircraft.

(5)
rapture of the deep—sScee nitrogen narcosis.
rate of decay—The time rate at which the sound
pressure level, or any other stated characteristic,
decreases at a given point in a given time. A
commonly used unit to express the rate of decay

131

RATIO OF RANGES
is the decibel per second. (3) See decay,
radioactive decay.

ratio of ranges—(or height ratio). The ratio of
the height of the tide at the secondary station
to the height of the tide at the reference station.

ray—Any of a large number of elasmobranchi of
the order Batoidei, in which the body generally
is compressed dorso-ventrally, the eyes are on the
upper surface, the gill clefts on the lower surface,
and the tail often is reduced to a whiplike
appendage. The order includes the electric
rays, stingrays, and manta rays.

rayl—See specific acoustic impedance.

ray path—The energy associated with a point ona
wave front that moves along an imaginary line
known as a ray path. The ray paths encoun-
tered in acoustics, which are commonly called
sound rays, are analogous to the light rays of
optics. Ray paths and wave fronts are mutually
perpendicular.

ray pattern—A graphic presentation of the paths
of sound rays in relation to depth and range.

ray theory—A method for determining the path
of transmitted underwater sound based on
Snell’s law. This law describes the change in
the sound ray path as it passes through different
density (sound velocity) layers.

peach gt An arm of the sea extending into the
land.

2. A straight section of restricted waterway
of considerable extent ; may be similar to a nar-
roe except much longer in extent.

(73)
recession— (also called retrogression). 1. A con-
tinuing landward movement of the shoreline.

2. A net landward movement of the shoreline
over a specified time.

(61)

recognition differential—The recognition differ-
ential for a specified listening system is that
amount by which the signal level exceeds the
noise level presented to the ear when there is a
ann probability of detection of the signal.
(3

recrystallization—The formation of new mineral
grains in a rock while in the solid state.

rectilinear current—Sce reversing current.

recurring polynya—See polynya.

recurved spit—(or hook, hooked spit). A. hook

developed when the end of a spit is turned
toward the shore by current deflection or by the
opposing action of two or more currents.

RECURVED SPIT

(AFTER: LEET, L. DON & JUDSON, SHELDON. PHYSICAL
GEOLOGY. NEW YORK: PRENTICE-HALL, INC. 1954, p. 264.)

red alga—One of a division or phylum (Rhodo-
phyta) (the Rhodophyceae of another scheme)
of reddish, filamentous, membranous, encrusting,
or complexly branched plants in which the color
is imparted by the predominance of 7-phycoery-
thrin over the chlorophylls and other pigments.
Some notable members of the group are the
sources of agar-agar, such as Gelidiuwm, Graci-
laria, and Hucheuma, Irish moss, Chondrus, and
the encrusting calcareous Lithothammion of
coral reefs. Red algae are worldwide in their
distribution, bemg more abundant in temperate
waters and ranging to greater depths than other
algae.

red mud—A reddish-brown terrigenous deep sea
mud containing up to 25 percent calcium car-
bonate which accumulates on the sea floor near
deserts and off the mouths of largerivers. (48)

red tide—A red or reddish-brown discoloration of
surface waters, most frequently in coastal
regions, caused by concentrations of certain
microscopic organisms, particularly dinoflagel-
lates. Toxins produced by the dinoflagellates
can cause mass kills of fishes and other marine
animals. Airborne particles which are optic and
respiratory irritants to humans and animals,
may be carried from red tide areas overland.
Red tides may develop rapidly, apparently as
a result of an abrupt change in one or more
environmental factors. In some regions at least,
notably off the west coast of Florida, the onset
of red tide appears to follow increased rainwater
runoff from the land; the introduction by this
means of one or more scarce nutrient elements
into the sea is believed to permit the dinoflagel-
lates to multiply rapidly. See discolored
water.

red water—WScee red tide, discolored water.

reef—An offshore consolidated rock hazard to
navigation with a least depth of 10 fathoms
(20 meters) or less. (62) See shoal. (See
figure for atoll and coral reef.)

Note: For many years, a depth of 6 fathoms
has been considered critical for navigational
safety. Because of the increased drafts of mod-
ern ships, a depth of 10 fathoms is now consid-
ered critical.

reef complex—The solid reef core and all con-
tinguous detrital limestone and coral and
genetically related sediments or rocks. (2)

reef conglomerate—Sce reef talus.

reef flank deposit—Scee reef talus.

reef flat—A flat expanse of dead reef rock which
is partly or entirely dry at low tide. Shallow
pools, potholes, gullies, and patches of coral
Hebe and sand are features of the reef flat. It
is divisible into outer and inner sections. (2)
(See figure for atoll.)

reef front—The upper seaward face of the reef,
extending above the dwindle point of abundant
living coral and coralline algae to the reef
edge. This zone commonly includes a shelf,

132

bench, or terrace that slopes to 8 to 15 fathoms,
as well as the living wave-breaking face of the
reef. The terrace is an eroded surface or is
veneered with organic growth. The living reef
front above the terrace in some places is smooth
and steep; in other places it is cut up by grooves
separated by ridges that together have been
called groove and spur systems, forming comb-
tooth patterns. (56) (See figure for atoll.)

reef patch—A term for all coral growths that
have grown up independently in lagoons of bar-
riers and atolls. They vary in extent from
expanses measuring several kilometers across to
coral pillars or even mushroom-shaped growths
consisting of a single large colony. The smaller
representatives are called coral knolls or coral
heads. (2) (See figure for atoll.)

reef segment—That portion of an organic reef
lying between passes, gaps, or channels. (2)

reef talus—(or reef conglomerate, reef flank de-
posit, off-reef facies). Massive inclined beds
of debris derived principally from a reef and
deposited along the seaward margin of a living
reef.

reference level—1. In underwater sound, the
standard to which other sound levels can be
related. Two reference levels commonly used
are: 1 dyne per square centimeter and 0.0002
dyne per square centimeter.

2. See chart datum.

reference plane—Sce chart datum.

reference point—A specified location (in plan
and/or elevation) to which measurements are
referred. (61)

reference station— (or standard station, standard
port). A place where tide or tidal current con-
stants have been determined from observations,
and which is used as a standard for the com-
parison of simultaneous observations at a sub-
ordinate station. It is also a place for which
independent daily predictions are given in the
tide or tidal current tables, from which corre-
sponding predictions are obtained for other loca-
tions by means of differences or factors.

reflectance—The ratio of light given off by an
object to the amount of light striking the object,
expressed as percentage.

reflectance function—The ratio of the upwelling
irradiance at a depth to the downwelling ir-
radiance at the same depth.

reflected wave—The wave that is returned sea-
ward when a wave impinges upon a very steep
beach, barrier, or other reflecting surface. (61)

reflection—The process whereby a surface of dis-
continuity turns back a portion of the incident
radiation into the medium through which the
radiation approached. (5)

reflection loss—The reflection loss at the junction
between an energy source and an energy load is
the transmission loss measured by the ratio of
(1) the load power which would be measured if
source and load were connected by a hypothetical

133

REGIONAL GRAVITY

transducer having an input impedance equal to
the source impedance of the source, an output
impedance equal to the load terminals as are
developed at its source terminals, to (2) the
actual load power when source and load are con-
nected directly to each other. (28)

reflection of sound—The process whereby a sur-
face of discontinuity turns back a portion of the
incident sound into the medium through which
the sound approached. (5)

reflectivity—A measure of the fraction of radia-
tion reflected by a given surface; defined as the
ratio of the radiant energy reflected to the total
that is incident upon that surface.

refraction—The process in which the direction of
energy propagation is changed as the result of a
change in density within the propagating
medium, or as the energy passes through the
interface representing a density discontinuity
between two media. (5)

refraction coefficient—In wave hydrodynamics,
the square root of the ratio of the spacing be-
tween adjacent orthogonals in deep water to
that at a selected point in shallow water. When
multiplied by the shoaling coefficient, this
becomes the wave height coefficient or the ratio
of the refracted wave height at any point to the
deepwater wave height. Also the square root of
the energy coefficient. See wave refraction, re-
fraction of water waves, index of refraction
(sense 3).

refraction diagram—A drawing showing posi-
tions of wave crests and/or orthogonals in a
given area for a specific deepwater wave period
and direction. (61) See figure on next page.

refraction index—Sce index of refraction.

refraction loss—That part of the transmission
loss due to refraction resulting from nonuni-
formity of the medium. (6)

refraction of water waves—1. The process by
which the direction of a wave moving in shallow
water at an angle to the contours is changed.
That part of the wave advancing in shallower
water moves more slowly than the other part still
advancing in deeper water, causing the wave
crest to bend toward alignment with the under-
water contours.

2. The bending of wave crests by currents.

(61)

refractive index—Sce index of refraction.

refractivity—Rare. See index of refraction
(sense 1).

regelation—The melting of ice by the application
of pressure and the refreezing of melt water
upon release of that pressure. (59)

regional clearing—wSce polynya.

regional gradient—See regional gravity, re-
gional magnetism.

regional gravity—(or regional gradient). In
gravity prospecting, contributions to the ob-
served anomalies due to density irregularities
at much greater depths than those of the possible

REGIONAL MAGNETISM

Ws

\
\
WAVE FRONTS

SUBMARINE CANYON

DIVERGENCE OF
ORTHOGONALS
PRODUCES LOW
WAVES IN THIS
_ AREA.

JS ARENA COVE

CONVERGENCE OF ORTHO-
GONALS PRODUCES HIGH
WAVES IN THIS AREA

— — — DEPTH CONTOURS
IN FATHOMS

12 SECOND PERIOD

S|
(0) 10,000 FT.
SCALE

REFRACTION DIAGRAM

structures, the location of which was the pur-
pose of the survey.

regional magnetism—In terrestrial magnetism,
that part of the observed magnetic field that is
attributed to the earth’s magnetic field or to
effects which are too deep, too broad, or too great
in relief to be possible expressions of structure
or other features of interest.

regolith—(or mantle, rock, saprolith). The sur-
face layer of sediment, rock waste, alluvium,
volcanic ash, glacial drift, organic matter and
windblown material which lies above bedrock.

regressive—A pplied to bodies of water and sedi-
ments deposited therein during withdrawal of
the water and/or emergence of the land. (2)

regressive reef—One of a series of reefs or bio-
herms cleveloped close to and generally parallel
to the shore as a result of a retreating sea or
rising landmass. (2)

relative biological effectiveness— (abbreviated
RBE). A factor which is used to compare the
biological effectiveness of absorbed radiation
doses (that is, rads) due to different types of
lonizing radiation. More specifically, it is the
ratio of an absorbed dose of X-rays or gamma
rays to the absorbed dose of a certain particulate
radiation required to produce an identical bio-
logical effect in a particular experimental organ-

(WIEGEL, 1953)

ism or tissue. This ratio is sometimes called
the relative biological efficient factor. (70)

relative current—The current which is a func-
tion of the dynamic slope of an isobaric surface
and which is determined from an assumed layer
of no motion. The current flows along the con-
tours of dynamic topography; the surface
slopes upward to the right of the current in the
Northern Hemisphere and to the left in the
Southern Hemisphere.

relative current speed—The speed determined
by the spacing of dynamic contours drawn at
equal intervals of dynamic height anomaly;
the speed is inversely proportional to the dis-
tance between contours.

relative index of refraction—See index of
refraction.

relative response—The relative response of a
transducer, in decibels, is the amount by which
the response under some particular condition
exceeds the response under a reference condition
that should be stated explicitly. (69)

relaxation time—In general, the time interval re-
quired for a system exposed to some discontinu-
ous change of environment to under the fraction
(1-e-1), or about 63 percent, of the total change
of state which it would exhibit after an indefi-
nitely long time.

134

The relaxation time of an instrument. is
commonly called its time constant or lag
coefficient. (5)

relief—The inequalities (elevations and depres-
sions) of thesea bottom. (2)

remanent magnetism—Permanent magnetism in-
cluded in a material by an applied magnetic
field. (2

Rennell’s Current—A relatively strong (1.0 to 1.5
knots) nonpermanent current that sets north-
ward across the western approaches to the Eng-
lish Channel. The current appears to be inde-
pendent of the North Atlantic Drift or local
winds and occurs most frequently during winter.

replacement—A nearly simultaneous capillary so-
lution and deposition by which a new mineral
may grow in the body of an old mineral or min-
eralageregate. (2)

residual deposits—Material formed by the decay
or disintegration of rock in place.

residual gravity—In gravity prospecting, the
portion of a gravity effect remaining after re-
moval of some type of regional, usually the
relatively small or local anomaly components of
the total or observed gravity field.

residual magnetic field—(also called anomalous
field). That part of the observed magnetic field
that remains after removal of the regional mag-
netic field.

resistivity—The electrical resistance per unit
length and per unit reciprocal cross section area
of a given material at a specified temperature.
It is also possible to define the resistivity of a
substance as the resistance of a cube of that sub-
stance having edges of unit lengths, with the
understanding that the current flows normal to
opposite faces and is distributed uniformly over
them. Resistivity is commonly expressed in
units of ohm centimeters.
tn reciprocal of resistivity is conductivity.

5

resolution—1. In gravity or magnetic pros-
pecting, the indication in some measured
quantity, such as the vertical component of
gravity, or the presence of two or more close but
separate disturbing bodies.

2. In wave theory, the separation of spectral
components.

resolution limit—In gravity and magnetic pros-
pecting, the separation of two disturbing bodies
at which some obvious indication in a measured
quantity of the presence of two separate bodies,
ceases to be visible.

resonance—1. The phenomenon of amplification
of a free wave or oscillation of a system by a
forced wave or oscillation of exactly equal
period. The forced wave may arise from an
impressed force upon the system or from a
boundary condition. The growth of the reso-
nant amplitude is characteristically lmear in
time. (5)

REVERSED TIDE

2. In tides, the water movement resulting from
the natural period of oscillation of a body of
water which approximates the period of one of
the tide-producing forces.

resonance angle—The angle at which the com-
ponents of the wind speed acting in the direction
of the waves is equal to the wave speed. It is
expressed as V cos 6=C, where V is the wind
speed, @ the resonance angle, and @ the wave
speed.

respiration—An oxidation-reduction process by
which chemically bound energy in food is trans-
formed to other kinds of energy upon which cer-
tain processes in all living cells are dependent.
The measurement of carbon dioxide as a product
of respiratory activity in marine phytoplankton
is essential in determining the net productivity.
(57)

response—The response of a device or system is
the motion or other output resulting from an
excitation or stimulus under special conditions.
(3)

response time—See time constant.

resultant current—(or vector mean). ‘The
vectorial average of all current observations
for a specified area, usually for a specified
period of time.

resurgence—The continued rising and falling of
a bay or semienclosed water body many hours
after the passage of a severe storm.

retardation—The amount of time by which cor-
responding tidal phases grow later day by day
(averages approximately 50 minutes). (61)

reticulated bars—Bars with a criss-cross pat-
tern, with both sets diagonal to the shoreline.
(73)

retrogression of a beach—WSce recession.

reverberation—Sound scattered towards the
source, principally from the ocean surface
(surface reverberation) or bottom (bottom re-
verberation), and from small scattering sources
in the medium such as bubbles of air and sus-
pended solid matter (volume reverberation).

reverberation index—The measure of the ability
of an echo-ranging transducer to distinguish
the desired echo from the reverberation.
Computed from the directivity patterns as ratio
in decibels of the bottom, surface, or volume re-
verberation response of a specific transducer to
the corresponding response of a nondirectional
transducer.

reverberation strength—The difference between
the level of a plane wave producing in a non-
directional transducer, a response equal to that
produced by the reverberation corresponding
to a range of one yard from the effective center
of the transducer and the index level of the pulse
transmitted, on any bearing, by the same
nondirectional transducer. (28)

reversed tide—A gravitational tide which is
completely out of phase with the apparent

135

REVERSIBLE TRANSDUCER

motions of the principal attracting body; the
least heights are directly under the tide-produc-
ing body, on opposite sides of the earth. See
direct tide.

reversible transducer—See
ducer.

reversing current—(or alternating current,
rectilinear current). A tidal current that
flows alternately in approximately opposite di-
rections, with a period of slack water at each
reversal of direction. Reversing currents us-
ually occur in rivers and straits where the flow
is restricted. When the flow is toward shore,
the current is flooding; when in the opposite
direction, it is ebbing.

reversing thermometer—A mercury-in-glass
thermometer that records temperature upon
being inverted and thereafter retains its reading
until returned to the first position. It consists
of a conventional bulb connected to a capillary
in which a constriction is placed so that upon
reversal the mercury column breaks off in a re-
producible manner. The mercury runs into a
smaller bulb at the other end of the capillary,
which is graduated to read temperature. A
360° turn in a locally widened portion of the
capillary serves as a trap to prevent further
addition of mercury if the thermometer is
warmed and the mercury expands past the
break-off point.

In measuring temperatures at depths in the
sea, both protected thermometers and un-
protected thermometers are used, each of
which is provided with an auxiliary thermom-
eter. They are generally used in pairs on
Nansen bottles. They are usually read to
0.01°C, and after the proper corrections have
been applied, their readings are considered re-
liable to 0.02°C. (Details of the correction
procedure are given in LaFond’s Tables (7.0.
Publication 614). (5)

Reynolds number—The nondimensional ratio of
the inertial force to the viscous force in fluid
motion,

Re= Buy

Vv

bilateral trans-

where Z is a characteristic length, v the kine-
matic viscosity, and UY a characteristic velocity.
The Reynolds number is of great importance
in the theory of hydrodynamic stability and the
origin of turbulence. (5)
rhabdolith—Minute calcareous bodies contained
in deep sea ooze, classed as protozoans by some
investigators and as algae by others. (53)
rheologic settling—The failure of a sediment
under load through plastic flow. See rheology.
rheology—The study of the flow of materials,
particularly the plastic flow of solids. (2)
rhizoid—A unicellular or uniseriate rootlike fila-
ment serving for attachment of algae. (13)

Ree
a
ult

santa

RHABDOLITHS (xX 2000)

(SHROCK & TWENHOFEL, 1953)

rhizome—A rootlike stem that creeps just below
the surface of the bottom, bearing at the nodes
erect stems or leaves and one or more roots.

rhodamine B dye—A synthetic red or pink dye
sometimes used as a tracer in studies of flow of
water, turbulence, pollution, etc., in rivers, estu-
aries, and the ocean.

rhumb line—(or loxodrome).
crosses all meridians at a constant angle. (87)

ria—Any broad river opening into the ocean. Not
necessarily a submerged river mouth or open
valley in a mountainous coast.

ria coast—A coast having drowned river valleys
characterized by long fiordlike bays which have
few branches. The bays differ from fiords in
origin and are shorter, shallower, and more
funnel shaped, broadening and deepening sea-

A curve which

ward. The type example is northwestern Spain.
2
Richter magnitude scale—Sce magnitude (sense
1)

ride-up—Scee run-up.

ridge—A long, narrow elevation of the sea floor
with steep sides and irregular topography. (62)

ridged ice —Pressure ice in linear formation.

ridging—The process that leads to the formation
of ridgedice. (65)

rift valley—=Scee fault block.

rill mark—A small groove, furrow, or channel
made in mud or sand on a beach by tiny streams
following an outflowing tide. (2)

rip current—The return flow of water piled up on
shore by incoming waves and wind; a strong
narrow surface current flowing away from the
shore. A rip current consists of three parts:
the feeder current flowing parallel to the shore
inside the breakers; the neck, where the feeder
currents converge and flow through the breakers
in a narrow band or “rip”; and the head, where
the current widens and slackens outside the

136

breaker line.

rent system.)
rip feeder current—Sce feeder current.
ripple—1. The ruflling of the surface of water,

hence a little curling wave or undulation. (61)

2, A wave controlled to a significant degree by
both surface tension and gravity.

ripple marks—Undulating surface features of
various shapes produced in unconsolidated sedi-
ments by wave or current action. Compound
ripples are characterized by systematically offset
crests and are produced by simultaneous inter-
ference of wave oscillation with current action.
Metaripples are asymmetrical sand ripples. As
size increases, ripples grade into sand waves,

sand ridges, sand dunes, and migratory sand-
banks or shoals.

rips—A turbulent agitation of water generally
caused by the interaction of currents and wind;
in nearshore regions rips may also be caused by
currents flowing swiftly over an irregular
bottom.

rip surf—Scee rip current.

rip tide—Scee rip current.

rise—1. A long, broad elevation that rises gently
and generally smoothly from the sea floor. (62)

2. The water level height measured above
chart datum.

rise of the tide—The height of the tide measured
above chart datum. (50)

rising tide—(sometimes called flood tide). The
portion of the tide cycle between low water and
the following high water. (5)

river discharge— (also called river outflow, river
runoff). The rate of flow of water past a point
in a stream, expressed as volume per unit time
(usually cubic feet per second, cfs). More
specifically, the volume of river water that flows
into the sea, usually measured in cubic kilo-
meters, cubic miles, cubic meters, or cubic feet,
and sometimes acre-feet.

River discharge may affect tidal currents con-
siderably, especially during rainy seasons, by in-
creasing the strength and duration of ebb and
decreasing the strength and duration of flood.

river igang ice formed in or carried by a
river. (68)

river outflow—WSce river discharge.

river runoff—Scee river discharge.

Roberts radio current meter—An electro-
mechanical current meter which measures cur-
rent speed and direction. This meter can be
suspended below an anchored buoy or ship which
is equipped with a radio transmitter that trans-
mits the current measurements to a ship or shore
based monitor station.

rock—The naturally occurring material that
forms the firm, hard, and solid masses of the
ocean floor. Also a collective term for masses
of hard material generally not smaller than 256
millimeters. See acid rock, basic rock.

(See figure for nearshore cur-

ROPNTGEN EQUIVALENT PHYSICAL

rock barnacle—Sce acorn barnacle.

rock borer—A member of any one of several
families, including the Mytilidae, Saxicavidae,
and the Pholadidae, of bivalves that live in
cavities they bore in soft rock, concrete, and
other materials. Boring generally is accom-
plished by rotating the shell, which bears
toothed or rasplike ‘projections; chemical solu-
tion of the rock may be a method used addi-
tionally by some. See marine borer.

rock flour—Finely ground rock particles, chiefly
silt size, resulting from glacial abrasion. A
component of marine deposits off glacial stream
mouths. (2)

rockweed—(or wrack). One of a group of
marine plants, principally of an order (Fucales)
of the brown algae, mostly multibranched and
leathery, which grow attached to rocks in the
intertidal zone by means of an organ called a
holdfast. The rockweed of the New England
clambake belongs to the genera Mucus and
Ascophyllum.

rocky area—(or fowl area).
bottom.

roentgen— (abbreviated r). An exposure dose
of X- or gamma radiation such that the associ-
ated corpuscular emission per 0.001293 grams of
air produces, in air, ions carrying 1 electrostatic
ek of quantity of electricity of either sign.
(70)

Roentgen equivalent man—(abbreviated rem).
A measure of any ionizing radiation to body
tissue in terms of its estimated biological effect
relative to a dose of one roentgen (r) of X-rays.
The relation of the rem to other dose units
depends upon the biological effect under consid-
eration and upon the conditions of the irradia-
tion. Practically speaking each of the following
is considered to be equivalent to a dose of one
rem: (1) A dose of 1 roentgen due to X- or

gamma radiation; (2) A dose of 1 rad due to X.,
gamma, or beta radiation ; (8) A dose of 0.1 rad
due to neutrons or high energy protons; and (4)
A dose of 0.5 rad due to particles heavier than
protons. (As defined by the Atomic Energy
Commission.) See radiation absorbed dose.

Roentgen equivalent physical—(abbreviated
rep). The rep is defined as the quantity of cor-
puscular radiation which produces in tissue, per
gram of tissue, ionization equivalent to the
quantity of ionization of 1 roentgen of gamma
radiation in air. However, in early practice
the rep was widely accepted as a unit of absorbed
dose representing 93 to 97 ergs per gram of soft
animal tissue. Although the rep unit is stil]
being used in some food irradiation studies and
other miscellaneous radiation experiments, it is
quite rapidly being replaced by the more easily
defined rad units. (70) See radiation
absorbed dose.

An area with a rocky

137

ROLL

roll—Scee ship motion.

roll angle—Scee angle of roll.

roller—1. An indefinite term, sometimes con-
sidered to denote one of a series of long-crested,
large waves which roll in upon a coast, as after a
storm.

2. Large breakers on exposed coasts formed
oe swell coming from a great distance.
3. See comber.
(61)

ropak—An extreme formation of ridged ice; a
pinnacle or slab of heavy sea ice standing verti-
cally on edge. (59)

rorqual—Any baleen whale of the family Bal-
aenopteridae, a group characterized by having a
triangular dorsal fin and a series of parallel
grooves running longitudinally on the under sur-
face of the throat and chest region ; for example,
the blue whale, fin whale, sei whale, minke
whale, and humpback whale.

Rossel Current—A seasonal current flowing west-
ward and northwestward along both the south-
ern and northeastern coasts of New Guinea
during May to September; the southern part
flows through Torres Strait and loses its identity
in the Arafura Sea, and the northern part curves
northeastward to join the Pacific Equatorial
Countercurrent. The Rossel Current is a weak
branch of the South Equatorial Current.
During the Northern Hemisphere winter it is
replaced by an east-flowing current from the
Indian Ocean.

rot—See disintegration.

rotary current—A tidal current that flows con-
tinually, with the direction of flow changing
through all points of the compass during a tide
cycle. Rotary currents usually occur offshore
where the direction of flow is not restricted;
unless modified by local conditions, the change
in direction is generally clockwise in the North-
ern Hemisphere and counterclockwise in the
Southern Hemisphere. The speed of the cur-
rent usually varies throughout the tide cycle,
passing through two maximums in approxi-
mately opposite directions and two minimums
where the direction of the current is approxi-

138

mately 90 degrees from the direction at time of
maximum speed. (See figure for current
ellipse.)

rotten ice—(also called spring sludge). Ice that
has become honeycombed in the course of melting
and is in an advanced state of disintegration.
(74)

Rotten ice may appear transparent (and thus
dark) when saturated with sea water, and thus
may easily be confused with newly forming
blackice. See candleice. (5)

rough ice—An expanse of ice having an uneven
surface caused by pressure ice formations or
growlers frozen in place. (59)

rubber ice—Elastic young sea ice, not strong
enough to bear the weight of a man standing
still. (59) Rare.

rubble—1. Fragments of hard sea ice, roughly
spherical and up to 5 feet in diameter, resulting
from the disintegration of larger ice forma-
tions. When afloat, commonly called brash ice.
(59)

2. Loose angular rock fragments.

rudite—(or rudyte). Rock or sediment deposits
composed of grains larger than 2 millimeters.
See psephite.

rudyte—See rudite.

runnel—A trough or corrugation formed in the
foreshore or in the bottom, immediately off-
shore, formed by waves or tidal currents. (2)

running ice—Ice in motion or capable of rapid
drifting. (59) Rare.

running mean—See consecutive mean.

runofft—The water derived from precipitation that
ultimately reaches stream channels; has a direct
influence upon the volume of river discharge.

runoff cycle—The part of the hydrologic cycle
undergone by water between the time it reaches
the land as precipitation and its subsequent
evapotranspiration or discharge through stream
channels. (5)

run-up—(or uprush). The rush of water up a
structure on the breaking of a wave. The
amount of run-up is the vertical height above
still water level that the rush of water reaches.
(61)

sabellid—Sce tubeworm.

sac—1. An indentation in the contours on a chart
showing submarine relief which is analogous to
a gulf on the surface. The opposite term is
submarine peninsula.

2. In biology, a sack, bag, or pouch.

saddle—A low part on a ridge or between
seamounts. (62)

sailing directions—Information published in
book form describing coasts, waters, channels,

harbor facilities, etc., for use of mariners. (30)
sailing ice—VSee scattered ice.
sailor’s purse—(or mermaid’s purse, skate

barrow). The tough egg capsule of skates and
certain rays, usually deposited on mud and sand
flats. The capsules are oblong with a horn ex-
tending lengthwise from each of the four cor-
ners and are blackish when seen on the beach.

St. Elmo’s fire—(also called Hlmo’s fire, corpo-
sant). A corona discharge.

salgaso—See aguaje.

salient point—A point formed by a conspicuous
projection extending outward from the general
trend of the coast.

salina—A salt marsh or salt pond separated
from the sea but flooded by high tides. Shallow
salt ponds are used to evaporate the water in
the commercial production of salt and are called
salt gardens or salterns.

salinity—A measure of the quantity of dissolved
salts in sea water. It is formally defined as the
total amount of dissolved solids in sea water in
parts per thousand (°/,.) by weight when all
the carbonate has been converted to oxide, the
bromide and iodide to chloride, and all organic
matter is completely oxidized. These qualifica-
tions result from the chemical difficulty in dry-
ing the salts in sea water. In practice, salinity
is not determined directly but is computed from
chlorinity, electrical conductivity, refractive
index, or some other property whose relation-
ship to salinity is well established.

Because of the Law of Constancy of Propor-
tions, the amount of chlorinity in a sea water
sample is used to establish the sample’s salinity.

The relationship between chlorinity C7 and
salinity S as set forth in Knudsen’s Tables is:

S=0.03+1.805 C1.

A joint committee of IAPO, UNESCO,
ICES, and SCOR proposed the universal adop-
tion of the following equation for determining

207-109 O—66——10

salinity from chlorinity: S=7.80655 Cl. It
was adopted by IAPO in 1963 and ICES in
1964.

salinity bridge—Scee salinometer.

salinometer—(or salinity bridge). Any device
or instrument for determining salinity, espe-
cially one based on electrical conductivity
methods. (5)

salp—Any one of a class (Thaliacea) of marine
animals which are transparent pelagic repre-
sentatives of the tunicates. The body is more
or less cylindrical and possesses conspicuous
ring-like muscle bands, the contraction of which
propels the animal through the water. Several
kinds are bioluminescent.

salt—Any substance which yields ions, other than
hydrogen or hydroxyl ions. A salt is obtained
by displacing the hydrogen of an acid by a
metal. (27)

saltation—That method of sand movement in a
fluid in which individual particles leave the bed
by bounding nearly vertically and, because the
motion of the fluid is not strong or turbulent
enough to retain them in suspension, return to
the bed at some distance downstream. (61)

salt crust—Salt that is forced out of young sea ice
by crystal growth, pushed upward, and deposited
on the surface of the ice. (A salt crust surface
is wet even at low temperatures.) (59)

salterns—See salina.

salt flower—WSee ice flower.

salt gardens—Scee salina.

salt marsh—Flat, poorly drained coastal swamps
which are flooded by most high tides.

salt pans—Shallow pools of brackish water used
for the natural evaporation of sea water to obtain
salt. (2, 30)

salt water—See sea water.

salt water wedge—An intrusion in a tidal estu-
ary of sea water in the form of a wedge charac-
terized by a pronounced increase in salinity from
surface to bottom.

sand—Loose material which consists of grains
ranging between 0.0625 and 2.0000 millimeters
in diameter. Sce phi grade scale.

sand apron—Sand deposited along the shore of a
reef lagoon. (2)

sand bar—1. See bar.

