N PS ARCHIVE 1968 BURROW, J. THE SUB-THERMOCLINE DUCT by James Bar ring ton Burrow UNITED STATES NAVAL POSTGRADUATE SCHOOL THESIS THE SUB-THERMOCLINE DUCT by James Barrinqton Burrow, Jr. December 1968 Tlvu> document ka& bzzn approved &oi public le- l&a&e. and 6aZz; JXi> dLUVUbuXion l& untimctzd. LIBRARY NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIF. 93940 THE SUB-THERMOCLINE DUCT by James Barrington Burrow, Jr. Lieutenant, United 'States Naw B.S., Naval Academy, 1962 Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN OCEANOGRAPHY from the NAVAL POSTGRADUATE SCHOOL December 1968 ABSTRACT This thesis describes a method by which near-surface temperature inversions in the ocean may be classified. Al- though categories of sub-thermocline ducts for sound trans- mission, formed as a result of these temperature inversions, have been studied in detail in the North Pacific Ocean, classifications are general enough to be applied to ducts in other regions. A considerable variety of sub-thermocline ducting is present in the North Pacific. This variability shows both a seasonal and a positional dependence which may be explained on a stability basis utilizing data obtained from selected Nansen casts reported for stations throughout the North Pacific. LIBRARY NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIF. 93940 TABLE OF CONTENTS CHAPTER PAGE I. INTRODUCTION 9 II. DUCT NOMENCLATURE 10 III. SUB-THERMOCLINE DUCT CLASSIFICATION ... 13 IV. SEASONAL VARIATIONS OF THE SUB- THERMOCLINE DUCT IN THE NORTH PACIFIC 30 V. POSITIONAL VARIATIONS OF THE SUB- THERMOCLINE DUCT IN THE NORTH PACIFIC 40 VI. CONCLUSIONS 53 VII. RECOMMENDATIONS 54 BIBLIOGRAPHY 55 LIST OF TABLES TABLE PAGE I. Numbers and Percentages of Ducts Drawn by Years 16 II. Numbers and Percentages of Ducts Drawn by Months 16 III. Duct Major Categories 19 IV. Numbers and Percentages of Ducts Drawn by Major Categories 19 V. Duct Sub-Categories 26 VI. Numbers and Percentages of Ducts Drawn by Sub-Categories 28 VII. Numbers and Percentages of Primary Ducts Found in the North Pacific by Sectors During the Heating Period 32 VIII. Numbers and Percentaqes of Primary Ducts Found in the North Pacific By Sectors During the Cooling Period 32 IX. Numbers of Primary Sub-Thermocline Ducts in Each Sub-Category Found During the Heating Period in Each Sector of the North Pacific 45 LIST OF ILLUSTRATIONS FIGURE PAGE 1. Sub-Thermocline Duct Nomenclature 11 2. Area of North Pacific Under Investigation . . 14 3. Subarctic Region Adapted From Tully (1964) . . 14 4. Typical Category A Duct 20 5. Typical Category B Duct 21 6. Typical Category C Duct 22 7. Typical Category D Duct 23 8. Typical Category E Duct 2 4 9. Subdivisions of North Pacific Region Under Investigation 31 10. Typical Temperature and Salinity Profiles for Heating and Cooling Periods at 52 N, 137 W 34 11. Typical Temperature and Salinity Profiles for Heating and Cooling Periods at 52 N, 175 E 35 12. Typical Temperature and Salinity Profiles for Heating and Cooling Periods at 47 N, 160 E 36 13. Typical Temperature and Salinity Profiles for Heating and Cooling Periods at 4 3 N, 146 E 37 14. Area of Probable Sub-Thermocline Ducting in the North Pacific 41 15. Area of North Pacific in Which Category A Ducts Were Found 47 16. Areas of North Pacific in Which Category B Ducts Were Found 48 17. Area of North Pacific in Which Categorv C Ducts Were Found 49 18. Areas of North Pacific in Which Category D Ducts Were Found 50 CHAPTER I INTRODUCTION The typical vertical temperature distribution in the open ocean is usually one of decreasing temperature with in- creasing depth. Although this is the general case, it is by no means completely universal, and variations are prominent in certain regions of the world ocean. Ten near-surface thermal structure types have been classified by Laevastu and Stevens (1968) . One of these is the sub-thermocline duct type, which can be