Oi i -0 ■ =o i '^ ■ a I "^ i □ I m ' CD ^ f^ 7^^^ ^ U.S. Department of Transportation United States Coast Guard %lkhr) of ^ Un.'AJ ^hh Cood (rjc^rcJ t Report of the International Ice Patrol in the North Atlantic ■ '^?^^^\ns]iM\Qn Marine Biotogical Laboratofy i LIBRARY APR 17 1986 Woods Hole, Mass. 1984 Season Bulletin No. 70 CG- 188-39 DEPARTMENT OF TRANSPORTATION UNITED STATES COAST GUARD MAILING ADDRESS G-OIO U. S. COAST GUARD WASHINGTON, D. C. 20593 (202) 426-1881 Bulletin No. 70 REPORT OF THE INTERNATIONAL ICE PATROL SERVICES IN THE NORTH ATLANTIC OCEAN Season of 198 A JUL 1985 CG-188-39 FOREWORD Marine Biclcgicai Uboratory ; APR 17 1986 Woods Hole, Mass. Forwarded herewith Is Bulletin No. 70 of the International Ice Patrol describing the Patrol's services, Ice observations and conditions during the 1984 season. ^- M. J. O'BRIEN _ Acting Chief, OJ/ice of Operatfons DISTRIBimON - SDL Nou 121 a b c d e f g h i J k 1 m n 0 P q r s t u V w X Y z 1* 1* 1 1 1* 1 ] in ? ? "i 1 1* 1* fin NON-STANDARD DISTRIBUTION: *A;abf LANTAREA only *B;b LANTAREA (5); B:b PACAREA (5) *C: aq LANTAREA only SML CG-4 Summary From 23 March to 7 September 1984, the International Ice Patrol (IIP), a unit of the U.S. Coast Guard, conducted the International Ice Patrol Service, which has been provided annually since the sinking of the RMS TITANIC on April 15, 1912. During past years. Coast Guard ships and/or aircraft have patrolled the shipping lanes off Newfoundland within the area delineated by 40ON - 520N, 390W - 57°W, detecting icebergs and warning mariners of these hazards. During the 1984 Ice Patrol season. Coast Guard HC- 1 30 aircraft deployed out of Gander, Newfoundland to search for icebergs in the Grand Banks region of the North Atlantic. These aircraft flew 78 ice reconnaissance sorties, logging over 476 flight hours. New detection equipment, the AN/APS-135 Side-Looking Airborne Radar (SLAR), was introduced into Ice Patrol duty during the 1983 season. It proved to be an excellent tool for the detection of both icebergs and sea ice, and alone provided 78 percent of the 1984 sightings on IIP reconnaisance flights. A total of 2202 icebergs were estimated south of 48°N latitude, a new record. The record number of icebergs south of 48°N this year was the result of colder than normal conditions (see Environmental Conditions section) and increased iceberg detection due to the use of SLAR (see Appendix C). To evaluate the iceberg drift and deterioration models used by International Ice Patrol, an oceanographic cruise was conducted by USCGC HORNBEAM. This cruise conducted the first hydrographic survey since 1978, and included drift and deterioration studies on a medium iceberg (see Appendix B). Introduction This is the 70ib annual report of the International Ice Patrol Service in the North Atlantic. It contains information on ice conditions and Ice Patrol operations for 1984. The U.S. Coast Guard conducts the International Ice Patrol Service in the North Atlantic under the provisions of Title 46, U.S. Code, Sections 738, 738a through 738d; and the International Convention for the Safety of Life at Sea (SOLAS), 1960, regulations 5-8. This service has been provided annually since the sinking of the RMS TITANIC on April 15, 1912. Commander, International Ice Patrol under Commander, Coast Guard Atlantic Area, directed the International Ice Patrol from offices located at Groton, Connecticut. The unit analyzes ice and environmental data, prepares the daily ice bulletins and facsimile charts, and replies to any requests for special ice information. It also controls the aerial Ice Reconnaisance Detachment and any surface patrol cutters when assigned, both of which patrol the southeastern, southern, and southwestern limits of the Grand Banks region (40°N to 52°N) and 39°W to 570W for icebergs. The International Ice Patrol makes twice-daily radio broadcasts to warn mariners of the limits of iceberg distribution. Vice Admiral Wayne E. Caldwell, U.S. Coast Guard, was Commander, Atlantic Area until he was relieved on 1 July 1 984. Vice Admiral P.A. Yost was Commander, Atlantic Area from then until the season's end on 7 September 1984. Commander Norman C. Edwards, Jr., U.S. Coast Guard, was Commander , International Ice Patrol during the 1984 Ice Patrol season. Two pre-season deployments were made from 31 January - 3 February and 7-1 4 f^arch 1 983 to determine the early season iceberg distribution. Based on these trips, regular deployments started on 21 March with the 1984 season officially opening on 22 March. From that date until 3 September 1 984, an aerial Ice Reconnaisance Detachment (ICERECDET) operated from Gander, Newfoundland one week out of every two. The season officially closed on 7 September 1984. No U.S. Coast Guard cutters were deployed to act as surface patrol vessels this year. The USCGC HORNBEAM was deployed to provide oceanographic support to Ice Patrol from 26 June - 31 July. During the 1984 season, an estimated 2202 icebergs drifted south of 48°N latitude. Table 1 shows monthly estimates of icebergs that crossed 48°N. Table 1. Icebergs South of 48° North Total Average Total Average 1984 1946-84 1946-84 1900-84 1900-84 OCT 0 2 NOV 0 4 DEC 0 13 JAN 0 74 FEB 0 437 MAR 101 1397 APR 953 4423 MAY 484 3842 JUN 227 2260 JUL 335 900 AUG 93 197 SEP 9 19 Annual t , 2 Ota! 202 13568 0 109 0 110 0 93 2 194 11 888 36 3499 113 9268 99 11025 58 5778 23 2096 5 586 0 265 347 33911 1 1 1 3 16 56 150 169 92 31 8 3 399 Data Collection and Dissemination Ice Reconnaisance Number Detachment No. of of Hours Deployments Flights Flown Pre-season ^^ ^5.2 In-season ^^ 543.1 Post-season ^ 10.7 Total 108 629.0 Note: In-season ICERECDET flights include transit and logis- tics flights to and from Gander during the Ice patrol season. There were 78 sorties dedica- ted solely to ice reconnaisance with a total of 476.1 flight hours. They are summarized as follows: Number f^onth of Sorties Flight Hours FEB 3 15.5 MAR 10 60.7 APR 16 101.0 MAY 15 93.6 JUN 10 59.5 JUL 10 60.1 AUG 12 74.8 SEP 2 10.9 TOTAL 78 476.1 1 Table 2. Aircraft Deployments from 1 October 1983 to 30 September 1984 During the 1 984 Ice Patrol year (from 1 October through 30 September 1984), 108 aircraft sorties were flown in support of the International Ice Patrol. These included pre-season flights, ice observation and logistics flights during the season, and post-season flights. Pre-season flights determined iceberg concentrations north of 48°N, necessary to estimate the time when icebergs would threaten the North Atlantic shipping lanes in the vicinity of the Grand Banks of Newfoundland. During the active season, ice observation flights tocated the southwestern, southern, and southeastern limits of icebergs. Logistics flights were necessary for unusual aircraft maintenance. Post-season flights were made to retrieve parts and equipment from Gander and to close out all business transactions from the season. U.S. Coast Guard aircraft, deployed from Coast Guard Air Station Elizabeth City, North Carolina, conducted all the aircraft missions. SLAR- equipped HC-1 30 aircraft were utilized exclusively for aerial ice reconnaisance, HU-25A aircraft were used on two logistics flights, and the VC-4A aircraft was utilized for post season deployment. Table 2 shows aircraft utilization during the 1984 season. U.S. Coast Guard Communications Station Boston, Massachusetts, NMF/NIK, was the primary radio station used for the dissemination of the daily ice bulletins and facsimile charts after preparation by the Ice Patrol office in Groton. Other transmitting stations for the OOOOZ and 1200Z ice bulletins included Canadian Coast Guard Radio Station St. John'sA/ON, Canadian Forces Radio Station Mill Cove/CFH, and U.S. Navy LCMP Broadcast Stations Norfolk/NAM; Thurso, Scotland; and Keflavik, Iceland. Canadian Forces Station Mill Cove/CFH as well as AM Radio Station Bracknell/GFE, United Kingdom are radio facsimile broadcasting stations which used Ice Patrol limits in their broadcasts. Canadian Coast Guard Radio Station St. John's/ VON provided special broadcasts. The International Ice Patrol requested that all ships transiting Table 3 Iceberg and SST Reports Number of ships furnishing Sea Surface Temperatuf'e (SST) repoils 86 1 Number of SST reports received 353 Number of ships furnishing ice reports 220 Number of ice reports received 586 First Ice Bulletin _„..... 230000Z MAR 84 Last Ice Bulletin 071200Z SEP 84 Number of facsimile charts transrtiitted 169 the area of the Grand Banks report ice sightings, weather, and sea surface temperatures via U.S. Coast Guard Communications Station Boston, NMF/NIK. Response to this request is shown in Table 3, and Appendix A lists all contributors. Commander, International Ice Patrol extends a sincere thank you to all stations and ships which contributed. Table 4 Sources of International Ice Patrol Iceberg Reports No. of %0f Sighting Source J sightings 2487 Total 49.3 Coast Guard SLAR Coast Guard Visual 722 14.3 CanadianRadar 10 0.2 Canadian Visual 48 1.0 CommercialRadar 367 7.3 CommercialVisual 1157 22.9 Mobil Oil Canada, LTD 171 3.4 Other 31 0.6 Environmental Conditions, 1984 Season Weather in Labrador and east Newfoundland during the 1984 international Ice Patrol season tended to be cooler and wetter than nornnal (Table 5). The weather stations listed were selected to give a cross section of weather patterns throughout the province. Months that ran contrary to the cool, wet trend were February and May, which were warmer than normal, and July, which was wanner and drier than normal. The overall wet, cool trend had the effect of allowing sea ice to persist tonger than normal in the Davis Strait and Labrador Sea, thereby offering some protection to icebergs in that region. January: The Iceland Low was deeperthan normal during January and the distribution of pressure funnelled in cold continental air (Figure 1), causing the air temperatures to lie well below normal (Table 5). February: The Iceland Low was again deeperthan normal, but pressure patterns allowed warm, moist marine air to flow over the Maritimes (Figure 2) and temperatures and precipitation were above normal. March: Average surface flow during the nnonth was almost the opposite of the normal pattern (Figure 3) with easterly and northeasterly winds, which brought cool, moist marine air over the Grand Banks and the Maritimes, resulting in slightly lower than normal temperatures and greater than normal precipitation. April: The unusual high pressure system over Labrador in April (Figure 4), coupled with lows south of the Avalon Peninsula and over Iceland, caused northeasterly flow across the Labrador coast and easterly flow across Newfoundland and the Grand Banks, with above average precipitation on the Avaton Peninsula (St. John's) and below average temperatures throughout the region (Table 5). May: Southwesterly flow over Newfoundland and Labrador (Figure 5) brought in marine air and raised temperatures and precipitation above normal. June: Underthe influence of low pressure over the Labrador Sea (Figure 6), southerly flow over the region brought in marine air which was cooler and moister than the continental air normal for June. July: With near nornial pressures (Figure 7), precipitation was slightly t)elow normal and temperatures slightly above normal during July, suggesting more of a continental influence than normal. August: With the cooling of the northern continental air mass that normally takes place in August, a stronger than normal marine influence (Figure 8) brought warmer temperatures and more precipitation over the region. September: The Bermuda High was farther south than normal in September (Figure 9), bringing marine air into the area and causing above normal precipitation with near normal temperatures. ....,..„.....................,.......„....,..,„........,„.....,........^ Environmental Conditions for 1984 International Ice Patrol Season Temp OC Total %of Normal %of Normal Monthly DIH. Station Mean from Norm. Precipitation (mm) Precipitation Snowfall Hopedale 1.8 -0.6 47.0 75 73 OCT 1983 Goose 2.6 -0.1 91.3 119 87 Gander 6.9 0.9 42.2 40 25 St. John's 7.7 0.8 214.6 147 27 Hopedale -3.8 -0.6 99.1 173 159 NOV Goose -4.9 -1.1 155.1 206 264 Gander 1.3 0.5 1264 118 168 St. John's 2.4 -1.0 118.9 73 84 Hopedale -13.6 -2.9 109.9 194 181 DEC Goose -15.3 -2.3 126.7 74 215 Gander -4.4 -0.6 844 78 92 St. John's -1.5 0.0 111.7 69 53 Hopedale -22.4 -6.6 34.4 55 48 JAN 1984 Goose -23.0 -6.6 51.8 70 82 Gander -9.4 -3.2 157.7 145 158 St. John's -5.5 -1.6 188.8 121 65 Hopedale -17.7 -2.6 111.6 223 174 FEB Goose -14.4 0.1 90.7 150 219 Gander -4.7 2.1 142.7 143 67 St. John's -1.9 2.6 151.1 108 10 Hopedale -12.1 -1.6 100.1 181 149 Goose -10.3 -1.7 82.9 115 116 MAR Gander -3.9 -0.4 1744 158 160 St. John's -1.6 0.7 142.7 108 173 Hopedale -6.9 -2.0 25.0 54 54 APR Goose -3.6 -1.9 50.8 83 108 Gander -0.6 -1.5 97.8 105 79 St. John's -0.2 -14 235.2 203 51 Hopedale 1.8 04 68.0 134 119 MAY Goose 5.8 0.8 89.6 140 143 Gander 8.9 2.7 92.2 132 31 St. John's 8.3 2.9 156.0 153 • Hopedale 4.7 -1.7 71.8 112 126 JUN Goose 9.3 -2.0 120.6 130 432 Gander 94 -2.4 115.9 144 36 St. John's 9.9 -1.0 144.0 168 * Hopedale 9.6 -0.9 178.3 211 * JUL Goose 16.8 1.0 91.8 87 Gander 18.0 1.5 63.2 92 • St. John's 17.9 24 414 50 * Goose 23.0 3.7 23.6 23 • AUG Gander 16.6 1.0 181.8 187 • St. John's 17.3 2.0 204.3 168 • Nain 5.1 134.3 _ Goose 13.0 -0.7 121.3 137 • SEP Gander 14.9 -0.7 1134 140 * St. John's 16.9 1.0 157.8 141 * * No snowfall recorded during this month. NOTE: In August 1984, the Canadian weather reporting at Hopedale was discontinued. The new station is at Nain on the Labrador coast, approximately 1 50km northwest of Hopedale. ::^Xi V < A \ J;ip ^^ s 00 \ ^•^^ Vir^ L_^ ° o o 1 V? Vl^ 4? 1 o \ % ?v^ ■^ y 5 \ 3 / (0 E ^ V V \ \ \ v^ > 00 o o \ C\J o \ \ ^^ ^ P 0 \ CD O 7 W^ >sr\ ^ ^ ■X / / CM 3 o> (0 E -^ ^ ***» CD ¥. ^^^ S vV "'^N>r^ \ # V 00 o (0 10 A < to >-,_ \ \\ ^101 O \ \ • ^^.^ -'-^-^ > <2s^ CD o o &^ K'^^^jj y\r o J \ y^M: ^m^Os mm S / J • D) (0 E 11 "Tl \ \( / [ *^JF y- i \ \ i'^r ^ 1 CD o CM O ^^^j^r^^rS^ JlwJf"^ V / \ lillli^ p ^ H M v__ f«--i||^^J^ !^ ^ 1 ^ . in o 3 O) (0 E 12 ^\ \ ^ 00 ^ 1 ) :5 ? i CVJ o ^ \ o O) 13 O) 14 3 O) il 15 O) 16 Ice Conditions 1984 Season October - November 1983: Temperatures were near normal and no sea ice formed south of 58°N during October and November (Figures 1 0 and 11). By \he end of November, Hudson Strait and the mouth of Ungava Bay were closed by sea ice with the southern part of Ungava Bay remaining ice-free. Iceberg sightings south of 52°N reported to International Ice Patrol during October were nearthe entrance to the Straits of Belle Isle and no sightings were reported south of 52°N during November. December 1 983: Early in the month, sea ice along the coast of Labrador was as far south as Lake Melville. By mid-month (Figure 1 2), sea ice was approaching, and by the end of the month had closed the Straits of Belle Isle. Seven icebergs were reported to International Ice Patrol south of 520N during December, all in the vicinity of the Straits of Belle Isle. January 1984: By mid-month (Figure 13), ice along the coast was south of Cape Bonavista. The Iceland Low was deeper than normal during January, and the distribution of pressure funnelled in cold continental air (Figure 1), causing air temperatures to be well below nonnal (Table 5). No new iceberg sightings were reported to International Ice Patrol south of 52°N during January. February 1984: Sea ice was as far south as Cape St. Francis throughout the month with a seaward penetration late in the month over the Grand Banks nearly reaching 46°N (Figure 1 4). the Iceland Low was again deeper than normal, but pressure patterns allowed warmer marine air to flow over the Maritimes (Figure 2), raising temperatures above normal. The first pre- season International Ice Patrol deployment took place 31 January - 3 February. Reconnaisance flights sighted 50 icebergs south of 520N, one of which was south of 49°N. The International Ice Patrol received only one ship sighting south of 520N during February. March 1984: Sea ice remained near Cape St. Francis throughout the month with heavy coverage over the Grand Banks (Figure 15). Average surface winds during the month were almost opposite the normal pattern (Figure 3), wrth the easterly and northeasterly flow holding the sea ice and icebergs toward the Newfoundland and Labrador coasts. The second pre- season deployment, 7-13 March, resulted in 54 sightings south of 52°N, 18 of which were south of 48°N. A second deployment was made 21-30 March with the 1984 Ice Patrol season officially opening on 23 March. Figure 22 shows the limits of all known ice south of 48°N. At the end of the month, 1 56 icebergs were on plot at the International Ice Patrol office in Groton, Connecticut. April 1984: Sea ice continued to persist along the coast as far south as Cape St. Francis throughout the month (Figure 1 6). The unusual high pressure system over Labrador in April (Figure 4), coupled with low pressure over Iceland, brought northerly flow into the Maritimes and lower than normal temperatures prevailed (Table 5). Under the influence of northerly winds and retreat of the sea ice westward, April was the heaviest iceberg nrxjnth with 1043 icebergs sighted, of which 953 passed south of 48° N. The first IC ER EC DET deployment for the nrKDnth was extremely busy, reporting large numtjers of icebergs daily while participating in both an airborne radar iceberg detection experiment and ice patrols over a two week period. On 1 5 April 1 984, a memorial wreath was dropped at the site of the HMS TITANIC sinking (41 01 6'N 51 OW) to commemorate the neariy 1 500 lives lost on 1 5 April 1912. At the end of the month, 1 56 icebergs were on plot at the Intemational Ice Patrol. May 1984: Sea ice in Davis Strait retreated to the west under the warm air temperatures of May, and at the same time receded northward along the the east coast of Greenland (Figure 1 7). In contrast, near normal weather conditions resulted in a light westeriy flow over the Newfoundland and Labrador coasts that did little to affect sea ice, which remained as far south as Cape St. Francis throughout the month. InMay, 1037 icebergs were sighted, of which 484 passed south of 48°N. At the end of the month, 1 98 17 Table 6. Explanation of Sea Ice Symbology used in Figures 10-21 icebergs were on plot at the International Ice Patrol. Icebergs on plot at the International Ice Patrol were widely distributed by mid-month and a second two- week ICERECDET was conducted. By month's end, several drifted outside the Ice Patrol area (west of 57°W longitude) and others extended the southernmost limits south of 40ON latitude (Figure 27). June 1984: As seen in Table 5, June was colder than normal and sea ice remained in the westem part of Davis Strait and off the Straits of Belle Isle (Figure 1 8). The number of icebergs on plot decreased during June, although the limits of all known ice remained well to the south and east, held there by widely scattered icebergs (Figures 28 and 29). The southemmost iceberg on plot for the season came on 6 June at 40O01 "N 45°51'W. There were 555 icebergs sighted in June, of which 227 drifted south of 48°N and several of these drifted outside the Ice Patrol area (east of 39° W or west of 57° W longitude) . At the end of the month, 149 were on the International Ice Patrol plot and widely scattered. July 1984: Underthe influence of warm but near-normal weather during July, the sea ice retreated north of 54°N by mid- month. Altfxjugh the number of icebergs on plot at the international Ice Patrol decreased throughout the month, the limits of all known ice continued to be C = Total Ice concentration In the area In tenths. C C C - Concentration of thickest ( C ), 2nd thickest (C), and 3rd thickest (C ). a b c a b c S S. S ' Stage of development of thickest (S ),2ndthickest(S^ ),and3rdthJckest(S ). a b c a b c ~C ' Concentration ol ice within areas of strips and patches. F F^F » Roe size of thickest (F ), 2nd thckestfF^), and 3rd thickest (F ). a b c a b c Staoe of Devetoorrent 0 1^ stage of devekiprnent 1 New ice 2 Nllas, ice rind 3 Young ice 4 Grey ice 5 Grey-white ice 6 First-yearice 7 Thin first-year ice 8 Thin first-year Ice, 30-50 cm 9 Thin first-year Ice, 50-70 cm 1' Medium first-year Ice 4- Thick first-year Ice 7- Old ice 8' Second-year Ice 9' Multi-yearice A Icebergs • Atraceof IcethlckerthanS a # Fourth type, If C C,.C do not add up to C a b c Floe Sizes 0 Pancake Ice 1 Brash, small ice cake 2 Icecake 3 Small floe 4 Medium floe 5 Big fk)e 6 Vast fkie 7 Giant floe 8 Growlers and floebergs 9 Icebergs / Undetennined or unknown much farther south and east than normal due to widely scattered icebergs at the limits (Figures 30 and 31). Of the 975 icebergs sighted and reported to the International Ice Patrol in July, 335 passed south of 48°N. Both numbers are greater than those of June, with the increase due to the release of icebergs by the retreating ice pack. August 1984: With air temperatures somewhat atjove normal, sea ice continued to retreat in August (Figure 20). Increasing sea surface temperatures accelerated iceberg melt and caused the limits of all known ice to move north (Figures 32 and 33). Of the 251 icebergs sighted in August, 93 passed south of 48°N and 46 remained on plot at the end of the month. September 1984: Sea ice continued to retreat rapidly, and by 18 September had disappeared from Davis and Hudson Straits (Figure 21) and completely melted in Baffin Bay to conclude this ice year. By the end of the 1 984 Intemational Ice Patrol season on 7 September, 1 24 icebergs had been sighted in September with only 9 drifting south of 48°N and 24 remaining on plot at the end of the season (Figure 34). 18 Figure 10 60 55 50 60 55 50 Sea Ice Conditions October 18, 1983 Sea Ice Boundary 45 45 19 Figure 11 60 55 50 60 55 Sea Ice Conditions November 15, 1983 Sea Ice Boundary 45 50 45 20 60 55 50 Figure 12 21 Figure 13 r-' GRNLD 60 55 50 Sea Ice Conditions January 17, 1984 Sea Ice Boundary 45 22 60 55 50 Figure 14 60 55 50 Sea Ice Conditions February 14, 1984 Sea Ice Boundary 45 60 55 50 45 23 Figure 15 60 55 50 24 Sea Ice Conditions March 13, 1984 Sea Ice Boundary Figure 16 60 55 50 Sea Ice Conditions April 17, 1984 Sea Ice Boundary 60 55 50 45 25 Figure 17 60 55 50 26 Sea Ice Conditions May 15, 1984 Sea Ice Boundary Figure 18 60 55 50 Sea Ice Conditions June 12, 1984 Sea Ice Boundary 60 55 50 45' 27 Figure 19 Sea Ice Conditions July 17, 1984 Sea Ice Boundary 28 60 55 50 Figure 20 60 55 50 Sea Ice Conditions August 14, 1984 Sea Ice Boundary 45 60 55 _ 50 45 29 Figure 21 30 Sea Ice Conditions September 18, 1984 Sea Ice Boundary 45 Figure 22 52 51° 50° 49° 48° 47° 46° 4b° 44° 43° 42° 41° 40° 57° 56° 55° 54° 53° 52° 51° 50° 49' 48» 47° 46° 45° 44° 43° 42° 41° 40° 39' 39' A NUMBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE. SYMBOLS INDICATE ACTUAL POSITIONS. 52° 51° 50° 49° 48° 47° 46° 45° 44? 43° 42° 41° 40° 39° 38 °T^ ' ij 1 1 ' I I I I I ' I I I I I ' I 1 1 I I ^ I I I I ' I I I I I ' : : I : I ' ■ : , I I ' I I I 1 1 ' 1 1 1 1 I ' I 1 1 I r ' I I I I I ' I I I 1 1 'i I 1 1 I ' I 1 1 I I ' M I I I ' ' i 1 1 i i ' R 8 ° 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG M GROWLER X RADAR TARGET/CONTACT FOR 1200 GMT 23 M A R 84 BASED ON OBSERVED AND FORECAST CONDITIONS 31 Figure 23 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46 45° 44° 43° 42° 41° 40° 39° ?^fl°l'l II II 'i I I I I ' I rrrr'Tnrr-^i i i i i ' I i i i i ' , : i : i ' ■ . , i : ' i i i 1 1 ' M I I I ' I I I i i ' ' i i i i i 'i i n i ' i 1 1 i i ' i i i i i ' i tttt 38° 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG FOR 1200 GMT30 MAR 84 M GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 32 Figure 24 57" 56" 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° 52° 51° 50 49 48 47° 46° 4b° 44° 43° 42° 41° 40° I irii I I I I I pm TTTTT TTTTT Tl I 11 I III! " I I I J I I I I _ I I I I I _ I I I M _ I I I I I _ I I I I I _ I I I I I M I I I _ I I I IJ 39' ESTIMATED LIMIT OF SEA ICE A NUMBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE. SYMBOLS INDICATE ACTUAL POSITIONS. 52° 51° 50° 49° K8° 47° 46° 45° 44? 430 42° 41° 40° 39° "^^''I^TTTi '[ I I I I 'mi I 1^ I I I I ' I I I I 1' 1 : I I I 'i, I 1' '11 n I 'ill ii'i I I I r '11 I II '11 II I ' I II I I'l I I I I '1 I I I 1' I ittt'RR ■ ' ■ ■ ■ ■ II I I I ■ ■ ■ ' ' ' ■ ■ ■ ' 1 I ' I I ■ ■ I ' I ' ■ > I ' I 1 1 1 J Mill Li-LJJ Mill Mill Mill 1 II 1 I 1 I ' ' I i ' I I 1 I 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39 A BERG FOR 1200 GMT 15 APR 84 A GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 33 Figure 25 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° 40' 39" A NUMBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE. SYMBOLS INDICATE ACTUAL POSITIONS. 52° 51° 50° 49° 48° 47° 46° 45° 44? 43° 42° 41° 40° 39° 38° 38' III II -I I I ii'i I M I 'TrnT'i I II I I'; : I : !■ i:i M'l I I iTn in'iniri I I I I -ii III ■im ri II I I i ii i i 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG FOR 1200 GMT 30 APR 84 m GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 34 Figure 26 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° 42° 41° 40' 39' 38' M I 1 1 ' I I I ri' r I I 1 1 'ttiti' I I M I ' I I I I I A NUMBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE. SYMBOLS INDICATE ACTUAL POSITIONS. I : I I I M M I I I I I I M I I I I I 1 I I I I I I I I I I I I I I I I M I ' I I M I' M I I I 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG FOR 1200 GMT 15 MAY 84 A GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 52° 51° 50° 49° 48° 47° 46° 45° 44? 43° 42° 41° 40° 39° 38° 35 Figure 27 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 4o' 45° 44° 43° 42° 41° 40° 39° *■ 1 I I 1 I L i I L 1 L-l igj— 1 J-l i J ,LJ i 1 i LJ L U L^.J-L.i ' ■ I ' ' I'll' III'' 1 1 1 1 i ' ' ' ' ' ' ' ■ ■ ' I ' ■ n 1 1 I 1 I 1 I I 1 I I I ; I ] I- 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG FOR 1200 GMT 30 MAY 84 M GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 36 Figure 28 57° 56* 55° 54° 53° 52° 51° SC" 49° 48' 47° 46° 45° 44*43° 42° 41° 40° 39* 39°- 38*1^™ A NUDiBER IN A ONE DEGREE RECTANGLE INDICATES THE NUIylBER OF ICEBERGS IN THAT RECTANGLE. SYMBOLS INDICATE ACTUAL POSITIONS. I 1 1 ' 1 1 1 1 [ I r I 1 1 I I ' 1 1 1 1 1 'i I 1 1 I ' I II 1 1 ' 1 1 I 1 1 ' 1 1 1 1 1' I ij I i'l!^R' 43° 42° 41° 40° 39° ■ I I' 'I liiM MM] II II I Mill i:mi iiiTi— rrrri tttti hi it iiiii | | | I 1 II II I I II I I I I I I I I I I I I ' " ' ' ■ 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39 A BERG FOR 1200 GMT 15 J (J (SJ 34 A GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 37 Figure 29 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42°^l° 40° 39° A BERG FOR 1200 GMT 30 JUN 84 m GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 38 Figure 30 57' 56° 55° 54" 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39' 41' 40' 39' A NUMBER IN A ONE DEGREE RECTANGLE INDICATES .THE NUMBER OF ICEBERGS IN THAT RECTANGLE. SYMBOLS INDICATE ACTUAL POSITIONS. 52° 51° 50° 49° 48° 47° 46° 45° 44? 43° 42° 41° 40° 39° 38° 38' riTTT I I I 1 1 ' r M 1 1 ' 1 1 1 1 I ' I I 1 1 I ' I I I 1 1 ' ; I I M ' I : I r I I I II I ' 1 1 I 1 1 iM'i I I -11 II I ■ Ml I ri I I 1 1 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG FOR 1200 GMT 15 JUL 84 A GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 39 Figure 31 57!