2. In a river, a ridge of sand built up to or

near the surface by river currents. (61)

sand dollar—See sea urchin.

139

SAND HORN

sand horn—A pointed sand deposit extending
from shore into shallow water. See also sand
lobe. (2)

sand lobe—A rounded sand deposit extending
from shore into shallow water. See also sand
horn. (2)

sand reef—WScee bar.

sandstone—(also called arenite, arenyte, psam-
mite, psammyte). Rock composed of cemented
sand sized grains, predominantly quartz.

sand wave—Sce megaripple.

saprolith—Scee regolith.

sapropel—An aquatic ooze or sludge that is rich
inorganic matter. (2)

saprophytic nutrition—That process by which an
organism absorbs organic food from its sur-
roundings, usually after digesting it externally.
See heterotrophic nutrition.

sargasso—1. See Sargassum.

2. Loosely, a large floating mass of seaweed.

)

Sargasso Sea—The region of the North Atlantic
Ocean to the east and south of the Gulf Stream
system. This is a region of convergence of the
surface waters and is characterized by clear,
warm water, a deep blue color, and large quan-

tities of floating Sargassum or gulfweed. (5)
sargasso weed—See Sargassum.
Sargassum—(or gulfweed, sargasso weed). 1. A

genus of brown algae.

2. The common name of a plant of this genus,
characterized by a bushy form, a substantial
holdfast when attached, and a yellowish brown,
greenish yellow, or orange color. Species of
the group have a large variety of forms and are
widely distributed in warm seas as attached and
free-floating plants. Two species (S. fluitans
and S. natans) make up 99 percent of the macro-
scopic vegetation in the Sargasso Sea.

sastrugi—Wavelike ridges of hard snow formed
a ; level surface by the action of the wind.

65

satin ice—See acicular ice.

saturation—The condition in which the partial
pressure of any fluid constituent is equal to its
maximum possible partial pressure under the
existing environmental conditions, such that any
increase in the amount of that constituent will
initiate within it a change to a more condensed
state. In molecular-kinetic terms, saturation is
attained when the rate of return of molecules of
a substance form the dissolved liquid or vapor
phase to the more condensed parent phase is
exactly equal to the rate of escape of molecules
from the parent phase. (5)

saturation vapor pressure—1. The vapor pres-
sure of a system, at a given temperature, where-
in the vapor of a substance is in equilibrium with
a plane surface of that substance’s pure liquid or
solid phase; that is, the vapor pressure of a sys-
tem that has attained saturation but not super-
saturation. The saturation vapor pressure of

any pure substance, with respect to a specified
parent phase, is an intrinsic property of that
substance, and is a function of temperature
alone.
9. See equilibrium vapor pressure.
5

sieonrt rotor current meter—A_ low-thresh-
hold current speed sensor composed of two
semicylindrical vanes disposed to form an S-
shaped rotor responsive to a wide spectrum of
horoizontal flow components. Present instru-
ments generally utilize paired Savonius rotors
with axes displaced by 90 degrees for a more
nearly uniform omnidirectional torque distribu-
tion. (19)

scalar irradiance—A quantitative measure of the
total radiant flux arriving at a poit for all
directions about a point. It is the measure of
the amount of radiant energy per unit volume
of space at a given point.

scalar mean—Scee mean current.

scale—The ratio between the linear dimensions of
a chart, drawing, etc., and the actual dimensions
of the object represented, expressed as a propor-
tion. Chart or map scales are conventionally
classed as large (larger than 1: 1,000,000), me-
dium (1:600,000 to 1:1,000,000), or small
(smaller than 1: 600,000).

scale error—See calibration error.

scaler—An electronic device which registers cur-
rent pulses received over a given time interval.
(70

scaphopod—Sce tooth shell.

scarp—See escarpment.

scatterance—The ratio of the radiant flux scat-
tered from a beam, to the incident flux. (8)

scatterance meter—An assembly of a collimated
light source and a radiance meter which di-
rectly measures the scatterance values of an
optical medium. Scatterance meters fall into
three main classes: free-angle, fixed-angle, and
integrating scatterance meters. The first type
is designed to determine in principle all values
of the volume scattering function at a given
point; the second is designed to determine the
function for a fixed angle; and the third type
is designed to integrate directly the function
over all angles so as to record the total scatter-
ing coefficient. (8)

scattered ice—(also called sazling ice). Sea ice
that covers from 1- to 5-tenths of the sea surface.
65
! NY ote: This term is being superseded by the
WMO term “very open pack ice”.

scattering—1. The random dispersal of sound
energy ‘after it is reflected from the sea surface
or sea bottom and/or off the surface of solid,
liquid, or gaseous particles suspended in the
water.

2. The dispersion of light when a beam strikes

very small particles suspended in air or water.

140

Theoretically, in light scattering, there is no loss
of intensity, but only a redirection of light.

3. Change of direction of a subatomic particle
tr photon as a result of a collision or interaction.

0)

scattering coefficient—(or total scattering coef-
ficient). A measure of the attenuation due to
scattering of radiation as it traverses a medium
containing scattering particles. (5)

scattering function—The intensity of scattered
radiation in a given direction per lumen of flux
incident upon the scattering material.

When the collection of scattering particles is
taken to be those in one unit volume, the associ-
ated scattering function is known as the volume
scattering function. (5)

scattering loss—That part of the transmission
loss which is due either to scattering within the
medium or due to roughness of the reflecting
surface. (6)

schistosome dermatitis— (or swimmer’s itch, sea-
bather’s eruption). An irritating skin condi-
tion incurred by bathers in both fresh and salt
waters and characterized by the eruption of red-
dish wheals and a severe itching sensation. The
cercarian larvae of certain parasitic trematode
worms produce the dermatitis when they enter
the skin and die.

schizopod stage—That stage in the development
of a decapod crustacean when it resembles an
adult. (26)

school—A large number of one kind of fish or
other aquatic animals swimming or feeding
together (a school of herring). See Shoal.

scintillation—1. A flash of light produced in a
phosphor by an ionizing agent. (41)

2. A generic term for rapid variations in ap-
parent position, brightness, or color of a distant
ae object viewed through the atmosphere.

5

scintillation counter—The combination of phos-
phor, photomultiplier tube, and associated cir-
cuits for counting light emissions produced in
the phosphors. (70) (See figure for photo-
multiplier tube.)

scintillation spectrometer—A_ scintillation
counter adapted to the study of energy distribu-
tions. (41)

scintillator—(or phosphor). A transparent ma-
terial, either crystalline, organic, or liquid, which
produces a flash of light asa result of fluorescent
radiation emitted by atoms of the material when
they return to their normal energy state after
having been ionized or excited by charged parti-
cles passing through the material. (18)

scoopfish bottom sampler—A small bottom sedi-
ment sampling device for underway use which
consists essentially of a streamlined weighted
tube with stabilizing fins. The leading end of
the tube is completely open so that a scooping
effect is achieved when the sampler is towed.

SEA BED

Bottom contact releases a spring activated cover
over the tube’s open end so that any sediment
sampled can be brought to the surface.
scoria—Volcanic rock fragments usually of basic
composition, characterized by marked vesicular-
ity, dark color, high density, and a partly crys-
talline texture. Fragments between 4 and 32
millimeters are equivalent to voleanic cinders.
scour—The downward and sideward erosion of
a sediment bed by wave or current action.
seree—Scee talus.
screw ice—1. See pressure ice.

2. Small ice fragments in heaps or ridges pro-
duced by the crushing together of ice cakes.
Also applied to small formations of ridged ice,
rafted ice,and hummockedice. (59)

screwing pack—<An ice pack in which the ice
floes or ice cakes are in rotary motion due to the
influence of wind and current. (68)

scyphozoan—One of a class (Scyphozoa or Scy-
phomedusae) of coelenterates in which the
polyp or hydroid stage is minimized or insigni-
ficant and the medusoid stage is well developed.
The true jellyfishes belong to this group.

sea—l. See ocean. (5)

2. A subdivision of an ocean.

All seas except inland seas are physically
interconnected parts of the earth’s total salt
water system. Two types are distinguished,
mediterranean and adjacent. Mediterraneans
are groups of seas, collectively separated from
the major water body as an individual sea.
Adjacent seas are those connected individually
tothelarger body. (5)

3. See Sea state.

4. Waves generated or sustained by winds
within their fetch; opposed toswell. See fully
developed sea.

sea anemone—Any of numerous anthozoans
(Actiniaria) whose form, bright colors, and ten-
tacles about the mouth often give them a super-
ficial resemblance to a flower.

sea arch—(or marine arch, natural arch, marine
bridge). Wave erosion of a cave or tunnel
through a headland leaving a bridge of rock
over the water.

sea arrow—(or flying squid). One of a family
(Ommastrephidae), but more particularly one
of a genus (Ommastrephes) of this family of
cephalopods which are elongated and stream-
lined and possess terminal fins which unite in a
point at the terminus of the body. These species
are capable of rapid swimming and can overtake
schools of fish on which they prey; they often
hurtle out of the water and sail through the air,
at times landing on the decks of ships.

sea bar—See belt.

seabather’s eruption—See schistosome derma-
titis.

seabeach—Sce beach.

sea bed—See sea floor.

141

SEA BLOOM

sea bloom—See plankton bloom.

seaboard—A general term for the rather extensive
coastal region bordering the sea. (68)

sea bottom—WScee sea floor.

sea breeze—A light wind blowing toward the
land caused by unequal heating of land and
water masses. (61)

sea butterfly—Scee pteropod.

sea cave—(or marine cave).
sea cliff by wave action.
level.

seachannel—A long, narrow, U-shaped or V-
shaped shallow depression of the sea floor,
usually occurring on a gently sloping plain or
fan. (62)

sea cliff—aA cliff situated at the seaward edge of
the coast. (61) (See figure for shore profile.)

sea clutter—Sce sea return.

sea cow—(or sirenian). An aquatic herbivorous
mammal of the order Sirenia which includes the
dugong, the manatee, and the allegedly extinct
Stellar sea cow.

sea cucumber—(or holothurian). One of a class
(Holothuroidea) of elongate, usually wormlike
echinoderms which have a flexible body wall
and creep over the bottom from shallow water
to great depths. They are eaten commonly in
the Orient as the trepang or béche-de-mer of the
Chinese.

sea fan—Any of a group of fanlike sessile
anthozoans.

sea feather—1. Any of a group of featherlike
sessile anthozoans.

2. Any of a group of featherlike sessile

crinoids.

sea fire—(or burning of the sea). A brilliant
display of bioluminescence; more commonly
described from tropical waters.

sea floor—(or sea bed, sea bottom). The bottom
of the ocean where there is a generally smooth,
gentle gradient. In many uses depth is dis-
regarded and the term may be used to designate
areas In basins or plains or on the continental
shelf.

sea fog—A type of advection fog formed when
air that has been lying over a warm water sur-
face is transported over a colder water surface,
resulting in cooling of the lower layer of air
below its dew point. (5)

a Senin restricted passage leading to the sea.
68

sea gooseberry—A luminescent ctenophore
(Pleurobrachia pileus) found in coastal waters.
Has the appearance of a transparent gooseberry.

sea grape—A small ascidian, particularly of the
species Molgula manhattensis, which grows in
large clusters on piles, rocks, and other under-
water objects.

seagrass—1. A member of either of two families
(Hydrocharitaceae and Zosteraceae) of usually
grasslike marine spermatophytes. Seagrasses
grow chiefly on sand or mud-sand bottoms and

A cave eroded in a
Tt usually is at sea

most abundantly in water less than 30 feet, but
some may grow on rock in the intertidal zone,
and others may range to depths of at least 200
feet. The eelgrass (Zostera marina), the turtle-
grass (Thalassia testudinum), and the manatee-
grass (Syringodium filiforme) are better known
members of these families.
2. Any grasslike marine alga.

sea ice—1. Specially, ice formed by the freezing
of sea water; opposed, principally to land ice.
In brief, it forms first as frazil crystals (lolly
ice), thickens into sludge, and coagulates into
sheet ice, pancake ice, or ice floes of various
shapes and sizes. Thereafter, sea ice may de-
velop into pack ice and/or become a form of
pressure ice.

2. Generally, any ice floating in the sea.
5)

oe ve shelf—Sea ice floating in the vicinity of its
formation and separated from fast ice, of which
it may have been a part, by a tide crack, or a
family of such cracks. (68)

seaknoll—See knoll.

sea lettuce—One of either of two genera (d/ono-
stroma and Ulva) of membranous green algae.

sea level—(or water level). The height of the
surface of the sea at any time.

sea level datum—Sce mean sea level.

sea lily—wScee crinoid.

sea mat—See bryozoan.

sea mist—Sce steam fog.

sea moat—Sce moat.

seamount—An elevation rising 500 fathoms
(1,000 meters) or more from the sea floor and of
limited extent across the summit. (62)

seamount chain—Several seamounts in a line
with bases separated by a relatively flat sea floor.

62

ae group—Several closely spaced sea-
mounts notinaline. (62)

seamount range—Several seamounts having
connected bases and aligned along a ridge or
rise. (62)

sea mud—A rich saline deposit from salt marshes
and seashores. (2)

seapeak— See seamount.

sea pen—Any of a group of penlike or featherlike
sessile anthozoans.

sea puss—A dangerous longshore current, a rip
current, caused by return flow, loosely the sub-
merged channel or inlet through a bar caused
by those currents. (61)

sea reach—The straight section of the lower course
of a river between the last bend and the sea.
(68)

sea return—(also called sea clutter). Radar
echoes reflected from the sea. (68)

seascarp—See escarpment.

seashore—The shore of a sea or ocean. (61)

seashore lake—A body of water isolated from the
sea by sediment bars or banks.

142

sea slick—An area of sea surface, variable in size
and markedly different in appearance, with color
and/or oiliness; usually caused by plankton
blooms.

sea slide—A submarine sediment slump o1 mass
movement which may evolve into a turbidity
flow. Analogous toa landslide. (2)

sea slug—See nudibranch.

sea snake—A reptile of the family Hydrophiidae ;
a& group comprising about 50 species of truly
marine forms distantly related to the cobras and
possessing similar venom. All are inhabitants
of warm coastal waters of the Indian Ocean and
western Pacific with one exception, the yellow-
bellied sea snake, which is oceanic and ranges
entirely across both the Indian and Pacific
Oceans in low latitudes.

sea snow—(also called plankton snow, marine
snow). Particles of organic detritus and living
forms. The downward drift of these particles

and living forms, especially in dense concentra-
tions, appears similar to a snowfall when viewed
by underwater investigators.

seasonal current—A current that changes with
seasonal winds.

sea spider—(or pycnogonid). One of a class
(Pyenogonida) of spiderlike benthic arthro-
pods which range from shallow water to great
depths. The species inhabiting shallow waters
range in size froma fraction of an inch to a few
inches; the deepwater species may attain a
spread of several feet.

sea squirt—= See ascidian.

sea stack—A tall, columnar rock isolated from the
coast by differential wave erosion. (2)

sea star—(or starfish). One of a class (Asteroi-
dea of echinoderms having a flat, usually five-
armed body. The body wall contains embedded
calcareous plates bearing spines or tubercles.
Some spines are modified into pincerlike organs,
called pedicellariae, which in some tropical
species are dangerously venomous to humans.

sea state—(or state of the sea). The numerical
or written description of ocean surface rough-
ness. For more precise usage sea state may be
defined as the average height of the highest one-
third of the waves observed in a wave train,
referred to a numerical code which covers an
increasing range of such heights as indicated by

WMO Code 75 table below:

Code Wave height (feet)
Qe Pees a BES ad ee 0
sli ee a be 0-14
Qian ee see ee PSL Y-1%,
Ee RAE SS BRE Se Od SE 1%4—-4
AN ES Carats} honey SB ey Webi dy Uri eS 4-8
{5 ee eee eee Se ee 8-138
(ee ee ee eee 13-20
1 ee ee ee ee ee 20-30
Bub send 2 eRe sae ae SS SS 3045
tt eee Sree een ee eae berets Over 45

SECOND

sea turtle—Any of various large marine turtles
belonging to the reptilian order Testudinata and
having the feet modified into paddle-like appen-
dages, including the leatherback, hawksbill, log-
gerhead, green, and Ridley turtles, and being
widely distributed in warm seas.

sea urchin—One of a class (Echinoidea) of
echinoderms in which the body is covered by
a hard shell (or test) composed of fitted im-
movable plates; spines articulated at their bases
and of various sizes, often large, and sharp are
present on the test; members of the class may be
spherical (the regular sea urchins), depressed
spherical (the cake urchins), discoidal (the sand
dollars), or round elongate (the heart urchins).
Many species of urchins have venomous spines.

sea valley—See valley.

sea wall—A manmade structure of rock or con-
erete built along a portion of coast to prevent
wave erosion of the beach. (2)

sea walnut—A transparent, luminescent cteno-
phore (IMnemiopsis). Often seen in large
swarms on the surface in coastal waters.

seaward beach—The seaward faciny beach of the
reef islands. (56) (See figure for atoll.)

seaward reef margin—The seaward edge of the
reef flat, marked in places by an algal ridge and
cut by surge channels, which are the landward
extensions of the reef-front grooves. (56)
(See figure for atoll.)

sea water—The water of the seas, distinguished
from fresh water by its appreciable salinity.
The amount of the salinity greatly affects the
water’s physical characteristics.

The distinction between the usage of salt water
and sea water is not very sharply drawn. Com-
monly, sea water is used as the antithesis of
specific types of fresh water, as river water, lake
water, rain water, etc., whereas salt water is
merely the antithesis of fresh water in general.

seawater batteries—Silver-zine batteries activa-
ted by flow of sea water through them.

seaweed—(or weed). Any macroscopic marine
alga or seagrass.

Secchi dise—A white, black, or varicolored disc,
30 centimeters (about 11.7 inches) in diameter,
used to measure water transparency (clarity).
The disc is lowered in the water and the depth
(in meters) at which it disappears from sight is
averaged with the depth at which it reappears.
This average value is used to represent sea water
transparency.

second—1. A term used to describe distance or
depth; one second refers to about 4,800 feet, or
the distance that sound will travel through sea
water during one second. Two ships may be
said to be 10 seconds apart when their positions
are separated by about 48,000 feet.

2. The sixtieth part of a minute of angular
measure.

143

SECONDARY CURRENT PATTERN

3. The sixtieth part of aminute oftime. (35)

secondary current pattern—A short-period vari-
ation of the prevailing current pattern.

secondary electron—An electron ejected from
an atom, molecule, or surface as a result of a
collision with a charged particle or photon.
(70)

secondary production—The organic matter pro-
duced by herbivores of the zooplankton in a
given area or volume in a given time. The sec-
ond trophic level.

secondary tide station—A place at which tide
observations are made over a short period.
(68) See subordinate station.

secular change—An increase or decrease of in-
tensity and/or change of direction of the total
magnetic field over a period of many years.

sediment—Particulate organic and inorganic
matter which accumulates in a loose unconsoli-
dated form. It may be chemically precipitated
from solution, secreted by organisms, or trans-
ported by air, ice, wind, or water and deposited.

sedimentary basin—A depression, often marine,
in which sediments are deposited. The deposits
are usually thickest in the center and thinner
toward theedges. (2)

sedimentary rocks—Rocks formed by the ac-
cumulation of sediment in water (aqueous de-
posits) or from air (eolian deposits). The sedi-
ment may consist of rock fragments or particles
of various sizes (conglomerate, sandstone,
shale) ; of the remains or products of animals or
plants (certain limestones and coal); of the
product of chemical action or of evaporation
(salt, gypsum, ete.); or of mixtures of these
materials. (2)

sedimentation—The process of breakup and
separation of particles from the parent rock,
their transportation, deposition, and consolida-
tion into another rock.

sedimentation method—A technique used in the
quantitative estimation and identification of
phytoplankton organisms. The plankton to be
measured is concentrated by settling in glass
cylinders and the organisms are counted or iden-
tified by using an inverted microscope.

sedimentation unit—That thickness of material
which are deposited under essentially constant
physical conditions. (2)

sedimentology—The study of sedimentary rocks
and the processes by which they were formed.
(2)

segmented worm—WScee annelid.

seiche—1. A standing wave oscillation of an
enclosed or semienclosed water body that con-
tinues, pendulum fashion, after the cessation of
the originating force, which may have been
either seismic, atmospheric, or wave induced.

2. An oscillation of a fluid body in response to

a disturbing force having the same frequency as
the natural frequency of the fluid system. Tides
are now considered to be seiches induced primar-

ily by the periodic forces caused by the sun and
moon.
(5)

seine—A type of net used to catch fish by encircle-
ment, usually by active closure of the two ends
but also including closure or pursing of the bot-
tom (purse seine).

seismic activity—= Sce seismicity.

seismicity—The phenomenon of earth movements.

seismic profile—The data resulting from a single
series of observations made at one geographic
location with a linear arrangement of seis-
mometers. (4)

seismic profiler—A continuous deep sea reflection
system used to study the structure beneath the
ocean floor to depths of 10,000 feet or more. The
reflections are recorded on a drum whose rotation
is actuated by the initial explosion. (4)

seismic reflection—The measurements, and rec-
ording in wave form, of the travel time of acous-
tic energy reflected back to detectors from rock
or sediment layers which have different elastic
wave velocities.

seismic sea wave—Sce tsunami.

seismograph—An instrument used to measure and
record earthquake vibrations and other earth
tremors. (5)

selachian—See shark.

selective filter—(or colored filter). An optical
filter which changes, by absorption, the spectral
distribution of the energy passing through it.
(8)

self noise—See own ship’s noise.

semidaily—Sce semidiurnal.

semidiurnal—(or semidaily). Having a period
or cycle of approximately half a lunar day
(12.42 solar hours). The tides and tidal cur-
rents are semidiurnal when two flood and two
ebb periods occur each lunar day.

semidiurnal constituent—A_ tidal constituent
that has two maximums and two minimums each
constituent day; its symbol is usually distin-
guished by the subscript 2, as A/2, S2, V2, etc.

semidiurnal current—The type of tidal current
having two flood and two ebb periods of nearly
the same duration during a tidal day; usually
associated with a semidiurnal tide.

semidiurnal tide—The type of tide having two
high waters and two low waters each tidal day,
with small inequalities between successive high
and successive low water heights and durations.
(See figure for types of tide.)

sensible heat—The portion of energy exchanged
between ocean and atmosphere which is utilized
in changing the temperature of the medium into
which it penetrates.

sensor—A technical means, usually electronic, to
extend man’s natural senses by means of energy
emitted or reflected. The energy may be nu-
clear, electromagnetic, including the visible and
invisible portions of the spectrum, chemical,
biological, thermal, or mechanical.

144

sequence of current—The order in which the four
tidal current strengths occur daily, with special
reference as to whether the stronger flood im-
mediately precedes or follows the stronger ebb.
Usually associated with mixed tidal currents
having inequalities in speeds and durations.

sequence of tide—The order in which the four
tides of a day occur, with special reference as to
whether the higher high water immediately
precedes or follows the lower low water.
Usually associated with a mixed tide having
inequalities in heights and durations. (50)

sergestid—One of a family (Sergestidae) of
usually deep pelagic shrimps or prawns.

serial station—(also called hydrographic sta-
tion). An oceanographic station consisting
of one or more Nansen casts. (5)

serpulid—See tubeworm.

sessile—1. Attached directly by base, without
stipe or stalk.

2. Permanently attached; not free to move
about.

seston—The living and nonliving bodies which
swim or float in water.

set—1. (or current direction). The direction
toward which the current flows. Usually indi-
cated in degrees true or points of the compass.

2. (or settle). To attach to a surface, as by
the larvae of various marine invertebrates.

3. The periodic attachment of many larvae of
marine invertebrates, especially barnacles and
bivalves, to a surface.

settle—See set.

settling volume—The amount of plankton in a
container concentrated by gravity and having
variable quantities of interstitial water.

shadow zone—A region into which very little
sound energy penetrates.

shallow marginal seas—Sce shelf seas.

shallows—An indefinite term applied to expanses
of shoal or shallow water.

shallow scattering layer—The population(s) of
organisms in water over a continential shelf
which scatter sound. The organisms usually oc-
cur as separate groups or patches and are dis-
continuous horizontally. The horizontal dimen-
sions of such patches on the echo-sounder record
usually are less than the vertical dimensions.
See deep scattering layer, surface scattering
layer.

Shallow water—(or very shallow water). 1.
Commonly, water of such a depth that surface
waves are noticeably affected by bottom topog-
raphy. It is customary to consider water of
depths less than half the surface wavelength as
shallow water.

2. In hydrodynamics with regard to progres-
sive gravity waves, water in which the depth
i less than 1/25 the wavelength.

61)

shallow water constituent—A short-period har-

monic term introduced into the formula of ‘as-

SHELF SEAS

tronomical tide constitutents to take account of
the change in the form of a tide wave resulting
from shallow water conditions. Shallow water
constituents include overtides and compound
tides. (50)
shallow water wave—(also called very shallow
water wave). A progressive gravity wave
which is in water less than 1/25 the wavelength
indepth. (73)
shard—A curved, spiculelike fragment of vol-
canic glass. (2)
shark—(or selachian). Any of approximately
250 species of fishlike vertebrates belonging to
the elasmobranch order Selachii, and includin
the large plankton-feeding basking whale and
sharks, the predacious white, mako, tiger, blue,
hammerhead, sand, and gray sharks, and a
variety of others such as the cow, frill, horn,
thresher, nurse, cat, angel, and dogfish sharks.
shear crack—A crack in sea ice caused by two dit-
ferent, simultaneous forces acting in parallel
but opposite directions on adjacent portions of
the ice. The sheared parts undergo a displace-
ment parallel to the plane of the crack. (68)
shearing stress—Any of the tangential compo-
nents of the stress tensor. In oceanography,
the shearing stress exerted on the sea surface by
the wind.
sheet flow—Sce laminar flow.
sheet ice—Ice formed in a smooth thin layer on
a water surface by the coagulation of frazil or
sludge. (5)
sheet-type luminescence—1. A display of biolog-
ical light appearing diffuse or shimmering,
often making the sea surface appear milky or
greenish in color. This type of display usually
1s caused by masses of microscopic or tiny or-
ganisms. Displays may cover large areas of the
sea surface, at times causing a uniform glow
from horizon to horizon, or they may appear as
irregular patches or wide ribbons of light in an
otherwise dark sea. See bioluminescence.
2. Called “spilled luminescence” in Russian
papers,
shelf—1. This term is not recommended by
ACUF for a rock ledge, reef, or sandbank in the
sea.
2. Short form for continental (or island)
shelf.
shelf break—Scee shelf edge.
shelf edge—The line along which there is a
marked increase of slope at the outer margin of
a continental (or island) shelf. (62)
Note: Conventionally the shelf edge has been
taken at 100 fathoms (200 meters).
shelf ice—See ice shelf.
shelf seas—(or shallow marginal seas). Shallow
seas which occupy wide portions of a continen-
tal shelf. See also epeiric seas, inland seas,
epicontinental seas.

145

SHELL

shell—The hard outer covering of an inverte-
brate; a calcareous, siliceous, bony, horny, or
chitinous covering.

shellfish—Any aquatic invertebrate with a hard
external covering, but more commonly any
crustacean or mollusk, especially the edible
commercial species.

shell ice—(also called cat ice). Ice, on a body
of water, that remains as an unbroken surface
when the water level drops so that a cavity is
formed between the water surface and the ice.

5

Se pe iesmtion often flat waterworn rock fra-
ments larger than approximately 16 milli-
meters.

shingle barchanes—Ridges of shingle, with in-
tervening troughs of sand, formed in shallow
water at right angles to the beach.

shingle rampart—A ridge of shingle, about 3 to
6 feet (1 to 2 meters) high, built by waves on the
seaward edge of and parallel toa reef flat. (2)

shipboard synoptic system—Electronic ship-
board system (hove-to) that collects, records,
and prepares for radio transmission the profile
of temperature, salinity, and sound velocity with
depth.

shipborne expendable bathythermograph (BT)
—An instrument system designed to record
water temperature with depth from a ship mov-
ing at speeds up to 25 knots in sea states up to
6 (13 to 20 feet) without interference to normal
ship routine. It can provide measurements
from surface to 1,500 feet with an accuracy of
+2 percent or 15 feet whichever is greater and a
temperature accuracy of +0.4°F over a range
of 28° to 95°F.

ship motion—In perfectly calm water a carefully
steered ship moves along a straight course. A
point which corresponds to the center of gravity
of the ship also moves along this straight line
at a constant velocity. In a wave system, how-
ever, this point deviates from this simple,
straight line motion in six different ways:

1). Heave, the up-and-down motion of this
point as it travels along.

2). Surge, the fore-and-aft motion of this
point as the ship speeds up and slows down
when she encounters waves.

3). Sway, the athwartship motion as the
point departs from a straight line path.

4). Roll, the athwartships angular rotation
about this point which occurs as the ship heels
first to one side and then to the other.

5). Pitch, the fore-and-aft angular rotation
about this point which occurs as the bow and
stern alternately rise and fall.

6). Yaw, the horizontal angular rotation
about this point which occurs as the direction of
the ship’s keel is deflected from the direction
of her course.

The first three motions are translational mo-
tions, the last three are rotational motions. In

other words, the first three motions are motions
such that the center of gravity actually departs
from its straight line motion and the last three
motions are motions such that the center of grav-
a on not depart from its position.

46

ship observations—Meteorological and oceano-
graphic data taken for a specific location, ob-
served from a ship underway or at anchor.

ship report—The encoded and transmitted report
of a marine weather observation. (5)

ship synoptic code—A synoptic code for com-
municating marine weather observations. It is
a modification of the International Synoptic
Code. (5)

Ship Visit Report—A navigational report sub-
‘mitted by ship’s personnel. In addition to data
affecting the safety of navigation, the reports
involve such intelligence as marine and celestial
phenomena, weather routing, current data, etc.

shipworm—(or Zeredo). One of a family (Ter-
edinidae) of wormlike bivalves in which the
shells are limited to the head end. Larvae pene-
trate wood, plastics, and other material, and the
organisms excavate tunnels (in which they re-
main for life) as they grow by rasping away
the surrounding material with their ridged and
toothed shells. Incurrent and excurrent siphons
project from the original entrance hole, which
is never enlarged. Shipworms are one of the
two most destructive groups of marine borers.

shoal—1. A submerged ridge, bank, or bar con-
sisting of or covered by unconsolidated sedi-
ments (mud, sand, gravel) which is at or near
enough to the water surface to constitute a dan-
ger to navigation. If composed of rock or
coral, it is called a reef. (An offshore hazard
to navigation with a least depth of 10 fathoms
(20 meters) or less, composed of unconsolidated
material.) (62) See reef.