found in large areas of the North Pacific, or in smaller areas of the North Atlantic Ocean. To date few investigations into this particular feature have been made in any detail. An optimum region for the study of duct characteristics is the North Pacific Ocean be- cause of the great variety of ducts which exist there, and because of the extremely large area of the North Pacific over which the duct can be found. Therefore research into the sub-thermocline duct for purposes of this thesis has been limited to the North Pacific Ocean. Although limited in area of interest to the North Pacific Ocean, this thesis does describe the sub-thermocline duct with its seasonal and positional variations for that ocean in de- tail. To facilitate this purpose, duct types have been clas- sified into five major categories, each of which is sub- divided into smaller categories. Although classification is based on ducts observed in the North Pacific, these categories, defined here, should apply equally well to ducts found in other oceans. CHAPTER II DUCT NOMENCLATURE The sub-thermocline duct is a feature of the temperature- depth profile found where a temperature inversion exists be- low the thermocline. This duct, when present, is generally found in the upper few hundred meters of the ocean, and is not to be confused with the deep sound channel which is a general feature of ocean sound transmission below regions possessing thermoclines . Before an attempt is made to describe or classify a sub- thermocline duct, key features of the temperature profile, and of the duct itself, must be defined. These definitions are illustrated in Figure 1. The mixed layer depth is the depth to which water is mixed through wave action or thermohaline convection. Be- low the mixed layer is the thermocline, which is that portion of the temperature-depth profile showing a marked negative temperature gradient that is greater than the gradients above or below it. The magnitude of the thermocline is the total temperature change encountered along the thermocline. The first step in the treatment of the duct itself is to draw a vertical line from the point of maximum temperature in the inversion layer up to the point where it meets the thermo- cline. This line sets the vertical limits of the duct, and the length of this line is defined as the duct thickness. The top of the duct is defined by the point where the thickness 10 TEMPERATURE (°C) _!__!_ i— i (6 W E-t W Eh W Q SYMBOLS USED: 1. Mixed Layer Depth 2. Thermocline 3. Magnitude of Thermocline 4. Duct Thickness 5. Duct Magnitude 6. Depth of Duct Minimum Temperature 7. Depth of Duct Mean Axis 8. Top of Duct 9. Bottom of Duct Figure 1 SUB-THERMOCLINE DUCT NOMENCLATURE 11 line intersects the thermocline , and the bottom of the duct is the point of maximum temperature in the inversion layer. The duct magnitude is the difference in temperature en- countered between the duct minimum temperature and the thick- ness line, and the depth at which the magnitude is measured is the depth of duct minimum temperature. The majority of sub-thermocline ducts are not symmetric about an axis; however, some feature is needed to give the duct a relative position in a vertical water column. For this purpose, the depth of the duct mean axis is used, and this is the depth of the mid-point of the thickness line. 12 CHAPTER III SUB-THERMOCLINE DUCT CLASSIFICATION In this detailed investigation of the North Pacific Ocean, sub-thermocline ducts were generally not found south of 35 N. Into the Bering Sea, data becomes very sparse north of 60 N. With this in mind, extreme limits on the area of most detailed examination were set at a southern limit of 30 N, and a northern limit of 60 N. The eastern limits on the area of observation were fixed at the North American west coast. To the west the limits went along 140 E, then ud the eastern coast of Honshu, past the east coast of Hokkaido, along