_56* 55° 54» 53" 52° 51° 50° 49° 48° 47° 46° 45* 44° 43° 42° 41° 40° 39' 43' 42' 41 40' 39" 38' A NUNflBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE. SYMBOLS INDICATE ACTUAL POSITIONS. Ill II 'I I I I I'm I I r 1 1 1 1 I'l I 1 1 I ' M I 1 1'! I 1 1 r III I i' I I I M 'it l-l I 'nill'l I I IT I' I ii'iiiir mr \0 52° 51° 50° 49° 48° 47° 46° 45= 44? |43° 42° 41° 40° 39° 38° 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG FOR 1200 GMT 30 JUL 84 • GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 40 Figure 32 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° _j 43° O a: < 42° Q. y 4io < O 40' ^39' 38" I I I I I I ITTT TTTT liill I I I I I A NUMBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE. SYMBOLS INDICATE ACTUAL POSITIONS. I I I II ran ilJLL TTTT TTTTI I I M I TTTTT rnn 1 1 1 1 1 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG FOR 1200 GMT15AUG84 M GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 52° 51° 50° 49° 48° 7° 46° 45° 44° 43° 42° 41° 40° 39° 38° 41 Figure 33 57° 56° 53° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° 44° 43' 42' 41° 40' 39' A NUMBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE. SYMBOLS INDICATE ACTUAL POSITIONS. 44? 43° 42° 41° 40° 39° 38° 38°!' I II 1 1 'i I I 1 1' I irrrSTTi i ^ i 1 1 1 ' 1 1 i 1 1 ' ; : i : i ' i . , 1 1 ' ' 1 1 1 1 1 ' 1 1 1 1 1 ' 1 1 1 i i ' 1 1 1 ii 'i i 1 1 i ' i 1 1 i i ' 1 1 i 1 1 ' 1 1 MM 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG FOR 1200 GMT 30 AUG 84 M GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 42 Figure 34 57" 56* 55° 54' 53° 52° 5 1° 50° 49° 48° 47° 46° 45° 44° 43° 42* 41* 40* 39* -^D' 44' 43' 42' 40= 39' A NUMBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE . SYMBOLS INDICATE ACTUAL POSITIONS. 52° 51° 50° 49° K8° 7° 46° 45° 44? 43° 42° 41° 40° 39° 38 °i Ml II 'i I I I I'l I I iT-^rn iiVri i i ' I I I I I ' . : i : i ' . , i : ' i . i ] i ' 1 1 1 1 I ' I 1 1 1 1' I I I I I ' I I I I I 'l I 1 1 I I 1 1 I I ' I I I 1 1 ' I I I I I ' 1 1 1 I l' 1.3 8 ° 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG M GROWLER X RADAR TARGET/CONTACT FOR 1200 GMT 07 SEP 84 BASED ON OBSERVED AND FORECAST CONDITIONS 43 Discussion of Iceberg and Environmental Conditions The number of icebergs that pass south of 48°N in the International Ice Patrol area each year is the measure by which Intemationai Ice Patrol has judged the severity of each season since 1912 (Table 1). With 2202 icebergs south of 48°N, 1984 is the record year with the previous maximum in 1972 being 1587. This record number and the near- record for 1 983 ( 1 348, fourth highest on record) are partially the result of International Ice Patrol's increased iceberg detection capability due to the introduction of the AN/APS-1 35 Side-Looking Airbome Radar (SLAR) to ice reconnaisance flights. The impact of SLAR on Intemationai Ice Patrol iceberg detection is examined in Appendix C. During the period 2-7 April 1984, the Intemationai Ice Patrol participated in an airbome radar iceberg detection evaluation called Bergsearch '84. This experiment was sponsored by the Environmental Studies Revolving Funds (ESRF) administered by the Canada Oil and Gas Lands Administration (COGLA). TheAN/APS-135 SLAR was tested along with two APS-94 SLAR's and the two synthetic aperture radars (SAR's) to assess the capabilities of these modem airbome imaging radars in the detection of icebergs in open water. The Ice Patrol conducted 71 passes on five sorties over iceberg-infested waters while ground tmth was provided by the MA/ POLARIS and visual confirmations were made by a King Air aircraft. The detection data were taken with light to moderate sea conditions of less than 4 meters and included target type (icebergs, sea ice, ships), iceberg size, aircraft altitude, aspect angle relative to the wind (sea), and depression angle. Since the emphasis was placed upon determining the detection of smaller pieces of ice (growlers and small icebergs), the analysis, which was conducted by CANPOLAR Consultants Ltd. under contract to ESRF, dealt with primarily icebergs less than 30 meters long. Because the Ice Patrol has been using the new SLAR for two seasons, this evaluation was of considerable interest. Preliminary results indicate that the APS-1 35 SLAR has a detection probability of approximately 65% for 1 0-30m icebergs, and better than 95% for icebergs over 30m in length at sea states moderate and less (Rossiter, 1984). Also, the repeatability of sighting these icebergs fluctuates less than +/- 10%. As suspected, the detectability of icebergs appears to decrease with increasing sea state, particularly for smaller targets. For growlers (<100m2), the detection probability is very small (<5%). for they are often substantially submerged, hidden in the sea return or shadowed by the image of a parent iceberg. Of the 2202 icebergs sighted this past season, 83% were small, medium, large, or very large icebergs. Other sightings, which were not visually confirmed, may have been undersized from the SLAR imagery as growlers, since 45 the experiment illustrated that iceberg shape and size cannot be readily measured. In patrolling the southern, southeastern, and southwestern limits of the Grand Banks with SLAR during 1983 and 1 984, the iceberg detection capability has improved greatly (see Appendix C) over prior visual search years. SLAR has provided a more efficient Ice Patrol, since visual reconnaisance flights were conducted only 50% of the time, covering much smaller search areas with visibility partially obscured by fog or low clouds. Since the SLAR capability of detecting and identifying icebergs is unknown for more severe weather conditions, future experiments will need to be conducted. Since the numberof icebergs calved each year by Greenland's glaciers is in excess of 1 0,000 (Knutson, 1978), a sufficient numberof icebergs exist in Baffin Bay during any year. Therefore, annual fluctuations in the generation of Arctic Icebergs is not a significant factor in the numberof icebergs passing south of 48°N annually. The factors that determine the numberof icebergs passing south of 48°N each season can be divided into those affecting iceberg transport (currents, winds, and sea ice) and those affecting iceberg deterioration (wave action, sea surface temperature, and sea ice). Sea ice acts to impede the transport of icebergs by winds and currents and also protects icebergs from wave action, the major agent of iceberg deterioration. Although it slows current and wind transport of icebergs, sea ice is itself an active medium, for it is continually moving toward the ice edge where melt occurs. Therefore, icebergs in sea ice will eventually reach open water unless grounded. The melting of sea ice itself is affected by snow cover (which slows melting) and air and seawaterte mperat u res . As sea ice melt accelerates in the spring and early summer, trapped icebergs are rapidly released and then become subject to normal transport and deterioration. Under the influence of northerly winds over Davis Strait and the Labrador Sea, a large numberof icebergs entered the International Ice Patrol area in April, making it the heaviest iceberg month of the 1 984 season. Light westerly flow during May, which did little to assist the southward transport of icebergs, and the persistance of sea ice off Newfoundland and Labrador througfxjut the month resulted in a reduced numberof icebergs entering open water. The sea ice remained south of 52°N until mid-June, retarding iceberg drift and preserving the icebergs longer than normal (see SST chart for June 1 984 in Appendix B). During late June and early July, the sea ice retreated dramatically and the number of icebergs south of 48°N significantly increased in July. The sharp decrease in the number of icebergs in August and September was the result of the increase in air temperatures (Table 5) and the warming of surface waters on the Grand Banks, both of which accelerated iceberg melt. References Rossiter, J.R., L.D. Arsenault, A.L. Gray, E.V. Guy, D.J. Lapp, R.O. Ramseier, E. Wedler, (1984); Detection of Icebergs by Airtwrne Imaging Radars, Proceedings of the 9th Canadian Symposium on Remote Sensing, St. John's, Newfoundland Knutson, K.N. and T.J. Neill, (1978); Report of the International Ice Patrol Service in the North Atlantic Ocean forthe 1 977 Season, CG-188-32, U.S. Coast Guard, Washington, DC. Acknowledgements Commander, International Ice Patrol acknowledges the assistance and information provided by the Canadian Department of the Environment, the U.S. National Weather Service, the U.S. Naval Weather Service, and the U.S. Coast Guard Research and Development Center. We extend our sincere appreciation to the staffs of the Canadian Coast Guard Radio Station St. John's, NewfoundlandA/ON and the Gander Weather Office and to the personnel of U.S. Coast Guard Air Station Elizabeth City and the USCGC HORNBEAf^ for their excellent support during the 1984 International Ice Patrol season. 46 Appendix A International Ice Patrol SSI and Ice Reports for 1984 Country Ice SSI Ship's Name of Registry Reports Reports Acadian Gail Canada 2 Achilles Singapore 5 4 Admiral FarhiEngin Turkey 1 Aegis Britannic Panama 1 Aeneas Trinidad 2 Agip Abruzzo Italy 2 7 Akizuki Maru Japan 8 Akranes Iceland 3 Albright Explorer United Kingdom 9 1 Alexander Schroeder Germany 1 Alrazak France 1 Ambassador United Kingdom 7 Anangel Ares Greece 2 2 Anboto Liberia 4 Andes Traders United Kingdom 2 Angela Smith Netherlands 5 Aquarius Italy 1 Arctic Link United Kingdom 1 1 Arctic Lynx Canada 1 Arctic Shiko Canada 3 Atlantic Champagne France 2 Atlantic Cinderella Sweden 1 1 Atlantic Sage Sweden 1 Atlantic Service France 1 Banlett Chile 1 Batna Algeria 1 3 Benvorlich United Kingdom 1 Berljot Non«ay 1 Besor Liberia 1 Bischofstor Germany 12 Boujniba Morocco 2 Breslau 2 Panama 1 Belocean United Kingdom (i O Bridgewater Germany 3 Brittania United Kingdom 4 Brunto Nonway 5 Calanda Switzerland 1 Canadian Explorer United Kingdom 3 Canforces Tracker Canada 2 CapeCornwall Japan 3 Cape Lance Registry Unknown 2 2 Cape Roger Cape Syros Caribou Canada 2 < oreece Liberia I 3 2 Carsten Russ Panama 4 2 Cast Caribou Liberia 1 Cast Husky United Kingdom 1 Cast Muskox United Kingdom 6 Cast Polar Bear Liberia 2 15 Cast Salmon Poland 1 Century Hope United Kingdom 1 Chemspan Trinidad 1 1 City of Perth United Kingdom 4 7 Clymene United Kingdom 8 Colditz Germany 5 Crown Promise Liberia 3 Cyrena France 1 47 Appendix A (cont'd.) International Ice Patrol SST and Ice Reports for 1984 Ship's Name Dart Britain Dan Continent Dart Europe Dart Tiritian Dauogulf Dilderdijk Dole Vega Eastern Harjel Eastern Shell Edough Elareg Eleusis Elisabeth Elmina Erika Bolten Europe GB Falcon Falkoen Fanny Fames Federal Danube Federal Maas Federal Ottawa Federal Pioneer Federal Schelde Federal Thames Finn rose Fivestar Fogo Isle Fort Kipp Fort Ramezay Fort Steele Fossnes Frank Schroder Frimaro Gaviota General Dabrowski General Luma Golarl Petrosun Gulf Mackenzie sHalifax Hampton Lion Relate Helen Schulte Heritage Hohn USCGC HORNBEAM Hudson Hual Traveller Hunter Bow Husky Hydrolock Iguazu Imperial Quebec Ingua Pilot Invincible Irving Elm Country of Registry Colombia Czechoslovakia Belgium United Kingdom Phillipines Netherlands Antilles Brazil Colombia Czechoslovakia Algeria Canada Burundi Liberia Greece Panama Belguim Norway Sweden United Kingdom Liberia Belguim Belguim Belguim Union of Soviet Socialist Republics Liberia Belguim Finland Liberia Canada Great Britain Canada Great Britain Norway Germany Cuba Germany Poland Phillipines Liberia Canada Greece Liberia Panama Netherlands Greece Germany United States of America Canada Norway Liberia Panama United Kingdom Liberia Canada Panama United Kingdom Canada Ice Reports 1 2 1 3 1 1 1 3 3 1 1 1 1 4 1 1 1 3 1 1 1 5 1 SST Reports 1 3 1 2 2 3 1 1 1 7 15 1 1 1 2 1 4 1 1 4 12 3 2 2 1 3 2 14 8 3 48 Appendix A (cont'd.) International Ice Patrol SST and Ice Reports for 1984 Country Ice SST Ship's Name of Registry Reports Reports Irish Spruce ,,,,:.,,:,,,r,,,.,:^:.,:^,,,:^ ...........1.,,., Irving Forest United Kingdom 1 Irving Nordic Canada 1 Irving Ours Polaire Canada 2 Islander Malta 2 Ivan Derbenev Union of Soviet Socialist Republics 1 Jena Germany 4 JohnM Germany 5 1 Joseph Roty France 1 Judson Canada 1 Juventia Panama 5 Kemano United Kingdom 1 Kansas Getty Bahamas 10 Kapetan Yannis Greece 3 Katerina France 1 Koein Express Germany 1 Konkar Indo Kitable Greece 7 KurashimaMaru Japan 3 Labrador Canada 1 Lady Saunders Canada 1 Lake Anne Norway 2 Lake Biwa Chile 3 1 Lakeanina Nonway 1 Lalberte Liberia 2 Lantau Singapore 1 Leon Et Pierre Belguim 1 Lokvihar India 8 1 Lorena Spain 1 Louis L D. France 2 15 Louis S. St-Laurent Canada 1 Lousdrecht Netherlands 1 Ludoluf Oldendorff Singapore 2 Lumaaq Canada 1 Madeleine Great Britain 3 Maersk Triton Liberia 1 Mahone Bay Canada 1 Malabar Registry Unknown 1 2 Manchester Challenge United Kingdom 33 3 Marinz L Greece 1 Masovia Liberia 6 Mega Bay Norway 1 Mela Indonesia 3 Meltimi Greece 6 7 Mesange Canada 1 Michalis Greece 1 2 Mihalis Greece 2 MimiM Greece 2 Minerva Brazil 1 Mosbrook Norway 2 Moutsqina Greece 3 Myuta Panama 1 N. M. Engin Turkey 1 ■ Nautic Pioneer Liberia 1 Navimart Canada 2 Nihonkaimaru Japan 1 Noble Supporter Liberia 7 Nordstrand Burundi 1 49 Appendix A (cont'd.) International ice Patrol SST and Ice Reports for 1984 Country Ice SST Ship's Name of Registry Reports Reports USCGC NORTHWIND United States of America 69 25 Nyuta Panama 1 Olinda Singapore 1 Oriental Ruby Japan 9 Pacific Ciialienge United Kingdom 1 Pacific Courage United Kingdom 4 Pacific Freedom Liberia 1 Pacific Friendship Liberia 1 Pacific Progress United Kingdom 1 Palmstar Orchid Singapore 1 Pampero Panama 2 8 Panama Denmark 9 Parita Finland 4 Penmen France 3 9 s Perth United Kingdom 1 Permnitz Germany 4 Pharos Germany 3 Philippeld France 1 Pokkinen Finland 1 Polar Circle Canada 2 Polaris Togolese Republic 5 Precious Liberia 2 2 Premwitz Germany 1 Princess Panama 1 Primorsk Union of Soviet Socialist Republics 1 Queen Elizabeth II United Kingdom 3 : Rannoe Finland 6 Rebeka Romania 3 Regina Switzerland 2 Reynolds United Kingdom 7 Rich Alliance Panama 1 Rigoletto Sweden 3 Roman PazinskI Poland 3 Rubens United Kingdom 6 Ryokomaru Japan 1 Satu Mar Singapore 2 Schnoorturm Great Britain 1 Seaforth Atlantic Canada 1 Sealand Independence United States of America 1 Sealand Leader United States of America 1 Sealand Vokager United States of America 1 Sealve Sweden 1 Sekirex Japan 2 Shanadith 2 Registry Unknown 1 Shenandoah Greece 1 ShinreiMaru Japan 1 Smelly Union of Soviet Socialist Republics 1 USNS SOUTHERN CROSS United States of America 18 13 Steam Bollard Liberia 2 Stefan Batory Poland 7 Stefan Starzynski Poland 3 Stolt Castle Liberia 3 1 Stolt Sydness Liberia 2 2 Stovetrader Sweden 1 5 String Bridge ^.. Panama 6 Studlasfoss Iceland 2 50 Appendix A (cont'd.) International Ice Patrol SST and Ice Reports for 1984 Country Ice SST Ship's Name of Registry Reports Reports Takeshimamaru Japan Temse Belguim 1 Tatucareer Panama 1 Terra Nova Greece 3 Texaco Massachusetts United States of America 2 Transocean Transport Phillipines 2 Ungava Transport Canada 1 United Venture Singapxjre 1 Varjakka Finland 2 18 Vasiliki Greece 1 ;: Vasya Korokbo Ukranian Soviet Socialist Republics 1 Velizh Union of Soviet Socialist Republics 1 Vera Maretskaya Union of Soviet Socialist Republics 1 Verge Canada 8 Victor Bugaey Union of Soviet Socialist Republics 1 Vissani Panama 1 Vitosha Bulgaria 1 1 Viva Nonway 1 Vladimir Timofeyev Union of Soviet Socialist Republics 1 Watergeus Netherlands 3 Western Viking Panama 2 Western Harbour United States of America 3 WilfredTempleman Canada 1 World Agamemnon Greece 4 World Dawn Panama 1 Willow Peak Chile 1 Yevgenit Vaktangov Union of Soviet Socialist Republics 1 1 Yukona Liberia 4 1 Yukona Union of Soviet Socialist Republics 1 111 Zagreb Canada 1 Ziemia Bitostocka Poland 3 M^. Zim Geneva Israel 1 Zimberia Israel 1 51 Appendix B Introduction Forthe first time since 1978, International Ice Patrol conducted hydrographic measurements on the Grand Banks (the data report is still to be published). The cruise was divided into two parts; the first dedicated to a hydrographic survey, and the second to iceberg drift and deterioration. Due to an inoperative Ocean Sampling System (OSS), the hydrographic section of the cruise was conducted using Nansen casts. During the 1984 season, eleven satellite- tracked TIROS Oceanographic Drifters (TOD) were deployed in the IIP operating area. Nineof theTODs were deployed from an HC-1 30 aircraft during regular ice reconnaisance flights. The remaining two TODs were deployed from the USCGC HORNBEAM, the vessel used to conduct the IIP cruise. The two TODs deployed from HORNBEAM had been recovered after the 1983 season and were reconditioned and then deployed. Oceanographic Conditions on the Grand Banl tr e E X ra 60 40 20- 0 — July 1 Predicted Remaining Length Actual Length Observed wave height ? 0 () 1 1- w 0 03 22 July attitude to the wave field. The iceberg we observed rolled at least seven times in five days. Each time it rolled, a different section of the iceberg was exposed to wave erosion, therefore requiring their integration scheme to start over. Since iceberg rollover cannot be modelled, calving will not be included in our model until an acceptable scheme is available. This will allow the predictions from our model to remain on the conservative side. Radar ranges and bearings to the iceberg and HORNBEAM'S position as determined by LORAN-C were recorded every hour. The geographical position of the iceberg was then determined. On1 7 July, TOD #2632 was deployed within 400m of the iceberg in position 48°37.4'N 46O06.rW. The TOD drifted to the northeast at a speed slower than the iceberg. After five days, the TOD was located 1 6.5 nm away and bearing 252°T from the iceberg (Figure B-10). This is approximately upwind (using the average wind for the period) of the iceberg, indicating the difference between the iceberg and the TOD may be due to the different leeway of the iceberg and the drift buoy. The initial sighting position of the iceberg was entered into HP's iceberg drift model and allowed to drift until OOOOZ 22 July. FNOC winds and unmodified historical currents were used as the environmental inputs to the model. The maximum difference between the actual and predicted position of the iceberg was 7.2 nm and occurred 30 hours after the sighting. The error after five days was only 4.3 nm (Figure B- 11). This preliminary analysis of the drift data is encouraging because the accumulated error was so small. Further analysis of this and other iceberg drift data still needs to be done. 66 Conclusions The cruise has answered part of the question posed concerning the TOD's ability to follow the geostrophic flow. The data indicates that a TOD will follow the geostrophic flow as long as the drogue is below the thermocline. Fornext season, IIP intends to lengthen the drogue tethers on the buoys to 50m to place the drogues consistently below the surface layer and the thermocline in the area north of 43°N (Scobie and Schultz, 1976). This plan would eliminate the step of removing wind-driven current from the TOD motion to calculate geostrophic current. The comparisons of FNOC winds conducted in both 1 983 and Figure B-10. Actual iceberg and TOD drift from 17-22July.. The predicted iceberg motion is from the International Ice Patrol drift model. The model drift was begun on 16 July and all predicted motion is from this initial sighting. Tick marks are at OOOOZ each day. 49-OON 48-30N TOD Drift Observed Drift Predicted Drift 46-30W 46-OOW 45-30W 45-OOW Figure B-1 1 . The iceberg Drift model error plotted vs total distance the iceberg drifted. The iceberg was drifted continuously by the model from its initial sighting position on 16 July 1 984. 60 -, 50 Distance Drifted Since initial sighting 40 30 ra 5 20 -I 10 60 80 Hours after sighting 140 67 References 1 984 have indicated that the FNOC velocities are consistently too large. This was an added error source in computing geostrophic current motion using the existing method. By using a 50m tether and eliminating the step of removing the wind driven current, the new TOD motion should more closely measure the geostrophic current in our operating area. 1 1 P intends to continue using TODs to modify the historical current field on a real-time basis. The experiment of a TOD following the geostrophic current will be repeated on future hydrographic cruises using a CTD system rather than Nansen bottles to measure the water column characteristics. The results from the iceberg deterioration study are very encouraging, but our data set of one is not large enough to draw any conclusions. The deterioration model will be used in its present form, and a total deterioration percentage of 1 75% of the original length will be used as the point where deletion from the active iceberg list will be considered. IIP does not plan to make further changes to our iceberg drift model before next season. IIP plans to evaluate the drift model using the drift data obtained from HORNBEAM, datafromTIROS Arctic Drifters aboard icebergs during the 1983 season, and other sources. This analysis should allow IIP to evaluate the estimates of the model's error. Anderson, I. (1983a); "Oceanographic Conditions on the Grand Banks During the 1983 International Ice Patrol Season", Report of the International Ice Patrol Service in the North Atlantic Ocean, CG-1 88-38, p. 81 - B16. Anderson, I. (1983b); "Iceberg Deterioration Model", Report of the International Ice Patrol Service in the North Atlantic Ocean, CG-1 88-38, p. C1-C8. El-Tahan, M.; S. Ventatech; and H. El-Tahan (1984): "Validation and Quantitative Assessment of the Deterioration Mechanisms of Arctic Icebergs", Proceedings of the Third International Offshore Mechanics and Arctic Engineering Symposium, p. 1 8- 25. Kollmeyer, R.C.;T.C. Wolford; and R.M.Morse (1966): "Oceanography of the Grand Banks Region of Newfoundland in 1965), U.S. Coast Guard Oceanographic Report No. 11, CG-373-11,p.157. McNally, (1981); "Satellite Tracked Drift Buoy Observations of the Near-Surface Flow in the Eastern Mid-Latitude North Pacific", Journal of Geophysical Research, Vol. 86(C9), p. 8022- 8030. Scobie, R.W. and R.H., Schultz (1976); "Oceanography of the Grand Banks of Newfoundland, March 1971 - December 1972", U.S. Coast Guard Oceanographic Report No. 70, CG 373-70, p. 298. Shuhy,J.L(1981); "Oceanographic Conditions on the Grand Banks During the 1981 International Ice Patrol Season", Report of the International Ice Patrol Sen/ice in the North Atlantic Ocean, CG-1 88-36, p. A1 ■ A3. Soule, P.M. (1964); The Normal Topography of the Labrador Current and its Environs in the Vicinity of the Grand Banks During the Iceberg Season, WHOI Publication 64-36, p. 17. 68 Appendix C Effects of Side Looking Airborne Radar (SLAR) on Iceberg Detection During the 1983 and 1984 International Ice Patrol Seasons Lieutenant (jg) Neal Thayer, USCGR Introduction Discussion The AN/APS-135 Side-Looking Airborne Radar (SLAR) was introduced to international Ice Patrol (IIP) reconnaissance flights at the beginning of the 1 983 IIP season, the first continuous operational use of SLAR by IIP. The AN/APS-135 is a replacement forthe AN/APS-94D SLAR which was occasionally used by IIP on an experimental basis starting in 1 976. With this more powerful AN/APS-1 35 SLAR, visual reconnaissance was replaced by SLAR as the main search method, and reconnaissance coverage of the IIP region was significantly increased. Since the IIP region is an area of frequent heavy fog and bad weather, the all-weather capability offered by SLAR increased both the number of days that IIP could conduct reconnaissance flights and the amount of reconnaissance coverage of search areas under conditions of intermittent visibility. In addition, longerflights became possible with SLAR, and regular reconnaissance of the eastern part of the region began. This increased capability is evident in that prior to the 1 983 season, it was necessary to maintain an Ice Reconnaissance Detachment (ICERECDET) in Newfoundland continuously during the IIP season, while in 1 983 and 1 984, ICERECDET's were deployed every other week with the same number of flight hours as in previous years. The introduction of SLAR constitutes a major change in the IIP iceberg detection techniques. An important question arises from this change. What effect does SLAR have on the number of icebergs south of 48°N, the traditional indicator of the severity of an iceberg season? This question is addressed in Part b. of the following section using the IIP data base forthe years 1960 through 1984, data contained in the IIP historical data file. Part a. is a brief discussion of the effect on the number of icebergs estimated south of 48°N due to the introduction of the iceberg drift prediction model (IBERG) to International Ice Patrol operations in 1979. In 1900, the U.S. Naval Hydrographic Office began estimating the number of icebergs passing south of 48°N as a measure of the severity of each iceberg year. The International Ice Patrol, with its beginning in 1914, continued to keep records of this number. Prior to 1983, the mean annual number of icebergs south of 48°N was 364, with a range from 0 in 1 966 to a record of 1 584 in 1972. The number of icebergs south of 480N was 1348 in 1983, representing the fourth highest number on record, and 2202 in 1984, the new record. Given the increased iceberg detection capability offered by SLAR, it seems possible that these elevated figures for 1 983 and 1 984 are primarily the result of SLAR reconnaissance. As a result, comparing the 1 983 and 1 984 numbers of icebergs south of 48°N directly with those of previous years might provide a misleading indication of the severity of these two seasons. 