2. (or school). A great number of fish or
aquatic animals thronged together or con-
sidered as a group, for example, herring shoals.

3. Having little depth; to cause to become
shallow. (61)

4. To proceed from a greater to a lesser depth
of water. (61)

5. To become shallow gradually. (61)

shoal area—1. An area, dangerous to surface
ships, in which there are depths of 10 fathoms,
or less, over a bottom which is not rocky.

2. A shallow area.

shoaling—A bottom effect which describes the
height of the waves, but not the direction. It
can be divided into two parts which occur
simultaneously. The one part has to do with
the fact that waves become less dispersive close
to shore; therefore, since the same energy can
be carried by high waves of lesser height, this
effect. causes a gradual decrease in the wave
height. In the other part, the waves slow down,

146

the crests move closer together, and since the
energy between crests remains relatively fixed,
the waves can become higher near shore.

These effects are evidenced in the initial de-
crease in height of the incoming wave, then an
increase in height as the wave comes into shore.

shoaling coefficient—The ratio of the height of
a wave in water of any depth to its height in
deep water, with the effect of refraction elim-
inated. Sometimes called shoaling factor or
depthfactor. (61)

shoaling effect—The alteration of a wave proceed-
ing from deep water into shallow water. See
shoaling.

shoaling factor—See shoaling coefficient.

shoal patches—Individual and scattered eleva-
tions of the bottom, with depths of 10 fathoms
or less, but composed of any material except
rock or coral.

shoal reefs—Bank reefs; also irregular reef
patches among submerged shoals of calcareous
detritus. (2)

shock crack—See concussion crack.

Shoran—A precise short-range electronic naviga-
tion system which uses the time divergence of
pulse-type transmission from two or more fixed
stations. (This term is-derived from the words
“short-range navigation.”) (63)

shore—The narrow strip of land in immediate
contact with the sea, including the zone between
high and low water lines. (See figure for shore
profile.)

shore clearing— See shore lead.

shoreface—The narrow zone seaward from the
low tide shoreline permanently covered by
water, over which the beach sands and gravels
actively oscillate with changing wave conditions.
(61) (See figure for shore profile.)

shore ice—1. The basic form of fast ice. It isa
compact ice cover that is attached to the shore
and, in shallow water, also grounded. (74)

2. (or grounded ice). Sea ice that has been
beached by wind, tides, currents, or ice pressure.
It is a type of fast ice and may sometimes be
rafted ice. (5)

shore ice belt—Scee ice foot.

shore lead—A lead between pack ice and a nar-
row fringe of fast ice, or between pack ice and
the shore. (74)

It may be closed by wind or currents so that
only a tide crack remains. (5)

shoreline—The boundary line between a body of
water and the land at high tide (usually mean
high water). (68) See coastline. (See fig-
ure for nearshore current system.)

Shoreline and coastal classification—As sug-
gested by F. P. Shepard the following genetic
classification has two principal subdivisions,
Primary coasts and Secondary coasts; the for-
mer representing coasts and shorelines which
are essentially the result of the sea resting
against a landmass that owes its topography toa

SHRIMP TRAWL

terrestrial agency, whereas the latter are largely
the result of present day marine processes or
marine organisms.

I. Primary (Youthful) Shorelines and Coasts

A. Land Erosion Coasts—which includes
ria, drowned glacial erosion, and
drowned Karst topography.

B. Subaerial Deposition Coasts—which in-
cludes river deposition, glacial deposi-
tion plains, wind deposition coasts,
and landslide coasts.

C. Volcanic Coasts—which includes lava
flow coasts, tephra coasts, and volcanic
collapse or explosion coasts.

D. Shaped by Diastrophic Movements—
which includes fault coasts, fold coasts,
and sedimentary extrusions.

II. Secondary Coasts (may or may not have
been Primary Coasts before being shaped
by the sea)

A. Wave Erosion Coasts.

B. Marine Deposition Coasts—which in-
cludes barrier coasts, cuspate forelands,
beach plains, and mudflats or salt
marshes.

C. Coasts Built by Organisms—which in-
cludes coral reef, serpulid reef, oyster
reef, mangrove, and marsh grass
coasts.

(52)

shoreline of emergence—That shoreline result-
ing when the water surface comes to rest against
a partially emerged sea floor.

shoreline of submergence—That shoreline
produced when the water surface comes to rest
against a partially submerged land area.

shore polynya—A polynya along the coast,
formed either by current or wind. (74)

shore profile—The intersection of the ground sur-
face with a vertical plane; may extend from the
top of the dune line to the seaward limit of sand
movement. (61) See figure on next page.

short-crested wave—A wave, the crest length of
which is of the same order of magnitude as the
wavelength. A system of short-crested waves
has the appearance of hills being separated by
troughs. (73)

short wave—Waves under conditions where the
relative depth (water depth/wavelength) is
greater than 0.5, and where the phase velocity
is independent of water depth, but dependent
upon wavelength.

short-wave radiation—In oceanography, a term
used loosely to distinguish radiation in the visi-
ble and near-visible portions of the electromag-
netic spectrum (roughly 0.4 to 1.0 micron in
wavelength) from long-wave radiation (infra-
red radiation). (5)

shrimp trawl—A bottom trawl]; that is, a bag net
with a triangular shaped top and bottom, the
open end (base of the triangle) fishes in an oval
shape spread laterally by otter boards and ver-

147

SHUGA

SHORE PROFILE

1. Offshore; 3. Mean high water;
7. High
9. Shore or Beach;
11. Ordinary or Summer berm;
14. Coast;

18. Trough;

2. Shoreface or Inshore;
4. Mean low water; 5. Step; 6. Low tide shoreline;
tide shoreline; 8. Foreshore or Beach face;
10. Backshore or Backbeach;
12. Storm or Winter berm;
15. Sea cliff; 16. Coasfline;
19. Ball or Longshore bar.

13. Beach scarp;
17. Crest of berm;

(AFTER WIEGEL, 1953)

tically by floats on the head or top rope
and by weights on the lead or foot rope. Fish
entering the open end are trapped in the apex
or “cod” end of the net. Latera] dimensions of
ne net opening range from about 24 to 100
eet.

shuga—Spongy white ice lumps a few centimeters
in diameter (about one inch), formed of sludge
and sometimes of anchor ice, and emerging on
the surface.

Siberian anticyclone—Sce Siberian high.

Siberian high—(or Stberian anticyclone). An
area of high pressure which forms over Siberia
in winter, and which is particularly apparent
on mean charts of sea level pressure. It 1s cen-
tered near Lake Baikal, where the average sea
level pressure exceeds 1,030 millibars from late
November to early March.

This anticyclone is enhanced by the surround-
ing mountains which prevent the cold air from
flowing away readily. In the center of the anti-
cyclone the norma] clockwise circulation is re-
placed by katabatic winds down the river
valleys, but to the east along the Pacific coast
there is a belt of very strong northerly winds.

In summer the Siberian high is replaced by
alow pressure area. See monsoon. (5)

sieve—Wire cloth containers with mesh openings
graded increasingly in a fixed ratio. Coarse
bottom sediments such as sand are usually ana-
lyzed for size by sieving.

sigma limits—The interval about the mean ex-
pressed in units of standard deviation. In a
normal distribution , 2c limits on each side of a
mean include about 95 percent of the popula-
tion, 3c limits include 99 percent of the popula-
tion. (22)

148

sigma-t—(symbol o;). A conveniently abbrevi-
ated value of the density of a sea water sample
of temperature ¢ and salinity S:

or= (es, ty*) X 108,

where p:s,t) is the value of the sea water
density in cgs units at standard atmospheric
pressure. If, for example, pg, :)=1.02648, then
o:=26.48. (5)

sigma-zero—(symbol o.). Sigma-t at 0°C.
Knudsen’s Tables give values of sigma-zero as
a function of salinity or chlorinity, as well as
Ge to be applied to obtain sigma-t.

4)

signal—A disturbance which is used to carry in-
formation; opposed to noise.

signal wave—Any sound wave upon which it is
required to make an observation of any kind is
known as a signal wave, or more often, simply
asa signal. (28)

signature—1. The characteristic frequency pat-
tern of the target displayed by detection and
classification equipment. (63)

2. The graph of pressure versus time at a
point as a ship passes over it. Increased water
velocity in the constriction between the ship and
the bottom of the water basin causes the pres-
sure variation by the Venturi effect.

significant wave—A statistical term relating to
the one-third highest waves of a given grou
and defined by the average of their heights shel
periods.

The composition of the higher waves depends
upon the extent to which the lower waves are
considered. Experience so far indicates that a
careful observer who atempts to establish the
character of the higher waves will record values
which approximately fit the definition.

significant wave height— (or characteristic wave
height). The average height of the one-third
highest waves of a given wave group. Note
that the composition of the highest waves de-
pends upon the extent to which the lower waves
are considered. In wave record analysis, the
average height of the highest one-third of a
selected number of waves, this number being
determined by dividing the time of record by
the significant period. (61)

significant wave period—An arbitrary period
generally taken as the period of the one-third
highest waves within a given group. Note that
the composition of the highest waves depends
upon the extent to which the lower waves are
considered. In wave record analysis, the aver-
age period of the most frequently recurring of
the larger well-defined waves in the record un-
der study. (61)

sikussak—An Eskimo name for very old sea ice,
resembling glacier ice trapped in a fiord, and
having a snow accumulation on its surface which
contributes to its formation and perpetuation.
(59)

silicate silicon—Ionic form of silicon utilized by
various plankters, principally diatoms and
radiolarians. The measurement of silicates in
sea water is useful for determining diatom
productivity. ) r

siliceous ooze—A fine-grained pelagic sediment
containing more than 30 percent siliceous skel-
etal remains of pelagic plants and animals. _

silicoflagellate—Any of a group of microscopic
marine phytoplankton having siliceous shells
with radiating spines; they are inhabitants

rincipally of colder waters. ;

sill—The low part of the ridge or rise separating
ocean basins from one another or from the
adjacent sea floor. (62)

sill depth—The greatest depth over a sill. (62)

sill basin—(or barred basin). A submarine basin
separated from the main basin by a narrow sub-
merged ridge. Deep water in the silled basin
may be stagnant and anaerobic. An example
is Fossa de Cariaco, Venezuela. (2)

silt—An unconsolidated sediment whose particles
range in size from 0.0039 to 0.0625 millimeter
in diameter (between clay and sand sizes). See
phi grade scale.

simple harmonic wave—An oscillation translat-
ing with constant speed and amplitude, and rep-
resented mathematically by a trigonometric or
complex exponential function. Thus,

A sin (F X—ot-+9) or € exp 2 (= X-rtte)
represents a simple harmonic wave of amplitude
A, wavelength A, frequency v, and phase angle ¢.

In ocean wave studies, a simple harmonic
progressive wave is an idealized wave charac-
terized by constant speed of propagation and a
straight crest of indefinite length. (5)

simple sound source—A source that radiates
sound uniformly in al] directions under free-
field conditions. (6)

single day tide—British terminology for diurnal
tide. (68)

sinking—1. (or downwelling). A downward
movement of surface water generally caused by
converging currents or when a water mass be-
comes more dense than the surrounding water.
See upwelling.

2. In atmospheric optics, a refraction phe-
nomenon, the opposite of looming, in which an
object on or slightly above the geographic hori-
zon apparently sinks below it. Sinking occurs
whenever the rate of density with height
through the atmosphere is of smaller magnitude
than normal or, in extreme cases, where the
density actually increases with height. (5)

siphonophore—One of an order (Siphonophora)
of medusoid coelenterates. Many are lumi-
nescent, some are venomous, and some posses a
pneumatophore (an air-filled float), which im-
parts a sound scattering capacity to the orga-

SLIGHTLY STRATIFIED ESTUARY

nisms. A pneumatophore-bearing species has
been observed within the deep scattering layer.

sirenian—See sea cow.

size of floating ice—The linear extent of individ-
ual fragments of ice. In general, ice fragments
are angular or circular. The linear dimension
used for describing the size of an individual ice
fragment is an approximation of the diameter.
Size is usually observed either in feet and miles
or meters and kilometers, whichever is more
convenient or applicable. The terms most gen-
erally used to describe ice fragments accord-
ing to increasing size are in order: brash ice,
block, small ice floe, medium ice floe, giant
floe, and ice field. (65)

skate barrow—See sailor’s purse.

skerries—Low, small islands, reefs, and rocks
which form a broad belt (skjzrgard) extending
along a coast for hundreds of miles. Skerries
rise from a shallow coastal strand flat.

skin—The first film or crust of newly formed
ice, with some degree of hardness. (68)

skin diving—Free diving with or without
SCUBA gear.

skjzrgard—wWScee skerries.

sky map—A pattern on the underside of extensive
cloud areas created by the varying amounts of
light reflected from the earth’s surface. Snow
surfaces produce a white glare in the sky (snow
blink) and ice surfaces a yellowish-white glare
(ice blink). Bare land and water surfaces re-
flect little or no light and for this reason the
clouds above these surfaces are relatively dark
(land sky, water sky). Generally the same
conditions can be observed from an aircraft
above the clouds, when the thickness of the cloud
layer permits. (65)

slack ice—Sce broken ice.

slack tide—Sce slack water.

slack water—(sometimes called slack tide). The
interval when the speed of the tidal current is
very weak or zero; usually refers to the period
of reversa] between ebb and flood currents. In
some places slack water occurs near times of
high and low water, whereas in other localities
the slack water may occur midway between high
and low water. (See figure for current curve.)

slant path velocity—The mean velocity along one
cycle of a sound ray path.

slant range—The diagonal distance between a
point at’ one position and a point at another
position in a vertical plane.

slat-flecked ice—Ice swept clear of snow except
for wind ripples saturated with brine. (59)

slewing—In ice navigation, the act of forcing a
ship through ice by pushing apart adjoining ice
floes. (59)

slide—See slump.

slightly stratified estuary—aAn estuary in which
the salinity increases slightly with depth and
also increases noticeably along its length from
the head to the mouth.

149

SLIME

slime—Soft, fine, oozy mud or other substance of
similar consistency. (68)

slime film—wSee primary film.

slob ice—An accumulation of sludge, so dense
as to make the passage of small craft impossible.
(59)

slope—The degree of inclination to the horizontal.
Usually expressed as a ratio, such as 1:25 or 1
on 25, indicating 1 unit rise in 25 units of hori-
zontal distance; or in a decimal fraction (0.04) ;
degrees (2°18’) ; or percent (4%). It is some-
times described by such adjectives as: steep,
moderate, gentle, mild, or flat. (61)

slope current—See gradient current.

slope of foreshore—The angle between the tan-
gent to the beach at the high water line (or some
reference point) and the horizontal. (73)

slough—1. A small muddy marshland or tidal
waterway which usually connects other tidal
areas.

2. A tideland or bottomland creek.

(61)

slud—See young ice.

sludge—1. Spongy whitish ice lumps a few cen-
timeters across. They consist of slush, snow
slush, and sometimes of spongy ice lumps
formed on the bottom of a shallow sea and
emerging at the surface.

2. (also called slush, cream ice). Anaccumu-
lation of ice crystals which remain separate or
only slightly frozen together. It forms a thin
layer and gives the sea surface a grayish or
leaden-tinted color. With light winds no ripples
appear on the surface. See grease ice, ice
slush. (74)

sludge cake—An accumulation of sludge
hardened into a cake strong enough to bear the
weight of aman. (59)

sludge floe—A large sludge cake. (59)

sludge lump—An irregular mass of sludge
shaped by the action of strong winds. (59)

slump—(or s/ide). The slippage or sliding of a
mass of unconsolidated sediment down a sub-
marine or subaqueous slope. Slumps occur fre-
quently at the heads or along the sides
of submarine canyons. The sediment usually
moves as a unit mass initially but often becomes
a turbidity flow. It may be triggered by any
small or large earth shock.

slush—See sludge (sense 2) ; ice slush.

slush pond—A pool or lake containing slush.
(Slush ponds are common in summer on ablation
surfaces of glaciers and ice caps.) (59)

small calorie—(abbreviated cal). See calorie.

small diurnal range—The average difference in
height between mean lower high water and mean
higher low water, measured over a 19-year
period, or its computed equivalent. See diurnal
range. (50)

small field of ice—Sce small ice field.

small floe—Sce small ice floe.

small ice cake—An ice cake less than 2 meters
(6.6 feet) across. (74)

small ice field—(or small field of ice). 1. An
ice field 10 to 15 kilometers (5.4 to 8.1 n. miles)
across. (74)

2. A Russian term for an ice field between
500 meters and 2 kilometers (1,640 feet to 1.1 n.
miles) in width:

small ice floe—1. See ice floe.

2. A floe of sea ice 30 to 600 feet across. (59)
Obsolete.

small ice skylight—See ice skylight.

small scale—Scee scale.

small tropic range—The average difference in
height between all tropic lower high waters
and all tropic higher low waters which occur
twice monthly when the moon’s north and south
declinations are greatest. See lunar declina-
tion, tropic range.

smoothing—An averaging of data in space or
time, designed to compensate for random errors
or fluctuations of a scale smaller than that pre-
sumed significant to the problem at hand. For
example, a thermometer smooths the tempera-
G reading on the scale of its time constant.

5

smooth sea—Sea with waves no higher than
ripples or small wavelets. (68)

snail—See gastropod.

snapper—See clamshell snapper.

snapping shrimp—(or pistol shrimp). Certain
species of shrimp belonging to the family
Alpheidae, chiefly in the genera Alpheus and
Synalpheus, that are capable of producing sharp
cracking sounds by the rapid closure of an en-
larged claw. These shrimps form large popula-
tions in warm shallow waters on shell, rock, or
coral bottoms where their sounds constitute a
major component of underwater background
noise. Shrimp noise ranges in frequency from
about 500 to 50,000 eps, with principal compo-
nents between 2,000 and 20,000 eps.

Snell’s law—When a wave (light or sound)
travels obliquely from one medium into another,
the ratio of the sine of the angle of incidence
to the sine of the angle of refraction is the
same as the ratio of the respective wave veloci-
ties in these mediums and is a constant for two
particular mediums.

snow blink—(also called snow sky). A bright,
white glare on the underside of clouds, produced
by the reflection of light from a snow covered
surface. This term is used in polar regions
with reference to the sky map; snow blink is
lighter than ice blink, and much lighter than
land sky or water sky. (5)

snow-covered ice—Ice covered with snow. (74)

snow ice—Ice crust on a water surface contain-
ing a large proportion of fallen or drifted snow..
(59) See ice rind.

snow sky—Scee snow blink.

150

snow sludge—A soft elastic crust formed on
fallen snow on a water surface. (59)

snow slush—A viscous mass formed as a result of
athick snowfall into cooled water. (74)

snow water on the ice—(or puddle). Ice whose
surface is covered with snow water (that is, an
accumulation on the ice of melt water mainly
due to snow melting).

sofar—t. An acronym derived from the expres-
sion “sound fixing and ranging.”

2. A position-fixing system by which hyper-
bolic lines of position are determined by measur-
ing, at shore listening stations, the difference in
the time of reception of sound signals produced
in a sound channel in the sea. (66)

sofar channel—Sce sound channel.

solar constant—The rate at which solar radiation
is received outside the earth’s atmosphere on a
surface normal to the incident radiation, and at
the earth’s mean distance from the sun. For
decades the tentative result was 1.94 or 1.95
gram-calories per square centimeter per minute,
however recent studies of the infrared and ultra-
violet portions of the solar spectrum suggest a
value of about 2.00 gram-calories per square
centimeter per minute. (5)

solar declination—The angular distance of the
sun expressed north or south of the celestial
equator; it is indicated as (+) when north and
(—) when south of the equator. Maximum
declination is about 2314 degrees north and south
of the Equator; maximum north declination oc-
curs about June 21 and maximum south declina-
tion about December 21. (50) ;

solar tide—The tide caused solely by the tide-
producing forces of the sun. (50)

solid—A state of matter in which the relative
motion of the molecules is restricted and they
tend to retain a definite fixed position relative
to each other, giving rise to crystal structure.
A solid may be said to have a definite shape and
volume. (27)

solitary wave—A wave consisting of a single ele-
vation (above the water surface), its height
not necessarily small compared to the depth,
and neither followed nor preceded by another
fohoan or depression of the water surface.

61)

solstice—One of the two points in the sun’s orbit
(the ecliptic) farthest from the celestial equa-
tor; the instant when the sun’s declination is
maximum. See summer solstice, winter sol-
stice.

solstitial tide—The tide occurring near the times
of the solstices when the sun reaches maximum
north and south declinations; the tropic range
at these times is greatest.

solubility—The extent to which a substance
(solute) mixes with a liquid (solvent) to pro-
duce a homogeneous system (solution).

solution—The state in which a substance, or
solute, is homogeneously mixed with a liquid

SONIC MARINE MAMMALS

called the solvent. Thus, pure water is a sol-
vent and sea water is a solution of many
substances.

solution basin—A shallow depression on a reef or
beach rock surface produced by solution of the
surface. (2)

Somali Current—Sce East Africa Coast Cur-
rent.

sonar—1. An acronym derived from the expres-
sion “sound navigation gnd ranging.” The
method or the equipment for determining by
underwater sound techniques the presence, lo-
cation, or nature of objects in the sea. (3)

2. A system for determining distance of an
underwater object by measuring the interval of
time between transmission of an underwater
sonic or ultrasonic signal and return of its echo.
(66) See active sonar, passive sonar.

sonar background noise—Sce background noise.

sonar projector—Scee transducer.

sonar performance figure—The source level of
a surface ship active sonar minus the equivalent
plane wave noise in the receiving band.

sonic bearing—(or acoustic bearing). A bearing
determined by measuring the direction from
which a sound wave is coming.

sonic fishes—(or soniferous fishes). Those fishes
which are capable of producing sounds, usually
by means of specialized organs such as the air
bladder or pharyngeal teeth. The spectra of
fish sounds generally have their limits between
50 and 5,000 cps, with most of the sound energy
concentrated between 100 and 800 cps. Air
bladder sounds range from about 50 to 1,500
cps, with principal frequencies in the region of
100 to 800 cps; sounds produced by stridulation
of hard parts, such as teeth or spines, may have
components from 50 to 800 eps or more, but
typically show the greatest energy from about
500 to 3,000 eps.

sonic frequency—Scee audio frequency.

sonic layer depth—The depth of the surface layer
into which sound rays are trapped by upward
refraction effects. The sonic layer depth is in-
dicated on a sound velocity versus depth trace
by the point of near surface maximum sound
velocity.

sonic marine animals—(or soniferous marine
animals). Organisms living in the sea which
are capable of producing sounds, either purpose-
ful by means of specialized organs, or incidental
to the course of normal activity such as
feeding or swimming. These animals include
certain invertebrates (principally crusta-
ceans), several groups of fishes, and most
marinemammals. See snapping shrimp, sonic
fishes, sonic marine mammals.

sonic marine mammals—(or soniferous marine
mammals). Those mammals which are capable
of producing sounds, including most, perhaps
all, of the whales, porpoises, and seals. A great
variety of sound has been recorded from ceta-

151

SONIC WAVE

ceans, ranging in frequency from the low 40-cps
moans of the fin whale to the echolocation
clicks of the bottlenose porpoise, which have
high energy between 20,000 and 30,000 cps and
may have minor components in the region of
200,000 cps. Recent investigations of under-
water sounds emitted by seals and sea lions in-
dicate that several pinnipeds produce sharp
clicks ranging from about 100 to at least 30,000
eps, with principal frequencies between 2,000
and 12,000 eps.

sonic wave—See sound wave.

soniferous fishes—Sce sonic fishes.

soniferous marine animals—Sce sonic marine
animals.

soniferous marine mammals—Scee sonic marine
mammals.

sonobuoy—A free floating or anchored device
that includes a buoy with radio telemetering
equipment and a hydrophone suspended be-
neath. Sound signals received at the hydro-
phone are transmitted to a nearby receiver for
analysis.

sonodivers—Untethered, unmanned, submersible
vehicles, launched from ships for recording
ambient noises and supplementary informa-
tion capable of sampling noise at depths from
100 to 20,000 feet over a frequency range of 10
to 50,000 cps.

sonoprobe—A low frequency echo sounder which
generates sound waves and records their re-
flections from one or more sediment layers
beneath the sediment/water interface. (2)
See subbottom reflection.

sound—1. The periodic variation in pressure,
particle displacement, or particle velocity in an
elastic medium. See sound velocity.

2. A long arm of the sea which forms a chan-
nel between an island and the mainland or a
sea and ocean. It is usually wider and longer
than a strait. (2)

3. To dive suddenly toward deep water,
usually from the surface or upper water levels,
as a fish or whale when hooked or harpooned,
or a submarine attempting to escape detection or
attack by enemy craft.

4. To measure or ascertain the depth of water
as with sounding lines. (61)

sound absorption—Sce absorption.

sound channel—The region in the water column
where sound velocity first decreases to a mini-
mum value with depth and then increases in
value as a result of pressure. Above the mini-
mum value sound rays are bent downward,
and below the minimum value sound rays are
bent upward; the rays are thus trapped in this
channel. Sound traveling in a deep channel can
be detected thousands of miles from the sound
source. '

sound channel axis—The depth at which mini-
mum sound velocity occurs.

sound energy density—The sound energy density
at a point in a sound field is the sound energy
contained in a given infinitesimal part of the
medium divided by the volume of that part of
the medium. (6)

soundhead—An enclosure containing the trans-
mitting projector and the receiving hydrophone.

sounding—1. The measurement of the depth of
water beneath a ship.

2. In geophysics, any penetration of the nat-
ural environment for scientific observation. (5)

sounding datum—The plane to which soundings
are referred. See alsochart datum. (61)

sounding line—See lead line.

sound intensity—1. At a point the average rate
of sound energy transmitted in a specified direc-
tion through a unit area normal to this
direction at the point considered. (6)

2. In practice, considered as the square of the
sound pressure.

sound pressure—The instantaneous pressure at
a point in a medium in the presence of a sound
wave, minus the static pressure at that point.

sound pressure level—Twenty times the loga-
rithm to the base 10 of the ratio of the pressure
of sound to the reference pressure, in decibels
at a specific point. The reference pressure shall
be explicitly stated.

sound velocity—The rate of travel at which
which sound energy moves through a medium,
usually expressed in feet per second.

The velocity of sound in sea water is a func-
tion of temperature, salinity, and the changes
in pressure associated with changes in depth.
An increase in any of these factors tends to in-
crease the velocity. Sound is propagated at a
speed of 4,742 feet per second at 32°F, one at-
mospheric pressure, and a salinity of 35 per
mille.

sound wave—(also called acoustic wave, sonic
wave). A mechanical disturbance advancing
with finite velocity through an elastic medium
and consisting of longitudinal displacements of
the ultimate particles of the medium, that is,
consisting of compressional and rarefactional
displacements parallel to the direction of ad-
vance of the disturbance; a longitudinal wave.
(5)

source level—The sound output of a source as
expressed in decibels relative to 1 dyne per
square centimeter at a distance of 1 yard from
the sound source.

source region—The extensive area of the oceans
where a water mass acquired its basic charac-
teristics.

South Atlantic Current—An eastward flowing
current of the South Atlantic Ocean that is con-
tinuous with the northern edge of the West
Wind Drift. (5)

152

South Equatorial Current—Any of several
ocean currents driven by the southeast trade
winds flowing over the tropical oceans of the
Southern Hemisphere.

In the Atlantic Ocean it is known as the At-
lantic South Equatorial Current and flows west-
ward with its axis through 2°N., 25°W. Part.
flows northwest along the northeast coast of
South America (the Guianas) as the Guiana
Current. The other part turns below Natal
and flows south along the coast of Brazil as the
Brazil Current.

In the Pacific Ocean, the Pacific South Equa-
torial Current flows westward between approxi-
mately 3°N and 10°S. Much of it turns south
in midocean, forming a large anticyclonic whirl.
The portion that continues across the ocean
divides as it approaches Australia, part moving
north toward New Guinea and part turning
south along the east coast of Australia as the
East Australia Current.

In the Indian Ocean, the Indian South Equa-
torial Current axis is located at about 12°S and
as it approaches the east coast of Africa it turns
south, joining the Agulhas Current. See also
monsoon current.

South Indian Current—An eastward flowing
current of the southern Indian Ocean that is
continuous with the northern edge of the West
Wind Drift.

South Pacific Current—An eastward flowing
current of the South Pacific Ocean that is con-
tinuous with the northern edge of the West
Wind Drift. (5)

spark-type luminescence—A display of biologi-
cal light appearing as innumerable flickering
pinpoints of light, particularly conspicuous in
the wake of a ship, along the hull line, or in
agitated waters. Crustaceans, such as cope-
pods and euphausiids, cause this type of dis-
play. See bioluminescence.

spat—The spawn or young of bivalve mollusks.

species—Scee classification of organisms.

specific acoustic impedance—The ratio of
acoustic pressure in a medium to the particle
velocity of the medium. The meter-kilogram-
second unit of specific acoustic impedance is a
kilogram per square meter second orrayl. (33)

specific activity—1. The activity of a radioiso-
tope of an element per unit weight of element
present in the sample.

2. The activity per unit mass of a pure
radionuclide.

3. The activity per unit weight of any sample
of radioactive material.

(41)

specific gravity—The ratio of the density of a
given substance to that of distilled water usually
at 4°C and at a pressure of one atmosphere.
Since the density of pure water depends on its
isotopic composition, unless the isotopic com-
position of the distilled water can be specified,

SPECTRUM DENSITY

the term specific gravity should not be used
when the intention is to state a precise value.
Values derived from Knudsen’s Tables are of
specific gravity, not density.

specific heat—The heat capacity of a system per
unit mass, that is, the ratio of the heat absorbed
(or released) by unit mass of the system to the
corresponding temperature rise (or fall).

The amount of heat required to raise the tem-
perature of 1 gram of water by 1°C. The spe-
cific heat of water is usually measured at
constant pressure but may also be measured at
constant volume.

The specific heat of water, which for pure
water at 17.5°C (63.5°F) is 1 calorie per gram,
decreases with increasing temperature and
salinity. (5, 54)

specific volume—The volume per unit mass of a
substance, or the reciprocal of density. (5)
In oceanographic practice, specific volume is
taken as the reciprocal of specific gravity.
specific volume anomaly—(or anomaly of spe-
cific volume; also called steric anomaly; eytibol
8). In oceanography, the excess uf the actual
specific volume of the sea water at any point in
the ocean over the specific volume of sea water
of salinity 35 per mille and temperature 0°C at
the same pressure. The integral of specific vol-
ume anomaly with depth is the dynamic height
anomaly. See thermosteric anomaly. (5)

Since oceanographic tables actually list re-
ciprocal density rather than specific volume, the
quantity used in oceanography is actually ‘“re-
ciprocal density anomaly.” However, a “reci-
procal density anomaly” is numerically equal
to a specific volume anomaly to as many signifi-
cant figures as are desirable in oceanographic
work.

spectral distribution curve—A curve represent-
ing the spectral concentration of a quantity as
a function of wavelength (or frequency). (8)

spectrophotometer—A device for the measure-
ment and analysis of both emitted and absorbed
radiant energy. Appropriate identifications
of the composition or the constituents of organic
and inorganic matter may be made. Quantita-
tive information derived from a determination
of the intensity or density of specific spectral
lines may also be measured.

spectrum—A visual] display, a photographic rec-
ord, or a plot of the distribution of the intensity
of energy dispersion of a given kind as a func-
tion of its wavelength, energy, frequency,
Gowen? mass, or any related quantity.