the Kurile Islands, and finally along the eastern coast of the Kamchatka Peninsula. The area of investigation is shown in Figure 2. Tully (1964) set limits on four recrions of water mass formation in the North Pacific Ocean. Of these four regions, the Subarctic Region, as shown in Figure 3, is of primary im- portance, as this region is included entirely within the area under investigation. Data were obtained primarily from Nansen casts as re- ported in Oceanic Observations of the Pacific (Pre-1949, 1949, 1955 NORPAC Data, and 1959). Because of the type of data used, duct measurements depend heavily on personal interpreta- tion, and measurements can vary slightly dependinq on how tem- perature profiles are constructed between sampling depths. At many stations a duct was obviously present, but vertical spacing of 100 to 150 meters between Nansen bottles made even reasonably accurate estimates of duct measurements impossible 13 60 - 50 - 40 30 20 140 160 180 160 140 120 Figure 2. AREA OF NORTH PACIFIC UNDER INVESTIGATION 140 160 180 160 140 120 Figure 3 SUBARCTIC REGION ADAPTED FROM TULLY (19 64) 14 for these stations. The number of stations considered reached well into the thousands; however, useful data could be collec- ted at only approximately 750 of these stations. Ideally, data for this type of study should be taken at fixed locations throughout the area of investigation for all seasons of the year. A major problem resulted from the fact that data were obtained only from specific cruises. This gave a large concentration of data in certain areas and sea- sons, and a marked lack of data in other areas and times. Because of the very rouqh sea conditions throughout the area of investigation during the winter months, data were scarce from mid-September to late Aoril, and the bulk of the winter data was taken from a single report on the Boreas Ex- pedition (1966). Classification of ducts and their trends depend heavily on some 36 6 ducts which were actually drawn and carefullv measured. These ducts ranged across the Subarctic Region; however, measurements in the south-central portion of the region were quite sparse. A heavy concentration of data taken in 1955 (the NORPAC data) was used in order to get a good indication of duct trends for the entire region of the Subarctic over a relatively short time span. The NORPAC data comprised 59.6 percent of those ducts drawn. Data from other years confirmed conditions found in 1955 and 1966. The num- ber of ducts actually drawn, by years, are presented in Table I, and the number of ducts drawn, by months, are presented in Table II. 15 TABLE I NUMBERS AND PERCENTAGES OF DUCTS DRAWN BY YEARS YEAR 1934 1947 1949 1955 1959 1966 NUMBER OF DUCTS 5 9 62 219 15 56 PERCENTAGE OF TOTAL 1.4 2.5 17.0 59.6 4.1 15.4 TABLE II NUMBERS AND PERCENTAGES OF DUCTS DRAWN BY MONTHS MONTH NUMBER OF DUCTS PERCENTAGE OF TOTAL JAN 7 2.0 FEB 44 12.0 MAR 9 2.5 APR 5 1.4 MAY 10 2.7 JUN 10 2.7 JUL 69 18.9 AUG 164 44.6 SEP 36 9.9 OCT 4 1.1 NOV 8 2.2 DEC 0 0.0 16 In the classification of ducts, three measurements are of primary importance. These are the duct magnitude, duct thickness, and depth of duct mean axis. A fourth measurement which was considered in detail because of its importance in sound studies in the ocean was the depth of duct minimum tem- perature. This fourth measurement was necessary due to the fact that very few ducts are symmetrical about their mean axis . Because of the major dependence of sound speed on tem- perature, the three common forms of single sub-thermocline ducts have been classified on the basis of duct maanitude. To complete the five major categories of ducts, two support- ing categories have been classified by other means. Category A ducts (small ducts) are all single ducts be- low the thermocline with a magnitude of less than 1.00 C. In data collection those ducts of magnitude less than 0.10 C normally were not