69 a. Iceberg Drift Prediction Model In investigating tiie effect of SLAR, it was first necessary to assess the possible impact of tlie IBERG drift and deterioration model on the number of icebergs estimated south of 48°N, with its introduction to IIP operations in 1979. Any significant effect on the number of icebergs estimated south of 48°N would necessitate treating the IBERG and pre- IBERG data separately in the SLAR analysis. The IBERG impact was analyzed by comparing the number of icebergs south of 48°N with the number of sightings south of 48°N. Table C-1 shows the number of non-growler sightings south of 48°N from the International Ice Patrol historical data file for 1 960 through 1 984. Since the number of icebergs estimated south of 48°N does not include growlers, growler sightings were removed from the data. The ratio of non-growler sightings south of 48°N to icebergs estimated south of 48°N has three groups of values with significantly different ranges: prior to 1965 (9.9to 16.4), 1965 through 1978 (0 to 39.8), and after 1978 (90.5 to 800). The change in this value in 1965 is not explicable through any change in methods mentioned in International Ice Patrol records. After 1979, the change in this ratio was due to the introduction of the iceberg drift prediction model (IBERG) to International Ice Patrol operations. It is important to note that the ratio increased dramatically in 1979, and that in 1 980, the "sense" of the ratio changed; that is, the number of icebergs south of 48°N became greater than the number of sightings received. With the introductbn of this model, the number of icebergs south of 48°N became an estimate based on both sighting reports received south of 48°N and icebergs drifted south of 48°N by the model. The model also made it possible to more accurately determine if a report was a resight of an iceberg or an original sighting. Since some resighting was done before IBERG, the net effect of introducing the model should be to increase the number of icebergs south of 48°N, due to the icebergs drifted across 48°N by the model. Examination of Table C-2 , however, shows no significant change in the relationship between icebergs south of 48°N and the iceberg sighting ratio, a measure of iceberg season severity discussed in Part b. Therefore, IBERG and pre-IBERG data will be combined in the following analysis of the effect of SLAR on IIP iceberg detection. b. Icebergs South of 48°N In this section we seek to evaluate the impact of SLAR on the 1 983 and 1 984 seasons by establishing an alternate indicator of the severity of an iceberg season. Overthe years, ships transiting the IIP region have furnished regular sea surface temperature (SST) reports and sighting reports for any iceljergs encountered. These ship reports provide a sample of iceberg population data which is independent of IIP detection techniques. Since the numljer of iceberg reports received is dependent on both iceberg density in the shipping lanes and the amount of maritime traffic, the number of reports alone cannot be used to indicate the severity of an iceberg year. Ships making SST reports, assumed to be the nrwst consistent iceberg reporters, make their SST reports in numbers independent of iceberg density and provide a measure of the annual traffic. Therefore, by dividing the number of ship iceberg reports by the number of ship sea surface temperature reports, a term representing iceberg density, independent of traffic, is obtained. (Regression analysis of SST reports versus icebergs estimated south of 480N for 1 970- 82 yield an F value of .004, cleariy demonstrating independence, assuming nomrial distribution.) We will call this term the iceberg sighting ratio. Although the iceberg sighting ratio is independent of the 70 amount of traffic, it is sensitive to the marine traffic patterns in the IIP region. Throughout the iceberg season, typically March through June, ship traffic passes through the area south of the Grand Banks between latitudes 48°Nand440N. Late in the season, when the Straits of Belle Isle become ice-free, a large amount of traffic transits the northern part of the International Ice Patrol area, north of 50°N. This paper assumes that this traffic pattern does not vary widely from year to year and gives a consistent annual sample of the iceberg population in the IIP area. The number of icebergs encountered by ships in the southern traffic lanes is assumed to have a direct relationship to the numberof icebergs south of 48°N that year, dependent on the amount of traffic. It is further assumed that the number of icebergs sighted and reported by ships in the northern traffic lanes is related to the number of icebergs passing south of 48°N and that this relationship does not vary widely from year to year. These assumptions regarding the relationship of iceberg sightings to the number of icebergs south of 48°N have two weaknesses. First, during especially light or heavy iceberg years, the normal traffic pattern is disturbed. Presumably, even though shipping tracks may be displaced to the north or south during these years, the relationship between iceberg density and the probability of iceberg sighting by individual ships should not be Table C-1 Icebergs South of 48°N: South of 48° N Icebergs Year Est. 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 253 117 120 25 369 76 0 441 226 57 85 73 Sightings, All Sources 1538 1286 1072 163 3712 277 13 1448 719 171 324 222 Ratio i^t XI 00) Sighting 16.4 9.1 11.2 15.3 9.9 27.4 0.0 30.5 31.4 33.3 26.2 32.9 Year 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 Estimated vs Sightings South of 48°N Ratio Icebergs Sightings, (Est x^qq> Est. All Sources sighting 1548 850 682 101 151 22 75 152 24 63 188 1348 2202 3978 2980 3355 331 454 84 341 168 3 26 70 620 1106 39.8 28.5 20.3 30.5 33.3 26.2 22.0 90.5 800.0 242.3 268.6 217.4 198.3 greatly affected, since ships will tend to travel through waters of "normal" (i.e., low) iceberg density even in abnormal years. Second, as icebergs drift south from the northern lanes, they are subject to varying environmental conditions (sea surface temperatures, wave heights, winds and currents) that affect iceberg deterioration and transport. The fraction of the icebergs sighted in the northern lanes that eventually reach 48°N varies with these changing environmental conditions. However, since these environmental conditions usually follow predictable seasonal patterns and long-term variations from seasonal norms (e.g., 1972 and 1966) are rare, it is reasonable to assume that the relationship between the number of sightings in the northern lanes and the number of icebergs south of 48°N does not vary widely. Table C-2 contains totals of ship iceberg and SST reports, numbers of sightings south of 48°N from the International Ice Patrol historical data file (which contains information for 1960 through 1984), and the computed iceberg sighting ratio for each year. It is important to point out that ships often report more than one iceberg sighting on a single report. The term "ship iceberg reports" in Table C-2 represents the total number of 71 ship iceberg reports received by International Ice Patrol throughout the IIP area tor any given year, while "sightings south of 48°N" is the total number of sightings south of 48°N from all sources recorded as individual icebergs at IIP. Icebergs estimated south of 48°N are the total number determined by the International Ice Patrol to have actually passed south of 48°N during the season and reported in the annual Ice Bulletin. There is an abrupt change in the iceberg sighting ratio in 1970, which could be attributed to the disestablishment of Coast Guard Radio Station Argentia in 1969. Since 1970, the International Ice Patrol has broadcast daily ice bulletins and facsimile charts to ships from Coast Guard Communications Station Boston, but has no direct communications with vessels transitting the Grand Banks. This lack of direct contact is believed to be the cause of the significant decrease in the number of SST reports received by the International Ice Patrol. Sea surface temperature reports decreased by a factor of 1 4 in the mean annual number between the two periods. Therefore, these two periods will be treated independently in this analysis. Table C-2 also shows that the previous record year of 1972 still holds the record as the most severe iceberg year on record if the iceberg sighting ratio is used as the evaluating criterion. Using this criterion, 1984 is unquestionably a severe iceberg year, but not as severe as 1 972. Table C-2 Icebergs South of 48° N vs. Iceberg Sighting Ratio South of 48 °N Iceberg Icebergs Sightings, Ship Iceberg SST Sighting Ratio % Year Estimated All Sources Reports Reports (Berg RPT/SST) 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 253 117 120 25 369 76 0 441 226 57 85 73 1584 850 682 101 151 22 75 152 24 63 188 1348 2202 1538 1286 1072 163 3712 277 13 1448 719 171 324 222 3978 2980 3355 331 454 84 341 168 3 26 70 620 1106 1008 928 1077 251 1362 227 51 524 384 139 439 162 1151 842 540 197 312 316 399 183 40 39 92 148 586 7436 8342 7916 4633 9147 6347 1592 3194 2271 1985 1014 159 432 381 215 260 297 257 478 397 215 302 434 334 353 13.6 11.1 13.6 5.4 14.9 3.6 3.2 16.4 16.9 7.0 43.3 101.9 614.0 191.4 179.5 77.9 59.3 117.1 68.4 46.6 34.8 17.4 21.2 44.3 166.0 Although the 1 983 number of 1 348 icebergs south of 48°N makes it appear as a very severe year, the iceberg sighting ratio suggests that it is a light year. Comparison to 1 975, the median year with respect to icebergs south of 48°N, indicates that 1 983 would have fewer icebergs south of 48°N than that year and that 1 984 would have more. Figures C-1 and C-2 show plots of the iceberg sighting ratio versus icebergs south of 48°N for the periods 1960 through 1969 and 1 970 through 1 982 and the linear regression fits of those data. In Figure C-2, the iceberg sighting ratio has been adjusted by removing iceberg sighting and SST reports received from Coast Guard vessels from the data. Coast Guard vessels, when deployed in the IIP area, typically contribute a significant number of iceberg and SST reports to IIP. They do not operate within the normal traffic pattern described above, often actively search for icebergs and have operational requirements to submit regular SST reports, all of which might bias the Coast Guard component of the iceberg sighting ratio. The number of reports contributed by individual vessels, including Coast Guard vessels, was not recorded in the International Ice Patrol Bulletin priorto 1972 so this adjustment could not be made to eadier data. Using the regression fit shown and the 72 Figure C-1 Plot of iceberg sighting ratio vs icebergs south of48'N for 1960 through 1969 with linear regression fit of the date 6 8 10 12 14 Iceberg Sighting Ratio (%) 1960 - 69 16 18 Figure C-2 Plot of iceberg sighting ratio vs icebergs south ofAS'N for 1970 through 1982 with linear regression fit of the data. Iceberg sighting ratios for 1983 and 1984 are shown with the predicted numbers of icebergs south of 48' N for those years and their 95% confidence intervals. § 3 O CO E o 100 200 300 400 500 Iceberg Sighting Ratio (%) 1970 - 82 600 700 73 Conclusion iceberg sighting ratios for 1 983 and 1984, the solved-for values are 1 02 (W- 483 at the 95% confidence level) and 430 (+/- 41 7 at the 95% confidence level) , respectively. The data clearly shows the existence of a SLAR effect for both years, since the number of icelsergs estimated south of 48°N each year far exceeds the values predicted by the iceberg sighting ratio, even at the upper limits of the 95% confidemce interval (Figure C-2). Given the small number of observations (n=1 3) used in performing this analysis and the large confidence intervals (due in part to the scatter of the data) , this estimate only denranstrates that the effect of SLAR on iceberg reconnaisance exists and should not be used to compare the SLAR and pre-SLAR data numerically. In addifion to improved iceberg detection with SLAR, the increase may also be partly caused by misidentification of non-iceberg targets as icebergs, due both to unfamiliarity with the new technology and the inherent ambiguities of SLAR imagery. It is important to note that data presented throughout this appendix was collected and analyzed overthe years by a constantly changing International Ice Patrol staff, using techniques that undoubtedly varied somewhat with the tumover in personnel. Therefore, this data should be examined with that caution in mind. 74 The effect of introducing the iceberg drift prediction model (IBERG) to International Ice Patrol operations on 1 979 was analyzed by examining the relationship of icebergs estimated south of 48°N to iceberg sighting reports south of 480N for 1960 through 1984. These values had a close linear relationship for the years 1965 through 1978 and their ratio showed a marked increase with the introduction of the model. But since the relationship of the number of icebergs estimated south of 48°N due to the iceberg sighting ratio appeared to be unchanged after 1979, we assume that the effects of the side-looking airtwrne radar (SLAR) on the number of icebergs estimated south of 48°N are much greater than those of the IBERG nrwdel. The introduction of SLAR to IIP in 1983 significantly changed the nature of IIP iceberg reconnaissance. Reconnaissance no longer depended on visibility, complete coverage of search areas was possible under conditions of intermittent visibility, and longer flights made it possible to search the outlying areas of the IIP region. These improvements, together with possible misidentification of non-iceberg SLAR targets due to inexperience and the limitations of SLAR imagery resulted in elevated estimates of icebergs south of 48°N in 1 983 and 1 984. This conclusion is supported by relating pre-SLAR numbers of icebergs south of 48° N with the ■iJr U. S. GOVERNMENT PRINTING OFFICE: 1986--600-8'46 --20 , 197 corresponding values for 1 983 and 1984. These values were compared using the ratio of the ship iceberg reports and the ship SST reports, an iceberg density function called the iceberg sighting ratio. The apparent increase in iceberg detection due to SLAR is by an order of magnitude in 1 983 and by half that in 1984, with large confidence intervals at the 95% confidence level. The analysis of the effect of SLAR reconnaissance presented here provides only a preliminary investigation of the issue. In no way can an evaluation of two years of SLAR data identify the long-term effect of SLAR on IIP operations. Neithercanit adequately place the 1983 and 1 984 icet)erg seasons in the context of the previous years of HP history. It is clear that SLAR has increased the number of icebergs detected by IIP and that with several more years of SLAR data, and with the research currently being conducted on iceberg detection and identification by SLAR, we should be able to address this issue with more confidence. U.S. Department of Transportation United States Coast Guard Report of the International Ice Patrol in the North Atlantic 1985 Season Bulletin No. 71 CG- 188-40 Marine Biological Laboratory ; LIBRARY j AUG 1 9 1987 Woods Hole, Mass. J International Ice Patrol US Department of Transportation lMt9d Slulvs Coast Guard W ^ Commandant mailing address G-OIO Uniled Slates Coast Guard u. S. COAST GUARD WASHINGTON, D.C. 20593-0001 (202) 267-1458 ' 7 MAR 1887 Bulletin No. 71 REPORT OF THE INTERNATIONAL ICE PATROL SERVICES IN THE NORTH ATLANTIC OCEAN Season of 1985 CG-188-40 Marine Biological Laboratory LIBRARY AUG 19 1987 Woods Hole, Mass. FOREWORD Forwarded herewith is bulletin No. 71 of the International Ice Patrol describing the Patrol's services, ice observations and conditions during the 1985 season. ^^^yp^^^^ DISTRIBUTION - SDL Nol 124 a b c d e f g h 1 ) k 1 m n 0 P q r s t u V w X Y 2 1* 1* 1 1 1* 1^ 1* 1* 1 10 2 2 5 1 1* 1* 60 NONSTANDARD DISTRIBUTION: *A;abf"gh LANTAREA only *B;b LANTAREA (5); *C:aq LANTAREA only SML CG-4 B;b PACAREA (1) International Ice Patrol 1985 Annual Report Contents 2 3 5 6 41 43 43 45 53 56 68 79 85 Introduction Summary of Operations, 1985 Iceberg Reconnaissance and Communications Environmental Conditions, 1985 Season Ice Conditions, 1985 Season Discussion of Icebergs and Environmental Conditions References 44 Acknowledgements Appendices A. List of Participating Vessels, 1 985 B. Iceberg / Ship Target Discrimination with SLAR C. Oceanographic Conditions on the Grand Banks, 1 985 D. Evaluation of the International Ice Patrol Iceberg Drift Model E. Eddy Formation in the Vicinity of the Grand Banks F. SLAR Detection of Ocean Features Introduction This is the 71 ^t annual report of the International Ice Patrol Sen/ice in the North Atlantic. It contains information on ice conditions and Ice Patrol operations for 1985. The U.S. Coast Guard conducts the International Ice Patrol Service in the North Atlantic under the provisions of Title 46, U.S. Code, Sections 738, 738a through 738d; and the International Convention for the Safety of Life at Sea (SOLAS), 1974 regulations 5-8. This service was initiated shortly after the sinking of the RI^S TITANIC on April 15, 1912. Commander, International Ice Patrol under Commander, Coast Guard Atlantic Area, directed the International Ice Patrol from offices located at Groton, Connecticut. The unit analyzes ice and environmental data, prepares the daily ice bulletins and facsimile charts, and replies to any requests for special ice information. It also controls the aerial Ice Reconnaisance Detachment and any surface patrol cutters when assigned, both of which patrol the southeastern, southern, and southwestern limits of the Grand Banks of Newfoundland for icebergs. The International Ice Patrol makes twice-daily radio broadcasts to warn mariners of the limits of iceberg distribution. During the 1 985 season. International Ice Patrol reconnaissance was conducted by U. S. Coast Guard HC-130 aircraft equipped with Side- Looking Airtwme Radar (SLAR), operating from Gander, Newfoundland. No U. S. Coast Guard cutters were depbyed as surface patrol vessels this year. There were 1 ,063 icebergs estimated south of 48°N this year, the traditional measure of the severity of an IIP season. Vice Admiral P. A. Yost was Commander, Atlantic Area from the start of the 1 985 season, 1 4 March until its end on 29 August 1985. Commander Norman C. Edwards, Jr., U.S. Coast Guard, was Commander, International Ice Patrol during the Ice Patrol season. Summary of Operations, 1985 From 14 March to 29 August 1985, the International Ice Patrol (IIP), a unit of the U.S. Coast Guard, conducted the International Ice Patrol Service, which has been provided annually since the sinking of the RMSTITANIConAprillS, 1912. During past years, Coast Guard ships and/or aircraft have patrolled the shipping lanes off Newfoundland within the area delineated by 4(fiN - 52PU. 390W - 57**W, detecting icebergs and warning mariners of these hazards. Duringthe 1985 Ice Patrol season. Coast Guard HC- 130 aircraft flew 72 ice reconnaissance sorties, bgging over 507 flight hours. The AN/APS-1 35 Side-Looking Airt)ome Radar (SLAR), which was introduced into Ice Patrol duty during the 1983 season, again proved to be an excellent all- weather tool for the detection of both icebergs and sea ice as demonstrated during the BergSearch *84 experiment (Rossiter, efa/.,1984). On IIP reconnaissance flights alone , the SLAR provided 53 percent of the 1985 sightings. A deployment was made from 20- 25 February to determine the pre- season iceberg distribution. Based on this trip, regular deployments started on 1 2 March with the 1 985 season opening on 14 March. From that date until 29 August 1985, an aerial Iceberg Reconnaissance Detachment (ICERECDET) operated from Gander, Newfoundland one week out of every two. The season officially closed on 29 August 1985. During the 1 985 season, an estimated 1 ,063 icebergs drifted south of 48°N latitude. Table 1 shiows nronthly estimates of the number of icebergs that crossed 48°N. No U. S. Coast Guard cutters were deployed to act as surface patrol vessels this year. The USCGC EVERGREEN and USCGC NORTHWIND were deployed to conduct oceanographic research for the Ice Patrol during the periods 1 0 April - 1 0 May and 1 -9 August. On board EVERGREEN, the IIP iceberg drift and deterioration models were evaluated (See Appendices C and D), hydrographic equipment was evaluated, and a joint IIP/USCG Research and Development Center study of surface craft and iceberg target detection performance by the AN/APS-1 35 SLAR was conducted (Robe, et al., 1985). The NORTHWIND hydrographic cmise was cancelled because of main diesel engine problems on board NORTHWIND. Other research conducted at IIP during 1985 included an analysis of eddy formation in the vicinity of the Grand Banks (Appendix E), an evaluation of iceberg/ship SLAR target discrimination (Appendix B), and a comparison of ocean fronts detected on National Weather Service satellite imagery and IIP SLAR imagery (Appendix F). Table 1. Icebergs South of 48°North Avg Total Avg Total IQflS 1900-85 1900-85 1946-85 1946-85 1 90vl OCT 1 112 0 5 3 NOV 1 121 0 15 11 DEC 1 100 1 20 7 JAN 2 196 2 76 2 FEB 11 945 12 494 57 MAR 42 3628 38 1526 129 APR 110 9476 116 4631 208 MAY 131 11230 104 4147 205 JUN 70 6025 63 2507 247 JUL 26 2219 26 1023 123 AUG 7 625 6 236 39 SEP 3 297 1 ■ 51 32 Annual Total 405 34974 368 14631 1063 As explained in the 1984 Ice Patrol Bulletin (Thayer, 1984), the methodology and technology of iceberg reconnaissance and data analysis have changed significantly overthe past 40 years. A change is evident in the source distribution of iceberg sightings in that SLAR accounted for 78% of the USCG iceberg sightings in 1 984 (49% of sightings from all sources) but only accounted for 53% of USCG sightings in 1985 (13% of all sightings) (Table 2). (An increased emphasis on icebergs by Canadian Atmospheric and Environmental Service flights and an increased contribution by the commercial shipping community account for other changes in the overall figures.) With icebergs more widely dispersed than normal during much of the 1985 IIP season, it was frequently necessary to search the eastern part of the IIP area. To conserve fuel during these long searches, high altitude legs were flown to and from the search areas. Although SLAR was not operated during these high altitude legs, icebergs could still be sighted in large numbers during good weather. These high-altitude fligNs were much more frequent during 1985 than 1984. The large number of USCG visual sightings on these flights, together with the changes in reconnaissance procedures described below, greatly decreased the percentage of USCG iceberg sightings that were SLAR-only during 1985. Further evaluation of SLAR's capability confirms its usefulness in detecting icebergs (Robe, et al., 1 985) and the necessity for specific SLAR iceberg reconnaissance procedures to assist with iceberg/ship target discrimination (Appendix B). Specific changes in SLAR reconnaissance procedures were made to maximize visual confirmation of SLAR targets and aid target identification during 1985. These changes consisted of selecting daily search areas for optimal visibility, subjecting SLAR films to more post-flight analysis and making more use of supporting data from other sources. Table 2 — Sources of IIP Iceberg Reports by Size Sighting Source Growler Small Med. Large Radar Target ToUl %of Total Coast Guard SLAR 65 194 182 113 10 564 13.3 Coast Guard Visual 60 155 177 107 0 499 11.8 Canadian SLAR 17 56 115 21 229 438 10.3 Canadian Visual 19 239 187 65 4 514 12.1 Commercial Radar 7 30 114 33 124 308 7.3 Commercial Visual 122 300 808 279 15 1524 36.0 Mobil Oil Canada. LTD 12 81 98 18 18 227 5.4 Lighthouse/Shore Other 0 4 2 52 13 47 9 28 0 5 24 136 0.6 3.2 Total 306 1109 1741 673 405 4234 100 Table 3 — Aircraft Deployments from 10/1/84 to 9/30/85 Ice Raconnalsance Detachment Deployments Pre-season In-season Post-season Total No. of Hours Flown 29.6 631.0 11.3 671.9 Note: In-season ICERECDET flights include transit and logistics flights to and from Gander during the Ice Patrol season. A significantly large number of logistic flights, 14 sorties and 86.1 hours were conducted. There were 72 sorties dedicated solely to ice reconnaisance with a total of 507.8 flight hours. They are summarized as follows: Number of Flight Month Sorties Hours FEB 4 23.6 MAR 5 38.7 APR 12 85.8 MAY 15 107.5 JUN 13 87.3 JUL 11 83.9 AUG 11 75.7 SEP 1 5.3 TOTAL 72 507.8 Iceberg Reconnaissance and Communications During the 1985 Ice Patrol year (from 1 October 1 984 through 30 September 1 985), 98 aircraft sorties were f town in support of the Intemattonal Ice Patrol. These included pre- season flights, ice observation and logistics flights during the season, and post-season flights. Pre-season flights detemriined iceberg concentrations north of 48*^, necessary to estimate the time when icebergs would threaten the North Atlantic shipping lanes in the vtoinity of the Grand Banks of Newfoundland. During the active season, ice observation flights located the southwestern, southem, and southeastern limits of icebergs. Logistics flights were necessary due to aircraft maintenance problems. Post- season flights were made to retrieve parts and equipment from Gander and to close out all business transactions from the season. U.S. Coast Guard aircraft, deployed from Coast Guard Air Station Elizabeth City, North Carolina, conducted all the aircraft missions. SLAR-equipped HC- 1 30 aircraft were utilized exclusively for aerial ice reconnaissance, and HC-130 and HU-25A aircraft were used on logistics flights. Table 3 (left) shows aircraft utilization during the 1985 season. During the 1 984 season, only 5% of the deployed days were spent on the ground in Gander. In 1985, this figure climbed to 1 4%. After an aircraft mishap in Groton in March, IIP relied on a single SLAR-equipped HC-1 30 for much of the 1 985 season. The increased use of this one aircraft and its SLAR resulted in an increased number of maintenance problems. U.S. Coast Guard Communications Station Boston, Massachusetts, NMF/NIK, was the primary rado station used for the dissemination of the daily ice bulletins and facsimile charts after preparatbn by the Ice Patrol office in Groton. Other transmitting stations for the OOOOZ and 1 200Z ice bulletins included Canadian Coast Guard Radio Station St. John'sA/ON, Canadian Forces Radio Station Mill Cove/CFH, and U.S. Navy LCMP Broadcast Stattons Norfolk/NAM ; Thurso, Scotland; and Keflavik, Iceland. Canadian Forces Station Mill Cove/CFH as well as AM Radio Statton Bracknell/GFE, United Kingdom are radtofacsimile broadcasting stations which used Ice Patrol limits in their broadcasts. Canadian Coast Guard Radio Station St. John's/ VON provided special broadcasts. The International Ice Patrol requested that all ships transrtting the area of the Grand Banks refxjrt ice sightings, weather, and sea surface temperatures via U.S. Coast Guard Communications Station Boston, NMF/NIK. Response to this request is shown in Table 4, and Appendix A lists all contributors. Commander, Intemattonal Ice Patrol extends a sincere thank you to all stattons and ships which contributed. Table 4. Iceberg and SST Reports Number of ships furnishing Sea Surface Terrperature (SST) reports 1 03 Number of SST reports received 505 Number of ships furnishing ice reports 497 Number of ice reports received 673 First Ice Bulletin 1 40000Z MAR 85 Last Ice Bulletin 291 200Z AUG 85 Number of fa<»im4le charts transmitted 169 Environmental Conditions 1985 Season Weather in Labrador and East Newfoundland during the 1985 International Ice Patrol season tended to be colder and dryer than normal during the winter and warmer and wetter than normal during the summer (Table 5). The weather stations listed in Table 5 were selected to give a cross-section of weather conditions throughout the province. The colder than normal rrxjnths of December 1 984 through March 1985 caused an early accumulation of sea ice which expanded south of 43°N and persisted longer than nomnal. This sea ice forced oil drilling rigs off the Grand Banks and protected the icebergs moving into the region. January: With the Iceland Low southwest of its normal position and deeperthan normal (Figure 1 ), the maritimes experienced a strong northerly flow that brought lower than nonnal temperatures. February: The Iceland Low was deeperthan norma! (Figure 2), causing northwest winds to bring in cold continental air, resulting in below normal temperatures and precipitation in Newfoundland and Labrador (Table 5). March: During March, the Iceland Low was southwest of rts normal position (Figure 3), bringing more continental air than normal into the maritimes and lowering temperatures (Table 5). April : Surface pressure was near normal during April (Figure 4). With a westerly flow returning to Newfoundland, temperatures and precipitation were normal (Table 5). May: The Iceland Low was farther west and deeper than normal during May (Figure 5), bringing more marine air into St. John's and greater than normal precipitation (Table 5). June: Flow, normally southwesterly over Newfoundland, was southerly in June (Figure 6), bringing greater than normal precipitation to Gander (Table 5). July : Direction of surface winds was normal in July, but the stronger than normal pressure gradient (Figure 7) caused greater southerly flow, bringing above normal precipitation. August: August temperatures and precipitation were above nomial(Table5). The shape of the isobars in Figure 8 were near normal, but the pressure gradient between a deeper Iceland Low and the Bermuda High caused increased southwest flow bringing in more warm, nrwist air than normal (Table 5). September: With the Iceland Low deeper than normal (Figure 9), a westerly flow dominated, bringing warmer, drier air over the maritimes resulting in above normal temperatures (Table 5). Ice Conditions, 1985 Season Table 5. Environmental Conditions for 1985 International Ice Patrol Season Temp°C o/^ of Monthly Ditf. Total Normal Station Mean from Norm. Precipitation (mm) Precipitation Naitn ^^^::ifffff::f^:^^- ^g ^^2 118.2% OCT 1984 Goose 2.1 0.6 38.7 50.5% Gander 3.8 2.2 59.4 56.7% St. John's 5.0 1.9 80.7 55.5% %of Normal Snowfall 217.9% 62.8% 141.0% 59.1% NOV DEC JAN 1985 FEB MAR APR MAY JUN JUL AUG SEP Nain -4.6 Goose -3.8 Gander 1.0 St. John's 2.8 Nain -17.2 Goose -17.2 Gander -4.3 St. John's ♦2.0 Nain -12.6 Goose -15.6 Gander -7.4 St. John's -5.9 Nain -16.2 Goose -14.5 Gander -7.4 St. John's -5.9 Nain -12.0 Goose -9.3 Gander -5.8 St. John's -5.1 Nain -8.1 Goose -3.2 Gander -0.6 St. John's -0.1 Nain -1.0 Goose 2.8 Gander 5.7 St. John's 4.4 Nain 6.9 Goose 11.0 Gander 11.8 St. John's 10.4 Nain 10.8 Goose 15.5 Gander 17.7 St. John's 17.5 Nain 10.2 Goose 14.6 Gander 14.9 St. John's 13.9 Nain 8.0 Goose 9.9 Gander 11.0 St. John's 11.0 -1.4 0.0 0.8 0.6 •6.5 -4.2 -0.5 -0.5 -3.2 -0.8 •1.7 -1.3 -1.1 0.0 -0.6 -1.4 -1.5 -1.1 -2.7 -3.2 -3.2 -1.5 0.3 1.1 0.4 -2.6 0.5 1.0 0.5 0.3 0.0 0.5 0.3 0.3 1.2 2.0 4.7 0.7 1.4 0.8 4.6 4.9 141.1 117.0 73.6 100.6 67.8 112.5 68.2 109.2 210.7 134.0 96.0 111.6 124.3 25.1 91.4 96.3 124.3 56.5 51.0 102.3 119.6 52.8 86.6 96.2 52.2 66.5 37.2 168.6 22.4 85.8 124.2 88.9 89.6 235.3 107.8 108.8 46.0 153.3 110.0 100.9 60.5 81.6 75.6 54.2 245.8% 155.6% 68.6% 61.9% 119.6% 154.7% 63.0% 67.7% 338.7% 180.1% 88.0% 71 .6% 248.1% 41 .4% 91 .7% 68.7% 224.4% 78.3% 46.3% 77.6% 257.2% 86.3% 92.9% 83.2% 103.0% 104.2% 53.1% 1 65.6% 35.1% 92.2% 154.7% 103.9% 106.0% 223.9% 156.2% 130.9% 148.5% 113.1% 83.0% 96.6% 93.1% 48.4% 263.3% 206.8% 118.9% 50.5% 1 1 1 .3% 194.6% 80.4% 52.7% 291 .0% 293.9% 1 22.5% 102.6% 189.9% 66.7% 108.9% 97.5% 193.3% 146.6% 57.3% 78.6% 253.6% 101.2% 112.1% 125.4% 42.6% 100.0% 88.5% 81.1% 58.1% 91 .9% 0.0% 0.0% 0.0% No snowfall recorded during this month Figure 1. January normal sea level pressure (mb) (1948 — 1970) Sea level pressure (mb) Monthly mean January 1985 L-:. _l^).;;^BA 8 Figure 2. ^rtjiJ/ 7 1 ^K \Ji\ ^^t \ AAA • r*^ 1/ mM ^^^- 1 <^^v^l / ^*< ^\ vi^ — J m -», \ " '01-\l-l i^ (. \x'^'*v\/ 1* &^9^ *v\ •ef^^Y* JAs^'Yv V' ^jr^^*^\ /I 1 M tfjlr— ^ I i ^^ sy>>^ ^S JriS f m ^ ^10l» / 7^ 3 1 hVu. j^ \ / "» /^ ^^/ d — -X^=^ ■" • \ March normal sea level pressure (mb) V. (1948 — 1970) \ 1 ^ ^_^ ^ __ 1 Sea level pressure (mb) Monthly mean March 1985 10 Figure 4. 