0

spectrum density—The mean-square amplitude
of the output of an ideal filter with unity gain
responding to the oscillation, per unit band-
width; that is, the limit for vanishingly small
bandwidth of the quotient of the mean-square
amplitude divided by the bandwidth.

153

SPECTRUM LEVEL

spectrum level—The level of that part of a sig-
nal contained with a band one cycle per second
wide, centered at the particular frequency.
Ordinarily this has significance only for a signal
having a continuous distribution of components
within the frequency range under consideration.
The phrase “spectrum level” cannot be used
alone, but must appear in combination with a
modifier, as, for example, pressure, velocity,
voltage, etc. (3)

spectrum stripper—The electronic accessory of a
multichannel analyzer which performs spec-
trum stripping.

spectrum stripping—The process of subtracting
known components of a gamma ray spectra to
reveal otherwise obscured spectral components.

specular reflection—A mirrorlike or perfect re-
flection of sound rays from a smooth surface
or bottom.

speed of advance—(abbreviated SOA). The ex-
pected speed to be made good over the earth’s
surface.

spermatophyte—One of a division (Sperma-
tophyta) of plants, most of which possess true
stems, leaves, and roots, and all of which produce
seeds. Only a small group of seed plants are
marine. See seagrass.

sperm whale—Largest of the toothed whales, or
odontocetes, attaining a length of about 60 feet.
It has a large blunt head and a dispropor-
tionately small lower jaw bearing a series of
large conical teeth. A single species, Physeter
catodon, is recognized, occurring in all warm
seas. See toothed whale.

spherical irradiance—Limit of the ratio of
radiant flux onto a spherical surface to the area
of the surface, as the radius of the sphere tends
toward zero with its center fixed. Unit of
(ves es is watt per square meter (W/m?).
8)

spherical irradiance meter—A radiant flux
meter with spherical collecting surface of effec-
tive area A, every elemental area of which is a
cosine collector. If / is the radiant flux re-
corded by the meter, then the associated spheri-
eal irradiance is#,=F/A. (8)

spherical spreading— See spreading of sound.

spherical wave—A wave whose wave front sur-
faces are concentric spheres. Such waves prop-
agate from a point source.

spicule—A minute needlelike or multiradiate cal-
careous or siliceous body in sponges, radio-
larians, primitive chitons, and echinoderms.
They frequently are identified in marine
sediment samples.

Spilhaus-Miller sea sampler—A bathythermo-
graph with attached containers designed to col-
lect sea water samples at predetermined
depths. The sample bottles are triggered to
close at both ends by the pressure sensing ele-
ment of the bathythermograph.

spilling breaker—Scee breaker.
spiny lobster—One of a tribe (Palinura) of
crustaceans, individuals of which are prized
as food and are reported to make sounds of con-
siderable magnitude.
spit—A small point of land or narrow shoal
projecting into a body of water from the shore.
(2) (See figure for recurved spit.)
Spitsbergen Current—An ocean current flowing
northward and westward from a point south
of Spitsbergen, and gradually merging with the
East Greenland Current in the Greenland Sea.
The Spitsbergen Current is the continuation of
the northwestern branch of the Norway Cur-
rent. (68)
splashnik—An expendable accelerometer tele-
metering buoy which provides surface wave
data.
spoil banks—Submerged accumulations of
dumped material dredged from channels or har-
bors. The region where such material is
dumped is called spoil ground.
spoil ground—An area where dredged material
is deposited. See dumping ground. (68)
sponge—One of a phylum (Porifera) of solitary
or colonial, sessile animals of simple construc-
tion. Sponges are of many sizes and forms and
varied in color.
spongin—A protein secretion, closely akin to silk,
which forms the skeleton of a fibrous sponge.
spouting horn—Marine caves eroded in coastal
rocks which have openings to the air through
which water spouts or sprays as waves surge into
the cavern beneath.
spray ice—Ice formed from blown spray, which
may occur along shore, on floating ice, on ships
or seaplanes. (59)
spray ridge—One of a series of ice formations on
an ice foot, formed by the freezing of spray
blown from the waves by the wind.
spreading anomaly—That part of the propaga-
tion anomaly which may be identified with the
geometry of the ray paths. (28)
spreading of sound—The phenomenon whereby
transmitted sound intensity decreases in a con-
stant relation to distance from the sound source.
Three laws govern spreading, all relating sound
intensity to a ratio of distance from the sound
source. These spreading laws are:
[=1/r (cylindrical spreading)
[=1/r* (inverse law or spherical spreading)
I=1/r* (dipolar spreading), where 7=sound
intensity and r=distance from sound
source.
spring flowering—See spring maximum.
spring high water—See mean high water
springs.
spring low water—Sce mean low water springs.
spring maximum—(or spring flowering). The
abundance of marine phytoplankton (predomi-
nately diatoms) after a winter minimum. The
production of phytoplankton is generally the

154

highest for the year during this period. This
condition occurs most frequently in regions of
the higher latitudes which experience some form
of vertical mixing.

spring range—Sce mean spring range.

spring rise—Sce mean spring rise.

spring—wWScee spring tides.

spring sludge—See rotten ice.

spring tide—(or springs). Tide of increased
range which occurs about every two weeks when
the moon is new or full (syzygy). (50) (See
figure for tide cycle.)

spur—1. A subordinate elevation, ridge, or rise
projecting outward from a larger feature. (62)

2. A ridge, usually composed of sand or
gravel, which extends into the sea from the shore
or from a larger submarine elevation. (68)

3. Seeram. (59)

squeeze—(or barotrauma). A type of injury
occurring in divers, usually during descent,
which comes about because of inability to equal-
ize pressure between a closed air space, such as
the middle ear, and outside water pressure.

squid—(or decapod mollusk). One of an order
(Decapoda) of cephalopods in which the body
is cigar shaped or globose and bears ten arms,
eight of which are of equal length with suckers
along the entire length and two of which are
longer with suckers only on a broad terminal
portion; shell, in most, is embedded in the body
or absent. Some species (the sea arrows) are
among the faster nekton, one species (the giant
squid) is the largest known invertebrate and a
food of the sperm whale, and others have been
suggested as possible sound scattering compo-
nents of the deep scattering layer. —

Staballoy slide*—A trade name for a gold-plated
glass slide used in the mechanical bathythermo-
graph to record the temperature versus depth
trace.

stability—The resistance to overturning or mix-
ing in the water column, resulting from the pres-
ence of a positive density gradient.

stabilizing force—The ordinary restoring force
in an unstable-type gravimeter.

stable gravimeter—A gravimeter having a sin-
gle weight or a spring such that the sensitivity is
proportional to the square of its period.

stable isotope—1. An isotope of an element
which is not radioactive.

2. A mixture of isotopic nonradioactive nu-
clides of composition different from that occur-
ring in nature, as an article of commerce.

3. In common usage, any stable nuclide (not

preferred).

stable polynya—See polynya.

stable-type gravimeter—A gravimeter which
uses a high order of optical and/or mechanical
magnification so that a change in position of a
weight or associated property is measured
directly.

207-109 O—66——11

STANDING WAVE

stagnant glacier—An inactive glacier. (65)

stalked barnacle—(or goose barnacle, gooseneck
barnacle). A barnacle whose body is differen-
tiated into the body proper, which usually is
covered by a two-valved shell, and a stalk at
the base, by which the animal is attached to a
firm surface. Many are pelagic or deep living,
and some are attached to free-floating objects,
floating seaweed, hulls of ships, and whales.

stamuhka—A Russian word for sea ice stranded
on a shoal or shallows.

stand—Scee stand of tide.

standard depth—A depth below the sea surface
at which water properties should be measured
and reported, either directly or by interpolation,
according to the proposal by the /nternational
Association of Physical Oceanography in 1936.
The accepted depths (in meters) are: 0, 10, 20,
30, 50, 75, 100, 150, 200, 250, 300, 400, 500, 600,
800, 1000, 1200, 1500, 2000, 2500, 3000, 4000,
5000, 6000; 7000, 8000, 9000, 10000, to which
NODC has added 125, 700, 900, 1100, 1300, 1400,
and 1750.

standard deviation—(symbol co). The positive
square root of the variance o?. This is a meas-
ure of the scatter or spread in a series of obser-
vations. (5)

standard displacement—The surface displace-
ment of a submarine, exclusive of the water in
nonwatertight structure, when fully manned, en-
gined, and equipped for sea duty, including all
armament and ammunition, equipment, provi-
sions for crews, miscellaneous stores, and imple-
ments of every description that are intended to
be carried in war but excluding fuel, lubricating
oil, fresh water, or ballast water of any kind.
This definition was established by the 1930 Zon-
don Treaty for the Limitation of Armaments.

64

standard port—British term for reference sta-
tion.

standard sea water—Sce normal water.

standard station—Sce reference station.

standard temperature and pressure—(abbrevi-
ated S.T.P.; also called normal temperature and
pressure.). A phrase used in physics to indicate
a temperature of 0°C and a pressure of one
standard atmosphere. (5)

standing crop—See biomass.

standing floe—1. A separate ice floe standing ver-
tically or inclined and enclosed by rather smooth
ice. (74)

2. See ropak.

standing oscillation—Sce standing wave.

standing stock—See biomass.

standing wave—(or stationary wave, standing
oscillation). A type of wave in which the sur-
face of the water oscillates vertically between
fixed points, called nodes, without progression.
The points of maximum vertical rise and fall are
called antinodes or loops. At the nodes, the
underlying water particles exhibit no vertical

155

STAND OF TIDE

motion but maximum horizontal motion. At
the antinodes the underlying water particles
have no horizontal motion and maximum verti-
cal motion. They may be the result of two
equal progressive wave trains _ travelin
(61

through each other in opposite directions.

LEGEND
——-—-— PROGRESSIVE WAVE
REFLECTED PROGRESSIVE WAVE

RESULTING STANDING WAVE
ARROWS INDICATE DIRECTION OF WAVES

FORMATION OF A STANDING WAVE BY REFLECTION OF A
PROGRESSIVE WAVE

(AFTER KING, 1962)

stand of tide—(or stand, tidal stand). The in-
terval at high or low water when there is no
appreciable change in the height of the tide;
its duration will depend on the range of the tide,
being longer when the tide range is small and
shorter when the tide range is large. Where a
double tide occurs, the stand may last for sev-
eral hours even with a large range of tide.

starfish—Scee sea star.

state of sea—See sea state.

static instability—Sce instability.

station—1. In oceanography, the geographic loca-
tion at which any set of oceanographic observa-
tions was taken; also, the observations recorded
at the location. The appropriate verbal phrase
is “occupy a station.”

2. In science generally, a permanent or tem-
porary location where scientific observations and
measurements are made.

( 3. See also serial station, ocean station.
5)
stationary field—A natural field of force as a
gravimetric or magnetic field.
stationary wave—See standing wave.

stationary wave theory—A theory which assumes
that the basic tide motion in the open ocean con-
sists of a system of standing wave oscillations;
progressive waves are of secondary importance
except where the tide advances into tributary
waters.

station data—Data collected by an oceanographic
ship while taking a station. Station data usu-
ally consists of identifying information, weather
data, and water temperature, salinity, and chem-
ical composition at specified depths.

statistical oceanography—The study of the
oceanic environment by use of statistical meth-
ods uninfluenced by physical theories.

statistical prediction—Prediction of the future
state.of the ocean environment by use of ob-
served variables which show correlation with
unobserved and predictive variables.

steadiness—S¢ee persistence.

steam fog—(or sea smoke, also called arctic sea
smoke, arctic smoke, frost smoke, water smoke,
sea mist, steam mist). Fog formed when water
vapor is added to air which is much colder than
the vapor’s source; most commonly, when very
cold air drifts across relatively! warm water.

No matter what the nature of the vapor source
(warm water, industrial combustion, exhaust,
exhaled breath), its equilibrium vapor pres-
sure is greater than that which corresponds to
the colder air; thus, the water vapor, upon be-
coming mixed with and cooled by the cold air,
rapidly condenses. It should be noted that al-
though advection of air is necessary to produce
steam fog, it differs greatly from an advection
fog, in the usual sense, which is caused by warm,
moist air moving over a cold surface.

Steam fog is commonly observed over lakes
and streams on cold autumn mornings, as well
as in polar regions. It is sometimes confused
with ice fog, but its particles are entirely liquid.
At temperatures below —20°F, these may freeze
into droxtals (ice crystals) and create a type of

ice fog which may be known as frost smoke. (5)
steam mist—See steam fog.
Stefan-Boltzmann law—(or Stefan’s law).

One of the radiation laws which states that the
amount of energy radiated per unit time from a
unit surface area of an ideal black body is pro-
portional to the fourth power of the absolute
temperature of the black body. (5)

Stefan’s law—See Stefan-Boltzmann law.

stenohaline—Capable of existence only within a
narrow range of salinity, as certain marine
organisms.

stenothermic—Tolerant of only a very narrow
range of temperature.
(58)

step—The nearly horizontal section which more
or less divides the beach from the shoreface.
(See figure for shore profile.)

156

stereographic projection—A perspective, con-
formal, azimuthal map projection in which
points on the surface of a sphere are conceived
as projected by radial lines from any point on
the surface to a plane tangent to the antipode of
the point of the projection. Circles project as
circles except for great circles through the point
of tangency which project as straight lines.

steric anomaly—See specific volume anomaly.

steric level—The mean dynamic depth (or
height) for the month minus the annual mean
dynamic depth to the same isobaric reference
level.

still water level—The level that the sea surface
would assume in the absence of wind waves;
not to be confused with mean sea level or half-
tide level. (5) (See figures for wave and
surf zone.)

stingray—Scee ray, venomous marine animals.

stipe—The basal, stemlike part of the thallus of an
alga beneath an erect blade. (13)

Stokes law—An expression of the relation be-
tween the size of spherical particles and their
settling velocity in a fluid. The law is used in
determining the proportion and size distribu-
tion of silt and clay in sediment samples.

stolonate bryozoan—See erect bryozoan.

stone—A general term for rock fragments and
rock ranging from pebbles and gravels to boul-
ders or large rock masses.

stone reef—Ofishore bars converted into solid
rock reefs by the calcium carbonate cementation
of sand grains in the upper 10 to 15 feet of the
reef. (2)

stones—Detached particles of rock usually smaller
than 256 millimeters in diameter.

stopped—The condition of a ship without power;
contrasted with hove-to.

stop trim—The condition of trim when net buoy-
ancy is zero whereby a stationary submarine can
maintain its depth.

storis—The Scandinavian name for the pack of
heavy ice floes which drifts from the Arctic
Ocean along the east coast of Greenland, around
Kap Farvel, and northward along the west
coast of Greenland where it melts.

storm ice foot—An ice foot produced by the
breaking of a heavy sea or the freezing of wind
driven spray. (68)

storm surge—(or storm tide, storm wave, tidal
wave). A rise above normal water level on the
open coast due only to the action of wind stress
on the water surface. Storm surge resulting
from a hurricane or other intense storm also
includes the rise in level due to atmospheric pres-
sure reduction as well as that due to wind stress.
A storm surge is more severe when it occurs in
conjunction with a high tide.

storm tide—1. See storm surge.

STREAM

2. The height of a storm surge (or hurricane
wave) above the astronomically predicted level
of the sea.

(5)

storm track—The path followed by a center of
low atmospheric pressure. (5)

storm wave—1. wind-generated sea surface
wave of great height.

2. See storm surge.

3. See hurricane wave.

(5

strain crack—(also called tension crack). A
crack in sea ice caused by stretching of the ice
beyond its elastic limit, usually due to motion of
underlying water. (68)

strain gauge—See dynamometer.

strait—A narrow sea channel which separates
two landmasses.

strand—The portion of the seashore between
high and low water line. (2)

stranded ice—Sce shore ice.

stranded ice foot—An ice foot formed by the
stranding of ice floes or small icebergs along a
shore. It may be built up by freezing spray or
breaking seas. (68)

stranded pressure ridge—A large pressure
ridge formed when ice is forced against the
shore.

strandflat—A low, broad coastal flat, slightly
submerged, supporting thousands of low small
islands, reefs, and rocks. It may extend for
hundreds of miles along a coast.

strath—A broad elongated depression with rela-
tively steep walls located on a continental shelf.
The longitudinal profile of the floor is gently
undulating, with the greatest depths often being
found in the inshore portion. (62)

straticulate—Having numerous thin layers, either
of sedimentary deposition from suspension as by
tee motion, or of deposition from solution.
48)

stratification—The state of a fluid that consists of
two or more horizontal layers arranged accord-
ing to their density, the hghtest layer being on
top and the heaviest at the bottom.

stratigraphy—The branch of geology which
treats of the formation, composition, sequence,
and correlation of layered or bedded rocks.
(2)

stratosphere—From an imperfect analogy with
the atmosphere, a term applied by some oceanog-
raphers to the nearly uniform masses of cold
deep and bottom water of middle and low lati-
tudes. This layer is separated from the tropo-
sphere by the thermocline. (54)

stratum—A single sedimentary bed or layer of
generally homogenous rock, independent of
thickness. See bed.

stream—Not to be confused with current.
strip.

See

157

STREAM CURRENT

stream current—A narrow, deep, and fast-
moving current as opposed to a relatively wide
and weak drift current; for example, the Gulf
Stream, the Kuroshio, and the Cromwell
Undercurrent.

streamline flow—See laminar flow.

strength of current—1. The greatest speed of the
tidal current; usually referenced in knots and
in hours before or after low and high water.
(See figure for current ellipse.)

2. For nontidal currents, the average of the
highest speeds observed, usually determined
from the highest 10 percent of the observations.

strength of ebb—(also called ebd strength). ‘The
ebb current at the time of maximum speed.

strength of ebb interval—The time interval be-
tween the transit (upper or lower) of the moon
and the next maximum ebb current at a place.
Usually shortened to ebb interval. (68)

strength of flood—(also called flood strength).
The flood current at the time of maximum
speed.

strength of flood interval—The time interval be-
tween the transit (upper or lower) of the moon
and the next maximum flood current at a place.
Usually shortened to flood interval. (68)

stress tensor—The complete set of stress compo-
nents in a medium, which are written as a ten-
sor ti;._ It has nine components, one for each

of the coordinate faces of an imaginary fluid
element upon which the stress acts (j=a, y, 2)
and for each direction in which the stress is
directed (=a, y,2). (5)

stridulatory sound—The noise produced by hard
skeletal parts of an animal rubbing together or
vibrating as the rasping of pharyngeal teeth in
certain fishes or the rattle of the spiny lobster’s
antennae against a toothed ridge on the
carapace.

string—WSee strip.

strip— (or tce stream, ice strip, stream string). A
long narrow area of pack ice, more limited than
a belt, bounded by open water or land. Strips
are usually about one kilometer (3,281 feet) or
less in width, and are composed of small frag-
ments detached from the main mass of ice run
together under the influence of wind, swell, or
current. (74)

S. constituent—The principal solar semidiurnal
constituent of the theoretical tide-producing
forces. (See figure for partial tide.)

Subarctic Current—An eastward flowing ocean
current which les north of the North Pacific
Current. It originates from part of the Aleu-
tian Current and from outflow of water from
the Bering Sea. As it approaches the coast of
North America it divides to join the northward-
flowing Alaska Current, and the southward-
flowing California Current.

subbottom reflection—The return of sound
energy from a discontinuity in material below
the sea bottom surface.

subclass—See classification of organisms.

subcoastal plains—Submerged plains of a conti-
nental shelf. (2)

subkingdom—See classification of organisms.

sublimation—The transition of the solid phase of
certain substances into the gaseous and vice
versa without passing through the usual liquid
phase. Water possesses this property ; thus, ice
can change directly to water vapor or water
vapor to ice. Strictly speaking, the word sub-
limation means the evaporation of ice and its
immediate recondensation elsewhere, but it is
also used to denote the single process of the con-
densation of water vapor into ice. (65)

sublittoral—That benthic region extending from
mean low water toa depth of about 100 fathoms
(200 meters), or the edge of a continental shelf.
(2) (See figure for classification of marine
environments. )

submarine alluvial fan—This term is not recom-
mended by the ACUF for a fan composed of
sedimentary deposits. See fan.

submarine best depth—The optimum depth for
a submarine to operate to avoid detection.

submarine bulge—WSee fan.

submarine canyon—S¢ce canyon.

submarine delta—See fan.

submarine geology—Sece geological oceanog-
raphy.

submarine geomorphology—The branch of geol-
ogy that deals with the features of the sea floor,
their form, origin, and development, and the
changes they are undergoing.

submarine isthmus—A submarine elevation join-
ing two land regions and separating two basins
by a depth less than that of the basins. (68)

submarine peninsula—An elevated portion of
the submarine relief resembling a peninsula.
The opposite is sac. (68) See peninsula.

submarine pit—Sce submarine well.

submarine valley—WScee valley.

submarine well—A cavity on the sea bottom; also
called a submarine pit. (68)

submerged breakwater—A breakwater with its
top below the still water level. When this
structure is struck by a wave part of the wave
energy is reflected seaward. The remaining
energy is largely dissipated in a breaker, trans-
mitted shoreward as a multiple crest system, or
transmitted shoreward as a simple wave system.

suborder—See classification of organisms.

subordinate station—1. One of the places for
which tide or tidal current predictions are deter-
mined by applying a correction to the predic-
tions of a reference station. (68)

9. A tide or tidal current station at which a
short series of observations has been made, which
are reduced by comparison with simultaneous ob-
servations at a reference station. (68)

3. Called secondary port in British terminol-
ogy. (68)

4, See tide station.

158

subphylum—See classification of organisms.

subsequent penetration—The depth to which a
mine sinks into the bottom after the initial
impact.

subsurface current—A current usually flowing
below the thermocline, generally at slower
speeds and frequently in a different direction
from the currents near the surface.

subtropical anticyclone—Sce subtropical high.

Subtropical Convergence—(or Subtropical Con-
vergence zone, Subtropical Convergence line).
The zone of converging currents generally lo-
cated in midlatitudes. It is fairly well defined
in the Southern Hemisphere where it appears as
an earth-girding region within which the sur-
face temperature increases equatorward.

Subtropical Convergence line—Sce Subtropical
Convergence.

Subtropical Convergence zone—Sce Subtropi-
cal Convergence.

subtropical high—(or subtropical anticyclone,
oceanic anticyclone, oceanic high). One of the
semipermanent highs of the subtropical high
pressure belt. They lie over oceans, and are
best developed in the summer season. See
Azores high, Bermuda high, Pacific high. (5)

sugar berg—Scee sugar iceberg.

sugar iceberg—(or sugar berg). An iceberg
composed of the more porous type of glacier ice.
Such ice is formed at very low temperatures, is
loosely constructed, and fallsapart easily. (65)

sugarloaf sea—See intersecting waves.

summer minimum—The scarcity of phytoplank-
ton (generally diatoms) noted after the abund-
ance in the spring. Grazing by zooplankton
and depletion of essential nutrients are the main
factors in reducing the phytoplankton popu-
lation.

summer solstice—For either hemisphere, the
solstice at which the sun is above that hemi-
sphere. In northern latitudes, this occurs
approximately on 21 June. (5)

sun zenith distance—The angle between the
zenith and the sun’s disk. (8)

superfamily—Scee classification of organisms.

superoceanic deep—See hadal.

supralittoral—(or swpratidal). The shore zone
immediately above high tide level, commonly the
zone kept more or less moist by waves and spray.
(2) (See figure for classification of marine
environments. )

supratidal—See supralittoral.

surf—1. Collective term for breakers. (73)

2. The wave activity in the area between the

ce and the outermost limit of breakers.
61

surface anomalies—Irregularities at the earth’s
surface, in the weathering zone, or in near sur-
face beds which interfere with geophysical
measurements.

SURFACE TEMPERATURE

surface corrections—Corrections of geophysical
measurements for surface anomalies and
ground elevations.

surface current—A general term meaning that
part of a directly observed movement of water
which, in nearshore areas, does not extend more
than 3 to 10 feet (1 to 3 meters) below the sur-
face; in deep, or open ocean areas, surface cur-
rents generally are considered to extend from
the surface to depths of about 33 feet (10
meters).

When surface currents are computed by theo-
retical methods, the volume of water in the
mixed layer (above the thermocline) from the
surface to depths of about 165 to 495 feet (50 to
150 meters), generally is referred to as surface
current.

surface density—The density of the surface ma-
terial within the range of elevation differences
of the gravitational survey. Both the Bouguer
correction and the terrain corrections depend
on the density of the surface materials.

surface duct—A zone immediately below the
sea surface where sound rays are refracted to-
ward the surface and then reflected. They are
refracted because the sound velocity at some
depth near the surface is greater than at the
surface.

The rays alternately are refracted and re-
flected along the duct to considerable distances
from the sound source.

surface energy—Scee surface tension.

surface free energy—Sce surface tension.

surface of discontinuity—Sce interface.

surface of no motion—Scee layer of no motion.

surface path—(or direct path, near surface
path). Sound paths which go no deeper than
1,000 feet from the surface.

surface probe—A thermistor that is towed
along the surface to record a continuous sea
surface temperature.

surface reflection—The return of sound rays to
depth after striking the sea surface.

surface reverberation—Sce reverberation.

surface scattering layer—The population(s) of
organisms in the surface layers of the ocean
which scatter sound. The organisms may
occur in a uniform layer extending from the sur-
face to a depth as great as 100 fathoms. On the
echo-sounder record, several layers or patches
of discrete scatterers may be conspicuous within
the uniform layer. See deep scattering layer,
shallow scattering layer.

surface temperature—1. In oceanography, the
temperature of the layer of sea water nearest the
atmosphere. It is generally determined either
as bucket temperature or injection tempera-
ture.

2. In meteorology, the temperature of the air
near the surface of the earth, almost invariably

159

SURFACE TENSION

determined by a thermometer in an instrument
shelter.
Chie

surface tension— (also called surface energy, sur-
face free energy, capillary forces, interfacial
tension). A phenomenon peculiar to the sur-
face of liquids, caused by a strong attraction to-
wards the interior of the liquid acting on the
liquid molecules in or near the surface in such
a way to reduce the surface area. An actual
tension results and is usually expressed in dyne
per centimeter or erg per square centimeter.
(5)

surface water—Sce mixed layer.

surface wave—A progressive gravity wave in
which the disturbance (that is, the particle
movement in the fluid mass as well as the sur-
face movement) is confined to the upper limits
of a body of water. Strictly speaking this term
applies to those progressive gravity waves whose
celerity depends only upon the wavelength
(73)

surf beat—Irregular oscillations of the nearshore
water level, with periods of the order of several
minutes. (61) See beating.

surf zone—The area between the outermost
breaker and the limit of wave uprush. (61)

surge—1. The name applied to wave motion with
a period intermediate between that of the ordi-
nary wind wave and that of the tide, from about
1% to 60 minutes. It is of low height, usually
less than 0.3 foot. (61)

2. Horizontal oscillation of water with com-
parative short period accompanying a Seiche.
(73) Seestorm surge.

3. See ship motion.

surge channel—A transverse channel cutting the
outer edge of an organic reef in which the water
level fluctuates with wave or tidal action. (2)

surging breaker—See breaker.

surveillance—The systematic observation of air,
surface, or subsurface areas by visual, electronic,
photographic, or other means.

suspended load—VSee load.

suspension current—See turbidity current.

sverdrup—A unit of volume transport equal to
one million cubic meters (35.318 million cubic
feet) persecond. (45)

Swallow float—A tubular buoy, usually made of
aluminum, that can be adjusted to remain at a
selected density level to drift with the motion
of that water mass. The float is tracked by
shipboard listening devices and current veloci-
ties can be determined.

swash—(or uprush, run-up). 1. The rush of
water up onto the beach following the breaking
of a wave.

2. A narrow channel or sound within a sand-
bank, or between a sandbank and the shore.
(68)

3. Also a bar over which the sea washes. (68)

swash channel—1. On the open shore, a channel
cut by flowing water in its return to the parent
body (that is, a rip channel).

2. A secondary channel passing through or
shoreward of an inlet or river bar. (See figure
for bars.)

(61)

swash mark—The thin wavy line of fine sand,
mica scales, bits of seaweed, etc., left by the up-
rush when it recedes from its upward limit of
movement on the beach face. (61)

SCHEMATIC DIAGRAM OF WAVES IN THE BREAKER ZONE

3. Inner line of
5. Reformed oscillatory wave;
7. Still water level; 8. Waves flatten
9. Waves break up but do not break on this bar at high

1. Surf or Breaker zone; 2. Translatory waves;
breakers; 4. Peaked up wave;
6. Outerline of breakers;
again;

160

tide; 10. Limit of uprush; 11. Uprush; 12. Backrush; 13.
Beach face; 14. Inner bar; 15. Outer bar (inner bar at Low
tide); 16. Deep bar (outer bar at low tide); 17. Mean lower
low water (MLLW); 18. Breaker depth =1.3 height

19. Plunge point

OES, TR-4, 1954)

sway—wSee ship motion.

swell—1. Ocean waves which have traveled out
of their generating area. Swell characteristi-
cally exhibits a more regular and longer period
and has flatter crests than waves within their
fetch. (5)

2. See rise.

swept area—An area determined to be clear of
navigational danger.

swim bladder—Scee air bladder.

swimmer’s itch—See schistosome dermatitis.

symbiosis—A relationship between two species in
which one or both species are benefitted and
neither is harmed. Some authorities restrict
the meaning of symbiosis to those interrelation-
ships between certain plants and animals. See
commensalism, mutualism, inquilinism.

synchronous resonant wave—One wave whose

161

SYZYGY

pened is equal to the natural period of the water

asin, or the period of roll of a ship.

syncline—A_ fold or arch of rock in which the
strata dip inward toward the plane of the axis.
See anticline.

synoptic chart—Any chart or map on which data
and analyses are presented that describe the
state of the marine environment over an area
at a given moment in time.

synoptic oceanography—The study of the physi-
cal spatial field of parameters through analysis
of simultaneous observations from many plat-
forms. The regular repetition of a pattern of
simultaneous observations.

syzygy—tThe two points in the moon’s orbit when
the moon is in conjunction or opposition to the
sun relative to the earth; time of new or full
moon in the cycle of phases. (See figure for
tide cycle.) |

table iceberg—Sce tabular iceberg.

tableknoll—A knoll with a comparatively
smooth, flat top. (62)

tablemount—A seamount having a compara-
tively smooth, flat top. (62)

table reef—A small isolated reef, with or without
islands, which has no lagoon. (2)

tabular iceberg—(or barrier iceberg, table ice-
berg). A flat-topped iceberg showing horizon-
tal firn-snow layers, usually calved from an ice-
shelf formation. (74)

Newly formed tabular icebergs have nearly
vertical sides and flat tops. In the antarctic
where they are most numerous, tabular icebergs
may be tens of miles wide, up to 100 miles long,
and as much as 1,000 feet thick with about 100
feet exposed above the sea surface. In the arc-
tic, the large icebergs of this type are called ice
islands, but they are considerably smaller than
the largest of the antarctic variety. (5)

tail wind—See crosswind, following wind.
talus—1. A slope.