considered. Category B ducts (moderate ducts) are all single ducts below the thermocline whose magnitude is between 1.0 0 and 1.99 C. Category C ducts (large ducts) are all single ducts be- low the thermocline with a magnitude of 2.00 C or greater. Category D ducts are multiple ducts below the thermo- cline, and for this major category, no limitation is placed on the magnitudes of the ducts. Invariably ducts falling into this category consisted of two separate ducts. Manv large single ducts which were actuallv drawn did appear to be in the process of being split into two smaller ducts; however, 17 as long as the intermediate temperature inversion splitting the duct did not reach the temperature at the thickness line these ducts were not considered as Category D ducts. Although surface ducts do not fit the definition of a sub-thermocline duct as such, they are quite predominant throughout the region under investigation during winter months, and they play an important role in the actual formation of the sub-thermocline ducts in the Subarctic Region. For these rea- sons, Category E, which is a supporting category, is that of the surface duct. Category E ducts may have small ducts be- low the major surface duct. The five major duct categories are summarized in Table III, and a breakdown of the 366 ducts drawn is presented in Table IV. Common examples of each major category of duct are shown in Figures 4, 5, 6, 7, and 8. Once a single sub-thermocline duct has been placed into one of its three major categories, further classification is desirable, primarily to give the duct a relative position in a vertical water column. This is necessary because of the large range of values through which the duct thickness and the depth of duct mean axis can vary for category A, B, and C ducts. Category D ducts are best sub-classified on the basis of duct magnitudes and the vertical separation between ducts , and category E ducts on the basis of duct magnitude and duct thickness. All duct sub-categories are defined in Table V. 18 TABLE III DUCT MAJOR CATEGORIES CATEGORY B E DUCT TYPE Small duct below the thermocline Moderate duct below the thermocline Large duct below the thermocline Multiple ducts below the thermocline Surfact duct MAGNITUDE Less than 1.00 C 1.00 to 1.99 C 2.00 C and greater TABLE IV NUMBERS AND PERCENTAGES OF DUCTS DRAWN BY MAJOR CATEGORIES CATEGORY NUMBER OF DUCTS PERCENTAGE OF TOTAL A 191 52.0 B 52 14.3 C 28 7.7 D 35 9.6 E 60 16.4 19 TEMPERATURE (°C) 11 12 w E-i w r En U Q 100 - 200 - 300 - 400 _ 3 August 195 5 54° 15' N, 140° 38' W Maqnitude: 0.51 C Thickness: 72 meters Depth of duct mean axis: 107 meters Depth of duct minimum temperature: 94 meters Figure 4 TYPICAL CATEGORY A DUCT 20 TEMPERATURE (°C) 100 200- « w W T. K Eh W Q 300- 30 June 1955 53° 02' N, 170° 00' E Magnitude: 1.95 C Thickness: 249 meters Deoth of duct mean axis: 172 meters Depth of duct minimum temperature: 100 meters 400_ Figure 5 TYPICAL CATEGORY B DUCT 21 TEMPERATURE (°C) 4 5 6 7 100 _ w w Q 200 - 300 - 400- 10 11 12 _l I I 4 July 1955 58° 29' N, 166° 32' E Magnitude: 2. 85 C Thickness: 247 meters Depth of duct mean axis: 157 meters Depth of duct minimum temperature: 8 0 meters Figure 6 TYPICAL CATEGORY C DUCT 22 TEMPERATURE (°C) 100 - 10 11 « W Eh as W Q 200 - 300 12 -I 9 July 1955 52° 30' N, 178° 54' W Upoer Duct Magnitude: 0.32 C Thickness: 40 meters Depth of duct mean axis: 68 meters Depth of duct minimum temperature: 66 meters Lower Duct Magnitude: 0.67 C Thickness: 205 meters Depth of duct mean axis: 222 meters Depth of duct minimum temperature: 182 meters 400 - Figure 7 TYPICAL CATEGORY D DUCT 23 in w Eh W s E-« W Q 100 - 200- 300- TEMPERATURE (°C) 4 5 6 7 8 J I I I L >- 10 11 12 12 March 1966 47° 31' N, 159° 53' E Magnitude: 3.46 C Thickness: 219 meters Depth of duct minimum temperature: 117 meters 400- Figure 8 TYPICAL CATEGORY E DUCT 24 Table V gives a sub-category with a