1 I \ iL^^-^-^^T"!^ JJ4W ^iV~~J L^ II ri/ 1 \\V^'^09 V\ "tfU ^ ^LrTsZf ^^n^rT\~-J~. 1 \ vyj^*"^^. V \ / f^&i yN^^ysC^^^/ Nb /^ y 1 \\\ >v\ / , X >A\S/A ^^ k \/ /v "im/ /I ^^ />>. /A / N\ y \ X,^'^'^^^— ipu\/' 'V — ^ ,\. / —T — -=• V"^a 0 :W\ ■ V^ April normal sea level pressure (mb) (1948 — 1970) Sea level pressure (mb) Monthly mean April 1985 101 GROW 11 Figure 5. May normal sea level pressure (mb) (1948 — 1970) Sea level pressure (mb) Monthly mean May 1985 - lOE- r. ^ 12 Figure 6. June normal sea level pressure (mb) (1948 — 1970) Sea level pressure (mb) Monthly mean June 1985 in ins : ^ y 13 Figure 7. 1 \* I^^JViUV-'"''^ 1 /'>f3M^r~T f:~:^^d' ^^ i A f L-jArfr ^^'^*^^'\^ A XAVV^^ vo) \\ \-"'''ti '^^. - -^vCwi^-Vsr rm N ^^*""&oy""W_ y / V I "^ — r^ v^^^sv"^^^ M^^^^vv^N/yO^*^?<£\ A / /Y^'^v/^ §§M>X>6/^^^->^^ 1\<7 1 ' ^1 / }^ csw \ Jr /\ / xy 7«N. \ / \\ \ T^'^^ J'i}/ A>4-1 ^y^^i^%sV X/jC lD^/v N./ ^vo^ ^V^^M^^m^l -^Y Y^/\" ••?0 *=»'wV2^ M>\ /X7 / 1 \ ft ,-^*.j^^VjS-{ ^ \Za ^^^-"nT y^ ^•'•S/ ^ J/(/ /\A WY V ^ ^\ / ^^^ m ) ^*^ ^^^^^SO^ vx \ •• ' - ^S?P-e — •+~v.... V^ \ ,' July normal sea level pressure (mb) .V-:^\ . X (1948 — 1970) LICIO Sea level pressure (mb) Monthly mean July 1985 incN - jic. ^Htir I icvti MhsuHC ni noHtNiy ncAU ,4* »»•» \ / ••»Q 1... 14 Figures. k \!v X ^Li^-^^^C^'^A ^ f /-wV^-^T^^f*-*.^ "T" 1 X / } 1 \ IV,^ VL 11 \L-**^ y-^ / 1 1 ''^\ ^T'-t/ 1 L.r^■^i . . . >-\ L 1 \ ~A \\Xr^'l^^??^^i-^^ v^y^^ts^ 1 --W oJ ^\55 ion /v ^V>\^\Vy \V ,/V,1fl^ > 1 ) >5) /' >J^^ pjrfA,^ \/S/ /yOv X\l V* o^y^ /' vJKn;. / yuT" pT^^*\y\/^y^/. ^>7 y/*"""*"^ N /^vl .^^s/ jC« X^ 'J I ^^^ j^ ^ j^ y ^^ ■ i/** ^^ 1 \ \/^^^\ / ^_/ '^^\. \ ^>^4^«^ \^^ r-^z-^X V \ . / *• 1009^1/ 7^^^^ \ -W^ /X' / M V \ ^-\^ \ s, X \ . \^-^ J\ / 1 r X Y"~^^s^:9^ ST^^,.,^ ^. a"^ \/^ \ 1 / / /V ^— ^SLT t — *v Ta ^ "\ .^^\ August normal sea level pressure (mb) \ ^'''^'^^^ \ \ y (1948 — 1970) -•"^"^"^ \ y \ Sea level pressure (mb) Monthly mean August 1985 \ sc* icvtL m'cjsuu nt noatNir nCM 06 If IS 15 Figure 9. Sea level pressure (mb) Monthly mean September 1985 N - CU^ ':l«ir K ^ ^ 16 Figure 10. 16 October 1984 50 Sea Ice Free 45 Sea Ice Conditions Sea Ice Limit of all known ice (concentrations in tenths) Greenland Sea Ice Free 60 55 50 65 60 55 50 45 45 17 Figure 11. 13 November 1984 18 Figure 12. 18 December 1984 Sea Ice Conditions 18 December 1984 Sea Ice Limit of all known ice (concentrations in tenths) 60 55 Greenland 50 45 45 19 Figure 13. 15 January 1985 Sea Ice Conditions 15 JAN 85 Sea Ice Limit of all known ice (concentrations in tenths) Greenland 45 60 55 50 45 20 Figure 14. 12 February 1985 Labrador Sea Ice Conditions 12 FEB 85 Sea Ice Limit of all known ice (concentrations in tenths) 60 55 Greenland 65 55 50 45 50 45 21 Figure 15. 12 March 1985 Sea Ice Conditions 12 J1AR 85 Sea Ice Limit of all known ice (concentrations in tenths) Greenland 22 Figure 16. 16 April 1985 55 50 Labrador Sea Ice Conditions 16 APR 85 Sea Ice Limit of all known ice (concentrations in tenths) 60 55 Greenland 45 50 45 23 Figure 17. 14 May 1985 24 Figure 18. 18 June 1985 Sea Ice Conditions 18 JUN 85 Sea Ice Limit of all known ice (concentrations in tenths) 60 55 SEA ICE FREE 45 50 45 25 Figure 19. 16 July 1985 Sea Ice Conditions 16 JUL 85 Sea Ice Limit of ail known ice (concentrations in tenths) Greenland 60 55 55 50 SEA ICE FREE 45 50 45 26 Figure 20. 13 August 1985 Sea Ice Conditions 13 AUG 85 Sea Ice Limit of all known ice (concentrations in tenths) 45 Greenland SEA ICE FREE SEA ICE FREE SEA ICE FREE 60 55 50 65 60 55 50 45 45 27 Figure 21. 17 September 1985 70 65 60 55 50 45 65 60 55 50 ^ 1 SEA ICE FREE 1 Greenland jj » ^"Y \ SEA ICE FREE Labrador P SEA ICE FREE Sea Ice Conditions ^foundfa « • 17 SEP 85 v"^-^ XJl SEA ICE FREE Sea Ice Limit of all known ice (concentrations in tenths) 65 60 55 50 45 60 55 50 45 28 Figure 22. 15 March 1985 52 51° 50° 49° 48° 47° 4C° 4D° 44° 43° 42° 41° 40° 39° 38' 57° 56° 55° 54° 53° 52° 51° 5C'' 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A NUMBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE . SYMBOLS INDICATE ACTUAL POSITIONS. Mill' ' I I 11 I ' rrirr-Vrn i ' ' . : , . I ' , i ; ' i , i 1 1 ' n i i i ' I I 1 1 i ii I I i ' I ii i i 'i i 1 1 i ' i 1 1 i i ' i I M I ' I I I I i ' 1 1 1 i i 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° ▲ BERG FOR 1200 GMT 15 MAR 85 A GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 40° 39° 38° 29 Figure 23. 30 March 1985 57" 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° ^6° 45° 44° 43° 42° 41° 40° 39° 52 51° 50° 49° 48° 47° 40° 44° 43° 42° 41° 40° 39° 38° A NUMBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE . SYMBOLS INDICATE ACTUAL POSITIONS. 1 II II M I I Mill thtt' I I I I I ' I I I I I ' ; : :- I I I M 'ii in iliii TTTTT TTTTr 41° 40° 39° ^ .1 i I M 1-1. 1 -L ' LJ i-LJ Li 1 1 J L I M I L.L 1 -U ' ■ ' • I ■ ■ I ■ Mill I I I I I I I I I 1 I I I I I Mill I | I 1 i I ,1 ^ I ' I I I I 1 T T T 1 ) I M f T I. 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 4 2* 41° 40° 39' A BERG FOR 1200 GMT 30MAR 85 M GROWLER BASED ON OBSERVED AND X RADAR TARGET/CO' "\CJ FORECAST CONDITIONS 38= Figure 24. 15 April 1985 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° 38" A NUMBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE. SYMBOLS INDICATE ESTIMATED POSITIONS. rmr 1 1 1 1 1 I I M I I M I M I I M I I I I I I I I I I I I I I I I I I I I I I I I I I I I I M I I I I I I 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG FOR 1200 GMT15APR 85 m GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 6° 45° 44° 43° 42° 41° 40° 39° 38° 31 Figure 25. 30 April 1985 57» 5» 5y 54^ 53* S2° sr so- 4y 4a* 47* ¥t 45* 44* 43* 42* 4i- 40- ai- 52». . 1 1 ■ ly ■ .^. ■ Iff I'l" " \ M^ k f^ 1 51 ; \j _> 50° 49° 48° 47° 46° 45° 44° 43° 42° /j ESTIM ftTED LIMI r OF SEA 1 CE \ i 10 1 i i t t t t I w h \ X 6 \^ 5 A A i ■:-i A A X A A A 5 M> mf^ i^ 1 k **- i ^ " A A 5 10 it^ty^ \ 4 1 \ t J i\ r ! 4 AX 8 ^A 12 1 t' X '_• — - \ j A 1 AA A' X 11 iJ 1 \ 1 h* 1 "i X 6 ■-■ 1 1 ^ A A* A / ^ 1 1 1 1 1 A / 41° '- ' 1 1 1 -n ■ r ■ t 1 A NUMBER IN A ONE DEGREE RECTANGLE INDICATES!, 1 THE NUMBER OF ICEBERGS IN THAT RECTANGLE . 40° 39° 3R^ - ' SYMBOLS INDICATE ESTIMATED POSITIONS. i ; 1 1 1 1 1 ', ' r I I r I ' 1 ' 1 ] 1 1 1 * 1 ] 1 1 1 ' 't-t- '. . n . . I C .7° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39 o A BERG FOR 1200 GMT 30 APR 8 5 • GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 32 Figure 26. 15 May 1985 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 4l°l40°3 ^_„i 1 1 1 iT — — — rt-r-n — r 11 1 1 1 1 1 1 1 1 M 1 1 Mill Trfc — 1 1 1 IJ 3° ]52° 51° 50° 52° ^ f ■"^^^ MATE D LIK . A 7 Itk. ^ 1 51 50° I / ICE 6 8. ( i 10 5 / / u^ '/ -^ .^ " — *— \12 k *i fiT / 49° }8° -fC° ^ *■ 1m -- ^ ^A^ " \ \ J^^ AIA A i f 49° 48° 47° 46° < Y- f .5 30 12 5. A AA A A / ft' ■-? JS ^ f' ^ 7 'a A i 1 i A 'i 1 ( I' A A A A /' i L* /A J A AA i < /i"" ■ 4° - TO ■ _/ 1 -Vo' 45° 44° 43° A i w A X Ig A \. / > s -/ X A 8 ^AA 11 - £K AX AA 51° 50° 49° -i A^ - AA < A V-^ ^ i 10 A -• A SO" 49° ESTIM ATED LIMI > T OF SEA CE ^ A^ A ' AA 1 A • X 1 AA A I V — -^ A i X 10 7 10 16 20 A 48° /'' ?^ A AA A / .;8° . V J i A / f n- :^ JS \ ^i 7 A 11 12 /^„ 4C' 44^ Uo ■zL^ ( %^ 7 11 i' ■ / -1 1 HO° 145° \ ii4° A X A X < A AA AA A L A / / ' A AA A" AA AX A / 1^ I 43° 42° ^ST-ZA, ^tTd I-IMI X ^^ 1 430 ^2° ^ '^OWt^ "Jce AEA IC ^A \ \ »A A ^A J N 52° 51° 50° 49° 48° ,1 / A ) /7 f .-^ 15 A X / y ^ 1^ ^» A A A A *A A A > / < ■> 6 34 '\ X / 48° •o-^ <^ ;S^ n %" ' m 7 \ ^ A 5 ^A / 47° 46° 45° 44° ft' V^/ ^n ( J 47° 46° 45° 44? f iCL-*^ ( 5 ^20 i A A A A A X 1 1 i 7 ▲ i A A k A 5 ) A A L 6 5 .i /° ^ A A J A^ 43° ^V^ '-'A U j \f? 43° w / '^' 42° "^ '\. 9 42° <,^ m / V 5 » > ' 41° 40° 41° 40° ^ ^ A y ■aQo ^ kll lUDC D IM A nur ncfioc c Dcr TAUft c lur ir ATCQ THE NUMBER OF ICEBERGS IN THAT RECTANGLE. 39° SYMBOLS INDICATE ESTIMATED POSITIONS . 38'* 'iiiir ■ 1 1 1 1 1 ■ 1 1 1 1 J- 1 1 1 1 1 ■ [ 1 1 1 I- 1 : 1 1 1 ■ 1 : , M ■ 1 1 M 1 ■ 1 1 1 1 1 ■ 1 1 1 1 [ iiiii run iiiii — i 1 1 i i win i r r 1 1 mil 38° c 7° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 3S »° A BERG FOR 1200 GMT 30 JUN 85 m GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 36 Figure 30. 15 July 1985 57« S & 55» 54^ 53° 52° Sf 50* <^ 4r 47* 4$- 45' 44*43* 42* 41* 40* 3 52° 51° 50° 49° 46 52' 51' 50° 49° ^ 1?^^*^ 4 5 7 X A^ ^ *»i / y 5 X ^M 4 5 12 10 11 25 16 5 A ^^ 1 1 ^1 ^ 7 * A 9 k 9 5 ~ ^ ■A * 15 11 5 14 7 48° .^ M gfi.''2 1 1 X ▲ i 1 1 47° 4 6° _fti ^ A in |y I 1'^ < A ' ^ 47 46 4? 44 43 42 4 mtA. "'x' 41 ' / tl Ill k 1 . 1 1 5 7^^ / ^ 45° 44° 43° 42° 41° 40° 7 A V" X i ■ '* i. :y ""'i A i t A ./ 1 1 1 i ^ i A 1 Ml V NOWN ICE / >^ X -] 1 1 [ 1 ESTIM 1 ftTED LIMIT ur ^^- 1 1 THE NUMBER OF ICEBERGS IN THAT RECTANGLE. SYMBOLS INDICATE ESTIMATED POSITIONS. 41 40 i 39° ■ 39° \ 38'' 38° 5 7° 5 6° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39 A BERG FOR 1200 GMT 15 JUL 8 5 A GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 37 Figure 31. 30 July 1985 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 4o° 45° 44° 43° 42°. 41° 40° 39' 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° -^R°l III n' 'nil l^ I I I I ' I I I I i'. : I ; I ' I., I I'l I I II 'i I II I 'i iiii'i I M I 'i M II 'ii M I ' 'i i i i A NUMBER IN A ONE DEGREE RECTANGLE INDICATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE SYMBOLS INDICATE ESTIMATED POSITIONS. TTTTT 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG FOR 1200 GMT30JUL85 A GROWLER BASED ON OBSERVED AND X RADAR 1 mKGET/CONTACT FORECAST CONDITIONS 50° 49° 48'' 47' 46" 45° 44? 43° 42° 41° 40° 39° 38° 38 Figure 32. 15 August 1985 p 7° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° ^o° 45° 44° 43° 42° 41° 40° 39° 52° 51° 50° 49° 48° :^ A A i4 5 6 _A_A J \\ r .52° 51° € / A A A A 9 5 7 18 6 i*A 1 / tr \ 7) A A A i X A / 50° 49° 48° < ^. ? »d I A A A Ka ^ k 6 / / us A / "^—^f. -^ M \ "^ f/^ / 47° ft' /J ) / 47° ilo s£^ c ^ ; / 46° \ A >j 46° S^ / 4b°; ^4°; 43°; N \ A / .*o* .-'^ 45° 44° 43° \ \ A L >^^ .^^ X A J t5> X ^• ' ; A NUMBER IN A ONE DEGREE RECTANGLE INDICATES 42°; 41°; 40°; . THF NIIMRFR np inFRFRRS IN THAT RFCTANfil F. 42° S> rMBOL S IND ICATE EST MATE D POS TION S. 41 40° 39°; 39° 38° ° ^^-r^^ 5 7° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39 A BERG FOR 1200 GMT15AUG 85 • GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 39 Figure 33. 29 August 1985 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° I Mil II I IJ 47° 46 45° 4 4° 43° 42° 41° 40° 39' A NUMBER IN A ONE DEGREE RECTANGLE INDICATES" THE NUMBER OF ICEBERGS IN THAT RECTANGLE . SYMBOLS INDICATE ESTIMATED POSITIONS. ^R°mTTTi'i I I ii'i I I II 'iiimS I I I I ' I I I I i'. ; I . I ' I., I I'li I II ' M II I 'i nil' ' i i i 1 1 'i i ii i ' i 1 1 i i ' 1 1 i 1 1 ' i i i i i ' i ittt 52° 51° 50° 49° 48'-' 47' 46" 45° 44? 43° 42° 41° 40° ,39° 38° 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° A BERG FOR 1200 GMT29AUG 85 » GROWLER BASED ON OBSERVED AND X RADAR TARGET/CONTACT FORECAST CONDITIONS 40 Ice Conditions 1 985 Season October - November 1984: Ice formation was delayed in October by warm temperatures (Figure 1 0 and Table 5) . By mid- November, some ice was forming in the Foxe Basin and Frobisher Bay (Figure 11). Freeze-up continued gradually through November and by the end of the month, Ungava Bay and Hudson Strait were completely covered by light ice. Much of Hudson Bay remained ice-free. There were 14 icebergs south of 48°N during October and November, which is unusually high. December 1984: By mid- month, sea ice had fomried south along the Labrador coast and closed the Strait of Belle Isle (Figure 12). It held this position through the rest of the month with some formation beginning in the Gulf of St. Lawrence. The colder temperatures experienced in December (Table 5) and the northerly flow over the region contributed to the advance of ice. During December, 7 more icebergs were sighted south of 48°N. January 1985: By January 15, the southem limit of sea ice had reached the vicinity of Cape Freels (Figure 13). On January 22, the sea ice had reached Cape Bonavista and a tongue of ice was being carried south in the Labrador Current to approximately 48°N 49°W. With continued low temperatures and northerly winds, sea ice fonned rapidly, expanding to the Grand Banks. This provided protection for icebergs moving south and also retarded their drift so that only two icebergs drifted south of 48°N during January. February 1985: On 12 February, a broad expanse of ice was as far south as Cape Race and extended out to 47°W from that point. A tongue of three- to five-tenths first year ice was estimated to extend approximately to 46°N 47°W (Figure 14) which terminated oil drilling operations on the Grand Banks for over 30 days. Sea ice formation progressed rapidly throughout the month and by 26 Febmary an expanse of nine- to ten-tenths first year ice covered the area from midway between Cape St. Francis and Cape Race to approximately 45°N 46°W. Due to the number of sightings in early February, an IIP pre-season flight was made 20-25 February, during which 64 k^bergs were sighted, 57 of which were south of 48°N. March 1985: A bng tongue of ice started forming in the Labrador Current during early March and by 1 2 March had reached 43°N 48°W (Figure 15). The first regular season ICERECDET, planned for 12 March, was delayed until 1 7-27 March by an aircraft mishap in Groton on 1 2 March. There were 1 29 cebergs estimated to have drifted south of 48°N during March and there were 168 icebergs on ptot at IIP on 29 March (Figure 23). April 1985: With near normal temperatures (Table 5) and westerly/southwesterly flow (Figure 4) , the sea ice had receded somewhat by 1 6 April and a small shore lead had opened along the northeast coast of Newfoundland (Figure 16). While on an ceberg reconnaissance flight on 1 5 April, HC-1 30 CG-1 504 dropped a memorial wreath at positon 4r56'N50°14'Wto commenrx)rate the tragic sinking of the RMS TITANIC 73 years earlier. During April, normally a heavy iceberg month, an estimated 208 icebergs drifted south of 48°N and 176 icebergs were on plot on 30 April (Figure 25). May 1985: Sea k:e retreated in May with a region of three- to five- tenths coverage remaining as far south as Cape Freels on 1 4 May (Figure 17). With the receding ice edge releasing k;ebergs to open water, May was a heavy kieberg month, with 205 icebergs estimated to have drifted south of 48°N. This large populatran of icebergs provided a good supply of experimental subjects for the detection , drift and deterioration experiments (Appendices B, C and D). There were 272 icebergs on plot on 30 May (Figure 27). June 1985: The retreat of sea ice continued in June (Figure 18). By 25 June only strips and patches remained south of Cape BaukJ. The shipping season for the Strait of Belle Isle was 41 delayed opening 2-3 weeks this year due to ice persisting longer than normal in the Strait. June was the heaviest iceberg month with 893 icebergs plotted by IIP during the month and 247 icebergs estimated south of 48°N. The largest number of icebergs on plot during any single day in 1985 was on 14 June (Figure 28), when there were 292 on plot. There were 242 icebergs on plot on 30 June (Figure 29) . July 1985: On 16 July, the Strait of Belle Isle was ice-free as was much of Davis Strait (Figure 1 9). The melt proceeded rapidly and by 30 July sea ice only extended as far south as Cape Mugford on the Labrador Coast. July also was a heavy iceberg month with 765 icebergs plotted during the rrxanth. However, only 1 23 icebergs were estimated to have passed south of 48°N and 227 icebergs remained on plot on 30 July (Figure 31). August 1985: With warmer than normal temperatures (Table 5) and favorable winds, the sea ice continued to melt rapidly and the iceberg population decreased dramatically. On the 6- 1 4 August ICERECDET deployment, only 30 icebergs were detected south of 50°N and the eastern limits of all known ice shifted 4 degrees west (Figure 32). On 13 August, Newfoundland and Labrador were nearly ice-free with some ice remaining in Hudson Strait and along the east coast of Baffin Island (Figure 20). August was a light iceberg month with only 32 42 icebergs south of 48''N. Asa result of the final ICERECDET on 20-28 August, the limit of all known ice shifted another 4 degrees west and north and the 1 985 Ice Patrol season was cbsed on 29 August with 64 kiebergs on plot at IIP, only three of which were south of 48°N (Figure 33). Septeniber1985: Labrador and the Davis Strait was entirely sea ice free by 1 7 September (Figure 21). There were an additional 32 icebergs sighted south of 48°N during September. Table 6. Explanation of Sea Ice Technology Used in Figures 10-21 C - Total loe oonosntratlon In the area In tenths. C C C - Conoentratlon of thickest ( C ), 2nd thickest (C ). and 3rd thickest (C ). a b c a b c S S^S - Stage of development of thk:kest (S ). 2nd thickest (S ), and 3rd thickest (S ). a b c a b c ^C > Concentration of loe within areas of strips and patches. F F.^F - Roe size of thickest (F ). 2nd thickest ( F^ ). and 3rd thickest (F ). a b c a b c Stage ot Development 0 No stage of development 1 New loe 2 Nllas, Ice rind 3 Young loe 4 Grey loe 5 Qrey-white Ice 6 Rrst-year loe 7 Thin first-year Ice 8 Thin first-year Ice. 30-50 cm 9 Thin first-year loe. SO-70 cm 1 - Medium first-year loe 4 - Thick first-year loe 7- Old Ice 8 ' Second-year loe 9 ' Multi-year Ice ▲ Icebergs A traoe of Ice thicker thanS # Fourth type. If C C C do not add up to C a b c Floe Sbea 0 Pancake Ice 1 Brash, small ice cake 2 tee cake 3 Small floe 4 Medium tk>e 5 Big floe 6 Vast floe 7 Qant floe 8 Growlers and floebergs 9 loetwrgs / Undetermined or unknown Discussion of Icebergs and Environmental Conditions The number of icebergs that pass south of 48°N in the International ice Patrol area each year is the measure by which International Ice Patrol has judged the severity of each season since 1912 (Tablet). With 1063 icebergs south of 48°N, 1 985 is the seventh highest year on record. Since the number of icebergs calved each year by Greenland's glaciers is in excess of 10.000 (Knutson and Neil!, 1978), a number of icebergs exist in Baffin Bay during any year. Therefore, annual fluctuations in the generation of arctic icebergs is not a significant factor in the number of icebergs passing south of 48°N annually. The factors that detennine the number of icebergs passing south of 48°N each season can be divided into those affecting iceberg transport (currents, winds, and sea ice) and those affecting iceberg deterioration (wave action, sea surface temperature, and sea ice). Sea ice acts to impede the transport of icebergs by winds and currents and also protects icebergs from wave action, the major agent of iceberg deterioration. Although it slows current and wind transport of icebergs, sea ce is itself an active medium, for it is continually moving toward the ice edge where melt occurs. Therefore, icebergs in sea ice will eventually reach open water unless grounded. The melting of sea ice itself is affected by snow cover (which slows melting) and air and sea water temperatures. As sea ice melt accelerates in the spring and early summer, trapped icebergs are rapidly released and then become subject to nonnal transport and deterioration. With sea ice extending south over the Grand Banks later than usual during the 1 985 season, icebergs were protected longerthan normal, making it possible for the icebergs to reach farther south than normal. References Knutson, K.N. and T.J. Neill, (1978); Report of the International Ice Patrol Service in the North Atlantic Ocean for the 1977 Season, CG-1 88-32, U.S. Coast Guard, Washington, DC. Robe, R.Q., N.C. Edwards, Jr., D.L Murphy, N.B. Thayer, G.L. Hover, and M.E.Kop, (1985); Evaluation of Surface Craft and Ice Target Detection Performance by the AN/APS- 135 Side- Looking Airborne Radar (SLAR), CG-D-02-86, U.S. Coast Guard, Washington, DC. Rossiter, J.R., L.D. Arsenault, A.L. Gray, E.V. Guy, D.J. Lapp, R.O. Ramseier, and E. Wedler, (1984); Detection of Icebergs by Airborne Imaging Radars, Proceedings of the 9th Canadian Symposium on Remote Sensing, St. John's, Newfoundland, August 1984. Thayer, N.B. (1984); Effectsof Side-Looking Airtxirne Radar (SLAR) on Iceberg Detection During the 1983 and 1984 International Ice Patrol Seasons; from Report of the International Ice Patrol in the North Atlantic, 1984 Season, CG-1 88-38, U.S. Coast Guard, Washington, DC. 43 Acknowledgements Commander, International Ice Patrol acknowledges the assistance and infonnation provided by the Canadian Department of the Environment, the U.S. National Weather Service, the U.S. Naval Weather Service, and the U.S. Coast Guard Research and Development Center. We extend our sincere appreciation to the staffs of the Canadian Coast Guard Radio Station St. John's, Newfoundland/VON and the Gander Weather Office and to the personnel of U.S. Coast Guard Air Station Elizabeth City and the USCGC EVERGREEN for their excellent support during the 1985 International Ice Patrol season. 44 Appendix A International Ice Patrol Ice and SST Reports for 1985 Country Ice SST Ship's Name of Registry Reports Reports Aberdeen -^ ^ ''^ '-- Panama 3 .^■■x Abitibi Concord Germany 7 Acadia Forest Liberia 1 Aeneas Singapore 2 Akizuki Maru ..•liS^^^K? Japan .^^^^ :SS:k-.-..-.-.-,-.™.-KSSj mm^mm:.... .. ' '' ^y ^ Albright Explorer United Kingdom 2 Alcona United States of America 1 Alexander Henry Canada 2 2 Alexandres F Greece 1 1 Alfanourious Liberia 1 1 Alfred Needier Canada 4 Algonquin Korea 1 27 Altamira Spain 3 Altay Union of Soviet Socialist Republics 1 Altts Ambassador Greece United Kingdom f 16 Ambrose Shea Caruida 2 Amstelwal Netheriands 3 4 Anagell Horizon Greece 1 m AnkaD Cyprus 1 Annoula Greece 4 7 Arctic Canada 2 Arctic Link United Kingdom 1 Arctic Viking Canada 2 Astron Canada 2 Atlantic Conveyer United Kingdom 1 Atlantic Link United Kingdom 4 15 Atlantic Saga Sweden 1 Atlantic Sen/ice France 2 Atlantic Star United Kingdom 2 1 August Thyssen i iKc^rfa 2 Lioena Australian Reefer Bahamas 2 Azalea mmm Korea wmmmmmmm w^mmmm mmmmmimmm ^^^^miimmm Badak Liberia 1 5 Bahia Portete Columbia ^ 1 Balder Hesnes Canada 3 Balder VJgra Canada 1 Balu Sri Lanka 1 Bandazul Spain 1 .;:;;:;: Bart Atlantica United Kingdom 1 Batna Beinir WmsmmMiiiMSimi/ Canada - ^ 4 Algeria Canada 4 T 4 Belle Etoile Mauritius 4 10 Bernhard Oldendorf Panama t Bernier United Kingdom 4 Bilderdyk Netheriands Antilles 1 Bissaya Barrero Portugal 6 Boltentor Canada 4 Bonavista Bay Canada 3 Boxy Wmmm" ' Sweden 3 Bridgewater Germany 7 45 Appendix A (cont'd.) International Ice Patrol Ice and SST Reports for 1985 Country Ice SST Ship's Name of Registry Reports Reports Bulkness ;«::l«ii:^;?*--^*-^^^-^ -* United Kingdom 3 Canada Marquis Canada 1 Canadian Explorer Canada 10 1 Cape Roger Canada 4 Capetan Costis Cyprus 9 Cast l-luslyyy:^,,-»: Finland 2 Finnrose Finland 2 11 Finn Oceanis Finland 2 Fiona Mary Panama 1 iiFirmes Liberia 12 Fjord Bridge Panama 2 S Flora Fogo Isle Fort Providence Greece 1 Canada 1 United Kingdom 1 Fortune Ace Panama 1 FredJ.Agnich Canada 1 Frithjof Germany 2 Fuji Reefer Japan 1 Garbanjs Bay Canada 9 Genoa Singapore 1 Germanic Federal Republic of Germany 3 ilGodafoss Iceland 1 Golden Rio Liberia 1 10 liGraiglas U)ited Kingdom 1 Grand Eagle Panama 9 Gnpo Finland 3 Gulf Grain Liberia 3 Hassho Panama 1 Heide Germany 1 Helena Federal Republic of Germany 1 Helen Schulte Cyprus 1 Hercules Bulker Liberia 3 Hofsjoull Iceland 1 li Hokusetmaru Lfriited States of America 1 Hual Trapper Liberia 1 1; Hudson Canada 6 3 Hugo Rnland 1 ,,,:,^,,,_^^^ Canada 2 Ifrtperfal Beatat&Mi--: Imperial Quebec Canada 2 Imperial St. Clair Canada 2 Inma Spain 1 47 Appendix A (cont'd.) International Ice Patrol Ice and S ST Reports for 1 985 Country Ice SST Ship's Name of Registry Reports Reports prenes Galaxy Panama 1 Iroquois Korea 8 1 Irwng Nordic Irving Ours Pollaire 1 Ivan Der Benev Canada ...........v..,..:..:.......v...i.v.™.v.v......:.:..............™ Canada 1 Union of Soviet Socialfsf Republics 2 Iver Libra Liberia 1 packamn Chile 1 Jade Kim Panama 2 1 Jan Wilheltm Germany 1 James Transport Canada 3 Jason :^^mmm&w^' i Je Bernier Canada 2 IJenniferJan© Cyprus 2 Jenny United Kingdom 1 wm Yugoslavia 1 Joao Ferreira Portugal 2 iPohn .i^ ^^j;;.;, .............. ....... .....Greec« v^^B^^^^^^^L .....................4............... John A. MacDonald Catnada 4 iiohn M, ■.■.■..■■■....■.........■...■.:■■.■■ p^g^jii R^^jb|jc of Germarify ' l^^KF'^^^'^^^'"^^ ' ■■■"■-■-■-■■•■■■■■-■-■■■■■-■"■=■■*■"=■■■■■■■■■--* Johnson Chemstream Singapore 1 liugoagent Yugoslavia 2 14 Juventia Panama 1 PKaladla India 3 Kapitan Chukhchinche Union of Soviet Socialist Republics 4 Keenaviga :;:;:;:s;s™:;:;«^^^^^^^ m>:mmm^^gl^ g^simiimiMWiAi Khiko Panama 1 i; Klippergracht Netherlands 1 Koein Express Germany 10 iKorea Pacific Korea 4 Kyoushi Waru Japan 2 LakeAnina, Liberia 2 Lake Biwa United States of America 1 |:Lak© Shelf ""■""■"•■■""■ Canada 1 ■.yy. ■. % La Pampa United Kingdom 7 iLa F6dharda(s France 2 3 Lamara Singapore 1 Larrado Canada 2 Laurentian France 9 Laurerifian Forest .ffl::™ .-:.y..:.:K---.-:-:-:-:<-. Lena Philippines 8 Leninsk Union of SowiliSoaalisf Republics' 1 Leros Challenger Malta 1 iLevantes Liberia 1 Liberian Badak Liberia 1 i tJqiiid Bulker Liria Panama^^ .:.:.. 