2. (also called scree). The debris at the foot
of a cliff or slope, particularly that actumulated
as a result of gravitational roll or slide.

(68)

tangential stressses—The components of the
stress tensor which are tangential to the faces
of the fluid element. (5)

tangue—Very fine calcareous silt and clay derived
from banks of coquina limestone and which is
deposited in estuaries and along the coast of the
Bay of Biscay. (2)

tape gage—A tide gage which consists essen-
tially of a float attached to a tape and counter-
poise. (50)

target strength—A measure of the reflecting
power of the target. The ratio, in decibels, of
the reradiated sound (target echo) measured one
yard from the target to the sound incident on
the target.

taut-wire mooring—A mooring arrangement in
which a submerged float provides the upward
force necessary to maintain the system in a fixed
position with reference to the sea bottom. Taut-
wire moors may be single, double, or multipoint
according to design requirements of the system
and the speed and variability of the ambient
currents.

tectonics—The study of origin and development
of the broad structural features of the earth.

telementry—The study and technique involved in
measuring a quantity or quantities in_place,
transmitting this value to a station, and there

interpreting, indicating, or recording the
quantities.

telescoped ice—S¢ce rafted ice.

telluric current—(or earth current). Natural

electric currents that flow on or near the earth’s
surface in large sheets. Methods have been de-
veloped for using these currents to make resistiv-
ity surveys.

temperature—In general, the degree of hotness or
coldness as measured on some definite tempera-
ture scale by means of any of various types of
thermometers. (5)

temperature inversion—In oceanography, a layer
in which.temperature increases with depth.

temperature-salinity diagram—(or 7-S dia-
gram, T-S curve, T-S relation). The plot of
temperature versus salinity data of a water col-
umn. The result is a diagram which identifies
the water masses within the column, the col-
umn’s stability, and indicates the o; value, and
allows an estimate of the accuracy of the tem-
perature and salinity measurements.

temperature scale—(or thermometric scale). A
graduated scale for measuring the temperature
of matter, usually based on the freezing and
boiling points of pure water at standard atmo-
spheric pressure. The temperature scales most
commonly used are the Celsius (centigrade)
scale, the Kelvin (or absolute) scale, and the
Fahrenheit scale.

temporary anchorage—S¢ee anchorage.

tension crack—Scee strain crack, shear crack.

tented ice—Pressure ice in which two ice floes
have been pushed into the air, leaving an air
space underneath. (5)

tent fish—Sce Alexander’s acres.

tenting—The vertical displacement upward of ice
under pressure to form a flatsided arch with a
cavity beneath. See bending, rafting. (68)

tephra—A collective term for all clastic volcanic
materials which during an eruption are ejected
from a crater or from some other type of vent
and transported through the air, including vol-
canic dust, ash, cinders, lapilli, scoria, pumice,
bombs, and blocks. (2)

Teredo—A genus of molluscan borers. Also the
common name of the animal. See shipworm.

terrace—A_ bench-like structure bordering an
undersea feature. (62)

162

terrain correction—(or topographic correction).
A correction applied to pocered values obtained
in geophysical surveys in order to remove the
effect of variations to the observations due to
the topography in the vicinity of the sites of
observation.

terrestrial magnetism—Scee geomagnetism.

terrestrial radiation—(also called eradiation,
earth radiation). The total infrared radiation
emitted from the earth’s surface including the
seas and oceans; to be carefully distinguished
from effective terrestrial radiation, atmo-
spheric radiation, and insolation. (5)

terrigenous sediments—Deposits consisting of
debris derived from the erosion of land areas
and usually deposited in the shallow parts of the
sea.

test—The hard covering or supporting structure
of many invertebrates, it may be enclosed
within an outer layer of living tissue; a shell.
(2)

test board—See fouling panel.

test panel—WSce fouling panel.

test plate—Sce fouling panel.

Texas Tower—A fixed tower mounted offshore on
the continental shelf or a shoal to provide
oceanographic and meteorological observations.

thalassic rocks—Strata formed in deep, still
water far from land, generally composed of very
fine grains. (48)

thallatogenic—The vertical movement of the sea
floor. (2)

thallophyte—One of an artificial grouping (Thal-
lophyta) of simple plants lacking true stems,
leaves, and roots and generally having one-celled
sex organs. The algae, fungi, and bacteria are
included in this group.

thalweg—The line connecting the deepest points
of the channel of a sea valley or submarine
canyon.

thawing holes in the ice—Ice pocked with open
holes, usually circular. These holes represent
a further stage of development of snow waters
by ice melting. (74)

theoretical gravity—The value of gravity calcu-
lated for a particular latitude according to an
accepted formula such as the 1924 International
Formula of Gravity.

thermal—Pertaining to temperature or heat. (5)

thermal capacity—~See heat capacity.

thermal conductivity— (also called heat conduc-
tivity, coefficient of thermal conduction, coeffi-
cient of heat conduction). The time rate of
transfer of heat by conduction, through unit
thickness, across unit area for unit difference
of temperature. It is measured as calories per
second per square centimeter for a thickness of
one centimeter and a difference of temperature
of 1°C. (27)

thermal energy—wS¢ee heat.

thermal equator—Sce oceanographic equator.

163

THERMOMETER

thermal expansion—That property of a substance
which causes it to change its volume with
changes in temperature.

thermal layer—Sce thermocline.

thermal noise—A very low level noise produced
by molecular movements in the sea.

thermal structure—The temperature variation
with depth in sea water.

thermal wake—A temperature change produced
on the sea surface by passage of a submerged
submarine; although small, it can sometimes be
detected with special sensors.

thermistor—A thermally sensitive resistor em-
ploying a semiconductor material (usually me-
tallic oxides) with a large negative resistance-
temperature coefficient. The response charac-
teristics of thermistors are generally dependent
upon ambient conditions, especially temperature,
and the nature and purity of the semiconductor
material. (34)

thermistor bolometer—A device which is very
sensitive to temperature changes resulting from
absorption of long wave infrared radiation.

thermistor chain—An instrument-carrying chain
(up to 1,200 feet long) generally towed astern
to get continuous temperature recordings from
upper water layersatsea. (35)

thermocline—A_ vertical negative temperature
gradient in some layer of a body of water, which
is appreciable greater than the gradients above
and below it; also a layer in which such a gradi-
ent occurs. The principal thermoclines in the
ocean are either seasonal, due to heating of the
surface water in summer, or permanent. (5)

thermodynamics—The science that treats of the
mechanical action or relations of heat.

thermogram—The record of a thermograph.
(5)

thermograph—A _self-recording thermometer.
The thermometric element is most commonly
either a bimetal strip or a Bourdon tube. (5)

In oceanography, the two most commonly

used thermographs are the Geodyne* (Bour-
don) and Braincon* (mercury thermometer,
radioactive source, and film).

thermohaline—Pertaining to both temperature
and salinity acting together; for example,
thermohaline circulation.

thermohaline circulation—Vertical circulation
induced by surface cooling, which causes convec-
tive overturning and consequent mixing.

thermohaline convection—Vertical movement of
water observed when sea water, because of its
decreasing temperature or increasing salinity,
becomes heavier than the water underneath it
and a disturbed vertical equilibrium results.
(25)

thermometer—An instrument for measuring tem-
perature by utilizing the variation of the physi-
cal properties of substances according to their
thermal states. (5)

THERMOMETER FRAME

thermometer frame—A frame designed to hold
2, 8, and in some cases 4 reversing thermome-
ters. It can be quickly attached to or removed
from a Nansen bottle. The frame consists of
tubes arranged for reading the thermometers
and perforations to permit water circulation
around the mercury reservoir.

thermometer reader C viewer—A 6-—X lense
mounted in a tube for ease and increased ac-
curacy in reading reversing therometer tem-
peratures.

thermometric conductivity— (also called thermal
diffusivity, heat conductivity). The ratio of the
thermal conductivity of a substance to the
product of its specific heat and its density. For
a finid, ¢ is the specific heat at constant pressure.
The thermometric conductivity determines the
rate of heating due to a given temperature dis-
tribution. (5

thermometric depth—The depth, in meters, at
which paired protected and unprotected ther-
mometers attached to a Nansen bottle are re-
versed. The difference between the corrected
readings of the 2 thermometers represents the
effect of the hydrostatic pressure at the depth
of reversal. This depth may then be determined
by formula or form a depth anomaly (AZ)
graph. Depths obtained by this means are of
greatest value when a wire angle occurs.

thermometric scale—Sce temperature scale.

thermonuclear reaction—A nuclear reaction in
which the energy necessary for the reaction is
provided by colliding particles that have kinetic
energy by virtue of their thermal agitation.
Such reactions occur at appreciable rates only
for temperatures of millions of degrees and
higher, the rate increasing, enormously with the
temperature. The energy of most stars is be-
lieved to be derived from exothermic thermo-
nuclear reactions. (70)

thermoprobe—A transducer used to measure
temperature in situ of ocean bottom sediments at
depths beneath the bottom. Such measurements
when combined with heat conductivity informa-
tion provide a measurement of heat flow through
the ocean bottom. (4)

thermosteric anomaly—The specific volume
anomaly (steric anomaly) that the sea watef
at any point would attain if the sea water were
brought isothermally to a pressure of one stand-
ard atmosphere. In other words, thermosteric
anomaly is the specific volume anomaly calcu-
lated for the given salinity and temperature but
for a standard pressure. (5)

thick winter ice—Winter ice more than 30 cen-
timeters (12 inches) thick. (74)

thorium series—The series of nuclides resulting
from the decays of Th?**. (41)

thorofare—Deep channels in the lagoon marshes
behind barriers and spits.

threshold depth—Scee sill depth.

ete, ragged, rocky headland swept by the

sea. (2

tickle—Any narrow passage connecting two large
bodies of water. In the Gulf of St. Lawrence
it is restricted to an inlet between the sea and
a lagoon. (2

tidal basin—A basin affected by tides, particu-
larly one in which water can be kept at a desired
level by means of a gate. (68)

tidal bore—See bore.

tidal component—See partial tide.

tidal constants—Tidal relations that remain es-
sentially the same for any particular locality.
Tidal constants are classed as harmonic and non-
harmonic, the harmonic constants consisting
of the amplitudes and epochs, and the nonhar-
monic constants including those values deter-
mined directly from observations, such as tidal
ranges and intervals. (68)

tidal constituent—Scee constituent, partial tide.

tidal correction—A correction applied to gravi-
tational observations to remove the effect of
earth tides on gravimetric observations. The
value of gravity at any point varies in a cyclical
manner during the course of a day due to the
changing positions of the sun and the moon
relative to the area being investigated. The
tidal correction is commonly included in the
drift correction and may be determined by a
series of observations at a fixed base station.

tidal crack—Scee tide crack.

tidal current—(sometimes called tidal stream).
The alternating horizontal movement of water
associated with the rise and fall of the tide
caused by the astronomical tide-producing
forces.

In relatively open locations, the direction of
tidal currents rotates continuously through 360
degrees diurnally or semidiurnally. In coastal
regions, the nature of tidal currents will be de-
termined by local topography as well. See flood
current, ebb current, reversing current, ro-
tary current. (5)

tidal current chart—A chart showing, by arrows
and numbers, the average direction and speed
of tidal currents at a particular part of the
current cycle. A number of such charts, one for
each hour of the current cycle, usually are pub-
lished together. A current diagram is a graph
showing average speeds of flood and ebb cur-
rents throughout the current cycle for a con-
siderable part of a tidal waterway. (68)

tidal current curve—Scee current curve.

tidal current cycle—The period which includes
a flood and an ebb from one high water to the
next succeeding high water. The duration of
a semidiurnal tide approximates 12.42 hours;
that of a diurnal tide approximates 24.84 hours.
See tide curve, tide cycle.

tidal current diagram—Scee current diagram.

tidal cycle—Scee tide cycle.

tidal datum—See chart datum.

164

tidal datum plane—Sce chart datum.

tidal day—See lunar day.

tidal delta—Sand bars or shoals formed in the
entrance of inlets by reversing tidal currents.

2

tidal difference—The difference in time or height
of a high or low water between a subordinate
station and a reference station. The differ-
ence is applied to the prediction at the reference
station to obtain the time or height of the tide
at a subordinate station. These differences are
available in tide tables.

tidal epoch—See epoch.

tidal flat—A marsh or sandy or muddy coastal
flatland which is covered and uncovered by the
rise and fall of the tide. (2)

tidal glacier—(or tidewater glacier). A glacier
whose terminus is in tidewater. (59)

tidal inlet—Sce inlet.

tidal movement—The movement which includes
both the vertical rise and fall of the tide, and
the horizontal flow of the tidal currents. This
movement, is associated with the astronomical
tide-producing forces of the moon and sun act-
ing upon the rotating earth.

tidal outlet—VSee inlet.

tidal platform ice foot—An ice foot between
high and low water levels, produced by the rise
and fall of the tide. (68)

tidal pool—A pool of water remaining on a beach
or reef after recession of the tide. (73)

tidal prediction—See tide prediction.

tidal pressure ridge—A pressure ridge in sea
ice caused by forces exerted on the ice by the
tide. (59)

tidal prism—The difference between the mean
high water volume and the mean low water
volume of an estuary.

tidal prism method—A theoretical procedure for
determining the flushing time of a harbor or
estuary. The method assumes that the contami-
nant is initially distributed uniformly through-
out the harbor or estuary, and that during each
tide cycle a volume of water and contained con-
taminant equal to the tidal prism is removed
from the harbor and replaced by a new volume
of sea water which mixes completely and uni-
formly with the water present in the estuary
at low water. Therefore, the amount of con-

rn) s P e E

DAYS e,

TIDE CURVE

taminating material removed on each tidal cycle
may be expressed as a percentage of the con-
taminant in the harbor during the previous tidal
cycle:
tidal prism volume
high water volume of harbor

X (100) =percent of con-
taminant re-
moved from
harbor.

tidal range—WSee tide range.

tidal rise—Scee rise of the tide.

tidal scour—The erosion of the bottom by tidal

currents with formation of deep channels and
holes. (2)

tidal stand—See stand of tide.

tidal stream—See tidal current.

tidal water—Scee tidewater.

tidal wave—1. The wave motion of the tides.

2. In popular usage, any unusually high (and
therefore destructive) water level along a shore.
It usually refers to either a storm surge or
tsunami.

(5)
tide—The periodic rising and falling of the earth’s

oceans and atmosphere. It results from the
tide-producing forces of the moon and sun act-
ing upon the rotating earth. This disturbance
actually propagates as a wave through the at-
mosphere and through the surface layer of the
oceans.

Atmospheric tides are always so designated,
whereas the term “tide” alone applies to the
water level. Sometimes, the periodic horizontal
movements of the water along coast lines is also
called “tide,” but it is more correct to designate
the latter as tidal current, reserving the name
tide for the periodic vertical movements.

tide amplitude—One-half of the difference in
height between consecutive high water and low
water; hence, half of the tide range. (5)

tide bulge—Scee tide wave.

tide crack—1. A crack formed between shore ice
and the ice foot as a result of changing sea level.
(74)

2. A crack between the moving sea ice and the
unmoving ice foot. It may widen to form a
shorelead. Seecrack. (5)

tide curve—A graphic presentation of the rise
and fall of tide; time (in hours or days) is rep-
resented by the abscissa and height by the
ordinate. See marigram.

Sy 0 PT oo

Twa ra aay awa a ae eee
ISUAUAUAUAUCUAGLOUCU AME ua

PU VU VU

marin DIURNAL INEQUALITY (LOW WATER)
-———TIME LAG-——_

eet rf

TYPICAL TIDE CURVE
165

TIDE CYCLE

tide cycle—A period which includes a complete
set of tide conditions or characteristics, such as
a tidal day, a lunar month, or the Metonic cycle.
See tidal current cycle. (68)

FIRST QUARTER

NEAP TIDE

SYZYGY
QUADRATURE (CONJUNCTION)

FULL
MOON

NEW
MOON

SPRING
TIDE

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SYZYGY
(OPPOSITION)

QUADRATURE
LAST
QUARTER

NEAP TIDE

TIDE CYCLE

tide gage—A device for measuring the height of
tide. It may be simply a graduated staff in a
sheltered location where visual observations can
be made at any desired time; or it may consist
of an elaborate recording instrument (some-
times called marigraph) making a continuous
graphic record of tide height against time. Such
an instrument is usually actuated by a float in
a pipe communicating with the sea through a
small hole which filters out shorter waves.
See automatic tide gage, box gage, pressure
gage, tape gage, tide staff. (5)
tidehead—The inland limit of water affected by
a tide. (68)
tide indicator—A form of tide gage designed for
the purpose of clearly indicating the height and
time of the tide measured from a predetermined
plane of reference.
tideland—Land which is under water at high tide
and uncovered at low tide. Tideland, ‘beach,
strand, and seashore have nearly the same
meanings. Tideland refers to the land some-
times covered by tidewater. (68)
tidemark—1. A high water mark left by tidal
water.
2. The highest point reached by a high tide.
3. A mark placed to indicate the highest point
reached by a high tide, or occasionally, any
specified state of tide.
(68)
tide pole—See tide staff.
tide-predicting machine—An instrument that
computes, sometimes for years in advance, the
times and heights of high and low waters at a
reference station by mechanically summing the
harmonic constituents of which the tide is
composed.

tide prediction—Predetermined time and height
of high or low water at a reference station.
May be computed years in advance by mechani-
cally summing the harmonic constituents of
which the tide is composed. Used to compile
tide tables.

tide-producing force(s)—The slight local differ-
ence between the gravitational attraction of two
astronomical bodies and the centrifugal force
that holds them apart. These forces are exactly
equal and opposite at the center of gravity of
either of the bodies, but, since gravitational at-
traction is inversely proportional to the square
of the distance, it varies from point to point on
the surface of the bodies. Therefore, gravita-
tional attraction predominates at the surface
point nearest to the other body, while centrifu-
gal “repulsion” predominates at the surface
point farthest from the other body. Hence there
are two regions where tide-producing forces
are at a maximum, and normally there are two
tides each lunar day and solar day. (5)

tide race—A very rapid tidal current in a nar-
row channel or passage.

tide range—The difference in height between con-
secutive high and low waters. Where the type
of tide is diurnal the mean range is the same
as the diurnal range.

See diurnal range, great diurnal range,
mean range, apogean range, perigean range,
great tropic range, small tropic range, mean
tropic range.

MEAN HIGH WATER SPRINGS

MEAN HIGH WATER

MEAN HIGH WATER NEAPS

MEAN TIDE LEVEL

es
MEAN RANGE

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MEAN LOW WATER NEAPS

SPRING RANGE

MEAN LOW WATER

MEAN LOW WATER SPRINGS

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CHART DATUM

TIDE RANGES FROM CHART DATUM

tide rip—A misnomer for rips.

tide rise—Sce rise (sense 1).

tide staff—(also called tide pole). A tide gage
consisting of a vertical graduated staff from

166

which the height of the tide at any time can
be read directly. (50)

tide station—A place where tide observations are
obtained. It is a primary tide station when
continuous observations are available for a sufli-
cient number of years to determine the charac-
teristic tide features for the locality. A second-
ary tide station is operated during a short period
of time to obtain data for a specific purpose.
(50) See secondary tide station, reference
station.

tide tables—Tables which give daily predictions,
usually a year in advance, of the times and
heights of the tide. These predictions are usu-
ally supplemented by tidal differences and con-
stants by means of which additional predictions
can be obtained for numerous other places. (50)
See tide prediction, tidal difference.

tidewater—(or tidal water). Water affected by
tides or sometimes that part of it which covers
the tideland. The term is sometimes used
broadly to designate the seaboard. (68)

tidewater glacier—Sce tidal glacier.

tide wave—(or tide bulge). A long-period wave
associated with the tide-producing forces of
the moon and sun; identified with the risin,
and falling of the tide. (50) See tide, tida
movement, stand of tide.

tideway—A channel through which a tidal cur-
rent flows. (68)

tilted iceberg—A tabular iceberg that has be-
come unbalanced, so that the flat, level top is
inclined. (68)

time—Time is measured by the rotation of the
earth with respect to some point in the celestial
sphere and may be designated as sidereal, solar,
or lunar, according to whether the measurement
is taken in reference to the vernal equinox, the
sun, or the moon. Solar time may be Apparent
or Mean, according to whether the reference is
to the actual sun or the mean sun. Mean solar
time may be local or standard according to
whether it is based upon the transit of the sun
over the local meridian or a selected meridian
adopted as a standard over a considerable area.
Greenwich time is standard time based upon the
meridian of Greenwich, England. In Civil time
the day commences at midnight, while in As-
tronomical time as used prior to 1925 the be-
ginning of the day was reckoned from the noon
of the civil day of the same date. The name
Universal Time is now applied to the Greenwich
Civil Time. On 1 January 1953, the term Green-
wich Mean Time replaced the term Greenwich
Civil Time in the United States. (73)

time constant— (also called lag coefficient). Gen-
erally, the time required for an instrument to
indicate a given percentage of the final reading
resulting from an input signal; the relaxation
time of an instrument. In the case of instru-
ments such as thermometers, whose response to

TONGUE OF THE OCEAN

step changes in an applied signal is exponential
in character, the time constant is equal to the
time required for the instrument to indicate 63.2
percent of the total change, that is, when the
transient error is reduced to 1/e of the original
signal change. (5)

time series—Values of a variable during a finite
time period.

tintinnid—Any of a suborder (Tintinnoinea) of
microscopic planktonic Protozoa which possess
a tubular or vase-shaped outer shell. Several
species are luminescent.

titration—A chemical method for determining the
concentration of a substance in solution. This
concentration is established in terms of the
smallest amount of the substance required to
bring about a given effect in reaction with an-
other known solution or substance. The most
common titration is that for chlorinity.

tombolo—A bar or spit connecting or “tying” an
isiand to the mainland or to another island. (2)

ST
Se 3 5

23

TOMBOLO

(BEB; TR4, 1954)

tongue—1. A projection of the ice edge up to sev-
eral kilometers in length. It is caused by winds
or currents. (74)

2. A narrow peninsula formed by a glacier
and a steep, narrow cliff of ice rising high above
glacial néve is called an ice tongue. An exten-
sion of a glacier into the sea is called a glacier
tongue, and, if the end is afloat, an ice tongue
afloat. .(68)

3. Aninlet. (68)

4. A narrow, rapid current. (68)

5. Protrusion of water into a region of differ-
ent temperature. A tongue is cold when it ex-
tends into an area of warmer water, or warm
when it extends into an area of colder water.

Tongue of the Ocean—(abbreviated TOTO). A
steep-sided, deepwater embayment approxi-
mately 100 nautical miles long, 20 nautical miles
wide, and one nautical mile deep, connected to the
Atlantic Ocean by Northeast Providence Chan-

167

TOOTHED CETACEAN

nel and Northwest Providence Channel and
trends southeast into the Great Bahama Bank,
terminating in a circular cul-de-sac. (11)

toothed cetacean—Sce toothed whale.

toothed whale— (or odontocete, toothed cetacean).
A member of the cetacean suborder Odontoceti,
which comprises the dolphins, porpoises, killer
whales, beaked whales, and sperm whales.

tooth shell— (or tusk shell, scaphopod). One of a
class (Scaphopoda) of benthic marine mollusks
having tubular, tapering, slightly curved shells,
open at both ends; the body has no distinct head
but possesses a foot.

topographic correction—Scee terrain correction.

topography—The configuration of a surface in-
cluding its relief. In oceanography the term is
applied to a surface such as the sea bottom or a
surface of given characteristics within the water
mass.

torsion crack—A crack in sea ice, produced by
twisting of the ice beyond its elastic limit. (68)

tosca—A pplied in Argentina to a white calcareous
marl. In Colombia it is synonymous with vol-
canic tufa. (48)

total internal reflection—In wave refraction
theory, a term analogous to the phenomenon of
the total internal reflection of light at a 45-45-90
a) It occurs at a special type of caustic.

3

total magnetic intensity—The vector resultant of
the intensity of the horizontal and vertical com-
ponents of the earth’s magnetic field at a speci-
fied point.

total phosphorus—Includes both the soluble phos-
phorus (phosphate) and the organic phosphorus
contained in the plankton organisms and other
organic material in the water. (71)

total scattering coefficient—Sce scattering coe-
ficient.

tow—(or haul). A single haul of a net.

trace—1. (sometimes called profile). A line drawn
on a graph which shows the variation of an
oceanographic element such as temperature and
salinity usually with depth.

2. The indication of the recorded depth on an

echogram.

tracer—A foreign substance mixed with (or at-
tached to a given substance) to enable the dis-
tribution or location of the latter to be deter-
mined subsequently. A radioactive tracer is a
physical or chemical tracer having radioactivity
as its distinctive property. An isotopic tracer
is a radionuclide used as a chemical tracer for
the element with which it is isotopic. (41)

tracer studies—A technique for studying the role
of an element, a group of elements, or a com-
pound in a biological, chemical, or physical proc-
ess. In this technique an isotopic tracer is em-
ployed to follow the course of the bulk material
through the process. (41)

traction—See load.

traction load—See load.

trade winds—The wind system, occupying most
of the tropics, which blows from the subtropical
highs toward the equatorial trough; a major
component of the general circulation of the at-
mosphere. The winds are northeasterly in the
Northern Hemisphere and southeasterly in the
Southern Hemisphere. See antitrades. (5)

traffic noise—The general disturbance caused by
ships not associated with a specific ship or, more
significant, which has no definite directional dis-
tribution relative to a given observation point
and which shows little change in intensity with
change in position.
(28)

training wall—See jetty.

transducer—A device that converts electrical en-
ergy to sound energy, or the converse. When
sound energy received through the water is con-
verted to electrical energy, the device is termed
a hydrophone; conversely, when electrical en-
ergy is converted to sound energy and trans-
mitted through the water, the device is termed
a sonar projector or echo sounder.

transducer loss—The ratio of the available power
of the source to the power that the transducer
delivers to the load under specified operating
conditions. (6)

transgressive reef—One of a series of reefs or
bioherms developed close to and parallel to the
shore, by a net movement of the sea over the
land. (2)

transient thermocline—A small decrease in verti-
cal temperature observed above the thermo-
cline. It is a short-term phenomenon associated
primarily with diurnal heating and wind
mixing.

transit—The passage of the moon over the local
meridian; it is designated as upper transit when
it crosses the observers meridian and as lower
transit when it crosses the same meridian but
180 degrees from the observer’s location. When
specified, transit may be referred to the Green-
wich meridian.

transitional water wave—A progressive gravity
wave in water whose depth is less than 14 but
more than 14; the wavelength. Often called a
shallow water wave. (73)

transition zone—The water area between two op-
posing currents manifested by eddies, upwell-
ing, rips, and similar turbulent conditions oc-
curring either vertically or horizontally; or a
zone between two water masses of differing phys-
ical characteristics such as temperature and/or
salinity.

transmission anomaly—The difference (in deci-
bels) between the total transmission loss in
intensity and the reduction in intensity due to
an assumed inverse square divergence.

transmission gain—Whenever the transmission
factor is a number greater than unity, as it is in
the case of an amplifier, the transmission loss
would have a negative sign. In such cases the

168

logarithm of the reciprocal of the transmission
factor is written with a positive sign and desig-
nated as a transmission gain. (28)
transmission level—The energy at any point in
an energy transmission system is the rate of flow
of that energy as expressed in terms of (1) a
specified reference rate of flow and of (2) the
transmission loss by which the actual rate of
(08) must be reduced to equal the reference rate.
28
transmission loss—The energy lost in the trans-
mission of sound from one point to another; the
loss usually is expressed in decibels. In passive
sonar the loss is one way, whereas in active
sonar it is two way (travel from projector and
return of echo).
transmittance—The ratio of the transmitted ra-
diant flux to the incident radiant flux (in either
irradiance or radiance form). (8)
transparency—That property of water to trans-
mit light of different wavelengths. Transpar-
ency sometimes is measured in percent of radia-
tion that penetrates a distance of one meter;
sometimes it is expressed as the average depth
at which a Secchi dise disappears and reappears.
transponder—An automated receiver/transmitter
for transmitting signals when triggered by an
interrogating signal.
transport—1. The process by which a substance
or quantity is carried past a fixed point, or across
a fixed plane. In oceanography and meteorol-
ogy, such quantities are: heat, momentum, mass,
dissolved impurities, suspended particles, etc.
(5)
2. See flux.
tranverse bars—Slightly submerged sand ridges
ie extend at right angles to the shoreline.
2
a cylindrical orthomorphic projec-
tion—Scee transverse Mercator projection.
transverse Mercator projection—(also called
transverse cylindrical orthomorphic projection,
inverse Mercator projection, inverse cylindrical
orthomorphic projection). A conformal cylin-
drical map projection in which points on the
surface of a sphere or spheroid, such as the earth,
are conceived as developed by Mercator princi-
ples on a cylinder tangent along a meridian.
This projection is particularly useful for charts
of polar regions and for those extending a rela-
tively short distance from the tangent meridian.
It is frequently used for star charts. (68)
transverse wave—(also called distortional wave).
A wave in which the direction of propagation
of the wave is normal to the displacements of the
medium, for example, a vibrating string. The
gravity wave in which fluid parcels move in
circular orbits is an example ot a mixed trans-
verse-longitudinal wave. (5)
traumatic air embolism—Sce air embolism.
travel time—The time necessary for waves to
travel a given distance from the generating area.

169

TROPIC CURRENTS

trawl—1. A bag- or funnel-shaped net to catch
bottom fish by dragging along the bottom.

2. A large research net designed on bottom
trawl principles to catch large zooplankton and
fishes by towing in intermediate depths.

treibeis—Scee pack ice.

trench—A long, narrow and deep depression of
the sea floor, with relatively steep sides. (62)
See foredeep, hadal.

triangulation—The measurement of a series of
angles between points on the surface of the earth,
for the purpose of establishing relative posi-
tions of the points in surveying. (68)

Tridacna—See giant clam.

trim—1. The attitude of a submerged submarine
with respect to neutral buoyancy and fore-and-
aft balance.