combination letter and number designation. The letter portion of this designa- tion is retained from the duct major category. The number pertains to the appropriate description of the duct within that major category. Major category A, B, and C ducts are grouped together in Table V since the descriptive portion of the table applies equally to ducts in each of these catego- ries, regardless of magnitude. It is of interest in duct analysis to break down each duct sub-category into numbers and percentages of the total ducts within their respective major categories. This has been done in Table VI, but because of the type sampling, these figures cannot be considered representative of the en- tire region under consideration. This is particularlv true of category E ducts where, of the number of ducts considered but not drawn, the majority easily fell into sub-cateqory E-7. 25 TABLE V DUCT SUB-CATEGORIES SUB-CATEGORY DESCRIPTION Thickness less than 100 meters Duct mean axis above 200 meters A- ■1 B- -1 C- -1 A- -2 B- -2 C- -2 A- ■3 B- -3 C- -3 A- -4 B- -4 C- ■4 A- ■5 B- -5 C- •5 A- ■6 B- -6 c- -6 Thickness less than 100 meters Duct mean axis 200 meters and below Thickness between 100 and 250 meters Duct mean axis above 2 00 meters Thickness between 100 and 250 meters Duct mean axis 200 meters and below Thickness between 250 and 400 meters (No limitation on duct mean axis) Thickness greater than 400 meters (no limitation on duct mean axis) D-l Both ducts of magnitude less than 0.50 C Vertical separation between bottom of higher duct and top of lower duct less than 100 meters D-2 Both ducts of magnitude less than 0.50 C Vertical separation between bottom of higher duct and top of lower duct of 100 meters or greater D-3 Higher duct of magnitude 0.50 C or greater Lower duct of magnitude less than 0.50 C (No limit on vertical seoaration D-4 Higher duct of magnitude less than 0.50 C Lower duct of magnitude 0.50 C or greater (No limit on vertical separation) 26 TABLE V (Continued) SUB -CATEGORY DESCRIPTION D-5 Both ducts of magnitude 0.50 C or greater (No limit on vertical separation) E-l Surface duct of any magnitude with one or more smaller ducts below it E-2 Magnitude less than 1.00 C Thickness less than 200 meters E-3 Magnitude less than 1.00 C Thickness 200 meters or greater E-4 Magnitude of 1.00 to 2.00 C Thickness less than 200 meters E-5 Magnitude of 1.00 to 2.00 C Thickness of 200 meters or greater E-6 Magnitude greater than 2.00 C Thickness less than 200 meters E-7 Magnitude greater than 2.00 C Thickness of 200 meters or greater 27 TABLE VI NUMBERS AND PERCENTAGES OF DUCTS DRAWN BY SUB -CATEGORIES SUB -CATEGORY NUMBER OF DUCTS PERCENTAGE OF TOTAL CATEGORY A: 191 . DUCTS A-l 138 72.2 A- 2 1 0.5 A-3 17 8.9 A-4 19 10.0 A- 5 11 5.8 A- 6 5 2.6 CATEGORY B: 52 DUCTS B-l 5 9.6 B-2 1 1.9 B-3 13 25.0 B-4 1 1.9 B-5 10 19.2 B-6 22 42.4 CATEGORY C: 28 DUCTS C-l 0 0.0 C-2 0 0.0 C-3 12 42.8 C-4 1 3.6 C-5 8 28.6 C-6 7 25.0 28 TABLE VI (Continued) SUB-CATEGORY NUMBER OF DUCTS PERCENTAGE OF TOTAL CATEGORY D: 35 DUCTS D-l 17 48.6 D-2 5 14.3 D-3 7 20.0 D-4 4 11.4 D-5 2 5.7 CATEGORY E; 6 0 DUCTS E-l 4 6.7 E-2 22 36.7 E-3 7 11.7 E-4 12 20.0 E-5 5 8.3 E-6 2 3.3 E-7 8 13.3 29 CHAPTER IV SEASONAL VARIATIONS OF THE SUB-THERMOCLINE DUCT IN THE NORTH PACIFIC Ducts in the North Pacific Ocean show a definite sea- sonal cycle, as well as variation with location. Dodimead, Favorite, and Hirano (1962) have defined heating and cool- ing cycles of temperature structures at Ocean Station "P" which, when applied to the entire Subarctic Pacific, have proven useful in the description of duct variations. Ducts have been grouped according to heating and cooling periods, considering the average heating Deriod of the Sub- arctic Region as consisting of the months of April through September, and the average cooling period as October through March. The area of concentrated data collection (previouslv shown in