4 1 Spain 1 i.<* Nayak ■r" Lorme Canada 1 ; louts S. St. Laurent Canada 1 Ludolf Oldedorff Singapore 1 48 1 Appendix A (cont'd.) International Ice Patrol Ice and SST Reports for 1985 Country Ice SST Ship's Name of Registry Reports Reports Mafione Bay Canada 1 Maiakamd Pakistan 4 Manchester CKaDenge United Kingdom 10 2 Manga United Kingdom 1 Manila Triumph Philippines 1 Maratha Shogun India 2 Margit Gorthon Sweden 3 Maria Germany 1 Marine Reunion Liberia 1 Marine Star United Kingdom 1 Marques Debolarque Spain 1 Marshal Grechko Union of Soviet Socialist Republics 3 Meshill Norway 2 Meerdrecht Netherlands 1 Meerkatze Germany 6 Megastar Sri Lanka 2 Mela Panama 1 4 Mesarige Canada 1 Metro Star Canada 1 Mini Lot Panama 1 Mightious Panama 1 1 Miyashima Maru Japan 1 1 Mlljet Mongolia 2 Mobil Engineer Sweden 4 Mobil Oil Co. Bolivia 1 Monana D. Liberia 6 Montcalm United States of America 1 Monty Python Malta 1 Mosel Oredk, Liberia 1 Moshrouk Norway 1 Mouthaina Greece 3 M. Soveron Singapore 1 Musashi Greece 2 Musson Union of Soviet Socialist Republics 1 Nancy Bartlet Canada 1 Navtroll Liberia 1 2 Neckarore Liberia 1 Noble Supporter Panama 1 Nordertor Liberia 1 12 Nordheide Canada 3 Nordic Sun Singapore 4 Nordkap Liberia 3 Norshwisn Cyprus 1 7 Northern Lynx Liberia 1 USCGC NORTHWIND United States Of America 7 6 Nosira Lin United Kingdom 1 51 Nosira Madeleine United Kingdom 3 Nurnberg Express Germany 4 Ocean King Greece 1 Osolemio Overseas Argonaut Liberia 5 United Kingdom 1 2 49 - Appendix A (cont'd.) International Ice Patrol Ice and SST Reports for 1985 Country Ice SST Ship's Name of Registry Reports Reports Pacific Challenger United Kingdom 1 Pacific Courage United Kingdom 1 Pacific Defender Liberia 9 Pacific Express Liberia 1 Padfico Mexican© Panama 1 Pan Crystal Korea 1 Pantazis Greece 1 Pavel Vavilov Union of Soviet Socialist Republics 1 Pawnee United Kingdom 12 Petrodvorets Union of Soviet Socialist Republics 4 Philippeld France 1 Placentia Bay Canada 1 Planeta Germany 1 Polar Bear Liberia 2 iPolar Circle Canada 2 USCGC POLAR SEA United States of America 1 Port St. Jean Canada 2 Premnitz Germany 2 President Qmm ^ -^^^^^'"^^ Philippines 1 Priimorsk United Kingdom 2 Prins Mauri^^^;;^^^^ Netherlands 2 Pristina Yugoslavia 1 Proteus United Kingdoom 1 Puhos Finland 3 5 Quadra Canada 4 Queen Ellizabeth II United Kingdom 2 Quest Canada 1 Reginas Greece 1 Ruebens United Kingdom 1 Rio Frio Netherlands 1 Rio Plaata Liberia 1 Saar lore Liberia 2 Salvia Star Philppines 2 Saskatchewan Pioneer Canada 1 Scandinavia Maru Japan 1 Schnoorturm Canada 4 Seaforth Atlantic Canada 3 Seaforth Atlantic Cartwright 1 Canada 1 Sea Fortune Panama 3 Sealand Express United States of America 1 :Sealand Independence Mexico 1 Seijin Maru Japan 5 Selkirk Settler Canada 1 Senhora Das Candeias Portugal 4 Sentinel 2 France 1 Silverland Sweden 2 Sir Robert Bond Canada 7 Sir W. Alexander Canada 1 Sitia Glory Panama 2 Skaftefell Iceland 1 Stefan Batory :.™.™.:.:.:.:.POland 9 .:«::2.»:«::.:.:. Stefan Starzynski Poland 4 50 Appendix A (cont'd.) International Ice Patrol Ice and SST Reports for 1985 Country ice i SST Ship's Name of Registry Reports Reports Stolt Castle France Stolt Excellence Liberia Stratus Liberia 4 Stuttgart Express Germany 3 Suvretta Panama Tadeusz Kosciuszzko Poland Takapu Canada Teamhada Singapore 2 Techno St.. Laurent Canada Terra Nordica Canada 4 Thuleland Singapore Tina Cyprus 1 Toanui Canada 2 Tobruk Poland Totaarrow United Kingdom Torrent Liberia Trans Reefer Panama 1 Traquair United Kingdom 9 Travennar Africa Spain 6 Trinity Bay Canada 9 Tsukubamam Japan 1 1 ounuwvu 1 icu V Tuber Canada 1 Tuifias Sweden Tulsidas India Uniwersytet Slasky Pdand Uority Dolgarufiy Union of Soviet Socialist Republics VamandWave United Kingdom Vanil Sweden 5 Vaijakka Finland 2 Vimieiro Portugal Vascaya Norway Wanderer United Kingdom 4 ; Warnemundie Unkm of Soviet Socialist Republics 3 Wilfred Templeman Canada 2 1 Wise Cypais 6 World Agamemnon Greece 1 : World Argonaut Greece 1 World Nancy Panama 1 Yannis Greece 1 Yukona Liberia 3 1 1 Zeepaard Bahamas 1 Ziemia Opolska Poland 2 ZiemiaZamojska Poland ^^^ 3 4 51 Appendix B Iceberg / Ship Target Discrimination with Side-Looking Airborne Radar LTJG N. B. Thayer, USCGR CDR N. C. Edwards, USCG Introduction Since 1983, the International Ice Patrol (IIP) has been using a Motorola AN/APS- 135 Side-Looking Airtwrne MuHi- Mission Radar (SLAMMR) as its primary method of iceberg reconnaissance in the North Atlantic. The ability to detect icebergs with a side-looking airtxime radar (SI_AR) in poorer zero visibility, plus the ability to search larger areas, has resulted in a significant increase in the number of icebergs tracked by IIP. Because SLAR can be used with the sea surface obscured by clouds, IIP frequently conducts reconnaissance flights when visual confirmation of SLAR targets is not possible. Without visual confirmation, distinguishing between icebergs and vessels is sometimes difficult. Without visible cues on the SLAR film (target movement, wakes, brash, radar shadows, strength of return) which improve target identification, it is difficult to distinguish between targets with similar radar return, e.g., small teebergs and vessels. IIP has planned its search legs and the track spacing equal to one-half the total SLAR sweep width (i.e., 25 nm). This type of search plan gives 200% coverage between parallel legs and provides two views of each target within the search area. Despite these efforts to maximize cues, it is still sometimes difficult to distinguish vessels from small and medium icebergs . For example , fishing vessels often drift or move stowly, producing no wake and showing little or no nrxjvement between looks. In addition, the search legs going to and from the search area as well as the outlying legs of the search itself do not afford double SLAR coverage. As a result, approximately 35% of the search area is seen only once on SLAR, eliminating the chance to detect movement and decreasing the probability of picking up other cues from SLAR images. This study measures the en'or rate in SLAR target identifk»tk>n, using single looks at individual k^eberg and ship targets without visual cues. Methods To conduct this study, it was necessary to find a source of SLAR targets with visual confirmation. The best source of targets with positive identif Nation of both target size and type was the BERGSEARCH '84 (Rossiter, et al. , 1 984) data and the 1 985 SLAR experiment conducted by IIP and the Coast Guard Research and Devetopoment Center (Robe, era/., 1985). These two sources provided SLAR film from 7 days of IIP operattons with shipboard ground truth data, 1 60 ship and k^berg targets in all. All of the film used in this study was collected at an altitude of 8,000 feet on the 50 km SLAR range scale, standard conditions during IIP iceberg reconnaissance. The films were duplicated and the duplicate films were examined for suitable targets for the study. All targets without obvbus cues were used. Although targets were not selected for ambiguity, all of those used were quite ambiguous, since they were all single targets without accompanying visual cues. With the limited number of vessels and k;et)ergs involved in the two source experiments, some targets were used more than once, but separate SLAR passes 53 ResuKs provided different looks so that each image was used only once. To isolate individual targets and at the same time give the SLAR interpreters a surrounding piece of film to examine for background, each target was cut from a duplicate film and mounted on a 2 1/4" photo slide mount. Each target was randomly assigned a 2-3 digit identification number and each slide mount was labelled with that number, the lateral range to the target from the aircraft, and the sea conditions (from ship ground truth). These 74 slides (35 icebergs and 39 ships) were taken to U. S. Coast Guard Air Station Elizabeth City, North Carolina, for viewing by the Coast Guard Avionics Technicians who are the HP's SLAR interpreters, operators and technicians during ice reconnaissance flights. Four experienced technicians separately viewed the slides on a light table using an optical magnifier, conditions approximating the normal IIP post- flight analysis. Each technician was asked to identify each target as either a ship or an iceberg. Table B-1. Target Identification Table B-1 presents the raw test results, divided into the two target types: ships and icebergs. The "correct" column under each target type represents the number of times each observer identified that target correctly, while "incorrect" represents the number of times that type of target was misidentified. The data was subjected to Chi-square analysis (Lapin, 1975) to identify statistically significant differences in the error rates between the observers, and to look for differences in how the two target types were treated. The analysis revealed that there was too much difference in error rate and target treatment between the four observers to allow combining all the data. Also, obsen/ers 1 through 3 showed a bias toward icebergs, i.e., a tendency to identify ships as icebergs. This is a reflection of their IIP experience, since observers are taught to be consen/ative and identify doubtful targets as icebergs. Observers 1 and 3 were sufficiently similar in their treatment of the targets to allow combining their data. Finally, Observer Iceberg Correct Incorrect SI Correct lip 1 Incorrect | 24 1 1 31 4 15 2 23 12 7 32 3 28 7 15 24 4 20 15 24 15 TOTAL 102 38 61 95 observer 4 showed no bias toward icebergs. The results from observers 1 and 3 probably offer the most representative sample, since the bias they show toward icebergs reflects their IIP experience. Actually, while selection of different subsets of the data can be made based on bias shown or statistical judgements, the error rate for all targets is in the range of 40-45%, as shown in Table B-2. While these data sets cannot be combined or compared for statistical reasons, selecting any one of them yields essentially the same result, i.e., that the observers correctly identified all targets 55-60% of the time. Applied directly to all IIP SLAR detections, a possible 45% error rate would have alarming implications. The targets used in this study, however, represent only a subset of IIP SLAR targets. There are characteristics that limit the size of that subset and mitigate the 45% figure. First, the sizes of icebergs in BERGSEARCH '84 and the Table B-2. Error Rates Obser- Error Rate ver(s) (Ships & Icebergs) 1-4 45% 1 ,3 40% (Iceberg Bias) 4 40% (No Bias) 54 Table B-3. Iceberg Size Distribution (SLAR) 1984 - 1985 Year Growler Small Medium Large Radar Total 1984 370 441 418 211 21 1461 (25%) (30%) (29%) (14%) (1%) 1985 65 194 182 113 10 564 (11%) (34%) (32%) (20%) (1%) 1960- 8393 21353 15461 4854 7711 57772 1982 (15%) (37%) (27%) (8%) (13%) 1985 IIP experiment range from growler through medium. The targets selected for this study were small and medium icebergs (ground truthed by on-scene vessels) and ship targets of similar radar retum. Small and medium icebergs represent 59% of the icebergs recorded by IIP SLAR in 1 984 and 68% in 1 985, as shown in Table B-3. These percentages are comparable to the pre-SLAR value of 64% for the period 1 960 through 1982. The second mitigating factor is the ambiguity of the targets used, i.e., the absence of cues. Since the methods of this study eliminated these cues, the targets used represented the most ambiguous available. In order to assess the impact of these results on IIP iceberg reconnaissance, it is necessary to estimate the proportion of IIP SLAR targets that are cueless. It can be conservatively assumed that 40% of SLAR targets are cueless, based on IIP operational experience. Indications that this is a reasonably conservative assumption are that the data set used for this study in which 74 of 1 60 targets (46%) were cueless, and the fact that 65% of IIP search flight mileage offers 200% search coverage, which is assumed to greatly increase the probability of cues being present. A further assumptbn is that the presence of cues results in 1 00% correct identifcation Applying a worst-case error rate of 45% to the (estimated) cueless 40% of the small and medium icebergs detected by SLAR, yields an estimated SLAR error of 161 and 68 misidentified icebergs in 1 984 and 1 985, in the small and medium size range. Conclusions The probability of correctly identifying ambiguous (cueless) iceberg and ship SLAR targets is just above chance (55-60%). Therefore, the International Ice Patrol uses search tactics to maximize cues and visual confirmation during SLAR reconnaissance. Based on this limited study of cueless SLAR targets, the SLAR error rate and iceberg bias of SLAR operators could inflate the number of icebergs that IIP reports. This inflation is insignificant when compared with the increased efficiency that SLAR provides iceberg reconnaissance. Even though visual searches provide unquestionable identification, they were historically flown only on 50% of the deployment time and each visual flight covered one-third less area than a SLAR flight does. An important issue not addressed by this study is the SLAR identification error rate for unambiguous targets, i.e., targets with cues. If this error is quantified by further study, a better estimate of the overall error rate would be possible. References Lapin, L. 1975. Statistics: Meaning and Methods. Harcourt, Brace and Janovich. New Yort<. Robe, R.Q., N. C. Edwards, Jr., D. L. Murphy, N. B. Thayer, G. L. Hover, M.E.Kop. 1985. Evaluation of Surface Craft and Ice Target Detection Performance by the AN/APS- 135 Side- Lool— 40N -\ 1 i 1 1 1 f 1 1 1 1 1- 40N 57W 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39W 57 1985. The drift tracks of the TODs will be discussed below In chronological order according to when they were deployed. The number in parenthesis following dates are Julian dates and correspond to the dates on Figure C-1 . TOD #4526 TOD #4526 was deployed on 1 0 April (1 00) in the Flemish Pass in position 46°15.6'N 46°28.8*W (Figure C-1). Between 11 April and 3 June ( 1 54) , only one position was received from TOD #4526. This position on 26 May (1 46) at 47°35.4'N 44°1 5.0'W indicated TOD #4526 drifted north around Flemish Cap. From 3 June (1 54) to 7 June, TOD #4526 drifted from 46°48.6'N 44°07.2'W in a southwesterly directbn at an average velocity of 27 cm/s until it entered the North Atlantic Current. On 7 June (158), the sea surface temperature reading from TOD #4536 increased from 3°C to 5°C. Although TOD #4526 briefly drifted north of the IIP region between 7 July (1 88) and 1 1 July (192), the drift track of TOD #4526 after 7 June corresponds well with the isotherm pattern as depicted by the Canadian METOC SST charts (Figure C-3). An average velocity of 51 cm/s was maintained while TOD #4526 was in the North Atlantic Current until exiting the IIP region to the east on 22 July (203). During June when TOD #4526 was drifting north of Flemish Cap in the North Atlantic Current, the 8°C isotherm apparently indicated the westem edge of this branch of the North Atlantic Current. TOD #4526 continued to return data as it drifted across the Atlantic until its failure on 5 October. Throughout the period from 3 June until 5 October, the drogue sensor indicated the drogue was disconnected. 58 Figure 0-2. Velocity distributions for International Ice Patrol's 1985 TODs Figure C-2a TOD VELOCITY DISTRIBUTIONS £| o o 25 - 20 .. 15 .. 10 .. 5 •■ — TOD 4526 TOD 4541 TOD 4548 — TOD 4529 0 10 20 30 40 50 60 70 80 90 10 0 110 VELOCITY CM/S Figure C-2b TOD VELOCITY DISTRIBUTIONS — TOD 4536 TOD 4550 — TOD 4527 TOD 4544 0 10 20 30 40 50 60 70 80 90 100 110 VELOCITY CM/S TOD #4536 TOD #4536 was deployed on 7 May ( 1 27) in 500m of water on the eastern edge of the Grand Bank south of Flemish Pass in posrtion 45°42.0'N 48°09.6'W (Figure C- 1). TOD #4536 was carried south by the Labrador Current roughly following the 500m contour at an average velocity of 44 cm/s until passing south of the Tail of the Bankon17May(137). Between 17 May and 3 July (184), TOD #4536 meandered along the front between the Labrador Cun-ent and the North Atlantic Current at an average vetocity of 32 cm/s. The location of the front is particularly evident near42°N 47°W along the 1 0°C isotherm in the METOC SST chart of 14-1 7 June (Figure C-3). The large amount of time (47 days) that TOD #4536 spent in this relatively slow moving area explains the shift of the velocity distribution curve to the left (Figure C-2). On 3 July (184), the water temperature increased from 9°C to 1 1 °C and the velocity increased significantly from about 20 to 60 cm/s indicating TOD #4536 had been caught up in the North Altlantic Current. It remained in the North Atlantic Current until 25 July (206). From 25 July until 5 August (21 7), TOD #4536 drifted slowly at an average velocity of 1 0 cnn/s. On 5 August, TOD #4536 was picked up by a fishing vessel working out of New Bedford, Massachusetts and the TOD was subsequently retumed to the Ice Patrol. The exact date TOD #4536 was picked up by the fishing vessel is not certain. The drogue was attached to the TOD when it was recovered. TOD #4527 TOD #4527 was deployed between the 200m and 500m contours along the eastern Grand Bank in position 46°34.8'N 47°22.8'Won30May(150) (Figure C-1). It drifted south with the Labrador Current at an average velocity of 29 cm/s along the edge of the shelf until entering the North Atlantic Current on about 22 June (173). It remained in the North Atlantic Current travelling in a generally northeasterly direction at 47 cm/s until 4 July (185). Between 4 July and 18 August (230). TOD #4527 meandered generally northward at 26 cm/s completing one large cyclonic circle south of the Flemish Cap. This period of time was spent between the Labrador Current and the North Atlantic Current. On 18 August (230), TOD #4527 re-entered the North Atlantic Current and was carried again to the northeast at 74 cm/s. On 28 August (240), TOD #4527 began a slow cyclonic motion that followed the isotherm pattern at an average velocity of 27 cm/s (Figure C-3). TOD #4527 exited and re-entered the IIP region during this section of the drift. It continued this nx)tion until the TOD failed on 1 7 September (260). The drogue sensor indicated \he drogue remained attached until 1 1 September (254). TOD #4529 TOD #4529 was deployed on the north side of Sackville Spur in about 1 000m of water on 28 July (209) in position 48°21.0'N 46''48.0'W (Figure C-1). It drifted around the top of Flemish Cap at an average velocity of 21 cm/s until 1 8 August (230) when it was caught up in the North Atlantic Current. TOD #4529 was carried in a generally northierly direction at 36 cm/s until it exited the IIP region on 1 4 Septemtjer (257). This northward drift corresponds well with the 1 2°C isotherm as depicted on the 1 5- 1 9 August METOC SST chart Table C-2. 1984 IIP TIROS Oceanographic Drifters Grounding in Europe TOD# 4512 4528 4530 Deployment Date Deployment Position 27 APR 84 47°51.6N 47°30.0W 5 AUG 84 50°59.4N51°01.2W 6 AUG 84 46°46.8N 46°54.4W Grounding Date 27 SEP 85 12CX;T85 28 AUG 85 Grounding Position 49°36.6N 0r38.4W 57°03.0N 06°29.4W 50°01.2N05°15.6W 59 Figure C-3. Canadian lUIETOC Seas Surface Temperature Charts for the indicated periods (Figure 0-3). The SST sensor on TOD #4529 indicated between 1 1 °C and 1 3°C during this time period. TOD#4529drittedtothe northeast before turning south and re-entering the IIP regfon on 24 September (267). After re- entry, TOD #4529 drifted south until 28 September (271 ) when it turned cyclonically completing an ellipse with a major axis length of about 1 40 km on 6 October (279). The average velocity during the elliptical drift was 39 cm/s. TOD #4529 then drifted slowly to the northwest exiting the IIP region on 1 7 October (289). As of 30 October, TOD #4529 was still transmitting and the drogue sensor indicated the drogue was still attached. TOD #4550 TOD #4550 was deployed in about 750m of water north of the Grand Bank on 29 July (21 0) in position 50°30.0'N 50°29.4'W (Figure 0-1). It drifted southeast and then south with the Labrador Current through the Flemish Pass following the bathymetry until 20 August (232). During this bathymetrically guided drift period, the average velocity was 34 cm/s. TOD #4550 meandered in a southeasterly direction at an average velocity of 18 cm/s until 9 September (252). The SST values retumed from TOD #4550 rose from 1 2°C to 1 7°C between 9 and 1 0 September indicating TOD #4550 had been caught up in the North Atlantic Current. The North Atlantic Current carried TOD #4550 to the northeast at an average velocity of 97 cm/s until it 60 Figure C-3a. March 15-18, 1985 Figure C-3b. April 12-15, 1985 Figure C-3c. May 10-13, 1985 Figure C-3D. June 14-17, 1985 exited tlie IIP region on 19 September (262). TOD #4550 re- entered the IIP region briefly between 29 September (272) and 2 October (275). The drogue sensor indicated the drogue became disconnected from the TOD on 6 October. TOD #4550 is still transmitting. TOD #4541 TOD #4541 was deployed north of Sackville Spur in about 1 000m of water on 1 1 August (223) in position 48°1 7.4'N 47°00.6'W (Figure C-1). The drogue sensor indicated the drogue became disconnected on 1 5 August (227). TOD #4541 drifted to the southeast across the top of Flemish Cap, crossing isobaths, at an average velocity of 27 cm/s until 6 September (249). Between 6 and 8 September, the SST readings from TOD #4541 rose from 1 2°C to 1 6°C indicating TOD #4541 had entered the North Atlantic Current. From 6 September until TOD #4541 left the IIP region on 1 1 September (254), it drifted in an easterly direction at 70 cm/s. As of 30 October, TOD #4541 was still transmitting. TOD #4544 To detemriine the drift of the last concentration of icebergs for the season, TOD #4544 was deployed north of the Grand Banks in 500m of water on 26 August (238) in position 50°07.2"N 50°29.4'W (Figure C- 1). TOD #4544 drifted with the Labrador Current, following the bathymetry, through the Flemish Pass at an average velocity of 34 cnrVs until 27 September (270) . The drogue sensor indicated the drogue was attached only between 28 and 30 August. 61 From 27 September (270) until 1 6 October (289), TOD #4544 drifted in a southeasterly direction at 26 cm/s until it was caught in the North Atlantic Cun-ent. Between 16 October (289) and 30 October (303), TOD #4544 drifted with the North Atlantic Current at 53 cm/s. As of 30 October, TOD #4544 was still transmitting from within the IIP region. TOD Results and Conclusions The variability of the flow in the IIP region is again well-depicted by this year's TOD drift tracks. The areas northeast and south of Flemish Cap, in particular, illustrate the variability that exists in the IIP region making drift prediction so difficult without near- real-time inputs. As shown in previous years, the bathymetry of the Grand Bank and Flemish Cap plays a major role in guiding the drifts of TODs (Anderson, 1984). The only TOD (#4541) not apparently guided bathymetrically in this area apparently had lost its drogue. TODs continue to supply IIP with needed real-time current infomiation that is required to improve iceberg drift prediction. IIP intends to continue using TODs operationally. The data from all future TODs will be entered into the Global Telecommunications System (GTS). The historical current file east and north of Flemish Cap will be examined for possible changes based upon accumulated TOD drift tracks. As a footnote, three of the TODs released in 1984 have grounded in Europe. TOD #451 2 ran aground nearChertxjrg, France on 27 September 1985 and was taken to Brest, France, TOD #4528 grounded on the island of 62 Figure C-3e. July 12-15, 1985 Figure C-3f. August 16-19, 1985 Rhum in the Sea of The Herbides off Scotland on 1 2 October 1985, and TOD #4530 ran aground near Helston, England (near Lands End) on 28 August 1985 (Table C- 2). With the cooperation of the Royal Navy and the Military Airlift Command, TOD #4530 is being retumed to Ice Patrol. 1985 Iceberg Deterioration Observations In 1983 International Ice Patrol began using a computer model to predict iceberg deterioration. The model, based on White, et al., 1 980, uses melting due to insolation, vertical buoyant convection, wind-forced convection, and wave erosion to reduce the length of each iceberg. The details of the equations used by IIP to model these four processes can be found in Anderson, 1983. During the EVERGREEN cruise, measurements of the observed icebergs were made using a reticulated laser range finder. Measurements were made twice a day separated by 1 2 hours, weather and other operations permitting. Photographs of the iceberg were taken in conjunction with the measurements. Length and mass estimates were made from the measurements and photographs. These methods can lead to a large error in mass estimation, since none of the underside of the iceberg was observed. Sea surface temperature (SST), significant wave height and period data were also collected. The observed environmental data were used as the inputs for the deterioration rTX)del in the discussions that follow. In the operational use of the nrodel, the required environmental data is received 50 Sep n-it.itey Figure C-3g. September 13-16, 1985 Figure C-4. Iceberg #1, 19 April 1985, 0930Z. Est length,129 m. Table C-3. Characteristic Length of Iceberg Sizes from Fleet Numerical Oceanography Center (FNOC) in Monterey, CA. FNOC provides SST data in °C and wave heights in feet. For consistency, the following discussion uses the same units. Due to HP's reconnaissance methods, iceberg length (not mass) is the characteristic used to evaluate deterioration. Each of the four sizes of icebergs used by IIP is assigned a characteristic length based on our size definitions (Table C-3). Before each iceberg is eliminated from our list of active icebergs because of deterioration, it is allowed to melt to 1 75% of its original length. This figure, although selected arbitrarily, is used conservatively to ensure the iceberg has melted before elimination. In order to reduce this figure and still ensure complete deterioration before an iceberg is eliminated, field measurements of the deterioration of three icebergs were observed during the 1 985 EVERGREEN cruise, one during the first phase and two during the second phase. Comparisons of these observations to the predictions of the deterioration model are discussed below. The two icebergs observed during the second phase of the EVERGREEN cruise were used as targets for a side-looking airbome radar (SLAR) detection and identification experiment conducted between 27 April and 5 May 1985. Inorderforthe iceberg to be tracked during the SLAR experiment, it had to be detectable up to at least 5 nm (9 km) on EVERGREEN'S surface search radar. Melt Model Size IIP Definitions Length less than 16 m. 16 Growler Small greater than 1 6 m but less than 60 m 60 Medium greater than 60 m but less than 1 22 m 1 20 Large greater than 122 m 225 Figure C-5. Observed Vs. Model Predicted Iceberg Length ISO ^ 140<>' £ C en c cr 160 140 120 100 80 60 ^ 40 20 • 0 '^''--»-.-,- .<^" «:;^3-^.t- Ql f>- ~- -^.^.^^-_. '-"•■•'•'• : :;.^; u.--\-"~'(jF^-^"=^<^Q ■ ,..,- .... * ma)or caVing event I iceberg rollover/rlae I .<>-...