2. In a more restrictive sense, the adjustment
of submarine buoyancy.

3. The relation of the draft of a ship at the
bew and stern. (68)

tripton—(or abioseston). Collectively, all of the
dead suspended particulate matter in aquatic
habitats. (44)

Tritium— (abbreviated ,H* or 7). The hydrogen
isotope having one proton and two neutrons in
the nucleus (mass number 3). (70)

trochoidal wave—A progressive oscillatory wave
whose form is that of a prolate cycloid or tro-
choid. It is approximated by waves of small
amplitudes. (61)

trochophore—(or trochosphere). The free-swim-
ming pelagic larval stage of some annelids and
mollusks.

trochosphere—See trochophore.

trophic level—A successive stage of nourishment
as represented by links of the food chain. Pri-
mary producers (phytoplankton) constitute the
first trophic level, herbivorous zooplankton the
second trophic level, and carnivorous organisms
the third trophic level.

tropical air—A type of air whose characteristics
are developed over low latitudes. Maritime
tropical air (m7), the principal type, is pro-
duced over the tropical and subtropical seas. It
is very warm and humid, and is frequently car-
ried poleward on the western flanks of the sub-
tropical highs. Continental tropical air (¢7Z’)
is produced over subtropical arid regions, and is
hotand verydry. (5)

tropical cyclone—The general term for a cyclone
that originates over the tropical oceans. At ma-
turity, the tropical cyclone is one of the most
intense and feared storms of the world; winds
exceeding 175 knots (200 mph) have been meas-
ured, and its rains are torrential. See hurri-
cane. (5)

tropic currents—Tidal currents occurring twice
monthly when the effect of the moon’s maximum
declination is greatest. Greatest diurnal inequal-
ities between speeds and durations of successive

TROPIC HIGHER HIGH WATER

flood and successive ebb currents occur at this

time.
tropic higher high water—(abbreviated
TcHHW). The mean higher high water of

tropic tides. (68)

tropic higher high water interval— (abbreviated
(TcHHWI). The lunitidal interval pertaining
to the mean higher high waters at the time of
tropic tides. (68) See lunitidal interval.

tropic higher low water—(abbreviated
TcHLW). The mean higher low water of
tropic tides. (68)

tropic high water inequality— (abbreviated
HWQ). The average difference between the
heights of the two high waters of the tidal day
at the time of tropic tides. See diurnal in-
equality. (68)

tropic inequalities—Tropic high water inequal-
ity is the average difference between the two
high waters at the times of tropic tides. Tropic
low water inequality is the average difference
between the two low waters at the times of
tropic tides. The terms are applicable only
when the type of tide is semidiurnal or mixed.

tropic intervals—Tropic higher high water in-
terval is the lunitidal interval of the higher high
waters at the time of the tropic tides. Tropic
lower low water interval is the lunitidal inter-
val of the lower low waters at the time of the
tropic tides. See lunitidal interval.

tropic lower high water—(abbreviated Tc-
LHW). The mean lower high water of tropic
tides. (68)

tropic lower low water— (abbreviated TcLLW).
The mean lower low water of tropic tides.
(68)

tropic lower low water interval—(abbreviated
TcLLWI). The lunitidal interval pertaining
to the mean lower low waters at the time of
tropic tides. (68) See lunitidal interval.

tropic low water inequality— (abbreviated
LWQ). The average difference between the
heights of the two low waters of the tidal day
at the time of tropic tides. See diurnal in-
equality. (68)

tropic range—Contracted form of great tropic
range.

tropic tide—The tide that occurs twice monthly
when the effect of the moon’s maximum declina-
tion north or south of the Equator is greatest.
See tropic currents.

tropic velocity—The speed of the greater flood
or greater ebb tidal currents at the time of tropic
tides. (68)

troposphere—From an analogy with the atmos-
phere, the term applied by some oceanographers
to the upper layer of the oceans in middle and
low latitudes. This layer is characterized by
relatively high temperatures and strong cur-
rents, and is generally bounded by the top of
the thermocline. (54) See stratosphere.

trough—1. A long depression of the sea floor nor-

mally wider and shallower thanatrench. (62)
9. See wave trough.

try net—A small shrimp trawl 12 to 24 feet wide
designed for exploration of shrimp grounds.
This net is frequently used for biological sam-
pling of benthic fishes.

T-S curve—Scee temperature-salinity diagram.

T-S diagram—See temperature-salinity dia-
gram.

T-S relation—See temperature-salinity dia-
gram.

tsunami—(or ftunami, tidal wave, seismic sea
wave). A long-period sea wave produced by a
submarine earthquake or volcanic eruption. It
may travel unnoticed across the ocean for
thousands of miles from its point of origin and
builds up to great heights over shoal water.

Tsushima Current—That part of the Kuroshio
flowing northeastward through Korea Strait and
along the Japanese coast in the Sea of Japan;
it sets strongly eastward through Tsugaru Strait
at speeds to 7 knots.

T-3— (also called Fletcher's ice island, Drift Sta-
tion Bravo). A drifting ice island of the Arctic
Ocean, probably formed by the calving of shelf
ice from Ward Hunt Island in the Canadian
Archipelago. T-3 is short for Target-3, so
named because it was first observed by radar
from aircraft in July 1950. (T-1, originally
called Target-X, was first seen on radar in Au-
gust 1946.) T-3 has been occupied intermit-
tently as a scientific drift station since 1952,
first by the U. S. Air Force, and since February
1962 by the Arctic Research Laboratory of Point
Barrow, Alaska. During the IGY, it was known
as Drift Station Bravo. It is also known as
Fletcher’s ice island after Colonel Joseph O.
Fletcher, its first station leader.

tubeworm—Any polychaete, chiefly the serpulids
or sabellids, that builds a calcareous or leathery
tube on a submerged surface. Tubeworms are
notable fouling organisms.

tufa—aA chemical sedimentary rock composed of
caleium carbonate or silica, precipitated from
percolating ground water or from a spring.

tuff—Cemented consolidated volcanic ash.

tunami—See tsunami.

tunic—The outer cuticular covering of tunicates.
(47)

tunicate(s)—One of a subphylum (Tunicata or
Urochordata) of globular or cylindrical, often
saclike animals, many of which are covered by
a tough flexible tunic. Many are sessile, others
are pelagic, and some are strongly luminescent.
See ascidian, pyrosome, salp.

turbidite—Turbidity current deposits charac-
terized by both vertically and horizontally
graded bedding.

turbidity—Reduced water clarity resulting from
the presence of suspended matter. Water is con-
sidered turbid when its load of suspended matter

170

is visibly conspicuous, but all waters contain
some suspended matter and therefore are turbid.

turbidity current— (or density current, mud flow,
suspension current). A highly turbid, relatively
dense current carrying large quantities of clay,
silt, and sand in suspension which flows down
a submarine slope through less dense sea water.

turbulence—A state of fluid flow in which the in-
stantaneous velocities exhibit irregular and ap-
parently random fluctuations, so that in prac-
tice only statistical properties can be recognized
and subjected to analysis. These fluctuations
often constitute major deformations of the flow
and are capable of transporting momentum, en-
ergy, and suspended matter at rates far in excess
of the rate of transport by molecular diffusion
and conduction in a nonturbulent or laminar
flow. (5)

turbulent diffusion—Scee eddy diffusion.

turbulent flow—A flow characterized by irregu-
lar, random velocity fluctuations.

turn of the tide—Scee change of tide.

turnover rate—Usually, the net primary produc-
tion per unit primary standing crop (phyto-
plankton) under natural light conditions, or
more specifically, the production divided by the
standing stock (biomass).

turret ice—See ropak.

turtlegrass—See seagrass.

tusk shell—Sce tooth shell.

two-year ice—A_ Russian term for young polar
ice.

tychoplankton—Plankton consisting of animals
and plants which have temporarily migrated or
have been carried into the plankton from their
normal benthic habitat.

Tyler standard grade scale—A scale for sizing
particles based on the square root of 2 used as
specifications for sieve mesh. Alternate class
limits closely approximate the class limits on the
Udden grade scale, and the intermediate limits
are the geometric means of the Udden scale
values: 0.50, 0.71, 1.00, 1.41, 2.00. (2)

Tyndall flowers—Small water-filled cavities,
often of basically hexagonal shape, which appear
in the interior of ice masses upon which light is
falling. Their formation results from the melt-
ing ice by radiative absorption at points of de-
fect in the ice lattice. (5)

type of tide—The characteristic feature of the
tide (tidal current) determined from the com-
bination of its diurnal and semidiurnal com-

207-109 O - 66 - 12

TYPHOON

ponents. Tides are classified as semidiurnal,
mixed, and diurnal, but there are no sharply de-
fined limits separating the groups.

DAYS

HEIGHT OF TIDE

TYPES OF TIDE CURVES

typhon—WScee typhoon.
-typhoon— (also spelled typhon). <A severe tropi-
cal cyclone in the western Pacific. (5)

171

U

Udden grade scale—A grade scale for particle
size, with 1 millimeter as the reference point and
involving the fixed ratio 2 or 14, depending on
whether the scale is increasing or decreasing, as
V4, Yp,1,2,4. (5)

ultraplankton—Plankton smaller than 5 mi-
crons; includes bacteria and smaller flagellate
forms.

ultrasonics—The technology of sound at frequen-
cles above the audio range; that is, above 20,000
cycles per second. (3)

ultraviolet radiation—Electromagnetic radia-
tion of shorter wavelength than visible radiation
but longer than X-rays; roughly, radiation in
the wavelength interval from 10 to 4,000 ang-
stroms. (5)

umbrella—(or del/). The gelatinous body of a
jellyfish, usually bearing prominent tentacles.
It may be bell-, dome-, bow]-, or saucer-shaped
according to species.

unbroken ice—Sea ice which has not been dis-
turbed since its formation. It is usually fast
ice, although a single smooth ice floe could be
said to be unbroken ice.

unconformity iceberg— An iceberg consisting of
more than one kind of ice, such as blue water-
formed ice and névé. Such an iceberg often
contains many crevasses and silt bands. (68)

unconsolidated sediments—Sce sediment.

uncovers—(or dries). An area of a reef or other
projection from the bottom of a body of water
which periodically extends above and below the
surface. (30)

unda—The part of the ocean floor which lies in
the zone of wave action, in which the bottom
sediments are repeatedly stirred and reworked;
the topographic expression is termed undaform,
and the rock unit is termed undathem.

undaform—See unda.

undathem—Scee unda.

undercurrent—A water current flowing beneath
a surface current at a different speed or in a
different direction. (5)

underflow—Sce bottom flow.

undermelting—The melting from below of any
floating ice. (5)

undersea satellite—A basketball-size device con-
taining a gauge (to measure tides), a seismom-
eter, and a transmitter.

undertow—1. A seaward flow near the bottom of
a sloping beach.

172

2. The subsurface return by gravity flow of
the water carried up on shore by waves or break-
ers. See rip current. (50)

underwater gradient—Sce slope, gradient.

underwater ice—Sce anchor ice, frazil ice.

underwater sound—NSee sound.

underway—The condition in which a ship is mak-
ing headway against the seas; as opposed to
hove-to.

undulation—A continuously propagated motion
to and fro, in any fluid or elastic medium, with
no permanent translation of the particles them-
selves.

uniform flow—Any current in which neither con-
vergence nor divergence is present.

unilateral transducer—A transducer than can-
not be actuated at its outputs by waves in such
a manner as to supply related waves at its in-
puts. (69)

unprotected thermometer—A_ reversing ther-
mometer (for sea water temperature) which is
not protected against hydrostatic pressure. The
mercury bulb is therefore squeezed, and the
amount of mercury broken off on reversal is a
function both of temperature and hydrostatic
pressure.

When compared with the simultaneous read-
ing of a protected thermometer, which is af-
fected by temperature only, the unprotected
thermometer reading can be converted to pres-
sure, and then, by applying the mean density
of the water, todepth. (5)

unstable polynya—WSee polynya.

unstable-type gravimeter—A gravity meter
which utilizes a moving system which ap-
proaches a point of instability such that small
changes in gravity produce relatively large mo-
tions of the system.

upcoast—In United States usage, the coastal di-
rection generally trending toward the north.
(2)

updrift—The direction opposite that of the pre-
dominant movement of littoral materials. (61)

uplifted reef—A coral reef exposed above water
level. (2)

upper transit—wSee transit.

uprush—The rush of water up onto the beach fol-
lowing the breaking of a wave. See swash, run-
up. (61) (See figure for surf zone.)

upstream—Generally, in the direction from which
a fluid is flowing; the opposite of downstream.

(5)

upward irradiance—The radiant flux incident
on an infinitesimal element of the lower face
(180 to 360 degrees) of a horizontal surface con-
taining the point being considered, divided by
the area of that element. Unit of measurement
is watt per square meter (W/m?). (8)
upwelling—The process by which water rises from
a lower to a higher depth, usually as a result of
divergence and offshore currents. See sinking.
Upwelling is most prominent where persistent
wind blows parallel to a coastline so that the re-
sultant eincedriven current sets away from the
coast. See Ekman spiral. It constitutes a dis-

173

URANIUM SERIES

tinct climatogenetic influence by bringing colder
water to the surface. Over the open ocean, up-
welling occurs wherever the wind circulation is
cyclonic, but is appreciable only in areas where
that circulation is relatively permanent. It is
also observable when the southern trade winds
cross the Equator.

The upwelled water, besides being cooler, is
richer in plant nutrients, so that regions of up-
welling are generally also regions of rich fish-
eries. (5)

uranium series—The series of nuclides resulting

from the decay of U***. (41)

vacuum filtration—A method of extracting phy-
toplankton and bacteria from a water sample.
See Millepore* filter.

valence electron—An electron which is gained,
lost, or shared in a chemical reaction. (70)

valley—A relatively shallow, wide depression with
gentle slopes, the bottom of which grades con-
tinuously downward. The term is used for fea-
tures that do not have canyonlike characteristics
in any significant part of their extent. (62)

valley iceberg— (also called drydock iceberg). An
iceberg eroded in such a way that a large U-
shaped slot, which may be awash, extends
through its surface separating pinnacles or
slabs. (59)

valve—1. One of the pieces forming the shell of
a diatom.

2. Any of the pieces forming the shell of cer-
tain invertebrates, such as the mollusks and
barnacles.

vanishing tide—When a high and low water
“melt” together into a period of several hours
with a nearly constant water level, the tide is
in the diurnal category but is known as a van-
ishing tide.

DAYS

HEIGHT OF TIDE

VANISHING TIDE

vapor—Any substance existing in the gaseous state
at a temperature lower than that of its critical
point; that is, a gas cool enough to be liquified

if sufficient pressure were applied to it.
If any vapor is cooled sufficiently, say at con-

174

stant pressure, it ultimately reaches a state of
saturation such that further removal of heat is
accompanied by condensation to the liquid
phase. (5)

vaporization—Scee evaporation.

vapor pressure—(or vapor tension). The pres-
sure exerted by the molecules of a given vapor.
For a pure, confined vapor, it is that vapor’s
pressure on the walls of its containing vessel;
and for a vapor mixed with other vapors or
gases, it is that vapor’s contribution to the total
pressure (that is, its partial pressure).

In the atmosphere, vapor pressure is used al-
most exclusively to denote the partial pressure
of water vapor. Care must be exercised in inter-
preting the term’s meaning as used in other
branches of science. (5)

vapor tension—See vapor pressure.

variability of waves—1. The variation of heights
and periods between individual waves within a
wave train. (Wave trains are not composed of
waves of equal height and period, but rather of
waves with heights and periods which vary in a
statistical manner.)

2. The variation in direction of propagation
of waves leaving the generating area.

3. The variation in height along the coast, usu-
ally called “variation along the wave.”

(61)

variable—A quantity that may assume a number
of values. (22)

variable depth sonar—(abbreviated VDS). A
shipborne sonar system whereby the transducer
can be lowered below the thermal layer.

variance—A measure of variability denoted by
o? and defined as the mean-square deviation from
the mean, that is, the mean of the squares of the
differences between individual values of the vari-
able and its mean value.

variation—1. The range within which values of a
variable lie, as in the diurnal or annual varia-
tion.

2. See declination.

(5)

varve—A sedimentary deposit, bed, or lamination
deposited in one season. It is usually distin-
guished by color or composition and used as an
index to changes in the depositional environ-
ment.

vast ice floe—See ice floe.

vector mean—See resultant current.

veering—1. According to general international
usage, a change in wind direction in a clockwise
sense (for example, south to southwest to west)
in either hemisphere of the earth; the opposite
of backing.

2. According to widespread usage among
United States meteorologists, a change in wind
direction in a clockwise sense in the Northern
Hemisphere, counterclockwise in the Southern
Hemisphere; the opposite of backing.

(5)

vein—A narrow lead or lane in pack ice. (59)

veliger—The planktonic larval second stage of
many gastropods.

velocity discontinuity—An abrupt change of the
rate of propagation of seismic waves within the
earth, as at an interface. (35)

velocity hydrophone—A hydrophone in which
the electric output substantially corresponds to
the instantaneous particle velocity in the im-
pressed sound wave. (69)

velocity of sound—Scee sound velocity.

veneer—A thin layer of sediment covering a rocky
surface.

venomous marine animal—Any of various orga-
nisms living in the sea that are capable of in-
jecting venom into other organisms, either to
capture prey or in self-defense. This capability
is developed to the highest degree in some of the
jellyfishes, sea urchins, marine snails of the genus
Conus, stingrays, catfishes, scorpionfishes, and
sea snakes.

ventral—Pertaining to or situated on the lower
or abdominal surface; opposite of dorsal. (26)

vertex velocity—The velocity at which a sound
ray becomes horizontal (grazing angle equals
zero).

vertical haul—(or vertical tow). The lifting of
an open plankton net from a certain depth to
the surface while the ship or other platform is
on station. See horizontal haul, oblique haul.

vertical intensity—The magnetic intensity of the
vertical component of the earth’s magnetic field,
reckoned positive if downward, negative if
upward.

vertically mixed estuary—<An estuary in which
the salinity is homogeneous with depth but in-
creases along its length from the head to the
mouth.

vertical tow—Sce vertical haul.

very close drift ice—Sce very close pack ice.

very close pack ice—Sea ice whose concentration
is practically 10-tenths (8-eighths) with little
if any open water. (74)

very open drift ice—Sce very open pack ice.

very open pack ice—Sea ice whose concentration
ranges between 1- and 3-tenths (1- to 2-eighths).
(74)

very shallow water—Water of depths less than
165 the wavelength of surface waves.

very shallow water wave—Sce shallow water
wave.

175

VOLUME’ SCATTERING FUNCTION

vesicle—Sce pneumatocyst.

vigia—A rock or shoal in the sea, whose existence
or position is doubtful; also a warning note to
this effect ona nautical chart. (68)

viscosity— (or internal friction). That molecular
property of a fluid which enables it to support
tangential stresses for a finite time and thus to
resist deformation. (5)

viscous damping—The dissipation of energy that
occurs when a particle in a vibrating system is
resisted by a force whose magnitude is a con-
stant independent of displacement and velocity,
and whose direction is opposite to the direction
of the velocity of the particle. (6)

viscous stress—The resistive force of the water;
it is proportional to the speed of the current but
acts opposite to its direction of flow.

V,—tThe volume of mercury below the 0°C mark
determined at 0°C in the reversed main ther-
mometer. Expressed in degrees Celsius. V, is
found on the deep sea reversing thermometer
card. (67)

voe—An inlet, bay, orcreek. (2)

void ratio—The ratio of intergranular voids to
the volume of solid material ina sediment. (2)

volcanic ash—Uncemented pyroclastic material
consisting of fragments mostly under 4 milli-
meters in diameter. Coarse ash is 14 to 4 milli-
meters in grain size; fine ash is below 14 milli-
on A constituent of some marine sediments.
(2

voleanie blocks—FEssential, accessory, or acci-
dental volcanic ejecta, usually angular and
larger than 32 millimeters in diameter, erupted
ina solid state. (2)

voleanic bombs—Fragments or lava up to several
feet long thrown out of a volcano in a liquid,
semifluid, or plastic state and solidified in flight
or soon after landing.

voleanic breccia—A rock composed predomi-
nantly of angular volcanic fragments greater
than 2 millimeters in size set in a subordinate
matrix of any composition and texture, or with
no matrix; or composed of fragments other than
volcanic set ina voleanic matrix. (17)

voleanic cinders—See scoria.

volcanic cone—A conical hill or mountain with a
crater or cup-shaped hollow at the summit con-
structed of ash, scoria, lava, and other volcanic
materials discharged through the summit crater.
(See figure for compound volcano.)

volcanic ejecta—N¢ee tephra.

volcanic eruption—The emission or ejection of
volcanic material at the earth’s surface from a
crater or froma fissure. (2)

voleanic harbor—A bay formed by the flooding
of a volcanic crater through a gap in the rim.

volume reverberation—Sce reverberation.

volume scattering function—See scattering
function.

VOLUME TRANSPORT

volume transport—The volume of moving water
measured between two points of reference and
expressed in cubic meters per second. It is deter-
mined by measuring the cross-sectional areal
limits of the current and multiplying this figure
by the current speed.

volume velocity—The rate of alternating flow of
the medium through a specified surface due to
asound wave. (6)

176

von Arx current meter—A type of current meas-
uring device using electromagnetic induction to
determine speed and, in some models, direction
of deep sea currents. This meter provides con-
tinuous recordings of current by transmitting,
through a connecting cable, signals to a deck
unit that registers speed, direction, and instru-
ment depth.

vulgar establishment—See establishment of the

port.

Ww

wake—The region of turbulence immediately to
the rear of a solid body in motion relative to a
fluid. (5)

warm pool—A body of warm water entirely sur-
rounded by cold water.

wash and strain ice foot—aAn ice foot formed
from ice casts and slush and attached to a shelv-
ing beach, between the high and low water lines.
High waves and spray may cause it to build up
above the high water line. (68)

washovers—(or wave delta). Small deltas build
on the lagoon side of a bar separating the lagoon
from the open sea. Storm waves breaking over
the bar deposit sediment on the lagoon side in
the form of deltas. (2)

water—See fresh water, normal water, pure
water, sea water.

water color—The apparent color of the surface
layers of the sea caused by the reflection of cer-
tain components of the visible light spectrum
coupled with the effects of dissolved material,
concentration of plankton, detritus, or other
matter. Color of oceanic water varies from deep
blue to yellow and is expressed by number values
which are a variation of the Forel scale. Plank-
ton concentrations may cause a temporary ap-
pearance of red, green, white, or other colors.
See Forel scale.

water content—A ratio; 100 multiplied by the
weight of water in a bottom sediment sample
divided by the weight of the dried sample, ex-
pressed as a percentage.

water exchange—The volume and rate of water
replacement in a specific location controlled by
such factors as tides, winds, river discharge, and
currents.

water flea—(or cladoceran). One of a suborder
(Cladocera) of small crustaceans that swim in
a jerky or jumpy manner. Although abundant
in some shallow water environments, they are
not among the more abundant marine plankton.

water-laid rope—See cable-laid rope.

water level—Sce sea level.

water line—A juncture of land and sea. This line
fluctuates, changing with the tide or other fluc-
tuations in the water level. Where waves are
present on the beach, this line is also known as
the limit of backrush. (Approximately the
intersection of the land with the still water
level.) (61) See shoreline, coastline.

177

water mass—A body of water usually identified
by its T-S curve or chemical content, and nor-
mally consisting of a mixture of two or more
water types. (See temperature-salinity dia-
gram.)

The terms water mass and water type have
been used loosely and interchangeably in oceano-
graphic literature.

The major recognized water masses of the
oceans are shown in the figures on the following
pages. (32)

water opening—Sce opening.

water pocket—A water mass of limited size, fre-
quently in the form of a pocket, and having
properties different from those of the surround-
ing water. Water pockets are often located at
a meandering boundary where they usually are
partly or completely cut off from the original
main body of water. (25)

water sample—A portion of water brought up
from a certain depth to determine its composi-
tion.

water sky—The dark appearance of the underside
of a cloud layer due to the reflection of a surface
of open water surrounded or bounded by ice.
The area of open water may be beyond the range
of visibility. (74)

This term is used, largely in polar regions,
with reference to the sky map; water sky is
darker than land sky, and much darker than ice
blink or snow blink. (5)

water smoke—Scee steam fog.

waterspout—Usually, a tornado occurring over
water; rarely, a lesser whirlwind over water,
comparable in intensity to a dust devil over land.

aterspouts are most common over tropical

and subtropical waters. (5)

water tagging—The process of introducing for-
eign substances (tracers) into the ocean to de-
tect the movement of its waters by subsequent
measurement of the location and distribution of
the introduced substance. See tracer.

water transparency—Scee transparency.

water type—Sea water of a specified temperature
and salinity, and hence defined by a single point
on a temperature-salinity diagram. (5)

watt—A unit of power equal to one Joule per sec-
ond or 10’ ergs per second. (5)

wattenschlick—Tidal or intertidal mud. (2)

wave—1. A disturbance which moves through or
over the surface of the medium (here, the ocean),

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179

WAVE AGE

WAVE CHARACTERISTICS

1. Wave crest; 2. Wave length;

5. Wave trough;

with speed dependent upon the properties of the
medium.

2. A ridge, deformation, or undulation of the
surface of a liquid.

wave age—The state of development of a wind-
generated sea surface wave, conveniently ex-
pressed by the ratio of wave speed to wind speed.
Wind speed is usually measured at about 25 feet
(8 meters) above still water level. (5)

wave base—The depth at which wave action ceases
to stir the sediments. (2)

wave celerity—The magnitude of wave speed.

wave crest—The highest part of a wave. Also
that part of the wave above still water level.
(61) (See figure for wave.)

wave crest length— (or crest width). The length
of a wave along its crest. (61) (See figure
for wave.)

wave decay—The change which waves undergo
after they leave a generating area (fetch) and
pass through a calm, or region of lighter or op-
posing winds. In the process of decay, the sig-
nificant wave height decreases and the signifi-
cant wavelength increases. (61)

wave deltas—Sce washovers.

wave direction—The direction from which a wave
approaches. (61) (See figure for wave.)

wave filter—See filter.

wave forecasting—The theoretical determination
of future wave characteristics, usually from ob-
an or predicted meteorological phenomena.

61)

wave front—The leading side of a wave.
(See figure for refraction diagram. )

wave generation—1. The creation of waves by nat-
ural or mechanical means.

2. In wave forecasting the growth of waves
caused by a wind blowing over a water surface
for a certain period of time. The area involved
( ee the generating area or fetch.

61

(68)

3. Direction of wave travel;
6. Still water level;

4. Height;

7. Depth; 8. Ocean bottom

(WIEGEL, 1953)

wave group—A series of waves in which the wave
direction, wavelength, and wave height vary
only slightly. (61)

wave height—The vertical distance between a
wave crest and the preceding wave trough.
See also significant wave height. (61) (See
figure for wave.)

wave height coefficient—The ratio of the wave
height at a selected point in shallow water to
the deepwater wave height. The refraction co-
efficient multiplied by the shoaling factor. (61)

wave hindcasting—The calculation from historic
synoptic wind charts of the wave characteristics
that probably occurred at some past time. (61)

wave interference—The phenomenon which re-
sults when waves of the same or nearly the same
frequency are superposed. It is characterized
by a spatial or temporal distribution of ampli-
tude of some specified characteristic differing
from that of the individual superposed waves.
(6)

wavelength—1. The distance between correspond-
ing points of two successive periodic waves in
the direction of propagation, for which the os-
cillation has the same phase. Unit of measure-
ment is meters.

Note: The wavelength of monochromatic radi-
ant energy depends on the refractive index of
the medium. Unless otherwise stated, values of
wavelengths are those in air. (8)

2. The horizontal distance between points on
two successive waves measured perpendicularly
to the wave crest. (See figure for wave.) (61)

wavelength of sound—The distance between cor-
responding points of adjacent sound waves;
measurement is determined by the ratio of speed
to frequency.

wave level—The position of the sea surface above
or below a reference plane at any specific time in
the tide cycle.

180

wave meter—An instrument used to measure and
record wave heights.

wave of translation—A wave in which the water
particles are permanently displaced to a signifi-
cant degree in the direction of wave travel. (61)
(See figure for surf zone.)

wave period—The time, in seconds, required for
a wave crest to traverse a distance equal to one
wavelength. (73)

wave pole—(also called wave staff). A device for
measuring sea surface waves. It consists of a
weighted pole below which a disk is suspended
at a depth sufficiently deep for the wave motion
associated with deepwater waves to be negligi-
ble. The pole will then remain nearly steady
as if anchored to the bottom, and wave height
and period can be ascertained by observing or
recording the length of the pole that extends
above the surface. See wave recorder. (5)

wave ray—(or orthogonal). A line drawn every-
where perpendicular to the wave crests on a
refraction diagram. (See figure for refraction
diagram.)

wave recorder—An instrument for recording
ocean waves. Most wave recorders are designed
for recording wind waves, that is, waves of

se

ACTUAL WAVE CREST-ORTHOGONAL PATTERN
FOR WAVES PASSING OVER A CLOCK GLASS

WAVE STAFF

periods up to about 25 seconds, but some are
designed to record waves of longer periods such
as tsunamis, seiches, or tides. See tide gage.
(5)

wave refraction—1. The process by which the di-
rection of a train of waves moving in shallow
water at an angle to the contours is changed.
The part of the wave train advancing in shal-
lower water moves more slowly than that part
still advancing in deeper water, causing the
wave crests to bend toward alignment with the
underwater contours.

2. The bending of wave crests by currents.
(61)

wave signature—The graph of pressure versus
time at a point as a wave passes over lt.

wave spectrum—1. In ocean wave studies, a graph
showing the distribution of wave heights with
respect to frequency in a wave record. (5)

2. A concept used to describe by mathematical
function the distribution of wave energy (square
of wave height) with frequency (1/period). The
square of the wave height is related to the poten-
tial energy of the sea surface so that the spec-
trum can also be called the energy spectrum.

wave staff—wSce wave pole.