Figure 2) was subdivided into five sectors as shown in Figure 9 . Primary ducts considered as a basis for trend analysis consisted of the 366 ducts which were drawn as well as 96 category E ducts which were not drawn. These ducts were separated by heating and cooling periods and then by sectors. The number of ducts falling into each sector during the heat- ing period are shown in Table VII, and those in each sector during the cooling period in Table VIII. Uda (1963) has defined three zones in the salinity structure of the Subarctic Region. These are an upper zone, a transition zone, and a lower zone. It is the transition 30 < DC O U fa < U 3! U M 33 5 U M fa M fa X OC O z fa o < w PS < 47 *X) Q) U •H fa C fa w En U D P ffl o u w Eh < U s u H s 5 u H fa H u as Eh K O fa O w < 48 r- 0) >h 3 tn •H o W C/3 E-« U D P U o u w EH < u u M ac u M Oh M u < a. Eh Cd O 2 O < w < 49 00 U P •H Q C fa W in U D Q X Pi O o w Eh < U K U H K U H H u < a. B Eh O fa O < w « 50 in magnitude, but also in thickness, and their depths of duct mean axes deepened. In this part of sector 1, sub-category A-3, A-5 , B-3 , B-5 , C-3, and C-5 ducts were prevalent. It was in the northwest portion of sector 1 that category C ducts first appeared, and these ducts remained confined in sector 1 to that area north of 53 N and west of 178 W. The category C ducts continued west into sector 3 to the east coast of the Kamchatka Peninsula, and then south along a southwesterly belt running almost parallel to the western boundary of sector 3. Along this belt, duct thick- nesses grew, and sub-category C-5 and C-6 ducts became prom- inent. A dense grouping of sub-category B-6 ducts were clus- tered just off the Japanese islands of Honshu and Hokkaido, with sub-category A-4 ducts appearing frequently near the northern boundary of the Kuroshio. A probable contribution to the formation of these A-4 ducts was Kuroshio meanders. Where larger ducts may have existed, their upper portions were warmed by a Kuroshio meander, eliminating the top half or more of the ducts, but leaving deep category A remnants. The top of these A-4 ducts averaged 3 38 meters depth; how- ever, the duct mean axes averaged approximately 415 meters. This seems to agree with the depth reached by the upper layer of the Kuroshio, which Hidaka (1966) sets at about 400 meters. In sector 4 three category B ducts were observed in the far northwest corner. All other single ducts in this sector were in category A. Ducts east of 180 degrees longitude were 51 primarily in sub-category A-l; however, west of 180 deqrees longitude a combination of A-l, A-4 , A-5, and A-6 ducts were found, grouped randomly throughout this portion of the sec- tor, with the exception of the far northwest corner which contained only the three category B ducts. 52 CHAPTER VI CONCLUSIONS Sub-thermocline ducts have been shown to exist in the North Pacific Ocean from year to year, and can be considered characteristic of the North Pacific north of 42 N. These ducts show a definite pattern of seasonal and Dositional variations which can be predicted from historical analysis with some degree of accuracy. In the Subarctic North Pacific salinity in the charac- teristic halocline does not increase much more than one Dart per thousand, whereas temperature in that same halocline has been seen to increase up to three or four degrees Centigrade. Considering average salinity and temperature values for this region, a one part per thousand salinity increase holding temperature and depth constant will increase sound speed 1.4 meters per second. On the other hand a one degree Centigrade temperature change holding salinity and depth constant will increase sound speed 4.3 meters per second. With this ma-jor dependence of sound speed on the temperature profile, sub- thermocline duct knowledge can play a significant role in the study of sound in the sea. 53 CHAPTER VII RECOMMENDATIONS This work mainly sets up basic guidelines in a relatively untouched field of study of the ocean. The sub-thermocline duct should be studied in greater detail in the North Pacific Ocean in order to refine boundaries or limits on areas dis- cussed in this thesis. Investigation into sub-thermocline duct activity in other regions of the world ocean should also be conducted. Time did not permit the study of sub-thermocline duct effects on sound ray paths, and this should be accomplished considering various categories of ducts and various source and receiver depths in these ducts. 