„ o Q predicted length A observed length ^ observed length ■ observed length iceberg «1 iceberg #2 iceberg #3 1 Days After Initial Measurement Observed vs. remaining length predicted by Intemationai Ice Patrofs deterioration modet Observed wave tieight and sea surface lemperatum were used as the model Inputs. The Mi narks Indicate observed Instances ol iceberg rollover or rise whie the asterisks Indicais observed major caMng events. Fig. C-6. Iceberg #2 at 1000Z 28 April 1985. Est length 73m. 64 Figure C-7. Iceberg #3 at 2145Z 2 May 1985. Est length 48m. Figure C-8. Observed vs. FNCX« wm surface temperature (SST). The rise in observed SST between 30 April and 1 May was due to change in location of EVERGREEN Iceberg #1 A large pinnacled iceberg with an initial length and estimated mass of about 1 50m and 800,000 metric tons was located in Lilly Canyon in position 44°57N 49''03'W along the eastern edge of the Grand Bank on 1 6 April during the first phase of the cruise (Figure C-4). Subsequent position calculations showed that this iceberg was intermittently grounded, neverdrifting rrxjre than about 1 0 nm from the original sighted position. Poor visibility prevented the collection of size data on 1 6 April. Data on this iceberg were collected 1 7-22 April. The model-predicted waterline length matched the observed length fairly closely until the iceberg rolled on 19 April (Figure C-5). During the evening of 19 April, the iceberg rolled, increasing the maxirrxjm ot)served waterline from 129m to 157m. Due to continued deterioration on 19 April, part of the iceberg rose as it tilted, allowing the iceberg to increase in length again. Although the icet>erg increased in length between 1 7 and 22 April, it was obsen/ed to lose approximately 1 5% of its mass during the same period. Throughout the observation period, only a few minor calving events were observed. The average wave height and period were 5 feet and 4 to 5 seconds and the SST averaged 1 .2°C. 65 Iceberg #2 A medium drydock iceberg was located south of Flemish Cap in position 46''1 2'N 46°1 4'W on 27 April during the second phase of the EVERGREEN cruise (Figure C-6) . The initial length of the iceberg was approximately 75m. Due to the highly irregular shape, no quantitative estimates of the mass were made. Due to fog, no measurements were made on 29 April. The iceberg was observed until 30 April when it no longer was an acceptable target for the SLAR experiment. During the observation period, there were no observed incidents of iceberg roll over. Major calving events were observed on 27 April and 30 April. The event of 30 April caused a considerable loss of mass. The model predicted a stower deterioration than was actually observed (Figure C-5). SST averaged about 1 .5°C while the average wave height and period were 3 feet and 4 seconds for the obsen/ation period. Figure C-9. Iceberg #3 The last iceberg observed during the EVERGREEN cruise was a small drydock iceberg located in position 45°12"N 48°28*Won 1 May (Figure C-7). The initial length and mass were 60m and 35,000 metric tons respectively. Although this iceberg was never obsen/ed to have rolled over, there were frequent major calving events. A calving between 2 and 3 May caused a rise in the iceberg resulting in an increase in water- line length. The model does a fair job of predicting the deterioration rate until day 4 (5 May) when a major calving event significantly reduced the size of the icelserg (Figure C-5). On 5 May, the ice- berg calved 7 large pieces of ice with the largest being 20m in length and having a mass of about 4,000 metric tons. The mass of the iceberg after this event was reduced to about 8,000 metric tons. The average signif leant wave heigfit fortfie duration of the otjser-vations was 4 feet with a 5- to 6-second period. SST averaged about 1.0°C. Observed vs. FNOC predicted wave heights. Note the consistent over-estimation of wave height by FNOC for the obsen/ed period. 25 S- 20 g> 15 o X g 10 5 / N. PREDICTED OBSERVED \ A J \ V 16 17 IS 1S 20 21 22 23 24 25 26 27 28 20 30 1 S Dates Of Observation (1985) S Observed vs. FNOC Environmental Model Inputs Comparisons were made between the observed and FNOC SST and wave height data. Six hour averages before the synoptic hour of the observed data were used in thie comparisons below. The FNOC SST is reasonably close to the observed data (Figure C-8). The largest difference was 0.4°C. The magnitude of this difference is consistent with past comparisons (Anderson, 1983). Thechange in FNOC SST between 30 April and1 May was due to EVERGREEN'S change in position as k^berg #2 deteriorated substantially and fceberg #3 was located (Figure C- 5). The largest error of 2.5°C occurred during the observation of iceberg #3 on 1 May. The highest waves observed during the EVERGREEN cruise were 8 feet on 1 8 April (Figure C- 9). FNOC predicted the wave height for EVERGREEN'S position on 1 8 April to be 25 feet. The observed wave heights never were greater than one half of the wave height predated by FNOC with the average error being about 10 feet. These differences between the predicted and ot3sen/ed wave heights are consistent with comparisons made by IIP in previous years (Anderson, 1983). 66 Iceberg Deterioration Discussion and Conclusions Of the four physical processes used in the IIP nx)del to predict deterioration, wave erosion is responsible for the vast majority of the predicted erosion. This equation is dependent on SST, wave height, and period. (Calving of growlers from an iceberg is not directly modelled but is dependent on wave erosion.) The SST and wave heights experienced by the three icebergs observed in 1 985 were not significantly different. The amount of wave-induced erosion of an iceberg of a given length under the same environmental conditions is dependent on the shape of the iceberg and the amount of surface area exposed to wave action. The shape of an opening, large or small, in an iceberg can cofKentrate the wave energy on a small area creating faster erosion and subsequent calving. If an iceberg has a large exposed waterline-to-mass ratb, as did icebergs #2 and #3, wave erosion with associated calving is a more effective deterioration force than on an iceberg (like iceberg #1) with a relatively small exposed waterline-to-mass ratio. The model-predicted deteriorations for icebergs #2 and #3 were less than the observed rate over the entire observation period. The instances where the observed icebergs deteriorated much more rapidly than predicted by the model are correlated with observed calving events and no associated rollover or rise of the iceberg ( Figure C-5). The model- predicted deterioration for iceberg #1 was greater than that observed over the entire obsen/ation period. Iceberg #1 had no observed major calving events. The major reason for the model's poor perfonnance with iceberg #1 was the increase in maximum length due to rollover. Before the iceberg rolled over, the rrxjdel-predicted deterioration ctosely matched the observed deterioration, and after it stabilized on day 4, the observed deterioration again closely matched the model-predicted deterioration. Under operational conditions, the required environmental data for the deterioration model are supplied by FNOC. On their own, the observed errors in the wave height data would increase the modelled deterioration rate significantly. Part of this increase is, however, offset by the increased period of the bigger waves. (Wave height is in numerator while wave period is in the denominator of the wave erosion equatbn (Anderson, 1 983).) During the largest error in FNOC wave height (17 feet), the deterioration rate would have been increased by about 25 percent. Given accurate environmental data, the iceberg predictbn model used by IIP predicts the deterioration reasonably well. Because of errors introduced by our present methods of operation (FNOC data errors and SLAR sizing errors), IIP will continue its conservative approach and will require that an iceberg deteriorate! 75% of its original length before it is eliminated. Future IIP cmises will continue to gather iceberg drift and deterioration data to further evaluate the performance of the models. References Anderson, I. (1983); Iceberg Deterioration Model, Appendix C of the Report of the International Ice Patrol Service in the North Atlantic. Bulletin No. 69., CG- 188-38, Intemational Ice Patrol, Avery R.,Groton,CT 06340- 6096 Anderson, 1.(1984); Oceanographic Conditbns on the Grand Banldel has been possible, primarily because 68 adequate iceberg drift data, with accompanying environmental data, are expensive and often difficult to obtain. Moreover, only in the last few years has navigation in the operations area been accurate and reliable enough to permit the collection of good data. Mountain (1980) tested the nfX}del using the tracks of two large tabular icebergs, a large pinnacle iceberg, and a freely- drifting satellite-tracked buoy. The drift durations were from 3 to 25 days. The results were quite variable, ranging from a small 9km error for the 3-day drift to a constant 90-1 50km drift error in the 25-day case. Although he recognizes the limitations of this small data set, he suggests that the primary cause of the model error is due to inaccurate inputs, i.e., winds and cun-ents. This report describes the results of four case studies in which the perfonnance of the IIP iceberg drift model was examined at four different locations (Figure D-1) in the IIP operations area. The objectives were twofold: first, to test the accuracy of the drift predictions of the operational IIP iceberg drift model, and second, to investigate how the accuracy changes when on- scene measured wind and current data are used to drive the model. Model Description Mountain (1980) describes the details of the IIP operational drift model; thus, only a brief outline is presented here. The fundamental model balance is between iceberg acceleration, air and water drag, the Coriolis acceleration and a sea surface slope term. The resulting differential equations are solved using a fourth-order Runge-Kutta algorithm. The model is driven by a water cun'ent which combines a depth- and time-independent geostrophic f tow with a depth- and time-dependent current driven by the tocai wind (time- dependent Ekmanftow). When used operationally, the IIP drift nnodel emptoys a nnean geostrophic current field based on many years of hydrographic sun/eys (Scobie and Schultz, 1 976). It is on a grid of 20 minutes of latitude by 20 minutes of tongitude, except for the Labrador Cun-ent, which is defined on a more detailed grid of 10 minutes of tongitude. Wind data, on a 1 degree of latitude by 2 degrees of tongitude grid, are provided to the nrx>del every 1 2 hours from the surface-wind analysis of the U. S. Navy Fleet Numerical Oceanography Center (FNOC). Finally, the nxxJel requires as input the mass and cross- sectional area of the drifting iceberg. Obviously, IIP reconnaissance operations do not pennit precise measurement of each detected iceberg. Often, IIP tocates icebergs using the side-looking airtxime radar (SLAR) with no visual confirmatbn. As a result, IIP can only classify icebergs into the broad categories of growler, small, medium, and large, and assume characteristic mass and cross-sectional areas for each category. When visual confirmation is available, it is possible to distinguish between tabular and non-tabular icebergs, resulting in somewhat different mass and cross-sectional areas. Regardless of the size and shape of the iceberg, both the air and water drag coefficients are set to 1.5. Figure D-1. Area of Study Currently, IIP estimates that the model drift error is 1 0nm (~ 18.5km) for the first 24-hour period and an additional 5nm {~9km) for each additional 24 hours of drift, up to a maximum error of 30nm (~56km). The accuracy of this error estimate is evaluated in this report. In 1983 IIP began using observed-current data derived from the trajectories of freely- drifting satellite-tracked buoys to modify the mean geostrophic field (Summy and Anderson, 1983) during operational model mns. The modifications are both temporary and localized in that they are only applicable during the period that a buoy is in that specific region, after which the currents revert back to the mean geostrophic currents. It is not the intent of the present report to address this practice directly, but rather to compare the drift-model accuracy using two sets of input data: mean geostrophic data with FNOC wind and on-scene measured data. In doing so, the importance of using on-scene data becomes clear. Figure D-2. Iceberg and TOD trajectories for Case I (1983) Data Description The data used in this study were collected from 1 983 through 1 985. All of the cases were drifts of short duration, with a maximum drift period of 4.5 days. In all fourcases, the drifting icetjerg was ctose to at least one freely-drifting TIROS Oceanographic Drifter (TOD), from which local currents were determined. The TOD hull was a 3m spar and was fitted with a 2m x 1 0m window-shade drogue at the end of a tether. The drogue depths presented here refer to the depth of the center of the drogue. The TOD's were tracked by the NOAA/TIROS series satellites and the data provided to IIP by Sen/ice ARGOS, with a position accuracy well within 500m (Bessis, 1981). In three of the cases (11,111, and IV), a surface vessel near the iceberg was collecting local wind data. The data for each case are discussed separately. The numbers in parentheses after each date are Julian year dates, that is, dates numbered sequentially from 1 January. Case I This case consists of a 2.5- day drift of a large tabular iceberg wrth a TIROS Arctic Drifter (TAD) aboard. The TAD, which is essentially a TOD with different packaging, had been deployed onto the iceberg on 27 March 1983 (86) by IIP, in cooperation with the U. S. Coast Guard Research and Development Center (R&DC). 70 47' ICEBERG (A ▲) TOD 38m{o— — 0) 46 o 133/ooz • 134/boz /* 135/ ooz 48' 47' The test period began at 1600Zon12May1983(132) when a TOD, drogued at 38m, was air-deployed from a HC-1 30 aircraft at a location approximately 1 km from the iceberg, which at the time was nroving southward in the Labrador Current (Figure D- 2). The test period ended on 1 5 May (1 35) shortly t>efore the iceberg grounded for a 4-day period. The iceberg was last sighted with the TAD aboard on 21 May (141) by Mobil Oil Company, Canada (Anderson, 1983). On this date the iceberg was still classified as large, with estimated dimensions of 1 50mx 1 1 0mx30m. During the test period, the maximum separation tjetween the TAD (icet)erg) and the TOD was less than 25km. No on-scene wind data were available. 49' 48'^0' ICEBERG(a — a) TOD 58m ( »-— o) 205 jf^ 205A2Z / . 202/I2Z 202 /; '■20I/I2Z 2oi^y 200^ 200/I2Z I99/2Z 46°30' 46° 45° Figure D-3. Iceberg and TOD trajectories for Case II (1984) Case II This case is a 4.5-day segment of an iceberg track obtained in 1984 by USCGC HORNBEAM. The test period began17July(199)at1300Z when HORNBEAM deployed a TODdroguedat38m approximately 500m from a medium (120nnx1 15mx37rn) pinnacle iceberg in the region north of Flemish Cap. Although the iceberg was rapidly deteriorating, it was in the medium size range (>60m) for most of the drift period. Only in the last 24-30 hours of drift was it at or slightly below the medium/small border. Hourly iceberg positions were recorded using radar ranges and bearings and the HORNBEAM'S LORAN 0 position (Figure D-3). Hourly wind speed arid direction were measured using the shipboard anemometer (Figure D-4). The maximum separation between the iceberg and the TOD was less than 25km. Casein The third case is a 3.5-day [27 -30 April 1985(117-120)] trackof a medium (75mx56mx18m) drydock iceberg south of Flemish Pass obtained by USCGC EVERGREEN. Over the drift period, the target iceberg was deteriorating but only on the last day of drift did it fall into the upper part of the small range. Again, hourly iceberg position (Figure D-5) and wind data (Figure D-6) were collected using shipboard radar and anerTX)meter, respectively. Figure D-4. Hourly wind vectors for Case II <^ ///yJ///^//////A / / // 1 1 20I \\\\\\\k.UII/iJi ^^ / . // 002 I2z _i I i_ J I 232 10 KTS 71 Two TOD'S provided the current data. They were deployed, one drogued at 38m and the other at 58m, 300m from the iceberg on 27 April (117). Approximately halfway through the drift period, Ixjth buoys were retrieved and redeployed close to the iceberg to minimize the separation between the iceberg and the TOD'S. Upon redeployment, the drogue at 38m was set to 8m. The maximum separation between the iceberg and the TOD's, which occun-ed during the first part of the drift period, was approximately 35km. Case IV A 4-day drift [1-5 May 1985(121-125)]ofasmall (60mx40mx10m) drydock iceberg provides the data for Case IV. As in Case III, the area of study was south of Flemish Pass, and EVERGREEN tracked the target (Figure D-7) and obtained the wind data (Figure D-8). Two TOD's, one drogued at 8m and the other at 58m, were deployed onl May (121); they were retrieved and redeployed at the iceberg on 4 May (124). The maximum separation tietween the iceberg and the TOD's was approximately 30km. On the last day of the experiment, there was a major calving event that left two small icebergs. At this time the parent (larger) iceberg had a maximum wateriine length of 37m. Table D-1. Model Test Runs Summary Run Inputs b Case Size Number Winds Currents ■ 1 Large 1 SYS SYS 1 Large 2 SYS OBS (38m) II Medium 1 SYS SYS II Medium 2 OBS OBS (38m) III Medium 1 SYS SYS III Medium 2 OBS OBS (38m/8m) III Medium 3 OBS OBS (58m) IV Small 1 SYS SYS * IV Small 2 OBS OBS (8m) IV Small 3 OBS OBS (58m) Summary of the test runs. SYS= system, OBS -observed.The numbers in 1 parentheses indicate the depth of the drogue center. 1 * Note: The observed currents for this cas e were a combination of data | from buoys drogued at different depths: 38m for the first half of | the period and 8m for the second half. ^u,^ Test Runs Table D-1 summarizes the runs made during the model tests. For each case, the first run used the mean surface geostrophic current field from the IIP data base and wind data from FNOC. This set of inputs is referred to as system currents and system winds. The remaining mns for each case differed from the first run only in that available on-scene environmental data (observed) were used to drive the nnodel. The observed currents were obtained from the TOD trajectories by lineariy interpolating to positions at OOOOZ and 1 200Z each day, and then calculating the 1 2-hour averaged current. When wind data were available, 12-hour averages were computed for use in the model. When no observed wind data were available, FNOC data were employed. For each run, the model computed a predicted iceberg position at OOOOZ and 1 200Z on each date. The range and bearing from the actual to the predicted iceberg position were computed for these times. 72 Figure D-5. Iceberg and TOD trajectories for Case III Results Figures D-9 through D-12 show the magnitude of the drift errors as a function of elapsed time for each of the four cases. The II P error estimate of 1 0nm for the first 24-hour period and an addit'ional 5nm for each additional 24-hours of drift, up to a maximum error of 30nm, is also plotted. In Case I (Figure D-9), the system inputs result in drift errors that increase rapidly and persistently; after approximately 2.5 days they exceed 40nm (~75km). The magnitude of this error is 52% of the total predicted drift. When observed currents drive the model, the errors are substantially reduced so that they are nearly consistent with the currently-used IIP error estimate. In Case I, both the iceberg and the buoy were in the southward- flowing Labrador Current with typical current speeds of 0.4-0.5 m/s. In Case II (Figure D-10), the errors for the system/system run were less than 1 2nm (~22km) or 22% of the total predicted drift for the entire 1 04-hour drift period, well below the IIP en'or estimate. Using observed current and wind data improves the results; after 1 04 hours the error is 2.5nm (-4.6 km). The drift test was conducted north of Flemish Cap with typical current speeds of 0.2 m/s, approximately half that observed in Case I. 46°50' 46''I0' 1 20/OOz VOn Mno/ooz '^ .12Q'00Z AA9/00Z ^^ s(oo* 19/OC 119/002#-Ji ns/ooz ICEBERG (▲ ▲) TOD38^m ( • • ) TOD 58m( O---0) 46^0' 46* 73 Figure D-6. Hourly wind vectors for Case III The Case III system/system run (Figure D-1 1 ) produced errors that increased persistently, exceeding the IIP error estimate after about 36 hours of drift. At the end of the drift period, the errorwas overSOnm {--56km), which is 73% of the total predicted drift. In the early part of the drift perbd (<48hrs.), the use of the observed current and wind data produced no improvement in the results; indeed, at one point, the results were less accurate than the system/system case. This result is not surprising because the iceberg moved rapidly to the north while both buoys remained close to the deployment area. When the buoys were retrieved and redeployed at the iceberg (-60 hrs.), the mode! results computed using observed data improved somewhat. Using the observed data to drive the model in Case IV (Figure D-1 2) made an enormous improvement in the results. The system/system mn produced errors between 30-45nm (-56- 83km) while, for the observed data, the en-ors were approximately half those values. For most of the drift period, the currents measured at 58m provided more accurate model results than those measured at 8m. At 84 hours this situation reversed, and the 8m data produced better results. This is an expected result because as this small iceberg deteriorated, its rrxjtion should have been nxjre consistent with the 8m currents 74 <2> Dote 116 V/I // 117 /^. ; / / ^ .<::^:^^.\\\ / y llUl /.x , 118 119 120 I I 1 1 I I 1 1_ OOz I2z —I ■ ■ ■ i_ 10 KTS 23z W 85 than the 58m currents. However, the data are few and the difference between the results (8m vs. 58m) is small so there is no certainty that the reversal is meaningful. Conclusions No f inn conclusions can be drawn from this small data set, but there is some consistency in the results that is worthy of note. In all four cases, using on- scene measured data improved the model accuracy over the runs made using geostrophic cuaents and FNOC winds. The accuracy improvement was substantial in two cases: Case I and Case IV. Thus, the results of this study support the IIP practice of using TOD drift data to rrxxJify the geostrophic current. The more widespread the use of TOD's, the nrwre we can rely on the model results. No attempt was made to separate the improvements due to on-scene current data and on- scene wind data because of the small anxjunt of data. However, Case I, for which there were no on- scene wind data, showed considerable improvement when on-scene current data were used in the model predictions. In three of the four cases (Case II excepted), the observed drift error was larger than the IIP estimated error when the system Figure D-7. Iceberg and TOD trajectories for Case IV L Ad'^ZO 4 >» 125,00z 122^jt-^ i^73l00I / i "^Ll23 00z 125, OOJ--''"'' ./ 121001.' \ yr''^ * % .♦•■■■' 1^ I24;00Z 44*'50' ICEBERG (▲ ▲) TOD 8 m ••••■••) TOD 58m 0 0) 48^30' 48° winds and currents were used. For these three cases, the drift errors were 52-73% of the total predicted drift; for Case II the drift error was 22% of the total predicted drift. While it is tempting to suggest that the estimated position error be linked to the total length of the predicted drift (distance along the predicted path), no clear guidance can be given based on these results. The limited data show that if there is a TOD providing current information in the vicinity of a drifting iceberg, the model will probably produce positions that are wrthin the IIP error limits. If only geostrophic data are available, the errors can be substantially larger, even for drifts of short duration. This issue is particulariy important when an iceberg is being used to set the limits of iceberg threat. The importance of collecting current data as close as possible to the tracked iceberg cannot be overemphasized. Early in Case III, when the TOD's and the iceberg separated rapidly, there was no improvement in the model errors when observed inputs were entered. Later in the drift period (afterthe buoys were redeployed), the model errors were smaller when the observed data were used. Finally, the results of this study provide some guidance on the deployment of IIP operational TOD's. Although TOD drift data directly north of Flemish Cap are useful, the results of Case II showed that the model performed within the error estimates using the geostrophic currents. The TOD's deployed in the Labrador Cuaent (Case I) and south of Flemish Pass (Cases III and IV), on the other hand, provided bigger payoffs. 75 Figure D-8. Hourly wind vectors for Case IV References Anderson, I., 1983. Oceanographic Conditions on tlie Grand Banks During the 1983 International Ice Patrol Season. Appendix B of Report of the International Ice Patrol in the North Atlantic. Bulletin No. 69. CG-1 88-38. International Ice Patrol, Avery Point, Groton, CT 06340-6096, 73 pp. Bessis, J.L., 1981, Operational Data Collection and Platform Location by Satellite, Remote Sensing of the Environment, Vol II Mountain, D.G., 1 980. On Predicting Iceberg Drift, Cold Regions Science and Technology, Vol 1 (3/4): 273-282. Scobie, R.W., and R.H. Schultz, 1976. Oceanography of the Grand Banks Region of Newfoundland March 1971 - December 1972. Report No. 373-70. U. S. Coast Guard, Washington, DC, 298 pp. Summy, A.D., and I. Anderson, 1983. Operational Use of TIROS Oceanographic Drifters by International Ice Patrol (1978-1982). Proc. 1983 Symposium on Buoy Technology. Marine Technology Society, Gulf Coast Section, BIdg. 2204, NSTL, MS 39529, p. 246-250. ' ' ' ' OOz Dote 121 122 123 124 125 126 -> — I — I I I I I ■ ■ ■ ■ ■ ■ I2z -I I I I 10 KTS 23z W 85 76 Figure D-9. Case I model errors Figure D-10. Case II model errors Figure D-11. Case III model errors Figure D-12. Case IV model errors 50 „ 40 E c tt 30 o tr tr. ^ 20H CASE I SVS CuaiENIS t WINO(« •) 0«S cut CJIaVns WIN0(O---O) ,-a 10 20 D-9 30 40 50 TIME (hrs) 60 CASE II _30 E o q: a: UJ 10 SYS CURRENTS & WIND(* •) OBS CUR (38fn) A WIND (o o) cx. lo ■ O O ■o o 20 30 D-10 40 50 60 TIME (hrs) i59^ •■€>-■ 70 80 90 100 D-11 40- l30- 01 o 0:20- UJ 10- CASE III SYS CURRENTS a WIND (• • OBS CUR(38/8ni)& WIND (O— O OBS CUR (5Bm) & WIND D O) IIP FRBOR -.»-f2;» □•— " ESTIMITE ^,.