2 SCaustici

iF

SHADOWGRAPH FOR WAVES OF MOD-
ERATE LENGTH PASSING OVER A CLOCK
GLASS

WAVE REFRACTION—CAUSTIC

181

{AFTER WIEGEL, 19537

WAVE STEEPNESS

wave steepness—The ratio of the wave height to
wavelength. (73)

wave-straightened coast—A_ straight cliffed
coast which results from wave erosion of homo-
geneous coastal rocks; along a contact between
weak and resistant layers forming a hogback
coast; or along a fault with more resistant rocks
shoreward forming a fault-line coast. It has a
wave-cut beach at the base of the sea cliffs and
hanging valleys along the coast.

wave train—A series of waves moving in the same
direction.

wave trough—The lowest part of a wave form
between successive wave crests. Also that part
of a wave below still water level. (61) (See
figure for wave.)

wave velocity—1. The speed at which the individ-
ual wave form advances. (73)

2. A vector quantity that specifies the speed
and direction with which a sound wave travels
through a medium. (6)

weathered—Descriptive of ice or rock that has
been destroyed or partially destroyed by thermal,
chemical, and mechanical processes.

weathered ice—Hummocked polar ice subjected
to weathering which has given the hummocks
and pressure ridges a rounded form. If the
weathering continues, the surface may become
more or less level. (74)

weathered iceberg—An iceberg which is irregu-
lar in shape, due to an advanced stage of abla-
tion. It may have overturned. If the weather-
ing produces spires or pinnacles, a pinnacled,
pyramidal, or irregular iceberg results; if it
produces a large U-shaped slot extending
through the iceberg, a valley or drydock iceberg
results; and if it produces a large opening at the
water line, extending through the iceberg, an
arched iceberg results. (68)

weather patrol ship—Sce ocean station vessel.

weather routing—Sce optimum ship routing.

weather ship—See ocean station vessel.
weed—Scee seaweed.

weight crack—Scee hinge crack.

Wentworth grade scale—A logarithmic grade
scale for size classification of sediment particles,
starting at 1 millimeter and using the ratio of
1% in one direction (and 2 in the other), pro-
viding diameter limits to the size classes of 1,
14, 4, etc., and 1, 2,4, ete. This was adopted by
Wentworth from Udden’s scale with shght modi-
fication of grade terms and limits. (2) See
phi grade scale.

West Australia Current—The complex current
flowing along the west coast of Australia. It
flows northward and is stronger during Novem-
ber, December, and January; it is weakest and
tends to be variable in May, June, and July. It
curves toward the west to join the South Equa-
torial Current.

West Greenland Current—The current flowing
northward along the west coast of Greenland

182

into Davis Strait. It is formed by water of the
East Greenland and Irminger Currents. Part
of the West Greenland Current turns to the left
when approaching the Davis Strait and joins
the Labrador Current flowing southward; the
other part continues into Baffin Bay.

West Ice—1. The drifting ice of Baffin Bay.

2. To Norwegians, the drifting ice off the east
coast of Greenland.

(59)

West Wind Drift—(sometimes called Antarctic
Circumpolar Current). The ocean current with
the largest volume transport (approximately
110 X 10 © cubic centimeters-per second) ; it flows
from west to east around the Antarctic continent
and is formed partly by the strong westerly wind
in this region and partly by density differences.

wet density—The ratio of the weight of the solid
particles of a bottom sediment and the contained
moisture to its total volume.

wet weight—Quantitative measure of wet plank-
ton; the living weight. Although commonly
used, this measurement may lead to erroneous
results unless all extraneous water is removed by
blotting or draining.

whale—A cetacean. See baleen whale, toothed
whale.

whalebone—Sce baleen.

whalebone whale—Scee baleen whale.

whirlpool—Water moving rapidly in a circular
path; an eddy or vortex of water. See eddy,
gyre.

whiteeap—On the crest of a wave, the white froth
caused by wind. (61)

whitefish—1. Any of a family Coregonidae of
predominantly fresh-water fishes.

2. A menhaden, young bluefish, or whiting.

3. (chiefly British). Any of several commer-
cial fishes, such as cod, halibut, and sole, with
white nonoily flesh.

4. The beluga or white whale.

white ice—A Russian term for sea ice of 30 to 70
centimeters (12.0 to 27.5 inches) in thickness.

white noise—Noise whose spectrum density (or
spectrum level) is substantially independent of
frequency over a specified range. (6)

whiteout—(also called milky weather). An at-
mospheric optical phenomenon of the polar
regions in which the observer appears to be en-
gulfed in a uniformly white glow. Neither
shadows, horizon, nor clouds are discernible;
sense of depth and orientation is lost; only very
dark, nearby objects can be seen.

Whiteout occurs over an unbroken snow cover
and beneath a uniformly overcast sky, when,
with the aid of the snow blink effect, the light
from the sky is about equal to that from the snow
surface. Blowing snow may be an additional
cause.

This phenomenon is experienced in the air as
wellason the ground. (5

white water—1. Frothy water as in whitecaps or
breakers.
2. Light-colored water over a shoal.
68

Wiens law—One of the radiation laws which
states that the wavelength of maximum radia-
tion intensity for a black body is inversely pro-
portional to the absolute temperature of the
radiating black body. (5)

wind chill—That part of the total cooling of a
body caused by air motion. (5)

wind-chill factor—sSee wind-chill index.

wind-chill index—(also called wind-chill factor).
The cooling effect of any combination of tem-
perature and wind, expressed as the loss of body
heat in kilogram calories per hour per square
meter of skin surface. The wind-chill index is
based on the cooling rate of a nude body in the
shade; it is only an approximation because of
individual body variations in shape, size, and
metabolic rate. (5)

wind chop—WSee chop.

wind direction—The direction from which the
wind blows. (68)

wind drift—1. See drift current, wind-driven
current.

2. That portion of the total vector drift of sea
ice from which the effects of the current have
been subtracted.

wind-driven current—(sometimes called wind
drift, drift current). A current formed by the
force of the wind. Theoretically, currents pro-
duced by the wind will set to the right of the
direction of the wind in the Northern Hemi-
sphere and to the left in the Southern Hemi-
sphere. See Ekman spiral.

wind mixing—Mechanical stirrmg of water due
to motion, induced by the surface wind. Simi-
lar to mechanical mixing.

window—An unfrozen portion of a river, which
remains unfrozen all or part of the winter be-
cause of a strong current or a local inflow of
warm water. (59)

wind rose—1. A diagram showing the relative
frequency of winds blowing from different di-
rections. It may also show average speed or
frequency of occurrence of various speeds from
different directions.

9. A diagram showing the average relation be-
tween winds from different directions and the
occurrence of other meteorological phenomena,
such asrain. (68)

wind set-up—1. The vertical rise in the still water
level on the leeward side of a body of water
caused by wind stresses on the surface of the
water.

2. The difference in still water levels on the
windward and the leeward sides of a body
of water caused by wind stresses on the surface
of the water.

3. Synonymous with wind tide. Wind tide is
usually reserved for use on the ocean and large

183

WMO CODE

bodies of water. Wind set-up is usually reserved
for use on reservoirs and smaller bodies of water.
See meteorological tide.

(61)

wind stress—The force, per unit area, of the wind
acting on the water surface to produce waves and
currents; its magnitude depends on the wind
speed, air density, and roughness of the water
surface.

wind tide—Sce wind set-up, meteorological tide.

windward—The direction from which the wind is
blowing. (61)

wind wave—A wave resulting from the action of
wind on a water surface. While the wind is
acting on it, it is a Sea, thereafter, aswell. See
fetch. (5)

winged headland—A seacliff with two bays or
spits, one on either side. (2)

Winkler method—A chemical method for esti-
mating the dissolved oxygen in sea water. In
this method manganous hydroxide is allowed to
react with the oxygen of the sample to produce a
manganese compound which in the presence of
acid potassium iodide liberates an equivalent
quantity of iodine that can be titrated with
standard sodium thiosulphate.

winnow—In regard to current action, to sort se-
lectively and carry off fine sediment grains from
a heterogeneous sediment deposit, leaving the
coarse grains.

winter drift ice—Drift ice composed exclusively
of winter ice.

winter fast ice—1. Fast ice in fiords, gulfs, and
straits, mainly formed by growth from the shore,
but also by cementing of pack ice. Winter fast
ice rises and falls according to the tide. (74)

2. Fast ice made up of winter ice.

winter ice—1. Generally unbroken level ice of less
than one winter’s growth. It is between 15
centimeters and 2 meters (6.0 inches to 6.6 feet)
thick. See medium winter ice, thick winter
ice. é

2. Sea ice more than eight inches thick and
less than one year old; the stage which follows
young ice.

winter solstice—For either hemisphere, the sol-
stice at which the sun is above the opposite
hemisphere. In northern latitudes, the time of
this occurrence is approximately 22 December.
(5) See solstice.

wiping—WSee flashing.

wire angle—The angle measured between the
oceanographic wire and the vertical.

wire angle indicator—a<A device used to measure
the angle of the oceanographic wire from the
vertical. It consists of a protractor with a
weighted plumb arm. The indicator is sus-
pended from the wire at two points and the
plumb arm points to the wire angle.

WMO Code—An international nomenclature
adopted by the World Meteorological Organiza-
tion for use by all reporting nations.

WORKING

working—In sea ice navigation, making headway worm tube—A tube, usually of calcium carbonate
through an ice pack by boring, breaking, and or particles of mud or sand, built on a submerged
slewing. (59) surface by a polychaete worm.
wrack—The British term for rockweeds.

184

.¢

xanthophyll—A plant pigment. See nonastacin by the transitions of atoms from K, L, . . . en-
carotenoid. ergy states to lower energy states. In nuclear
X-rays—Electromagnetic radiation of wave- reactions it is customary to refer to photons orig-

inating in the nucleus as gamma rays, and to

lengths less than about 100 A (angstroms), pro- those originating in the extranuclear part of the

duced: (1) when electrons striking a target lose atom as X-rays. These rays are sometimes
kinetic energy in passing through the strong called Roentgen rays after their discoverer,
electric fields surrounding the target nuclei; (2) W.C. Roentgen. (41)

185

yaw—See ship motion.

yaw angle—WSee angle of yaw.

young ice—1. Newly formed level ice generally
in the transition stage of development from ice
rind or pancake ice to winter ice. It is 5 to 15
centimeters (2 to 6 inches) in thickness. (74)

2. Formerly newly formed level ice between

2 and 8 inches thick.

young polar ice—(also called two-year ice).
Polar ice that has survived its first summer of
melting and has passed on to its second year of
growth. At the end of its second winter, young

186

polar ice may become thicker than 2 meters (6.5
feet). It differs from one-year ice in that a
greater portion shows above the water surface
and any hummocks present show more weather-
ing. (74)

young shore ice—The primary stage of forma-
tion of shore ice. It is of local formation and
usually consists of ice rind or thin young ice
usually some 10 meters (32.8 feet.) wide, but
sometimes as wide as 100 to 200 meters (328 to
656 feet). (74)

yowling—See ice yowling.

Z

Z/L graph—A graph used to determine in situ
depths of oceanographic observations by the
thermometric depth versus wire depth ratio
method.

ZoBell bottle—A sterile bottle constructed to col-
lect sea water samples at a desired depth for bac-
teriological analysis. Multiple sampling can be
accomplished in a manner similar to an oceano-
graphic cast.

zoea—An early larval form of certain decapod
crustaceans. (26) See decapod.

zonal flow—Currents or winds moving east or
west along a latitude. (82)

zone time—The local mean time of a reference or
zone meridian whose time is kept throughout a
designated zone. The zone meridian is usually

207-109 O - 66 - 13

the nearest meridian whose longitude is exactly
divisible by 15 degrees.

zoogene—The environment and deposits char-
acterized by abundant lime-secreting organisms,
such asreefs. (2)

zooplankton—The animal forms of plankton.
They include various crustaceans, such as cope-
pods and euphausiids, jellyfishes, certain proto-
zoans, worms, mollusks, and the eggs and eae
of benthic and nektonic animals. They are the
principal consumers of the phytoplankton and,
in turn, are the principal food for a large num-
ber of squids, fishes, and baleen whales.

zooplankton equivalent—See plankton equiva-
ent.

187

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APPENDIX A

Abbreviations and Acronyms

A—1. Absolute temperature scale; same as Kelvin

temperature scale.
2. (or 4) Angstrom.

AA—Approximate absolute temperature scale.

ACIM—Axis-Crossing J/nterval J/eter (Sonar
signal analyzer OB).

ADA—British Action Data Automation System.

ADF—Automatic Direction Finding.

ADP—Automatic Data Processing.

AGM—(Auxiliary General d/issile) Designation
for U.S. Navy missile range instrumentation
ships.

AGOR—(Auxiliary General Oceanographic Re-
search) Designation for U.S. Navy oceano-

raphic resear' rch ships.

NESE (isliae ry General Survey) Designation
for U.S. Navy hydrographic survey ships.

AGSC—Auxiliary General Survey Coastal. Des-
ignation for U.S. Navy small coastal hydro-
graphic survey ships.

AGSS— (Auxiliary General Submarine) An ex-
perimental deep-diving submarine.

AMOS—Acoustic Meteorological Oceanographic
Survey.

AMR—Atlantic Afissile Range.

AN/AQS-10—A_ variable depth sonar
presently in use in the fleet.

AN/ASQ-12—A helicopter sonar.

AN/BOR-2B—A cylindrical or conformal passive
array of submarine hydrophones.

AN/BQN-3—A submarine secure depth sounder.

AN/BR-28—A cylindrical or conformal passive
array of submarine hydrophones.

ANIP—Army-Vavy /nstrumentation Program.

AN/SQQ-14—A mine location and classification
sonar.

AN/SQS-20—A scanning sonar.

AN/SQS-23—A sonar presently in use by surface
ships.

AN/SQS-26—A new, large, high-powered, low-
frequency sonar.

AN/UQC-1—An underwater telephone.

AOS—Amphibious Objective Studies.

AOU—Apparent Oxygen Utilization.

ARLIS—An abbreviation for Arctic Research
Laboratory /ce Station, ARLIS is a term used
to designate remote scientific stations established
on the Arctic Ocean by the Arctic Research Lab-
oratory of Barrow, Alaska.

(VDS)

ART—Airborne fadiation Thermometer.

ASDIC— (Anti-Submarine Development /nvesti-
gation Committee) British echo-ranging equip-
ment.

ODE ene Submarine Oceanographic

Digital Data System.

Asshss™(Analyticallstudios\of Surface bitects
of Submerged Submarines) A submarine detec-
tion method not dependent on acoustic phenom-
ena.

ASW—Antisubmarine Warfare.

ASWEPS—(Antisubmarine Warfare /nviron-
mental Prediction System) A research effort to
develop methods of forecasting changes in the
oceanographic environment.

AUTEC—A project to develop and install the At-
lantic Underwater Zest and Hvaluation Center
which is located in the Tongue of the Ocean with
installations ashore on Andros Island in the
Bahamas.

BC—Bathyconductograph.

BC chart—Sottom Contour chart.

Bev—Billion-electron-volts.

BOD—Siological Oxygen Demand.

BPF—Bottom Pressure Fluctuation.

BT—BAathythermograph.

B.T.U., Btu—British Thermal Unit.

c—curie.

C—Celsius temperature scale; formerly centigrade
temperature scale.

cal—Calorie; small calorie.

Cal—Large calorie; kilogram-calorie.

CANLANTNAV—Consecutively numbered radio
message originated by the Canadian Navy, Hali-
fax, Nova Scotia, to disseminate urgent infor-
mation affecting navigation in the northwest
portion of the North Atlantic Ocean.

CANPACNAV—Consecutively numbered radio
message originated by the Canadian Navy, Vic-
toria, B-C., to disseminate urgent information
affecting navigation in the water off the Cana-
dian Pacific coast.

CBASF—Current Bibliography for Aquatic Sci-
ences and Fisheries. (UN Food & Agriculture
Organization)

CG@C—Coast Guard Cutter.

CGOU—Coast Guard Oceanographic Unit.

cegs—Centimeter-gram-second.

Cl—Chlorinity.

193

CLIMAT SHIP

CLIMAT SHIP—Monthly means reported by
ocean weather ships (WMO Code FM 72B).
CLIMAT TEMP SHIP—Report of monthly
aerological means from an ocean weather ship

(WMO Code FM 76C).

CMR—Common J/ode Rejection.

Conshelf Two—Continental Shelf Station Num-
ber Z7’wo.

CRT—Cathode ray tube.

DAPAC—Abbreviation of Danger Areas Pacific,
a U.S. Naval Oceanographic Office publication
containing routing instructions for areas in Pa-
cific and Far East. waters declared dangerous
because of mines.

db—Decibel.

DDI— Depth Deviation /ndicator.

DHQ—Mean diurnal high water inequality.

DLQ—Mean diurnal /ow water inequality.

DRAI—Dead Reckoning Analog /ndicator.

DRT—Dead feckoning 7racer. A device for
continually recording track of own ship (as well
as other ships).

DRV—Deep Research Vehicle.

DSL—Deep Scattering Layer.

DSSP—Deep Submergence Systems Program.

DSSRG—Deep Submergence Systems esearch
Group.

DTG—Date-7ime-Group.

DUMS—Deep Unmanned Submersibles. A jet
propelled submersible designed to follow a pre-
scribed underwater path for collecting oceano-
graphic information or for mapping sea bottoms.

DUNC—Deep Underwater Nuclear Counter. An
ultrasensitive radiation measuring device for
analyzing the sea’s naturally occurring radio-
active sources.

EASTROPIC—Z astern Tropical Pacific (Pro-
gram).

ECM—Flectronic Counter J/easures.

EER—/xplosive Z'cho Ranging.

EQUALANT—/quatorial At/antic Survey.

EQUAPAC—£ quatorial Pacific Survey.

ESG—Flectrically Suspended Gyroscope.

ev—lectron-volt.

F—Fahrenheit temperature scale.

FLIP— (F/oating /nstrument Platform) Similar
in design to SPAR, and used as a base for
oceanographic research, FLIP is manned and
can drift with currents.

FLOOD—(F/eet Observation of Oceanographic
Data) A program of the U.S. Naval Oceano-
graphic Office to place oceanographic instru-
ments aboard ships of the regular fleet.

FM—Frequency Modulation.

FORD—Floaiing Ocean Research and Develop-
ment (Station).

FRV—Fisheries esearch Vessel.

GCT—Greenwich Civil Time.

GEBCO—General Bathymetric Chart of the
Oceans.

GEK—Geomagnetic Hlectrokinetograph.

GEM—Ground £'ffect M/achine.

GEON—(Gyro Frected Optical Vavigation) A
system of celestial navigation.

GMT—Greenwich Mean Time.

GTS—Guinean 7rawling Survey.

HHW—Aigher high water.

HHWI—Aigher high water interval.

HIRAN—Zgh Precision Shoran.

HLW—A/igher low water.

HLWI—Aigher low water interval.

HODS—/Aydrographic-Oceanographic Data
Sheets.
HUK—Auwnter-Ailler naval force or unit. An

ASW force.

HW—Aigh water.

HWF&C—AZigh water full and change.

HWI—Aigh water interval.

HWLI—Aiigh water /unitidal nterval.

HWN—Aigh water neaps.

HWOST—Aigh water of ordinary spring fides.

HWQ—Tropic high water inequality.

HWS—A/igh water springs.

HYDRA—A project to evaluate the impact of
radiation produced by the detonation of under-
water nuclear explosions.

HYDROLANT—Consecutively numbered radio
message originated by the U.S. Naval Oceano-
graphic Office, Washington, D.C., to disseminate
urgent information affecting navigation in the
Atlantic Ocean area. See NAVEAM.

HYDROPAC—A consecutively numbered radio
message originated by the U.S. Naval Branch
Oceanographic Office, Honolulu, Hawaii, to dis-
seminate urgent information affecting naviga-
tion in the Pacific Ocean area.

HYPSES— (Hydrographic Precision Scanning
Echo Sounder) An improved instrument for
conducting bathymetric surveys in deep oceanic
areas.

IAC—Weather analysis (WMO Code FM 45C).

IAC FLEET—Weather analysis in abbreviated
form (WMO Code FM 46C).

ICE—Prefix for ice group in a weather report.

ICECON—Controlled ice information in time of
war or emergency.

IF F—/dentification /riend or Foe.

IGY— (/nternational Geophysical Year) By inter-
national agreement, a period during which
greatly increased observation of worldwide geo-
physical phenomena is undertaken through the
co-operative effort of participating nations.
July 1957-December 1958 was the first. such
year; however, precedent was set. by the Inter-
national Polar Years of 1882 and 1932.

IHD—/nternational Hydrological Decade.

ILOE—(/nternational /ndian Ocean /xpedition)
An international effort to increase the knowledge
of the Indian Ocean. This project is current at
this writing.

ILW—/nternational /ow water.

IOSN—/ndian Ocean Standard Net.

IR—/nfrared radiation .

ITcal—/nternational Zable calorie.

194

Keal; kg-cal—/Vilogram-calorie.

Kev—A ilo-electron-volts.

km—A ilometer.

LD—Zayer depth.

LHW—Lower high water.

LHWI—Lower high water énterval.

LLW—Lower /ow water.

LLWI—Lower /ow water tnterval.

LOCO—Zong cores.

Loran—Zong range navigation.
quency )

LS—Light Ship.

LW—Low water.

LWI—Low water interval.

LWOST—Low water of ordinary spring fides.

LWQ—Tropic /ow water inequality.

MAD— (d/agnetic Anomaly Detector) Gear used
to detect local changes in the earth’s magnetic
field caused by a submerged submarine.

MAFOR~— Weather forecast for shipping (WMO
Code FM 61C).

MAGNET—Worldwide Airborne Magnetic Sur-
vey (by the U.S. Naval Oceanographic Office).

MAMOS—J/arine Automatic Meteorological
Oceanographic Station.

MARID—Ship reports of the sea surface tem-
perature (UK only).

MAWEC—A/ilitary Aircraft Weather Code.

mce—Millicurie.

Mev—ZJfillion-electron-volts.

MHHW—VJ/ean higher high water.

MHW—WJean high water.

MHWN—A/ean high water neaps.

MHWS—J/ean high water springs.

pe—Microcurie.

pye—Micro-microcurie.

MILS—ZWissile 7mpact Location Survey.

MLLW—WJ/ean lower low water.

MLR—J/arine Life Resources (Program).

MLW—ZAZean Jow water.

MLWN—AZean low water neaps.

MLWS—J/ean low water springs.

Mn—Mean range.

MOHO—JWohorovicié Discontinuity.

MOHOLE—ZJ/ohorovicié Hole (Project).

MONAB—Jobile Noise Analysis Barge.

MRI—Jean rise interval.

MSL—J/ean sea /evel.

MTL—ZJ/ean tide /evel.

MWL—Jean water /evel.

NACLI—Report of monthly means for North At-
lantic Ocean (WMO Code FM 73).

NAVEAM—A consecutively numbered radio mes-
sage originated by United Kingdom authorities
to disseminate urgent information affecting nav-
igation in North European and Mediterranean
waters. See HYDROLANT, HYDROPAC.

NEPAN TIROS—Cloud data obtained by satellite
photography.

NIS—Wationa] /ntelligence Survey.

(Low fre-

195

SCOMO

NOMAD—(Navy Oceanographic and J/eteoro-
logical Automatic Device) A platform de-
signed to monitor and report weather and ocean-
ographic data automatically.

NORPAC—Vorthern Pacific (Project).

NORWESTLANT—VWorthwest Atlantic (Proj-
ect).

Np—Neap range.

NP-1—N orth Pole-1; a Russian drift station.

N.T.P.—Vormal temperature and pressure.

OMEGA —A long-range navigation system, giving
worldwide coverage with six to ten transmitter

ground) stations, with an accuracy of 1 to 3
n. miles.

OOP—Oceanographic Observations of the Pacific.

OS—Ocean Station.

OSV—Ocean Station Vessel.

OTDHC—Oceanographic echnical Data Han-
dling Committee.

PDR—1. (Periscope Depth ange) The maxi-
mum range at which active sonar echo ranging
contact can be made with a submarine operating
at periscope depth.

(Precision Depth ecorder)
aan a sonic depth trace.

PGR—Precision Graphic Recorder.

PILOT SHIP—Upper wind report from ship
(WMO Code FM 33C).

PMR—Pacific Missile Range.

Pn—Perigean range.

PPI— (Plan Position ndicator) The usual
means of presentation of sonar and/or radar
signals.

PUFFS—Passive Underwater /ire Control Sonar
Feasibility Study.

PVC—Polyviny] corer.

r—Roentgen.

rad—fadiation absorbed dose.

RADIAC—(fadioactivity Detection /ndication
and Computation) A term devised to designate
various types of radiological measuring instru-
ments or equivalent.

RBE—Relative Biological /ffectiveness.

rem—/oentgen equivalent man.

REMPAC— “(Reflectivity Mfeasurements Pacific)
Twelve-ke normal incident bottom reflectivity
measurements. Using either towed or hull
mounted transducer.

rep—foentgen equivalent physical.

RF—Radio Frequency.

RUM—(femote Underwater Manipulator) A
device built to study the ocean bottom (down to
20,000 feet) for prolonged periods. It is
equipped with a mechanical arm and hand and
television cameras.

R/V—Research Vessel.

SAU—(Search/Attack Unit)
task group.

SBT—Submarine bathythermograph.

SCOMO—Satellite Collection of Afeteorological
Observations.

A device for

Part of an ASW

SCUBA

SCUBA— (Self-Contained Underwater Breath-
ing Apparatus) Refers to several types of
breathing apparatus by means of which a diver
carries his br eathing medium with him and thus
1s independent of surface conditions.

Sg—Spring range.

SHIP—Surface ‘weather report from ship (WMO
Code FM 23C or FM 22C).

shoran—Short range navigation (electronic posi-
tioning system).

SHRED—Ship report in
(WMO Code FM 23C).

SINS—Ships /nternal Vavigation System.

sofar—Sound fixing and ranging.

SOMACO chart—Sonar Magnetic Contour chart.

sonar—Sound navigation and ranging.

SNAP—Systems for Vuclear Auxiliary Power.

SOOP—Submarine Oceanographic Observation
Program.

SOA. Speed of advance.

SPAR—(Seagoing Platform for Acoustic He-
search ) ‘A 350-foot long tube (16-foot diam-
eter) partially submerged i in a vertical position
used as a stable unmanned platform for conduct-

ing acoustic research. See FLIP.

SPESH—Special weather report from a ship
(WMO Code FM 26B).

SPRC— (Self-Propelled Robot Craft) A craft
capable of making detailed data recordings for
long distances in 2 horizontal plane along the
ocean’s deeper levels.

SST—Sea surface temperature.

STOR—Scripps 7una Oceanographic esearch.

S.T.P.—Standard temperature and pressure.

STU—Submersible Zest Unit.

SVTP—Sound Velocity, Zemperature, and Pres-
sure unit.

SWM—(Shipboard Wave Meter) An _ instru-
ment to record the wave situation at sea.

EO Sa Communications Satel-

ite.

SYNOP—Surface weather report from a land
station (WMO Code FM 11C).

abbreviated form

TcHHW—7ropic higher high water.
TcHHWI—7ropic higher high water interval.
TeHLW—7ropic higher /ow water.
TecLHW—7ropic lower high water.
TcLLW—7vropic lower low water.
TeLLWI—7ropic lower dow water interval.
TEMP SHIP—Upper level pressure, temperature,
humidity (possibly wind report) from a ship
(WMO Code FM 36C).

TENOC—(7Zen Year Program in Oceanography)
The basic planning document for U.S. Navy
oceanography.

TOTO—7ongue Of The Ocean.

T-S—Temperature- salinity.

T-3—Fletcher’s ice island, Drift Station Bravo.

UDT—Underwater Demolition 7eam.

UHF—Utrahigh Frequency.

UMP—lUpper dantle Project.

UNIS—Underwater Television and /nspection
System.

USW—Undersea Warfare.

UTS— (Underwater Zelephone System) A dur-
able sonar system enabling surface ships or sub-
marine to communicate with one another via
sound waves.

VAMP-—Sisual-Acoustic-/agnetic jenassrze,

Variable Depth Sonar.

VHF—Very High Frequency.

VLF—VJery Low Frequency.

WATEN—Wave tendency report (WMO Code
FM 11C and FM 16A).

WAVES—Actual height of waves when height
is over 934 meters in reports from ships and
coastal stations.

WBAN—(Weather Sureau, Air Force, and
Navy) Term used to denote observational in-
structions or forms that are common to the three
principal meteorological agencies in the United
States.

WECON—Controlled weather information in time
of war or emergency.

WMO— World Meteorological Organization.

196

APPENDIX B

LIST OF OCEANOGRAPHIC INSTITUTIONS, AGENCIES, ACTIVITIES,
AND GROUPS

AAAS—American Association for the Advance-
ment of Science, Washington, D.C.

AANII—Arctic and Antarctic Research Institute,
Leningrad, U.S.S.R.

ACES—Antisubmarine Composite Engineering
Squadron. (Proposed Navy-Civilian ASW
squadron to pursue ASW development.)

ACMRR—Advisory Committee on Marine Re-
sources Research, Secretariat, Fisheries Biology
Branch (FAO), Rome, Italy.

ACS—American Chemical Society, Washington,
D.C

ACSM—American Congress of Surveying and
Mapping, Washington, D.C.

ADAC—Acoustic Data Analysis Center.

AEC—Atomic Energy Commission, Germantown,
Maryland.

AES—Atlantic Estuarine Society.

AFAC—American Fisheries Advisory Committee.

oo Fisheries Society, Washington,

AGI—American Geological Institute, Washing-
ton, D.C.

AGU—American Geophysical Union, Washing-
ton, D.C.

AIBS—American Institute of Biological Sciences,
Washington, D.C.

AID—Agency for International Development,
Washington, D.C.

AINA—Arctic Institute of North America, Wash-
ington, D.C.

AIOP—Association Internationale
graphie Physique. SeeIAPO.

ALS—American Littoral Society, Sandy Hook
Marine Laboratory, Highlands, New Jersey.

AMS—1. American Meteorological Society, Bos-
ton, Massachusetts.

2. Army Map Service, Washington, D.C.

AMSOC—American Miscellaneous Society, Wash-
ington,

ANARE—Australian National Antarctic Re-
poarch Expeditions, Melbourne, Victoria, Aus-
tralia.

d’Océano-

Note: Locations of organizations are given
only where readily available; some organiza-
tions have no permanent location.

ANZAAS—Australian and New Zealand Associa-
tion for the Advancement of Science.

AOG—Atlantic Oceanographic Group, Bedford
Institute of Oceanography, Dartmouth, Nova
Scotia, Canada.

APL—1. Applied Physics Laboratory, Johns
Hopkins University, Baltimore, Maryland.

2. Applied Physics Laboratory, University of
Washington, Seattle, Washington.

ARL—Arctic Research Laboratory, University of
Alaska, Point Barrow, Alaska.

ARPA—Advanced Research Projects Agency,
Washington, D.C.

ASA—American Shellfish Association.

ASAB—Association for Study of Animal Be-
haviour.

ASDEFORLANT — Antisubmarine Defense
Force, Atlantic Fleet, U.S. Naval Base, Norfolk,
Virginia.

ASII—American Science Information Institute,
Detroit, Michigan.

ASIRC—Aquatic Sciences Information Retrieval
Center, University of Rhode Island, Kingston,
Rhode Island.

ASLO—American Society of Limnology and
Oceanography.

ASMFC— Atlantic States Marine Fisheries Com-
mittee.

ASP—American Society of Photogrammetry,
Washington, D.C.

ASTM—American Society for Testing Materials,
Philadelphia, Pennsylvania.