54 BIBLIOGRAPHY 1. Dodimead, A. J., F. Favorite, and T. Hirano. Review of Oceanography of the Subarctic Pacific Region. International North Pacific Fisheries Commission. Rough Draft, 1 October 1962. 2. Hidaka, Koji. "Kuroshio Current," The Encyclopedia of Oceanography , 433-37. New York: Reinhold Publishing Corporation, 1966. 3. Laevastu, T., and P. D. Stevens. Near-surface Thermal Structure , Ray Trace Diagrams and Bathythermograph Records . Fleet Numerical Weather Facility/ Technical Note No. 33. Monterey, California, 1968. 4. Nagata, Yutaka. "Shallow Temperature Inversions in the Sea to the East of Honshu, Japan," Journal of the Oceanographical Society of Japan, XXIV (June , 19 68) , pp. 102-114. 5. NORPAC Committee. Oceanic Observations of the Pacific : 1955 , The NORPAC Data. Berkeley and Tokyo: University of California Press and University of Tokyo Press, 1960, 6. Scripps Institution of Oceanography, University of Calif- ornia. Data Report Physical and Chemical Data Boreas Expedition 27 January - 1_ April 1966 . SIO Reference 66-24. April 1966. 7. . Oceanic Observations of the Pacific: Pre-1949. Berkeley and Los Angeles : University of California Press, 1961. 8. . Oceanic Observations of the Pacific: 1949 . Berkeley and Los Angeles: University of California Press, 1957. 9. . Oceanic Observations of the Pacific : 1953. Berkeley and Los Angeles: University of California Press, 1965. 10. . Oceanic Observations of the Pacific: 1954 . Berkeley and Los Angeles: University of California Press, 1965. 11. . Oceanic Observations of the Pacific: 1957. Berkeley and Los Angeles: University of California Press, 1965. 55 12. . Oceanic Observations of the Pacific: 1959. Berkeley and Los Angeles: University of California Press, 1965. 13. Tully, John P. "Oceanographic Regions and Assessment of Temperature Structure in the Seasonal Zone of the North Pacific Ocean," Journal Fisheries Research Board of Canada, XXI, (1964) , pp. 941-970. 14. , and L. F. Giovando . "Seasonal Temperature Structure in the Eastern Subarctic Pacific Ocean," Marine Distributions . The Royal Society of Canada Special Publication No . 5_, 10-36. University of Toronto Press, 1963. 15. Uda, Michitaka. "Oceanography of the Subarctic Pacific Ocean," Journal Fisheries Research Board of Canada , XX (1963) , pp. 119-179. 56 INITIAL DISTRIBUTION LIST No. Copies 1. Defense Documentation Center 20 Cameron Station Alexandria, Virginia 22314 2. Library 2 Naval Postgraduate School Monterey, California 93940 3. Naval Weather Service Command 1 Washington Navy Yard Washington, D. C. 20390 4. Officer in Charge 1 Navy Weather Research Facility Naval Air Station, Building R-4 8 Norfolk, Virginia 23511 5. Officer in Charge 1 Naval Weather Service Environmental Detachment FPO New York, New York 09597 6. Commanding Officer 1 U. S. Fleet Weather Central COMNAVMARIANAS , Box 12 FPO San Francisco, California 96630 7. Commanding Officer 1 U. S. Fleet Weather Facility FPO New York, New York 09571 8. Commanding Officer 1 U. S. Fleet Weather Facility FPO Seattle, Washington 98790 9. Commanding Officer 2 Fleet Numerical Weather Central Naval Postgraduate School Monterey, California 93940 10. Commanding Officer 1 U. S. Fleet Weather Central Box 110 FPO San Francisco, California 96610 11. Commanding Officer 1 Fleet Weather Facility Naval Air Station Quonset Point, Rhode