-mf<^ 10 2'0 30 4'0 50 60 TIME hrs) 7'0 80 90 60n 50- CASE IV SYS CURBENTS t WIND (• •) OBS CUB (8n.) t WIND (C^--r.) OBS CUB (sSm) t WIND (a-— -a) 10 20 30 D-12 40 50 60 TIME (hrs) To §5 §5 i5o 77 Appendix E An Analysis of Eddy Formation in tlie Vicinity of the Grand Banlcs of Newfoundland LT F. J. Williams, USCG D. L. Murphy Introduction The International Ice Patrol conducted a study of the eddy population in the Newfoundland Basin region based on data from the period from November 1 981 to December1984to investigate the importance and basic character of eddy motion in the southern portion (40°N-45°N and 40°W-55°W) of our patrol area. This area (Figure E-1) contains the confluence of three surface currents and is bathy metrically dominated by the Grand Banks of Newfoundland, the Newfoundland Seamount Range and the Newfoundland Ridge. A similar study was conducted by Voorheis, Aagaard and Coachman in 1973. They researched hydrographic data collected during IIP cruises in an attempt to establish an eddy population. The present study encompasses a larger geographic area and also introduces infrared (IR) imagery. Voorheis, etal. looked for eddies in hydrographic data along standard IIP transects. The present study uses data collection specifically designed to locate eddies. Ocean frontal analysis charts maintained by National Weather Service (NWS) and Naval Eastern Ooeanographic Center (NEOC), and Canadian Forces METOC Center sea surface temperature data fomied the data base for the investigation. Analysts produce these charts from satellite IR imagery gathered predominantly from the GOES and NOAA 6 and 9 satellites. The research area is dominated by cloud and fog cover and so does not always present ideal conditions for use of IR imagery, but these charts represent the only complete data set displaying eddies. An explanation of the methodology is given in Williams (1985). Data analyzed include the number of eddies in the area, their average life span and size, the area of formation, generation and deterioration patterns, and their movement through the area. Eddies included in the study are only those in the southern portion of the area that had an IR signature. Other eddies may affect the operations area, but are not included. Eddy Population Eighty-five percent of the time at least one eddy was active in the research area, and on several occasions two or more were present. During the 38 months of the experiment the NWS and NEOC charts indicated 46 eddies in the area. The life of the eddies ranged from two to 218 days with an average life span of 42 days. Voorheis, era/. (1973), indicates an average life span of 30 to 120 days. Areas of Formation The positions of fonmation of the eddies as shown in Figure E-2 indicate that they formed in two major areas: over the Newfoundland Ridge and over the Newfoundland Seamount Range. Of the 46 observed eddies, 12 (26%) were first sighted directly over the Newfoundland Seanrxxjnt Range and 34 (74%) were first sighted west of the Newfoundland Ridge. These areas are both dominated by large, relatively shallow bathymetric features. Huppert and Bryan (1 976) have demonstrated that the Atlantis II Seamounts are instrumental to eddy 79 Figure E-1. The research area, showing major ocean currents and bathymetry 57U 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39U 52Ht ^ ' >— ' ' ' I ;, I, ' ' I I I ' I 1 • •— — t- S2N f SI 50 49 48 47 46 4S 44 43 42 41 40 39 38 37 36N 57W 56 55 54 S3 52 51 SO 49 48 47 46 45 44 43 42 41 40 39W formation. Voorheis efa/. (1 973) suggest eddies in the Newfoundland Basin are bathymetrically generated. The formation of eddies in this study near the bathymetric features support the theory that interaction of the ocean currents with the topography of theSeamounts or the Ridge is important to eddy generation. Figure E-2 indicates that except for these two regions the remainder of the area appears to be relatively eddy free. Generation and Deterioration IR signatures indicate that twenty-one of the eddies (46%) formed from pinched- off meanders, eight (17%) from interactions between currents. Seventeen eddies (37%) had no identifiable source. It is possible that the cloud cover hid the meander from which the eddy formed and that by the time visibility improved, the eddy was in place and the generative process was unobserved. Seven of these eddies were in the Seanrwunt area and ten were near the Ridge. Translation Through the Area Twenty-one eddies showed a net westward drift throughout their lives. Only three displayed a net eastward drift. The remaining 22 showed no net drift. Of the 22 showing no net drift, 18 had a fully- observed life span of fifteen days or less and so may not have had the opportunity to drift at all. Three were seen in periods of heavy cbuds arid so were carried in the original reported positbnfor a month and deleted from the NWS charts. The other four showing no net drift display an oscillatory drift, both east and west alternately. This motion is also displayed by many of the longer-lived eddies that show definite westward net drift. The motion may be explained by positioning errors due to the analysis of the satellite data. These same factors may have influended the three eddies that displayed a net eastward drift. Joyce (1984), wor+cing in an area bounded by 40°N - 45°N and 55°W - 75°W (immediately to the west of this study area), demonstrated that eddies interacting with the Gulf Stream display a predominantly westward drift. The present study shows similar results because of the 21 eddies showing westward drift, 1 2 interacted with the North Atlantic Current (NAC) during their life spans. Of the three that drifted east, one showed no interaction with the parent current. Interactions with the NAC then could not have caused the net eastward drift of the eddies. 80 Figure E-2. Initial reported positions of eddies in this study. Symbols indicate the source(s) of e act) eddy report, numbers indicate sequence of formation. predominantly westward drift. The present study shows similar results because of the 21 eddies showing westward drift, 1 2 interacted with the North Atlantic Current (NAC) during their life spans. Of the three that drifted east, one showed no interaction with the parent current. Interactions with the NAC then could not have caused the net eastward drift of the eddies. Eddy Size The eddies varied in shape from roughly circular to elongated ellipses and many had irregular circumferences. To estimate the average size, all eddies were assumed to be of circular form of diameter equal to the average of the major and minor axes. The mean characteristics are shown in Table E-1. Comparison of Eddy Characteristics in Two Areas The following discussion centers on whether or not the area of formation had any effect on eddy characteristics. The duration of eddies over the Seamounts ranged from six to 1 1 5 days with an average duration of 46 days. The same statistics for the 34 eddies formed near the Ridge show a range of two to 21 8 days with an average of 41 days. These figures indicate that the area of formation has no significant effect on the S7U 56 SS 54 S3 52 51 50 49 48 47 46 45 44 43 42 41 40 39U 38 37 36N 52N tsi 50 49 .. 48 . . 47 ..46 .45 44 .. 43 ..42 •■41 ..40 .39 •38 ■■37 I I I I I I I I I I I I I I I I I 57W 56 55 54 53 52 SI 50 49 48 47 46 45 44 43 42 41 40 39U 36N life span of the eddy. In general, eddies in this area have a shorter life span than the two to three year spans reported by Joyce (1984), Richardson (1980) and Richardson (1983) in other areas of the GuH Stream system. The area of the Seanx)unts showed eddy activity 63% of the time; the Ridge, 69% of the time. Both areas have equal potential for eddy activity. The areas of formation shows no apparent affect on the migration of the eddy through the area. The eddies that formed over the Seannounts showed a westward migration in six of twelve eddies while five showed no significant migration. The remaining eddy showed eastward migration. Those formed in conjunction with the Ridge topography showed westward migration in 1 6 of 34 eddies and 81 was cold c»re. Eight cold core eddies formed in the area of the Ridge. There are two possible explanations for this: either the cold-core eddies form more as an interaction with the NAC in the Newfoundland Ridge/Tail of the Bank area, or they drifted southeast out of the Seamount area hidden by cloud cover before they were reported. A much higher percentage of Seamount eddies had an unidentified generation mechanism. Seven out of twelve or 58% had an unknown source of origin as compared with ten out of 34 or 23% of the Ridge eddies. Labrador Current Eddies Perhaps one of the nnost interesting results of this study is the location of five cold-core eddies in the area north of the Gulf Stream in the normal domain ofwarm-core NAC eddies. A possible explanation for the presence of these eddies is the Labrador Current. No studies have been conducted on the generation of eddies by this current, but Hayes and Robe (1978) showed that the Labrador Current extends to the bottom and that the flow is variable and quite often influenced by the position of the NAC. If we make the assumption that the bottom features may cause the bifurcation noted in the current's flow, it is reasonable to assume the varied bathymetry can also cause meander and eddy generation in much the same way 82 as it does in the NAC. Research dedicated to the generation of eddies by the Labrador Current is necessary. Conclusions For the three-year period, this study evaluated data from several different sources and identified a total of 46 eddies in the research area. The research area was eddy free only 1 5% of the study period. This clearly indicates that eddies are frequently in the area and that they are important to the dynamics of the area. The eddies were concentrated near the Newfoundland Seanx)unt Range and the Newfoundland Ridge. Except for these two areas, the research area showed no sign of eddy activity. This distributbn suggests that the topography features had an influence on the formation of the eddies. This indicates that, at least in some areas, the NAC is influenced by the bottom in the Newfoundland Basin area. The study also suggests that the Labrador Current is capable of generating eddies. Five cold- core eddies were found in an area where they could not have been generated by the NAC. Kollmeyer, era/. (1965) documented the existence of a cold-core eddy spawned by the Labrador Current and recognized its importance as a cold trap for icebergs. However, no systematic study of Labrador Current cold-core eddies has yet been conducted. This is a subject that requires further investigation. /In their movement, the eddies followed the pattern predicted by Joyce (1 984) and drifted predominantly to the west. This was true even for those eddies that showed a considerable interaction with the eastward- flowing NAC. The most common method of formation was pinched- off meanders. Absorption back into the parent current by similar meanders was the most common method of deterioration. The area of formation had no apparent effect on the characteristics of the eddies. Those formed over the Seanrx>unts displayed features similar to those formed over the Ridge. All were of equivalent size and duration. The study indicates that the average eddy in the southern IIP operations area will be a warm core eddy approximately 1 1 6 km in diameter. It will forni over the Seamountsoroverthe Ridge, normally from a pinched-off meander, and will migrate to the west after formation. It will remain on plot for about 42 days and will normally be absorbed back into the parent current. We can expect to see an eddy similar to the one described here in the southern IIP operations area about80%ofthetinne. Table E-1. Average Characteristics of Eddies in study area Eddy Number of Type Obser- vations Average Size Average Life (days) Warm Core 38 117 "^L.^.: Cold Core 8 94 21 Table E-2. A Comparison of Characteristics of the Eddies near the Newfoundland Ridge and the Newfoundland Seamounts Warm Core Newfoundland Ridge 26 127 47 Newfoundland Seamounts 11 105 55 Cold Core Newfoundland Ridge 8 100 23 Newfoundland Seamounts 1 55 6 83 These figures are in general agreement with Voorheis etal. (1 973) . The only difference in the conclusions is the rotation of the eddies. Their data indicated cold core eddies are nxjre numerous. The present study indicates warm core eddies dominate. It is difficult to address this difference, but IR positively indicates the temperature differences in water masses. Additional long term analyses may resolve this discrepancy. References Hayes, R.M. and R.Q. Robe, 1978. Oceanography of the Grand Banks Region of Newfoundland, 1973. U.S. Coast Guard Oceanographic Report No. 13, CG-373-13, United States Coast Guard, Washington, DC 20593. Huppert, H.E. and K. Bryan, 1976. Topographically Generated Eddies". Deep-Sea Research, 23, 655-679. Joyce, T.M., 1 984. "Velocity and Hydrographic Structure of a Gulf Stream Warm-Core Ring". Journal of Physical Oceanography, 14(5), 936-941 . Kollmeyer, R.C., R.M. O'Hagan, R.M. Morse, D.A.McGill, and N. Cotwin, 1965. Oceanography of the Grand Banks Region and the Labrador Sea in 1964. U.S. Coast Guard Oceanographic Report 10, CG 373-10. United States Coast Guard, Washington, DC 20593. Lai, D.Y. and P.L. Richardson, 1977. "Distribution and Movement of Gulf Stream Rings". Journal of Physical Oceanography, 7(9), 670-683. Richardson, P.L.. 1980. "Gulf Stream Ring Trajectories". Journal of Physical Oceanography, 10(1), 90-104. Richardson, P.L., 1983. "Eddy Kinetic Energy in the North Atlantic Ocean from Surface Drifters". Journal of Geophysical Research, 88(C7), 4355-4367. Voortieis, G. M., K. Aagaard and L. K. Coachman, 1973. "Circulation Patterns Near the Tail of the Banks". Journal of Geophysical Research, 3(10), 397-405. Williams, F.J., 1985. Investigation into the Population and Motion of Eddies in the Southern International Ice Patrol Operations Area. Master of Science Thesis. Old Dominion University, Norfolk, Virginia. 84 Appendix F Detection of Ocean Fronts in the Gulf Stream / Labrador Current System by Side-Looking Airborne Radar LTJG N, B. Thayer, USCGR D. L. Murphy Introduction The Gulf Stream probably reaches its greatest complexity in the region south and southeast of Newfoundland where it interacts with complex bathymetry and the southward-flowing Labrador Current to produce an ever-changing system of fronts, eddies and associated features. This complex current system is responsible, in large part, for the distribution of icebergs in much of the Intemational Ice Patrol's (IIP) operating area. The IIP iceberg drift model, an integral part of the IIP operations, relies primarily on historically time- averaged cun-ents. Using these currents can lead to substantial drift errors, particularly in regions with large current fluctuations. To address this problem, IIP uses the drift of satellite-tracked drift buoys, deployed by IIP aircraft, to provide near real-time cun-ent data to the model. Although this program is successful, the updates to the current field are limited temporally and spatially to the period for which a buoy is drifting through a specific region. Renrx>te sensing techniques hold the nrx>st promise for providing current data for future IIP operations. For example, satellite infrared imagery is used successfully under certain cond'rtbns to define ocean frontal boundaries and, thus, infer circulation patterns for several ocean areas. Unfortunately, infrared imagery is of limited operational use in the IIP area due to persistent fog and cloud cover. However, active microwave systems (radars) are capable of penetrating clouds and, under the right circumstances, detecting frontal features. In 1985 IIP began investigating the feasibility of using imagery from a side-looking airtjome radar (SLAR) to map ocean fronts in the IIP area. This report desaibes some of the preliminary results of that investigation. Background The International Ice Patrol deploys one week out of two to Gander, Newfoundland, during the icebergs season, typically March through August. Using U.S. Coast Guard HC-130 aircraft, IIP conducts iceberg reconnaissance flights within the area bounded by 40°-52°North and 39°-57°West. Reconnaissance flights are made each day during the deptoyments, each flight approximately 3,1 50 km long (1 ,700 nm), covering approximately 65,000 square km. Since the spring of 1983, IIP has used SLAR as the main method of iceberg reconnaissance, replacing visual reconnaissance. SLAR is an X-band radar that scans the sea surface in a plane normal to the flight path. The radar image is displayed on a narrow CRT that produces a negative image on photographic film (Figure F-1 ). The standard altitude for IIP reconnaissance is 8,000 feet, with a SLAR swath width of 1 00 km, 50 km to each skje of the aircraft with an unimaged swath directly betow the aircraft of about 5 km. SLAR is largely unaffected by weather, with only heavy precipitation otscuring the view of the surface. Review of IIP SLAR films for 1 983- 1985, representing some 200 flights, has revealed that SLAR is capable of detecting the fronts of the Gulf Stream and Labrador Current, with the water nnasses of different temperatures showing up as different shades on the SLAR film's negative image, warm water appearing dark and cooler water appearing light. These con'espond to high radar backscatter and tow radar 85 55' 50- 45" GS - Gult Stream WE - Warm-core Eddy Ti — I — I — 1 — I — I — I — I — I — r ~^^ 1 0' / t / ^, v^ =^ \N. 40' * J I L J I L J I \ L 40' Jj35- Figure F-1. Reproduced National Earth Satellite Service (NESDIS) product from April 26, 1985. Inset — NESDIS worksheet from 25-26 April 1985. Figure F-2. A segment of SLAR film from the International Ice Patrol reconnaissance flight of April 28, 1985, with a photo mosaic of the same piece of film. Warm (rough) water appears dark. 86 52* 5^^ 50" 49' 48* 47" 46* , 200 m *■•... ,••* ^ / / f \ \ \ \ i \ "^ 1 — ^ N ^'^ 7 '^ J 43" 42' 41" Figure F-3. Superimposition of the ocean features detected by NESDIS (solid line) on 25- 26 April 1985 (see inset, Figure F-1) and features detected by IIP SLAR (dashed line) on 28 April 1985, some of which are visible in Figure F-2. backscatter respectively. The imagery frequently shows very sharply delineated fronts in great detail. Previous work using SLAR and satellite infrared in the Grand Banks area was done by LaViolette (1983), using an earlier Coast Guard SLAR and a NASA SLAR. The earlier SLAR's had lower power outputs and the images reproduced by LaViolette are apparently less sharp and less detailed than the ones produced by the present model, a Motorola AN/APS-1 35 Side-Looking Airtx)me Multi-Mission Radar (SLAM MR). The most extensive body of work involving detection of ocean features with an active microwave system has been done with SEASAT synthetic aperture radar (SAR) (Beal, etal, 1981). Some of the work done with SEASAT imagery has included comparison with satellite infrared imagery (Fu and Holt, 1982, 1983; Hayes, 1981). Although the precise mechanism is uncertain, it is clear that the difference in backscatter is due to a difference in surface roughness. Visual inspection of the sea surface during IIP flights has shown that the dark and light areas on the SLAR film correspond closely to rough and smooth areas visible under conditions of light wind. Also, the SLAR films contain many images of intemal wave trains, many of them closely linked to the bathymetry of the edge of the continental shelf. The alternate rough and smooth bands of intemal waves detected by SEASAT SAR have been described in Alpers and Salusti (1983) and Hughes and Gower (1983), among others. Discussions of the mechanism of detecting ocean features in radar imagery usually invoke Bragg scattering (Valenzuela, 1978; Brown, Elachi and Thompson, 1976), which defines a critk^l surface wavelength for maximum backscatter. FortheX-band SLAR and the range of incidence angles encountered in IIP operations, the range of ocean wavelengths causing Bragg scattering is approximatley 2-30 cm. The relationship between the rough and snnooth patches seen visually and the SLAR imagery reflects the relative spectral energy density in those patches, (i.e., the wave height at the Bragg wavelength). Results IIP SLAR imagery of ocean fronts has frequently been confirmed by the interpretations of Advanced Very High Resolution Radiometry (AVHRR) imagery by NOAA's National Environmental Satellite, Data and Information Service (NESDIS). A simplified reproduction of the NESDIS chart for 26 April 1 985 is seen in Figure F-1 , with an inset showing the interpreter's worksheet for the area outlined on the main chart. Figure F-2 is a SLAR image from 28 April, from the area outlined in Figures F-1 87 Discussion and F-3, showing a complex set of frontal features. The NESDIS worksheet and a SLAR interpretation are super- imposed in Figure F-3, showing a very close match of the features. In comparing the two images in Figure F-3, the similarities are apparent. The two fronts that converge to the east, the transverse north-south feature to the west and the area of sharp curvature on the western part of the southern front are present in both images, but differ somewhat in spatial orientation. The SLAR fails to detect the warm-core eddy shown on the final NESDIS chart (probably off the edge of the film), but SLAR shows an additional small-scale (1 0 km) eddy along the front. The differences between the SLAR interpretation and the NESDIS worksheet do not appear to be due to navigational displacement or rotation between the two, and are probably due to movement of the feature during the two day span between images. It is significant that by using the apparent SLAR temperature/backscatter relationship, the gradatbn of temperature from south to north is the same for both SLAR and AVHRR, i.e., a large area of warm water to the south (the Gulf Stream), a narrow band of cool water, a band of warm water and finally a band of cool water. Perhaps more important is tfiat, giving the good match of location, shape and apparent temperature gradients across fronts, both SLAR and AVHRR appear to be detecting the same features. The SLAR and satellite infrared imagery from 28 April and 26 April, respectively, show a good match of the features detected, both in location and overall shape. The particular SLAR image is a good illustration of how well the two sources can agree. Over the three years of SLAR operation at IIP, a large number of SLAR images of fronts have been collected. Of these, there have been a number of cases in which SLAR and AVHRR do not seem to agree both in k>cation and shape of features. Williams (1985) examines the match and mismatch of SLAR and AVHRR images in eddies and associated features in the IIP region. Most frequently the difference seems to be one of placement rattier than shape, reflecting a navigational discrepancy between the two sources. Of the tvw), SLAR offers the greater positional accuracy. It makes use of the aircraft's Inertial Navigation System (INS), yielding an accuracy of ±5 km (Thayer SLAR/LORAN,unpub.). Positioning on the NESDIS chart is done using visible known land forms on the image, which may be obscured by ctoud cover, making it less accurate, with errors possibly as rrxjch as 15-20 kilometers (personal communication, Jennifer Clark, NESDIS). Given the nature of the NESDIS product, i.e., the large area covered, more accurate F>ositioning is unnecessary. There are other cases in which there is considerable difference in overall shape between SLAR and the NESDIS product. This usually occurs when the area is obscured by ck>uds and NESDIS is estimating the kxjation and shape of features based on information that is up to several days okl. In worthing with the original satellite imagery, the wori->,.^j^:i. U.S. Department of Transportation United States Coast Guard Report of the International Ice Patrol in the North Atlantic Marine Biological Laboratory LIBRARY 'I DEC 3 0 1988 < Woods Hole, Mass. '• 1 986 Season Bulletin No. 72 CG- 188-41 International Ice Patrol U.S. Department of Transportation United States GKist Guard Commandant United States Coast Guard MAILING ADDRESS 2100 2nd St., S.W. Washington, D.C. 20593 (202) -267-1450 JAN 25 !988 Bulletin No. 72 REPORT OF THE INTERNATIONAL ICE PATROL SERVICES IN THE NORTH ATLANTIC OCEAN Season of 1986 CG-188-41 FOREWORD Marine Biological Laboratory ' LIBRARY ' DEC 3 0 1988 ! Woods Hole, Mass. • Forworded herewith is bulletin No. 72 of the Interrational Ice Patrol describing the Patrol's services, ice observations and conditions during the 1986 season. ^^u CLYDE E.ROBBINS CWef, Office flfOperafioDj DISTRIBUTION SDL No. 126 a b c d e f 9 h i J k 1 m n 0 P q r s t u V w X Y 2 A B *1 *1 b 2 2 2 1 C *1 *l D fin E F G H . NON-STANDARD DISTRIBUTION: *B:b LANTAREA (5), B:b PACAREA (1), B:c First, Fifth, Seventh Districts Only, *C:aq LANTAREA only, SML CG-4 International Ice Patrol 1986 Annual Report Contents 4 Introduction 5 Summary of Operations 7 Iceberg Reconnaissance and Communications 8 Environmental Conditions, 1986 Season 17 Ice Conditions, 1986 Season 38 Discussion of Iceberg and Environmental Conditions 38 Acknowledgements Appendices 39 A. List of Participating Vessels 45 B. TIROS Oceanographies Drifter Tracks on the Grand Banks During the 1986 International Ice Patrol Season 53 C. Observations of an Oceanic Front South of Flemish Pass Introduction This is the 72"" annual report of the International Ice Patrol Service in the North Atlantic. It contains information on ice conditions and Ice Patrol operations for 1986. The U.S. Coast Guard conducts the Interna- tional Ice Patrol Service in the North Atlantic under the provisions of U.S. Code, Title 46, Sections 738, 738a through 738d; and the International Convention for the Safety of Life at Sea (SOLAS), 1974, regulations 5-8. This service was initiated shortly after the sinking of the RMS TITANIC on April 15, 1912. Commander, International Ice Patrol, under Commander, Coast Guard Atlantic Area, directed the International Ice Patrol from offices located at Groton, Connecticut. International Ice Patrol analyzes ice and environmental data, prepares the daily ice bulletins and facsimile charts, and replies to any requests for special ice information. It also controls the aerial Ice Reconnaissance Detachment and any surface patrol cutters when assigned, both of which patrol the southeastern, southern, and southwestern limits of the Grand Banks of Newfoundland for icebergs. The International Ice Patrol makes twice-daily radio broadcasts to warn mariners of the limits of iceberg distribution. Vice Admiral P.A. Yost was Commander, Atlantic Area from the start of the 1986 season, March 27. Vice Admiral D.C.Thompson became Commander, Atlantic Area on May 27,1986. Commander Norman C. Edwards, Jr., U.S. Coast Guard, was Commander, Interna- tional Ice Patrol during the Ice Patrol season. Summary of Operations, 1986 During the 1986 Ice Patrol season, from March 27 to July 3, 1986, the International Ice Patrol (IIP), a unit of the U.S. Coast Guard, conducted the International Ice Patrol Service, which has been provided annually since the sinking of the RMS TITANIC on April 15, 1912. During past years, Coast Guard ships and/or aircraft have patrolled the shipping lanes off Newfoundland within the area delineated by 40°N - 52°N, 39°W - 57°W, detecting icebergs and warning mariners of these haz- ards. During the 1986 Ice Patrol season. Coast Guard HC-130 aircraft flew 45 ice reconnais- sance sorties, logging over 294 flight hours. The AN/APS-135 Side-Looking Airtwrne Radar (SLAR), which was introduced into Ice Patrol duty during the 1983 season, again proved to be an excellent all-weather tool for the detection of both icebergs and sea ice, providing 26.1 percent of all 1986 sightings. Deployments were made February 1- 5 and March 1 1-20 to deter- mine the pre-season iceberg distribution. Based on the latter trip, regular deployments started on March 25 with the 1986 season opening on March 27. From that date until July 2, 1986, an aerial Ice Reconnaissance Detachment (ICERECDET) operated from Gander, Newfoundland one week out of every two. The season officially closed on July 3, 1986. During the 1986 ice year, an esti- mated 204 icebergs drifted south of 48°N latitude. Table 1 shows monthly estimates of the number of icebergs that crossed 48°N. Six satellite-tracked oceano- graphic drifters were deployed to provide operational data for HP's iceberg drift model. The drift data from these buoys are discussed in Appendix B. No U. S. Coast Guard cutters were deployed to act as surface patrol vessels this year. The USCGC EVERGREEN was de- ployed to conduct oceanographic research for the Ice Patrol during the period April 22 through May 22. In 1986, research efforts were directed toward studying ocean frontal features associated with a warm core eddy between the Grand Bank and the North Atlantic Current. SLAR was used to map the surface roughness gradients across frontal boundaries. The study area was re-mapped weekly during the month of May. Based on the initial SLAR survey, a series of hydrographic transects were made of the eddy, and satellite-tracked drifting buoys were dsployed in the area. The results of this study are presented in Appendix C. Table 1. Icebergs South of 48° North The three periods shown are ship reconnaissance (1900-45), aircraft visual reconnaissance (1946-82) and SLAR reconnaissance (1983-85) Avg Avg Avg 1900-45 1946-82 1 983-85 1986 OCT 2 0 1 0 NOV 2 0 4 0 DEC 2 0 3 0 JAN 3 7 4 0 FEB 101 ^; 8 74 3 MAR 46 32 118 40 APR 105 85 :iiii^li:r500^-^-^ 60 MAY 154 81 384 59 JUN 77 ^'" ' 60 214 24 JUL 26 13 178 18 AUQ '-^Z y '^^^ftjpi^^^ ^u.