ATLANTNIRO—Atlantic Scientific Research In-
stitute of Fishing Economy and Oceanography,
Kaliningrad, U.S.S.R.

AUTEC— Atlantic Underwater Test and Evalua-
tion Center, Andros Island, Bahamas, B.W.I.
AZCHERNIRO—Azov and Black Sea Research
Institute of Marine Fisheries and Oceanog-

raphy, Kerch, U.S.S.R.

BALTNIRO—The Baltic Research Institute of
Marine Fisheries and Oceanography, Kalinin-
grad, U.S.S.R.

BCF—Bureau of Commercial Fisheries, U.S. De-
partment of Interior, Washington, D.C.

BCSO(NA)—British Commonwealth Scientific
Office (North America), Washington, D.C.

BEB—Beach Erosion Board. See CERC.

197

BIWS

BIWS—Bureau of International Whaling Statis-
tics, Sandefjord, Norway.

BM—Bureau of Mines, U.S. Department of the
Interior, Washington, D.C.

BMI—Battelle Memorial Institute, Columbus,
Ohio

BNCOR— British National Committee for Ocean-
ic Research, c/o Royal Society, Burlington
House, Piccadilly, London, England.

BSFW—Bureau of Sport Fisheries and Wildlife,
U.S. Department of the Interior, Fish and Wild-
life Service, Washington, D.C.

BUDOCKS—Bureau of Yards and Docks, U.S.
Navy, Washington, D.C.

BUMINES—Bureau of Mines, U.S. Department
of the Interior, Washington, D.C.

BUSHIPS—Bureau of Ships, U.S. Navy, Wash-
ington, D.C.

BUWEPS—Bureau of Naval Weapons, U.S.
Navy, Washington, D.C.

CAAS—Ceylon Association for the Advancement
of Science, Colombo, Ceylon.

CALCOFI—See CCOFI.

CBI—Chesapeake Bay Institute, Johns Hopkins
University, Baltimore, Maryland.

CBC—Conference of Baltic Oceanographers.

CCIR—International Radio Consultative Com-
mittee, Geneva, Switzerland.

CCO—Coordinating Committee on Oceanography.

CCOFI—California Cooperative Oceanic Fish-
eries Investigations, La Jolla, California.

CCOR—Co-ordinating Committee for Oceano-
graphic Research, Science Co-operation Divi-
sion, CSIR, Pretoria, Republic of South Africa.

CCTA—Commission for Technical Co-operation
in Africa South of the Sahara, Commission for
Scientific Council for Africa, Lagos, Nigeria.

CERBOM—Centre d’Etudes et de Recherches de
Biologie et dOcéanographie Médicale, Nice,
France.

CERC—Coastal Engineering Research Center
(formerly Beach Erosion Board), U.S. Army,
Washington, D.C.

CERN—European Organization for Nuclear Re-
search, Geneva, Switzerland.

CERS—Centre d’Etudes et de Recherches Scien-
tifiques, Biarritz, France.

CFRS—Central Fisheries Research Station, Pu-
san, Korea.

CHS—Canadian Hydrographic Service, Ottawa,
Ontario, Canada.

on Intelligence Agency, Washington,

CIESM—Commission Internationale pour l’Ex-
ploration Scientifique de la Méditerranée, Monte
Carlo, Monaco.

CIG—Comité International de
Paris, France.

CIOMS—Council for International Organizations
of Medical Sciences. See IUGG.

Géophysique,

CIPASH—Committee on International Programs
in Atmospheric Sciences and Hydrology of the
NAS/NRC, Washington, D.C.

CLAO—Consejo Latino-Americano de Oceano-
grafia, Montevideo, Uruguay.

CLARC—Consejo Latino-Americano de Radia-
ci6n Cosmica, Universidad Major de San An-
drés, LaPaz, Bolivia.

CMAe—Commission de Météorologie Aéronau-
tique. See WMO.

CMAS—Confédération Mondiale des Activités
Subaquatiques (World Underwater Federa-
tion), Paris, France.

CMM—Commission on Maritime Meteorology.

CNCOR—Chinese National Committee on Oceanic
Research, College of Science, National Taiwan
University, Taipei, Taiwan.

CNFRO—Comité National Francais de Recherche
Océanique, Paris, France.

CNMRO—Comité National Malgache de Re-
cherche Océanique, Centre d’Océanographie et
des Péches de Nosy Bé, Nosy Bé, Malagasy
Republic.

CNO—Chief of Naval Operations, U.S. Navy,
Washington, D.C.

CNPIO—Comissio Nacional Portuguesa para In-
vestigacao Oceanografico, Instituto Hidrogra-
fico, Lisbon, Portugal.

CNR—Consiglio Nazionale delle Richerche, Italy.

CNRS—Centre National de la Recherche Scien-
tifique, Paris, France.

CODC—Canadian Oceanographic Data Centre,
Ottawa, Ontario, Canada.

COEC—Comité Central d’Océanographie — et
d’Etude des Cétes, Paris, France.

COFI—See CCOFI.

COMASWFORLANT—Commander Antisubma-
rine Warfare Force, Atlantic Fleet, U.S. Naval
Base, Norfolk, Virginia.

COMASWFORPAC—Commander — Antisubma-
rine Warfare Force, U.S. Pacific Fleet. Pearl
Harbor, Honolulu, Hawaii. (Also referred to
as ASDEFORPAC).

COMEXO—Comité d’Exploitation des Océans,
Paris, France.

COMOPTEVFOR—Commander Operational
Test and Evaluation Force, U.S. Naval Base,
Norfolk, Virginia.

COSPAR—Committee on Space Research (Scien-
tific Committee of ICSU), s’Gravenhage, Neth-
erlands.

CPR—Committee on Polar Research of NAS/
NRC, Washington, D.C.

CREO—Centre de Recherches et d’Etudes Océano-
graphiques, Paris, France.

CRREL—Cold Regions Research and Engineer-
ing Laboratory (formerly SIPRE), Hanover,
New Hampshire.

CSAGI—Comité Spécial de l’Année Géophysique
Internationale (Special Committee of the
ICSU).

198

CSI—Coastal Studies Institute, Louisiana State
University, Baton Rouge, Louisiana.

CSIR—1. Council of Scientific and Industrial Re-
search, Pretoria, Republic of South Africa.

2. Council of Scientific and Industria] Re-

search, New Delhi, India.

CSIRO—Commonwealth Scientific and Industrial
Research Organization, Cronulla, Sydney, Aus-
tralia.

CTCA—See CCTA.

CUW—Committee on Undersea Warfare.

DDC—Defense Documentation Center, Washing-
ton, D.C.

DHI—Deutsches Hydrographisches
Hamburg, West Germany.

Be renee Intelligence Agency, Washington,

DMTS—Department of Mines and Technical Sur-
veys, Ottawa, Ontario, Canada.

DNHA—Departamento de Navegacién Hidrogra-
fia de la Armada, Valparaiso, Chile.

DOD—Department of Defense, Washington, D.C.

DOO—Director, Office of Oceanography (UNES-
CO), Paris, France.

DOR—Division of Oceanographie Research, De-
artment of Mines and Technical Surveys,
ttawa, Ontario, Canada.

DOT—Department of Transport, Ottawa, On-

tario, Canada.

DRB—Defence Research Board, Pacific Naval
Laboratory, Esquimalt, British Columbia, Can-
ada.

DTMB—David Taylor Model Basin, U.S. Navy,
Washington, D.C.

DVNIGMI—Far Eastern Scientific Hydrome-
teorologica] Institute, Vladivostok, U.S.S.R.

DWK—Deutsche Wissenschaftliche Kommission
fiir Meeresforschung, Hamburg, West Germany.

Institut,

EAEG—European Association of Exploration

Geophysicists, s’Gravenhage, Netherlands.
A—Economic Commission for Africa, Addis
Ababa, Ethiopia.

ECAFE—Economic Commission for Asia and the
Far Kast, Bangkok, Thailand.

ECE—Economic Commission for Europe (United
Nations), Paris, France.

ECLA—Economic Commission for Latin America,
Santiago, Chile.

ECOSOC—Economic and Social Council of
United Nations, New York, New York.

EPOC—Eastern Pacific Oceanic Conference.

ERDL—Engineer Research and Development
Laboratories, U.S. Army, Fort Belvoir, Vir-
ginia.

ESSA—Environmental Science Services Admin-
istration, U.S. Department of Commerce, Wash-
ington, D.C.

ETAP—Expanded Technical Assistance Pro-
gramme, United Nations, New York, New York.

IAF

FAC/SPC—Fisheries Advisory Committee of the
South Pacific Commission.

FAGS—Federation of Astronomical and Geo-
physical Services (ICSU), Paris, France.

FAO—Food and Agriculture Organization of the
United Nations, Rome, Italy.

FCST—Federal Council for Science and Tech-
nology, Washington, D.C.

FID—Fédération Internationale de Documenta-
tion, s’Gravenhage, Netherlands.

FRBC—Fisheries Research Board of Canada, St.
Andrews, New Brunswick, Canada.

FTC—Fisheries Technical Committee, Federal
Fisheries Service, Lagos, Nigeria.

FWS—See USFWS.

GCFI—Gulf and Caribbean Fisheries Institute,
Coral Gables, Florida.

GCRL—Gulf Coast Research Laboratory, Ocean
Springs, Mississippi.

GFCM—General Fisheries Council for the Medi-
terranean (FAO), Rome, Italy.

GGI—State Hydrological Institute, Leningrad,
U.S.S.R.

GIMRADA—Geodesy, Intelligence and Mapping
Research and Development Agency, U.S. Army
Engineers, Fort Belvoir, Virginia.

GNCOR—German National Committee for
Oceanic Research, Institut ftr Meereskunde,
Kiel, West Germany.

GOIN—State Institute of Oceanography, Moscow,
U.S.S.R.

GRB—Geophysical Research Board, National
Research Council, Washington, D.C.

GRD—Geophysics Research Directorate, Air
Force Cambridge Research Center, Bedford,
Massachusetts.

GS—Glaciological Society, Cambridge, England.

GUSMP—Main Administration of the Northern
Sea Route, Moscow, U.S.S.R.

HBRI—Hydrobiological Research Institute, Is-
tanbul, Turkey.

HEW—U.S. Department of Health, Education,
and Welfare, Washington, D.C.

HO—Hydrographic Office. In the U.S., now offi-
cially designated U.S. Naval Oceanographic
Office.

IAA—Instituto Antartico Argentino, Buenos
Aires, Argentina.

IAB—Abstracting Board (ICSU), Paris, France.

IAC—International Advisory Committee on Re-
search in the Natural Sciences (UNESCO),
Paris, France.

IACOMS— International Advisory Committee on
Marine Sciences (UNESCO), Paris France.

IAEA—International Atomic Energy Agency,
Vienna, Austria.

IAF—International
Baden, Switzerland.

Astronautical Federation,

199

IAG

I1AG—International Association
(IUGG), Paris, France.

IAGA—International Association of Geomagnet-
ism and Aeronomy (IUGG), Tortosa, Spain.

IAGS—Inter-American Geodetic Survey, Pan
American Union, Washington, D.C.

IAHR—International Association for Hydraulic
Research, Delft, Netherlands.

IAL—International Association of Theoretical
and Applied Limnology, Westmoreland, Eng-
land.

IAMAP—International Association of Meteorol-
ogy and Atmospheric Physics, Toronto, On-
tario, Canada.

IANEC—Inter-American Nuclear Energy Com-
mission, Pan American Union, Washington,
D.C.

IAPO—International Association of Physical
Oceanography (IUGG), Goteborg, Sweden.

IAS—International Association of Sedimentol-
ogy, La Jolla, California.

IASH—International Association of Scientific
Hydrology (IUGG), Gentbrugge, Belgium.

IASPEI—International Association for Seismol-
ogy and Physics of the LEarth’s Interior
(IUGG), Strasbourg, France.

IATA—International Air Transport Association,
Montreal, Quebec, Canada.

IATTC—See ITTC.

1AU—Internationa] Astronomical Union, Hail-
sham, Sussex, England.

ITA V—International Association of Volcanology

Ge) U.S. Geological Survey, Washington,

of Geodesy

IBP—International Biological Programme
(ICSU), Rome, Italy.

ICES—International Council for the Exploration
of the Sea, Charlottenlund, Denmark.

1CG—International Coordination Group for
ICITA,Washington, D.C.

ICITA—International Cooperative Investigations
of the Tropical Atlantic (UNESCO), Paris,
France.

ICMI—International Commission for Mathemati-
cal Instruction. See IMU.

ICNAF—International Commission for the
Northwest Atlantic Fisheries, Halifax, Nova
Scotia, Canada.

ICO—1. Interagency Committee on Oceanog-
raphy, Washington, D.C.

2. International Commission for Optics, Lon-

don, England.

ICOL—Italian Commission for Oceanography
and Limnology, Rome, Italy.

ICOR—Intergovernmental Conference on Oce-
anic Research. See IOC.

ICSEMS—International Commission for the
Scientific Exploration of the Mediterranean
Sea, Paris, France.

I1CSU—International
Unions, Rome, Italy.

Council of Scientific

IEEE—Institute of Electrical and Electronic
Engineers, New York, New York.

IFIPS—International Federation of Information
Processing Societies, Zurich, Switzerland.

IFM—1. Institut fiir Meereskunde, Universitit
Hamburg, Hamburg, West Germany.

2. Institut fir Meereskunde, Universitit Kiel,
Kiel, West Germany.

IFORS—International Federation of Operational
Research Societies, London, England.

IFR—Institute of Fisheries Research, University
oe North Carolina, Morehead City, North Caro-

ina.

1GC—International Geological Congress, Copen-
hagen, Denmark.

IGPP—Institute of Geophysics and Planetary
Physics (SIO), La Jolla, Californias

IGU—Internationa] Geographical Union, Zurich,
Switzerland.

IHB—International
Monte Carlo, Monaco.

I10E—International Indian Ocean Expedition.
See IOC.

11P—International Ice Patrol, U.S. Coast Guard,
Washington, D.C.

ILTS—Institute of Low Temperature Science,
Sapporo, Japan.

IM—Instytut Morski, Gdansk, Poland.

IMCO—Intergovernmental Maritime Consultative
Organisation, London, England.

IMS—1. Institute of Marine Science, University
of Alaska, College, Alaska.

2. Institute of Marine Science, University of
Texas, Port Aransas, Texas.

3. Institute of Marine Science, University of
Miami, Coral Gables, Florida.

IMU—International Mathematical Union, Bom-
bay, India.

INCOR—1. Israeli National Committee for
Oceanic Research, Jerusalem, Israel.

2. Indian National Committee on Oceanic Re-
search, Council of ‘Scientific and Industrial Re-
search, New Delhi, India.

INCP—Italian National Committee for Produc-
tivity, Rome, Italy.

INPFC—International North Pacific Fisheries
Commission, University of British Columbia,
Vancouver, British Columbia, Canada.

INQU A— Association Internationale pour l’Etude
du Quaternaire, Torun, Poland.

IOAN—Institute of Oceanology (Academy of
Sciences) , Moscow, U.S.S.R.

IOBC—Indian Ocean Biological Center, Cochin,
India.

1O0C—Intergovernmental Oceanographic Commis-
sion (UNESCO), Paris, France.

IOF—Internationa] Oceanographic Foundation,
Miami, Florida. ;

IOUBC—Institute of Oceanography, University
of British Columbia, Vancouver, British Colum-
bia, Canada.

Hydrographic Bureau,

200

IPF C—Indo-Pacific Fisheries Council, Bangkok,
Thailand.

IPHC—International Pacific Halibut Commis-
sion, Seattle, Washington.

IPMM—Institut des Péches Maritimes du Maroc,
Casablanca, Morocco.

IPSFC—International Pacific Salmon Fisheries
Commission, Vancouver, British Columbia,
Canada.

IRE—Institute of Radio Engineers. See IEEE.

ISA—Instrument Society of America, Pittsburgh,
Pennsylvania.

ISBB—International Society of Bioclimatology
and Biometeorology, Leiden, Netherlands.

ISO— International Organization for Standardi-
sation, Geneva, Switzerland.

ISTPM—Institut Scientifique et Technique des
Péches Maritimes, Paris, France.

ITIC—Internationa] Tsunami Information Cen-
ter, Honolulu, Hawaii.

ITTC—Inter-American Tropical Tuna Commis-
sion, Scripps Institution of Oceanography, La
Jolla, California.

ITU—tInternational Telecommunication Union,
Geneva, Switzerland.

IUB—International Union of Biochemistry, Lon-
don, England.

IUBS—International Union of Biological Sci-
ences, University of California, Davis, Cali-
fornia.

IUCN—International Union for the Conserva-
tion of Nature and Natural Resources, Brussels,
Belgium.

IUCr—International Union of Crystallography,
Groningen, Netherlands.

IUGG—International Union of Geodesy and Geo-
physics, Paris, France.

I1UGS—International Union of Geological Sci-
ences, Hellerup, Denmark.

IUHPS—International Union of the History and
Philosophy of Science, Paris, France.

IUPAC—International Union of Pure and Ap-
plied Chemistry, Basel, Switzerland.

IUPAP—International Union of Pure and Ap-
plied Physics, Paris, France.

IUPS—International Union of Physiological Sci-
ences, University of Rochester, Rochester, New
York.

IUTAM—International Union of Theoretical and
Applied Mechanics, Chatillon-sous-Bagneux,
France.

TUWDS—International Ursigram and World
Days Service (UNESCO), Utrecht, Nether-
lands.

TWC—International Whaling Commission, Lon-
don, England.

JCAM—Joint Commission on Atomic Masses.

JCAR—Joint Commission on Applied Radio-
activity (IUPAC), Gif-sur-Yvette, France.

JMA—Japan Meteorological Agency, Tokyo, Ja-
pan. :

NAVOCEANO

KASPNIRO—Caspian Institute of Marine Fish-
eries and Oceanography, Astrakhan, U.S.S.R.
KNMI—Koninklijk Nederlands, Meteorologisch

Instituut, De Bilt, Netherlands.

LASIL—Land-and-Sea Interaction Laboratory
(USC&GS), Norfolk, Virginia.

LGO—Lamont Geological @bsstuntory, Columbia
University, Palisades, New York.

MAMBO —Mediterranean Association for Marine
Biology and Oceanology, Valletta, Malta.
MARAD—USS. Maritime Administration, Wash-

ington, D.C.

MARINOSTAT—Hopkins Marine Station, Pa-
cific Grove, California.

MBA—Marine Biological Association, Plymouth,
England.

MBL—Marine Biological Laboratory, Woods
Hole, Massachusetts.

MDL—See USNMDL.

MESCO—Middle East Science Cooperation Of-
fice, Cairo, Egypt.

MIL-E-CON—Military Electronic
(Sponsored by IRE).

MIR—Morski Instytut Rybacki, Gdynia, Poland.

MLRG—Marine Life Research Group, Scripps In-
stitution of Oceanography, La Jolla, California.

MO—Meteorological Office, Bracknell, England.

MOHOLE—Mohorovicic Discontinuity Hole,
NAS/NRC, Washington, D.C.

MPL—Marine Physics Laboratory, Scripps Insti-
tution of Oceanography, San Diego, California.

MRI—Meteorological Research Institute, Tokyo,
Japan.

MSA—Maritime Safety Agency, Tokyo, Japan.

MSC—Marine Science Center, Lehigh University,
Bethlehem, Pennsylvania.

MSTS—AMilitary Sea Transport Service, U.S.
Navy, Washington, D.C.

MTS—Marine Technology Society, Washington,
D.C.

NADC—Naval Air Development Center, U.S.
Navy, Johnsville, Pennsylvania.
NAEC—Naval Air Engineering Center, U.S.
Navy, Philadelphia, Pennsylvania.
NAS—National Academy of Sciences, Washing-
ton, D.C.
NASA—National Aeronautics and Space Admin-
istration, Washington, D.C.
NASCAS—Committee on Atmospheric Sciences
(NAS/NRC), Washington, D.C.
NASCO—National Academy of Sciences, Com-
mittee on Oceanography, Washington, D.C.
NASL—Naval Applied Science Laboratory, U.S.
Navy, Brooklyn, New York.
NAS/NRC—National Academy of Sciences/Na-
tional Research Council, Washington, D.C.
NAVOCEANO—LUSS. Naval Oceanographic Of-
fice, Washington, D.C.

Conference

201

NBS

NBS—USS. National Bureau of Standards, Wash-
ington, D.C.

NCAR—National Center for Atmospheric Re-
search, Boulder, Colorado.

NCEL—Naval Civil Engineering Laboratory,
U.S. Navy (BuDocks), Port Hueneme, Cali-
fornia.

NCGG—National Committee for Geodesy and
Geophysics, Karachi, Pakistan.

NCMR—Netherlands Committee for Marine Re-
search, Den Helder, Netherlands.

NCOR—National Committee for Oceanographic
Research, Karachi, Pakistan.

NEAFC—North East Atlantic Fisheries Commis-
sion (Replaces PCIFC), London, England.
NEES—Naval Engineering Experimental Sta-

tion, U.S. Navy, Annapolis, Maryland.

NEL—Navy Electronics Laboratory, U.S. Navy,
San Diego, California.

NIO—National Institute of Oceanography, Worm-
ley, Godalming, Surrey, England.

NIRS—National Institute of Radiological Sci-
ences, Chiba, Japan.

NMDL—See USNMDL.

NMEL—Navy Marine Engineering Laboratory,
U.S. Navy, Annapolis, Maryland.

NML—Narragansett Marine Laboratory, Univer-
sity of Rhode Island, Kingston, Rhode Island.

NODC—National Oceanographic Data Center,
U.S. Naval Oceanographic Office, Washington,
D.C.

NOL—Naval Ordnance Laboratory, U.S. Navy,
White Oak, Maryland.

NOL CORONA—Naval Ordnance Laboratory,
U.S. Navy, Corona, California.

NOO—See NAVOCEANO.

NOTS—Naval Ordnance Test Station, U.S. Navy,
China Lake, California.

NPFSC—North Pacific Fur Seal Commission,
U.S. Department of the Interior, Washington,

NPI
Way.

NRC—National Research Council, Washington,
D.C.

NRDL—Navy Radiological Defense Laboratory,
U.S. Navy, San Francisco, California.

NRL—Naval Research Laboratory, U.S. Navy,
Washington, D.C.

Je

Norwegian Polar Institute, Bergen, Nor-

NSF—National Science Foundation, Washington,
D.C:
NSIA—National Security Industrial Association,

Washington, D.C.
NTU—National Taiwan
Taiwan.
NUOS—Naval Underwater Ordnance Station,
U.S. Navy, Newport, Rhode Island.
NUSL—See USNUSL.
NWL—Naval Weapons Laboratory, U.S. Navy,
Dahlgren, Virginia.
NWRC—National Weather
Asheville, North Carolina.

University, Taipei,

Records Center,

NWS—Navy Weather Service, U.S. Navy, Wash-
ington, D.C.

NZNCOR—New Zealand National Committee on
Oceanic Research, Dominion Museum, Welling-
ton, New Zealand.

NZOI—New Zealand Oceanographic Institute,
Wellington, New Zealand.

OACI—Organisation de l’Aviation Civile Inter-
nationale, Montreal, Quebec, Canada.
OASN—Office of the Assistant Secretary of the
Navy, U.S. Navy, Washington, D.C.
OCDE—Organisation de Coopération et de Dével-
oppement Economiques, Paris, France.
OECD—See OCDE.
OFRS—Office Francais de
Marine, Marseilles, France.
OIA—Oceanic Industries Association, Washing-
ton, D.C.
OIC—Oceanographic Instrumentation Center,
U.S. Naval Oceanographic Office, Washington,

Recherche Sous-

D.C.

OISA—Office of International Scientific Affairs,
U.S. Department of State, Washington, D.C.

OMM—Scee WMO.

ONI—Office of Naval Intelligence, U.S. Navy,
Washington, D.C.

ONR—Oftice of Naval Research, U.S. Navy,
Washington, D.C.

oe O— Office of Oceanography (UNESCO), Paris,

rance.

ORD—Oceanic Research Division (SIO), La
Jolla, California.

ORI—Ocean Research Institute, University of
Tokyo, Tokyo, Japan.

ORL—Ordnance Research Laboratory, Pennsyl-
vania State University, State College, Pennsyl-
vania.

ORSA—Operations Research Society of Amer-
ica, Baltimore, Maryland.

ORSOM—See ORSTOM.

ORSTOM— Office de la Recherche Scientifique et
Technique d’Outre-Mer, Bondy, France.

OSAP—Ocean Surveys Advisory Panel (ICO),
Washington, D.C.

OSE—Ocean Science and Engineering, Inc.,
Washington, D.C.

OSI—Ocean Systems, Incorporated, Washington,
D.C.

OST— Office of Science and Technology, Washing-
ton, D.C.

OSTAC—Ocean Science and Technology Advisory
Committee (NSIA), Washington, D.C.

OSW_— Office of Saline Water, U.S. Department of
the Interior, Washington, D.C.

PAIGH—Pan American Institute of Geography
and History, Mexico City, Mexico.

PAN—Polaska Akademia Nauk, Warsaw, Poland.

PBS—Pacific Biological Station, Nanaimo, Brit-
ish Columbia, Canada.

202

PCIFC—Permanent Commission of the Interna-
tional Fisheries Convention (Replaced by
NEAFC), London, England.

PHS—U.S. Public Health Service, Washington,
D.C.

PIHM—Panstwowy Instytut Hydroloczno-Mete-
orologiczny, Gdynia, Poland.

PINRO—Polar Research Institute for Marine

Fisheries and Oceanography, Murmansk,
S.S.R.
PIOSA—Pan-Indian Ocean Science Association,

Tejgaon Dacca, East Pakistan.

PIPICO—Panel on International Programs of the
ICO, Washington, D.C.

PMR—Pacific Missile Range, U.S. Navy, Point
Mugu, California.

PNL—Pacific Naval Laboratory, Esquimalt, Brit-
ish Columbia, Canada.

POFI—Pacific Oceanographic Fisheries Investi-
gation, Honolulu, Hawaii.

POG—Pacific Oceanographic Group, Nanaimo,
British Columbia, Canada.

PSA—Pacific Science Association,
Hawaii.

PSAC—President’s Science Advisory Council,
Washington, D.C.

PSC—Pacifie Science Council, Honolulu, Hawaii.

Honolulu,

RCN—Royal Canadian Navy, Ottawa, Ontario,
Canada.

RESA—Scientific Research Society of America,
New Haven, Connecticut.

RFCWA—Regional Fisheries Commission for
West Africa, Accra, Ghana.

SACFCO—Standing Advisory Committee on
Fisheries of the Caribbean Organization, Hato
Rey, Puerto Rico.

SACI—South Atlantic Cooperative Investiga-
tions.

SACLANTCEN—Supreme Allied Command for
the Atlantic Center (ASW Research Center),
La Spezia, Italy.

SAIL—Sea-Air Interaction Laboratory, U.S.
Weather Bureau, Washington, D.C.

SANAE—South African National Antarctic Ex-
peditions, Capetown, South Africa.

SANCAR—South African National Council for
Antarctic Research, Capetown, South Africa.

SCANDOC—Sceandinavian Documentation Cen-
ter, Washington, D.C.

SCAR—Special Committee for Antarctic Re-
search (ICSU), Cambridge, England.

SCG—Scientific Committee for Inter-Union Co-
operation in Geophysics.

SCIBP—Sectional Committee of the Internation-
al Biological Programme.

SCOR—1. Scientific Committee on Oceanic Re-

search, Hamburg, West Germany; Blindern,

Norway; Karachi, Pakistan; Sopot-molo,
Poland. :

203

USNHO

2. Special Committee for Oceanographic Re-

(UN), New York, New York.

SEAS—Committee for the Scientific Exploration
of the Atlantic Shelf.

SEASCO—South East Asia Science Co-operation
Office, New Delhi, India.

SHN—Servicio de Hidrografia Naval, Buenos
Aires, Argentina.

SI—Smithsonian Institution, Washington, D.C.

SIE—Science Information Exchange (SI), Wash-
ington, D.C.

$10—Scripps Institution of Oceanography, La
Jolla, California.

SIPRE—Snow, Ice, and Permafrost Research
Establishment. See CRREL.

SMBA—Scottish Marine Biological Association,
Edinburgh, Scotland.
SNEMSA—Southern New England Marine
Sciences Association, Kingston, Rhode Island.
SOGETRAM—Société Générale de Travaux
Maritimes at Fluviaux.

SPRI—Scott Polar Research Institute, Cam-
bridge, England.

SWAFAC—Southwest Atlantic Fisheries Ad-
visory Commission.

TINRO—Pacific Research Institute of Fisheries
and Oceanography, Vladivostok, U.S.S.R.

TWZO—Trade Wind Zone Oceanography (BCF),
Honolulu, Hawaii.

UDML— University of Delaware Marine Labora-
tories, Newark, Delaware.

UN—The United Nations, New York, New York.

UNESCO—United Nations Educational, Scien-
tific, and Cultural Organization, Paris, France.

UNSF—United Nations Special Fund, Paris,
France.

URSI—Union Radio Scientifique Internationale,
Brussels, Belgium.

USAID—U.S. Agency for International Develop-
ment, Washington, D.C.

USARP—U.S. Antarctic Research
Washington, D.C.
USCG—USS. Coast Guard, Washington, D.C.
USC&GS—USS. Coast and Geodetic Survey, U.S.
Department of Commerce, Washington, D.C.
USFWS—USS. Fish and Wildlife Service, U.S.
Department. of the Interior, Washington, D.C.

USGS—USS. Geological Survey, U.S. Department
of the Interior, Washington, D.C.

USMA—U.S. Maritime Administration, Wash-
ington, D.C.

USN—USS. Navy, Washington, D.C.

USNA—USS. Naval Academy, Annapolis, Mary-
land.

USNMDL—USS. Navy Mine Defense Laboratory,
Panama City, Florida.

USNHO—U.S. Navy Hydrographic Office (now
U.S. Naval Oceanographic Office), Washington,
D.C.

Program,

USNUSL

USNUSL—USS. Navy Underwater Sound Lab- WDC—World Data Center (WDC-A, Washing.
oratory, Fort Trumbull, New London, Connec- ton, D.C.), (WDC-B, Moscow, U.S. S.R ale
ticut. WHO—World Health Organization of the United
USWB—U.S. Weather Bureau, U.S. Department Nations, Geneva, Switzerland.
of Commerce, Washington, D.C. WHOI— Woods Hole, Oceanographic Institution,
Woods Hole, Massachusetts.
VIMS—Virginia Institute of Marine Science, WMO—World Meteorological Organization of
Gloucester Point, Virginia. the United Nations, Geneva, Switzerland.
VNIRO—AII-Union Research Institute of Marine
Fisheries and Oceanography, Moscow, U.S.S.R.

U.S. GOVERNMENT PRINTING OFFICE : 1966 O - 207-109 204

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