Island 02819 57 No. Conies 12. Commanding Officer 1 U. S. Fleet Weather Central Box 31 FPO New York, New York 09540 13. Commanding Officer 1 Fleet Weather Facility Navy Department Washington, D. C. 20390 14. Commanding Officer 1 U. S. Fleet Weather Facility, Box 68 FPO San Francisco, California 96662 15. Superintendent 1 Naval Academy Annapolis, Maryland 21402 16. Commanding Officer and Director 1 Navy Electronics Laboratory Attn: Code 2 230 San Diego, California 92152 17. Director, Naval Research Laboratory 1 Attn: Tech. Services Info. Officer Washington, D. C. 20390 18. Dr. Taivo Laevastu 5 Fleet Numerical Weather Central Monterey, California 93940 19. Department of Oceanography 3 Code 5 8 Naval Postgraduate School Monterey, California 93940 20. Department of Meteorology 1 Code 51 Naval Postgraduate School Monterey, California 93940 21. Oceanographer of the Navy 1 The Madison Building 732 N. Washington Street Alexandria, Virginia 22314 22. Naval Oceanographic Office 1 Attn: Library Washington, D. C. 20390 23. National Oceanographic Data Center 1 Washington, D. C. 20390 58 No. Copies 24. Mission Bay Research Foundation 1 7730 Herschel Avenue La Jolla, California 92038 25. Director, Maury Center for Ocean Sciences 1 Naval Research Laboratory Washington, D. C. 20390 26. Office of Naval Research 1 Attn: Special Projects (Code 418) Department of the Navy Washington, D. C. 20360 27. Office of Naval Research 1 Attn: Undersea Warfare (Code 466) Department of the Navy Washington, D. C. 20360 28. Office of Naval Research 1 Attn: Geophysics Branch (Code 416) Department of the Navy Washington, D. C. 20360 29. Professor G. H. Jung 3 Department of Oceanography Naval Postgraduate School Monterey, California 93940 30. Lt. J. B. Burrow, Jr., USN 2 533 McGilvra Blvd. E. Seattle, Washington 98102 59 UNCLASSIFIED ~v. urit\ I'l.issifii-iitmn DOCUMENT CONTROL DATA -R&D irits .!.<■■ »ifn .ifi.in el tith-. '""'i .-/ .ihtfr.n ( tttul itule ttiitinn n n f '/< tf/iferrd w/icn f/?r >,v r.tU report iiied) ■mi » c T i v i t > i I'lrrpomfe .11 itlmr 1 Naval Postgraduate School Monterey, California 93940 20. Rl ' ORT SECURITY CLASSIFICATION Unclassified sh. GROUP ' M ' Mill THE SUB-THERMOCLINE DUCT 4 . I ^oopt ivr_NOTFS( Typr of report .inc/. im'/u.srvi' dutrsj esis Th( •- &ii T..,^q,si ff'ifif name, mtddlc initial, la sf n.imi BURROW, JAMES BARRINGTON , JR., Lieutenant, USN k- RtfOni DATE December 19 6 8 la. TOTAL NO OF PAGES 5_9_ 76. NO OF REFS 15 S«. CONTRACT OR GRANT NO h. PROJECT NO 9fl. ORIGINATOR'S REPORT NUMBERIS) 9h. other REPORT NO(S) (Any other numbers that may be assigned this report) ■ DISTRIBUTION STATEMENT Distribution of this document is unlimited, II SUPI'LLMENIARV NOTES 12. SPONSORING MILITARY ACTIVITY Naval Postgraduate School Monterey, California 93940 13 ABSTRACT This thesis describes a method bv which near-surface temperature inversions in the ocean may be classified. Although categories of sub-thermocline ducts for sound transmission, formed as a result of these temoerature inversions, have been studied in detail in the North Pacific Ocean, classifications are general enough to be applied to ducts in other regions. A considerable variety of sub-thermocline ducting is present in the North Pacific. This variability shows both a seasonal and a positional dependence which may be ex- plained on a stability basis utilizing data obtained from selected Nansen casts reported for stations throughout the North Pacific. DD """ 1473 I NOV 65 I ™T I W S/N 0101 -807-681 1 (PAGE J) UNCLASSIFIED 61 Security Classification A- 31408 UNCLASSIFIED inv. i'l.is»sifii*atn>ri k r > rt o h .■> s SUB-THERMOCLINE DUCT TEMPERATURE INVERSION NORTH PACIFIC OCEAN SUBARCTIC REGION LINK A LINK L' DD .T.-..1473 j. ' K ) 62 UNCLASSIFIED Security Classificiitioi flora z=r SHILF BINDER ESS Syracuse, N. Y. i Slocklon, Calif. thesB8852 The sub-thermocline duct. 3 2768 002 08804 9 DUDLEY KNOX LIBRARY