>Aji^l ^^^PlH ^■B SEP Total 5 0 14 0 441 279 1539 204 Table 2. Source of International Ice Patrol Iceberg Reports by Size » Percent Sighting Source Growler Small Medium Large Radar Target Total of Total Coast Guard SLAR 44 101 37 13 10 205 26.1 ^' Coast Guard Visual 7 56 44 21 ^9.^. 128 16.3 CanadianSLAR '1 16 14 ' 1 ^^/- M^„VS■ ■<' *j97^ 12.4 Canadian Visual 0 20 16 1 0 37 4.7 Commercial Radar 8 10 10 1 31 60 7.6 Commercial Visual 5 33 112 26 0 176 22.4 Offshore Industry 0 3 0 1 2 6 0.8 Lighthouse/Shore 0 0 0 0 0 0 0.0 Other Total 1 66 31 270 35 268 ...............9,,.,:. 0 76 785 9.7 100.0 73 108 Table 2 shows the sightings reported to the International Ice Patrol in 1986, broken down by the source of the sighting and the size of iceberg sighted. It is important to note that the IIP side-looking airborne radar (SLAR) provided over 26% of the iceberg reports, the single largest source of icebergs sightings. Given that IIP SLAR reconnaissance usually takes place near the limit of all known ice, this sighting source becomes especially important. Iceberg Reconnaissance and Communications During the 1986 Ice Patrol year (from October 1 , 1985 through September 30,1986), 63 aircraft sorties were flown in support of the International Ice Patrol. These included pre-season flights, ice observation and logistics flights during the season, and post- season flights. Pre-season flights determined iceberg concentrations north of 48°N to estimate the time when icebergs would threaten the North Atlantic shipping lanes in the vicinity of the Grand Banks of Newfoundland. During the active season, ice observation flights located the southwestern, south- ern, and southeastern limits of icebergs. Logistics flights were necessary due to aircraft mainte- nance problems. Post-season flights were made to retrieve parts and equipment from Gander and to close out all business transac- tions from the season. U.S. Coast Guard aircraft, de- ployed from Coast Guard Air Station Elizabeth City, North Carolina, conducted all the aircraft missions. SLAR-equipped HC- 130 aircraft were utilized exclu- sively for aerial ice reconnais- sance, and HC-130and HU-25A aircraft were used on logistics flights. Table 3 shows aircraft utilization during the 1986 season. U.S. Coast Guard Communica- tions Station Boston, [Massachu- setts, NMF/NIK, was the primary radio station used for the dissemi- nation of the daily ice bulletins and facsimile charts after prepara- tion by the Ice Patrol office in Groton. Other transmitting Table 3. Aircraft Use During the 1986 IIP Year (October 1, 1985 to September 30, 1986) Aircraft Hours Deployment Flown Pre-season 63.1 Regular season 294.5 Post season 22.2 Total 379.8 Iceberg Reconnaissance Sorties by Month Flight Month Sorties hours Feb 2 13.7 Mar 9 40.7 Apr 7 50.9 May 14 99.1 Jun 10 74.4 Jul 3 15.2 Total 45 294.0 stations for the OOOOZ and 1 200Z ice bulletins included Canadian Coast Guard Radio Station St. John'sA/ON, Canadian Forces Radio Station f^ill Cove/CFH, and U.S. Navy LCf^P Broadcast Stations Norfoik/NAfvl; Thurso, Scotland; and Keflavik, Iceland. Canadian Forces Station Mill Cove/oFH as wellas Afvl Radio Station Bracknell/GFE, United Kingdom, are radiofacsimile broadcasting stations which used Ice Patrol limits in their broad- casts. Canadian Coast Guard Radio Station St. John's/ VON provided special broadcasts. The International Ice Patrol requested that all ships transiting the area of the Grand Banks report ice sightings, weather, and sea surface temperatures via the above communications/radio stations. Response to this request is shown in Table 4, and Appendix A lists all contributors. Commander, International Ice Patrol extends a sincere thank you to all stations and ships which contributed. Table 4. Iceberg and SST Reports Number of ships furnishing Sea Surface Temperature (SST) reports 49 Number of SST reports received 274 Number ot ships furnishing ice reports 21 1 Number of ice reports received 437 First Ice Bulletin * ' 270000ZMAR86 Last Ice Bulletin 031 200Z JUL 86 Number of: facsimile charts transmitted 97 Environmental Conditions 1986 Season January: The mean pressure distribution in Figure 1 shows a normal location for the Icelandic Low, with stronger than normal pressure gradients surrounding it. A westerly flow brought drier, somewhat warmer conditions to Newfoundland, while a northerly flow brought near-normal condi- tions to Labrador (Table 5). February: The Icelandic Low was deeper than normal and was south and west of its normal mean February location (Figure 2). The two Newfoundland stations had colder and wetter conditions than normal (Table 5), the result of increased flow from the Labrador Sea, providing a combination of moisture and cooling from the pack ice. Labrador (Goose Bay) was at or above normal tempera- ture and significantly drier than normal, the result of a stronger northerly flow. Marcfi: N/larch was significantly colder for all three stations, with precipitation below normal in Goose Bay and Gander and above normal in St. John's. This pattern was caused by a deeper than normal Icelandic Low, causing a colder, more westerly flow over the region (Figure 3). St. John's received moist marine flow from the Gulf of St. Lawrence while Gander and Goose Bay were under the influence of drier continental air. April: The Icelandic Low was farther east than normal, setting up southerly, even southeasterly flow over Newfoundland and Labrador (Figure 4). April was much warmer at all three locations and significantly wetter in New- foundland. These conditions were caused by the more southerly flow, bringing warm, moist marine air from the Atlantic, without the continental influence that normally moderates conditions. May: The mean surface pressure distribution was close to normal during May (Figure 5). The below- normal precipitation was caused by the trough-like feature south of Newfoundland, causing flow south of the island rather than over it. June: A more southerly flow over Newfoundland in June (Figure 6), brought rrroister, slightly warmer marine air, while Labrador re- ceived cooler, moister marine air from the Labrador Sea (Table 5). July: Labrador and Newfound- land were cut off from their normal southerly/southwesterly flow (Figure/). As a result, all three stations were cooler than normal. The two Newfoundland stations received a northeasterly flow, bringing above normal precipita- tion, while Labrador had a west- erly flow, bringing continental air and below normal precipitation. NOTE: Temperature and precipi- tation data for Nain, Labrador, are compared to 1985 values in Table 5. The reporting station at Hoped- ale, Labrador, was closed in 1984 and the Nain station opened. An historical mean for Nain does not exist. ^^^^^H ^^ Tables. Environmental Conditions for 1986 IIP Season Temp °C % of %of Monthly Diff. Total Normal Normal Station Mean from Norm. P recipitation (mm) Precipitation Snowfall Main 1.3 -0.5 56.7 76.4% OCT 1 985 Goose 1.8 -0.9 61.2 79.9% 90.7% Gander 4.5 -1.5 72.3 69.1% 229.5% St. John's 5.8 -1.1 85.9 59.0% 250.0% Nain -3.7 1.1 87.7 160.9% Goose -5.1 -1.3 24.3 32.3% 31.2% NOV Gander -1.2 -3.0 71.8 66.9% 74.2% St. John's 0.3 -3.1 103.7 63.8% 144.8% Nain -11.7 5.5 229.8 295.0% DEC Goose -14.2 -1.2 32.7 45.0% 51.4% Gander -5.3 -1.5 95.0 87.8% 98.4% St. John's -3.2 -1.7 113.9 70.7% 124.0% Nain -16.5 -3.9 125.3 59.5% JAN 1986 Goose -15.6 0.8 76.6 103.0% 117.4% Gander 4.8 1.4 73.4 67.3% 39.4% St. John's -2.7 1.2 117.3 75.3% 64.7% Nain -13.8 2.4 74.2 59.7% Goose -14.0 0.5 21.9 36.1% 47.4% FEB Gander -7.5 -0.7 124.8 125.2% 138.8% St. John's -5.5 -1.0 184.9 132.0% 87.9% Nain -17.6 -5.6 20.7 16.7% Goose -12.9 -4.3 44.3 61 .4% 65.3% MAR Gander -5.9 -2.4 85.3 77.7% 114.8% St. John's -3.8 -1.5 175.3 132.9% 71.2% Nain -3.3 4.8 44.8 37.5% Goose 0.8 2.5 61.0 99.7% 27.2% APR Gander 4.1 3.2 130.0 139.5% 18.7% St. John's 4.2 3.0 129.2 1 1 1 .8% 12.7% Nain 3.5 2.5 31.4 60.1% Goose 7.8 11.5 44.8 70.2% 32.6% MAY Gander 7.1 0.9 45.0 64.3% 145.0% St. John's 6.1 0.7 43.4 42.6% 182.9% Nain 3.6 -3.3 114.9 512.9% Goose 9.2 -2.1 115.9 124.5% 43.2% JUN Gander 12.1 0.3 96.8 120.5% 42.9% St. John's 11.9 1.0 130.2 152.1% * Nain 9.1 -1.7 59.1 66.0% Goose 13.3 -2.5 87.8 83.5% * JUL Gander 14.0 -2.5 113.2 164.1% * St. John's 13.0 -2.5 87.8 105.7% * Nain 11.2 1.0 68.7 149.3% Goose 15.4 -3.9 122.4 1 1 8.6% * AUG Gander 16.0 0.4 61.8 63.5% * St. John's 15.1 -0.2 60.6 49.8% * Nain 7.4 0.6 38.8 64.1%" SEP Goose 7.7 -1.4 115.2 136.3% * Gander 9.0 -6.6 138.5 170.6% * St. John's 9.7 -6.2 118.1 105.4% * No snowfall refcorded during this month SEA LEVEL PRESSURE MONTHLY MEAN JANUARY 1986 ? ^ / rx -*?s^ / \1 Figure 1. January 1986. Comparison of monthly mean surface pressure (bottom) with January historical average, 1948 - 1970 (top). 10 Figure 2. February 1986 11 Figures. March 1986 12 SEA LEVEL PRESSURE MONTHLY MEAN APRIL 1986 J2 \ / ^ '■^ / Figure 4. April 1986 13 SEA LEVEL PRESSURE MOffTHLY MEAN MAY 1986 -^ / v^v;: Figures. May 1986 14 Figure 6. June 1986 15 V ^^Wi^^Vr"^ — I-A ^^^_^^ ^''^^^^^S^^^^ mrr^ \)^/^^k: ^^W^^N/tCv^ ^^A A / J 1) / / / \ irA ^W^fKk ^^5c ■^m^' iw/vA . A^-V^ iA/^iSiji/^~ ^J^/ )^//\" '«! ^N '"^ ^^^ ■ 'X/'^^^AaOr&jfxv/. \ / \/ VC' 1016 x,/ MG^^rfX' V^ Ir^ffi ^PV V H^^f/^ CTKJ^-^ ^\ / ^"'^^^"**-*^ r ~ ) ^^^ ^"^ ^^^^v.,^-vL-.-'--''''\ \ Ox"' "■"■^^ / Ms-.liiU >-s::S c . \ ^ "^^ ""^ \ A ^1016^ H1016 , SEA LEVEL PRESSURE MONTHLY MEAN JULY 1986 J. 1 i. ^-N -V-t-^ / Figure?. July 1986 16 Ice Conditions 1986 Season October - November 1985: No sea ice was seen south of 65°N during these two months (Figures 8 and 9), however, sea ice forma- tion was at or ahead of normal north of 65°N, due to below normal temperatures (Table 5). There were no icebergs added to plot south of 52°N in October or November. December 1985: By mid- December (Figure 10), under the influence of continued below normal temperatures, Ungava Bay, Hudson and Davis Straits and the Labrador coast all showed 9-10 tenths coverage with new and young ice. Some sea ice formation was also taking place in the bays and coves of the northern Gulf of St. Lawrence. Consoli- dated first year ice extended as far south as Resolution Island in Hudson Strait. There were no icebergs added to plot south of 52°N in December. January 1986: Mid-January showed the advance of new/young ice to the northern Avalon Penin- sula in eastern Newfoundland (Figure 11). The boundary of first year ice was virtually unchanged from mid-December. There were no icebergs added to plot south of 52°N in January. February 1986: Under the influ- ence of a strong northerly flow in February (Figure 2), the sea ice advanced south along the Labra- dor coast and first year ice reached alnrwst to the Avalon Peninsula by mid-month (Figure 12). Six icebergs were added to plot south of 52°N in February, 3 of which were south of 48°N. March 1986: The ice edge continued to advance south (Figure 13), with a tongue of 9-10 tenths first year ice extending out to the vicinity of Flemish Pass by mid-March. The westerly flow over the region produced areas of somewhat lighter sea ice concen- tration along the east coasts of Baffin Island, Labrador and Newfoundland. During March, 42 icebergs were added to plot south of 52°N, 40 of which were south of 48°N. The high proportion south of 48°N was caused by icebergs being carried south and east of the ice pack by the Labrador Current. The 1986 International Ice Patrol season opened on March 27 (Figure 19). April 1986: The sea ice deterio- rated and retreated along the Labrador and Newfoundland coasts during April (Figure 14), normally a month of continued sea ice development in the area. This retreat was caused by the warm conditions and southerly flow (Figure 4) described previously. During April, 60 icebergs were added to plot south of 52°N, all of which were south of 48°N. At mid- month, the main concentration of icebergs on plot at IIP was in Flemish Pass and across the northern half of the Grand Bank (Figure 20). By April 30, icebergs were widely distributed across the area south of 48°N (Figure 21). May 1986: The ice edge contin- ued to retreat in May and by mid- month, the Strait of Belle Isle was ice-free (Figure 15). Of the 74 icebergs added to plot south of 52°N in May, 59 were south of 48°N, the most icebergs south of that latitude for any month in 1986. The southernmost iceberg of the 1986 season was on May 10 at position 41° 06'N 48°06'W. By May 1 6 (Figure 22), fewer ice- bergs were seen on the Grand Bank and south of Flemish Pass, while the number north of 48°N had increased. On May 30 (Figure 23), only 7 icebergs remained south of 48°N and the total number of icebergs on plot had greatly decreased since mid- month. June 1986: The ice edge was north of Goose Bay by mid-June and continuing to retreat (Figure 16). With 151 icebergs added to plot, June was the heaviest month for new icebergs, but only 24 new icebergs were south of 48°N. At mid-month, the only icebergs remaining south of 48°N were concentrated along the Newfound- land coast near Cape Race (Figure 24). On June 30, no ice- bergs remained south of 48'"N (Figure 25). July - September 1986: The ice edge continued to retreat in July and August (Figures 17 and 18) and by mid-September, there was no sea ice south of 65°N. There were no icebergs reported south of 48°N during July, August and September.. The 1986 Interna- tional Ice Patrol season closed on July 3 (Figure 26). 17 Table 6. Explanation of Sea Ice Symbols Used in Figures 8 — 18 Total ice concentration in the area in tenths. a b c Concentration of thickest (Cg ), 2nd thickest (Cb), 3rd thickest {Cq). SaSjjSc Stage of development of thickest (Sg ), 2nd thickest (Sjj), 3rd thickest (S q) Concentration of ice within areas of strips and patches. Floe size of thickest (Fg), 2nd thickest (Fj^), 3rd thickest (F^ ). Stage of Development 0 No stage of development 0 1 New ice 1 2 Nilas, ice rind 2 3 Young ice 3 4 Grey ice 4 5 Grey-white ice 5 6 First-year ice 6 7 Ttiin first-year ice 7 8 Thin first-year ice, 30-50 cm 8 9 Thin first-year ice, 50-70 cm 9 1- Medium first-year ice / 4 • Thick first-year ice 7 • Old ice 8 • Second-year ice 9 • IVIulti-year ice ▲ Icebergs A trace of ice thicker than S a # Fourth type, if C C C do not add up to C Floe Sizes Pancake ice Brash, small ice cake Ice cake Small floe Medium floe Big floe Vast floe Giant floe Growlers and floebergs Icebergs Undetermined or unknown 18 Figure 8. October 15, 1985 Sea Ice Conditions Sea Ice Limit of all known ice (concentrations in tenths) 60 55 Greenland 50 55 50 45 45 19 Figure 9. November 12, 1985 Sea Ice Conditions Sea Ice 60 Limit of all known ice (concentrations in tenths) 55 60 55 45 Greenland 65 50 60 55 50 45 45 20 Figure 10. December 17, 1985 Sea Ice Conditions Sea Ice Limit of all known ice (concentrations in tenths) 60 55 Greenland 55 50 45 50 45 21 Figure 11. January 14, 1986 50 Sea Ice Conditions Sea Ice Limit of all known ice (concentrations in tenths) 45 Greenland 65 60 55 50 60 55 50 45 45 22 Figure 12. February 18, 1986 50 Sea Ice Conditions Sea Ice Limit of all known ice (concentrations in tenths) Greenland 60 55 50 55 50 45 45 23 Figure 13. March 18, 1986 50 Greenland Sea Ice Conditions Sea Ice Limit of all known ice (concentrations in tenths) 60 55 50 45 45 24 Figure 14. April 15, 1986 50 Sea Ice Conditions Sea Ice Limit of ail known ice (concentrations in tenths) Greenland 60 55 50 65 45 45 25 Figure 15. May 13, 1986 45 Greenland 50 65 Sea Ice Conditions Sea Ice Limit of all known ice (concentrations in tenths) 60 55 50 60 55 50 45 45 26 Figure 16. June 17, 1986 50 Sea Ice Conditions Sea Ice Limit of all known ice (concentrations in tenths) 60 55 45 Greenland 50 65 60 55 50 45 45 27 Figure 17. July 15, 1986 50 Sea Ice Conditions Sea Ice Limit of all known ice (concentrations in tenths) 60 55 65 Greenland 50 55 50 45 45 28 Figure 18. August 18, 1986 29 Figure 19. March 27, 1986 57° 56° 55° 54° 53° 52° 51° 50' 49° 48° 47° ^6° 45° 44° 43° 42° 41° 40° 39° 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° LEGEND FOR 1200 GMT 27 MAR 86 BASED ON OBSERVED AND FORECAST CONDITIONS A BERG ^GROWLER X RADAR TARGET/CONTACT 30 Figure 20. April 15, 1986 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° rTTtTTTTTtiriiTlTiinbTiiitrtitil 1 11 II It lint III rill im I iiirTJ ttrTT+tttiil 1 1 1 1 il 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° LEGEND FOR 1200 GMT 15 APR 86 BASED ON OBSERVED AND FORECAST CONDITIONS A BERG ^GROWLER X RADAR TARGET/CONTACT 31 Figure 21. April 30, 1986 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° rmrtjiiii li 1 1 ii 1 1 1 1 1 il 1 1 1 1 1 I 1 1 1 1 1 ill iml i ii it+i 1 1 iihrtrtlTTrrttrrrrrl Iiiiiil iiii 40°fl 39-: 38^ A NUMBER IN A ONE DEGREE RECTANGLE INDIGATES THE NUMBER OF ICEBERGS IN THAT RECTANGLE. I ii[ II II I III I ii|i iiii|i I III I mill II iiijii iii|iiiii jiii II |iiiii |iiiii| iiiiij mil I iiiii| mil |i iiii|iiiii 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° LEGEND A BERG ^GROWLER X RADAR TARGET/CONTACT FOR 1200 GMT 30 APR R6 BASED ON OBSERVED AND FORECAST CONDITIONS 32 Figure 22. May 16, 1986 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° mil I II II I iinTtT""|i""|""i| III III iinrfrTTrTfTrrtiliiiii In ml |tiiii|iii 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° LEGEND FOR 1200 GMT16 MAY R6 BASED ON OBS€RVED AND FORECAST CONDITIONS A BERG ^GROWLER X RADAR TARGET/CONTACT 33 Figure 23. May 30, 1986 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° ittiIiiiiiLl ct o° 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° LEGEND FOR 1200 GMT 30 MAY 86 BASED ON OBSERVED AND FORECAST CONDITIONS A BERG ^GROWLER X RADAR TARGET/CONTACT 34 Figure 24. June 16, 1986 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 4 ^2°r|TTiii|jliJi III,!,! I I I mil |llirTtirTTTtTTinft11lr[Ttrtt]TTTtl 6° 45° 44° 43° 42° 41° 40° 39° tTprtnitTliTiti 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° LEGEND FOR 1200 GMTlfi JUN Rfi BASED ON OBSERVED AND FORECAST CONDITIONS A BERG m GROWLER X RADAR TARGET/CONTACT 35 Figure 25. June 30, 1986 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° ffTi II I |i 1 1 II 1 1 III 1 1 I mil I II iii| I'"" I |i mi |inii| iiiii| I 111! i| mil ||iiM|ii|ii[ I 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° LEGEND FOR 1200 GMT 30 J UN 86 BASED ON OBSERVED AND FORECAST CONDITIONS A BERG ^GROWLER X RADAR TARGET/CONTACT 36 Figure 26. July 3, 1986 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° rl I |i lll^Ttlll|llTTTf^TTrr|nTTl 1 1 1 1 1 il TrtrT|Ti»i I iniil ii 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° LEGEND FOR 1200 GMT(Z)3 JUL 86 BASED ON OBSERVED AND FORECAST CONDITIONS A BERG ^GROWLER X RADAR TARGET/ CONTACT 37 Discussion of Iceberg and Environmental Conditions The number of icebergs that pass south of 48°N in the International ice Patrol area each year is the measure by which International Ice Patrol has judged the severity of each season since 1912 (Table 1). With 204 icebergs south of 48°N, 1986 is the 49th most severe year on record, a relatively light year. Since the number of icebergs calved each year by Greenland's glaciers is in excess of 10,000, a sufficient number of icebergs exist in Baffin Bay during any year. Therefore, annual fluctuations in the generation of Arctic icebergs is not a significant factor in the number of icebergs passing south of 48''N annually. The factors that determine the number of icebergs passing south of 48°N each season can be divided into those affecting iceberg transport (cur- rents, winds, and sea ice) and those affecting iceberg deteriora- tion (wave action, sea surface temperature, and sea ice). Sea ice acts to impede the trans- port of icebergs by winds and currents and also protects ice- bergs from wave action, the major agent of iceberg deterioration. Although it slows current and wind transport of icebergs, sea ice is itself an active medium, for it is continually moving toward the ice edge where melt occurs. There- fore, icebergs in sea ice will eventually reach open water unless grounded. The melting of sea ice itself is affected by snow cover (which slows melting) and air and sea water temperatures. As sea ice melt accelerates in the spring and early summer, trapped icebergs are rapidly released and then become subject to normal transport and deterioration. Acknowledgements Commander, International Ice Patrol acknowledges the assis- tance and information provided by the Canadian Department of the Environment, the U.S. National Weather Service, the U.S. Naval Weather Service, and the U.S. Coast Guard Research and Development Center. We extend our sincere apprecia- tion to the staffs of the Canadian Coast Guard Radio Station St. John's, NewfoundlandA/ON, the Gander Weather Office, the per- sonnel of U.S. Coast Guard Air Station Elizabeth City, and the USCGC EVERGREEN for their excellent support during the 1986 International Ice Patrol season. It is also extremely important to recognize the efforts of the personnel of the International Ice Patrol: CDR N.C. Edwards, Jr., Dr. D.L. Murphy, LT F. J. Williams, LT I. Anderson, LTJG N.B. Thayer, MSTCS G.F. Wright, MSTC D.A. Eichmann, MST1 M.G. Barrett, YN1 S.A. Cooper, MST1 K.O. Pelletier, MSTI R. J. Uebelacker, MST2 A.A. Anzelmo, f^ST2 D.A. Hutchinson, MST2 R.L. Franco, MST2 J.K. Silves, MST3 W.A. Henry, MST3 K.A. Martin, MST3 C.F. Weiller. 38 Appendix A List of Participating Vessels ICE VESSEL NAME FLAG SST REPORTS ABITIBI CONCORD FEDERAL REPUBLIC OF GERMANY ACADIAN GAIL CANADA ACHILLES SINGAPORE 6 ACT 7 UNITED KINGDOM 3 AIME GAUDREAU CANADA AKRANES ICELAND AKTEA EGYPT ALBRIGHT UNITED KINGDOM ALRAZIQ REPUBLIC OF LIBERIA 9 AMBASSADOR UNITED KINGDOM AMBROSE SHEA CANADA 6 AMERICA EXPRESS FEDERAL REPUBLIC OF GERMANY 1 AMERSHAM PANAMA 2 AMITIBICORD FEDERAL REPUBLIC OF GERMANY ANANGEL HORIZON GREECE ARC MINOS GREECE 2 ARCTIC CANADA ARCTIC SHIKO UNKNOWN ARG0 2 PANAMA 1 ARTHUR W. RADFORD UNKNOWN ATLANTIC SERVICE FRANCE ATLANTIC STAR SINGAPORE 4 BADAK LIBERIA 3 BAKAR LIBERIA 3 BARTLETT CANADA 11 BARWA LIBERIA 7 BEAUSONGE MAURITIUS 2 BELLE ETOILE MAURITIUS 2 2 BHAVABHUTI INDIA 1 BISCHORSTOR PANAMA BIYO MARU JAPAN BOEFJORD PHILIPPINES BONAVISTA UNKNOWN BONNY BAHAMAS 8 3 BORIJINIBA UNKNOWN 1 B0WDRILL3 CANADA 2 BOXY SWEDEN 4 BRANT POINT UNITED KINGDOM 4 BRISTOL MARU JAPAN 1 BRITISH STEEL UNITED KINGDOM 6 BUDAPESHT SINGAPORE 1 CAMBRIDGE PANAMA 1 CANADA MARITIME SINGAPORE 2 CANADA MAROUIES CANADA 1 CANADIAN EXPLORER UNITED KINGDOM 7 39 ICE VESSEL NAME FLAG SSI REPORTS CANMAR AMBASSADOR CANADA 5 CANMAR (DART) EUROPE BELGIUM 4 CANMAR VENTURE UNITED KINGDOM 1 CANTIHOLANDIA FEDERAL REPUBLIC OF GERMANY 1 CAPE BALLARD CANADA 1 CAPE NORTH CANADA 5 CAPE RACE UNITED KINGDOM 3 CAPE ROGER CANADA 3 C A P ITAN C HU KAC H 1 N ^^"U N K N 0 WN""^^^^^"''"^^^"^^*"^^*"^"^^^^^^"^^"""^*^^^'^'^^^^^^^^^ 1 CARAVEL STAR PANAMA 1 CAST CARIBOU LIBERIA 14 7 CAST HUSKEY UNITED KINGDOM 4 CASTMUSKOX UNITED KINGDOM 1 CAST OTTER UNITED KINGDOM 2 CAST POLAR BEAR LIBERIA 9 5 CHARLOI lECASTIAN FEDERAL REPUBLIC OF GERMANY 1 CHEMICAL TRANSPORT CANADA 2 CHESTNUT HILL USA 1 CHIBA UNITED KINGDOM 1 CHIGNECTO BAY CANADA 3 CHIPPEWA LIBERIA 1 COMFORT COVE CANADA 2 CUNARD UNKNOWN 1 DANIELA BRAZIL 2 DANILOVGRAD YUGOSLAVIA 2 DART ATLANTIC UNITED KINGDOM 1 DARTBRITIAN UNITED KINGDOM 1 DONNY SWEDEN 2 DORIS FEDERAL REPUBLIC OF GERMANY 1 DUESSELDORE EXPRESS FEDERAL REPUBLIC OF GERMANY 1 EASTERN SHELL UNKNOWN 1 EASTERN UNICORN PANAMA 1 1 ESPANA 1 FEDERAL REPUBLIC OF GERMANY 1 EUROPE BELGIUM 5 EVA FRANCE 1 1 EVERGREEN USA 15 1 FALCON NORWAY 1 FALKNES NORWAY 1 FARLAND UNITED KINGDOM 1 FARNES LIBERIA 1 FEDERAL DANUBE BELGIUM 3 FEDERAL HURON PANAMA 1 2 FEDERAL LAKES USA 3 FEDERAL MAAS BELGIUM 5 FEDERAL OTTAWA BELGIUM 1 40 Appendix A ICE VESSEL NAME FLAG SST REPORTS FEDERAL RHINE LIBERIA 1 FEDERAL SCHELDE LIBERIA 3 FEDERAL THAMES BELGIUM 2 FERNGOLF LIBERIA 1 FERNWAVE LIBERIA 1 FINNARCTIS UNITED KINGDOM 1 FINNFIGHTER FINLAND 5 FINNPOLARIS UNITED KINGDOM 2 FINNSNES LIBERIA 1 FINNWHALE UNKNOWN 1 FJELLNESS PANAMA 1 FJORD MARINER PANAMA 2 FORT VICTORIA UNITED KINGDOM 1 GIZHIGA USSR 1 GOLDEAN PIONEER PHILIPPINES 1 GOLDEN GATE SUN SINGAPORE 2 GRENFELL CANADA 1 GUNRUNMAERS DENMARK 1 HIBISCUS MAURITIUS 1 HOLCAN ELBE FEDERAL REPUBLIC OF GERMANY 2 HOLCAN MAAS FEDERAL REPUBLIC OF GERMANY 2 HUDSON CANADA 14 HUMBERARM LIBERIA 4 IBERITA UNITED KINGDOM 2 IMPERIAL ACADIA CANADA 3 IMPERIAL ST. CLAIR CANADA 5 IVAN TEVOSYAN UNKNOWN 1 IRVING CEDAR UNITED KINGDOM 1 IRVING OURS POLARIS CANADA 2 JACKMANN CANADA 1 JADE KIM PANAMA 2 JENNA GERMAN DEMOCRATIC REPUBLIC 1 JOHANNA FEDERAL REPUBLIC OF GERMANY 1 JOHN C. HELMSING CYPRUS 2 JOKUFELL ICELAND 1 JUGOAGEN YUGOSLAVIA KAMENITZG BULGARIA 1 KANGUK CANADA 6 KHAIRPUR PAKISTAN 1 KIISLA FINLAND 1 K. OLSHANSKY USSR 1 KRISTINA LOGOS CANADA 1 L. ROSEI IE CANADA 4 LAKE ANINA NORWAY 1 LAKE SHELL CANADA 2 41 Appendix A VESSEL NAME LAWRENCE H. GIANELLA LE CREDE NO. 1 LENINSK LEONARD J. COWLEY LOKVIHAR LUCIEN PAQUIN LYRA M. W. NEAL MAGRITTE MAHONE BAY MANCHESTER CHALLENGE MARIA B. MARIA OLDENDORFF MAVRO VETRANIC MELLA MELISSA MARY MICHELLE C. MIJDRECHT MIRABELLA MONTCALM MOSELORE MYRSINIDI NARWIK2 NAVIOS COURIER NEDRILL NEWFOUNDLAND HAWK NORDSTAR NORTH WIND NORTHERN PRINCESS NORTHERN SHELL NORTRANS ELMA OCEAN LINK OFFSHORE HUNTER OLYMPIC RAINBOW ONTADOC PARADISE SOUND PASSAT PAULBUNYAN PAWEE PEGGY PLACENTIA BAY POINT ARMUR PRINSFREDRIKHENDRIK PRINSMAURITS PRISTINA FLAG SST UNKNOWN 21 CANADA USSR UNKNOWN INDIA CANADA POLAND UNITED KINGDOM BELGIUM CANADA UNITED KINGDOM UNKNOWN PANAMA 7 INDIA 3 PANAMA 5 LIBERIA PANAMA 8 NETHERLANDS NETHERLANDS ANTILLES FRANCE 1 LIBERIA LIBERIA POLAND LIBERIA 4 NETHERLANDS CANADA SINGAPORE USA 71 UNKNOWN CANADA PANAMA 3 UNITED KINGDOM 3 UNKNOWN GREECE CANADA UNKNOWN PANAMA USA UNITED KINGDOM 2 BAHAMAS 2 CANADA BAHAMAS 3 NETHERLANDS NETHERLANDS YUGOSLAVIA ICE REPORTS 4 3 5 1 2 1 1 3 1 7 2 1 2 2 1 1 1 5 4 2 1 1 1 1 2 2 1 1 1 2 3 42 Appendix A VESSEL NAME FLAG PUHOS ^^^ * UNITED KINGDOM RAINBOW HOPE UNKNOWN RANFORD UNKNOWN REED VOYAGER PANAMA ROBIN FRANCE SAAR PRE LIBERIA SAUNIERE CANADA SAYA YUGOSLAVIA SEA FORTH ATLANTIC CANADA SEA FORTH ISLAND CANADA SENTIS UNITED KINGDOM SHOWOLYMPIA PANAMA SIR HUMPHREY GILBERT CANADA SIR ROBERT BOND CANADA SENHOR DOS MARANTESPORTUGAL SOUNION CYPRUS SPYROSALEMOS GREECE STAR UNKNOWN STEFAN BATON Y POLAND STEPHANITOR PANAMA STOLT CASTLE LIBERIA STOLT TENACITY LIBERIA STOVE CAMPBELL NORWAY STUBBENHUK FEDERAL REPUBLIC OF GERMANY STUTTGART EXPRESS FEDERAL REPUBLIC OF GERMANY SUMMIT LIBERIA TELFAIR MARINER LIBERIA TEXACO BRAVE CANADA TOANUI CANADA TONGALA UNITED KINGDOM TRAWLER ZIDANI UNKNOWN TRINITY BAY CANADA TRONES PANAMA TUPPER CANADA VALCOURT LIBERIA VARJAKKA FINLAND VASILI SURIKOV USSR VENTURA FEDERAL REPUBLIC OF GERMANY VESALIUS BELGIUM VIKING HARRIER SINGAPORE VIKING OSPREY SINGAPORE VJAZMA USSR VOLGA UKRANIAN SSR VOLNA USSR WHIDBEY ISLAND UNKNOWN SST ICE REPORTS 7 3 1 1 4 ^ 1 1 ' 1 1 1 1 5 1 5 21 1 1 1 1 A A 4 ^ 1 1 1 7 1 1 1 9 2 1 2 1 1 1 1 3 1 3 1 1 1 2 1 1 1 1 1 1 2 1 1 43 Appendix A VESSEL NAME WINNA WORLD CONTAINER YAMAHMEMARU YAYAMARIA YUKONA ZAMBIA ZEILA ZIEMIAGNIEZMIESKA ZIEMIA KRAKOWSKA ZIEMIAOLSZTYNSKA ZIEMIA ZAMOJSKA ZIM SAVANNAH FLAG UNKNOWN PANAMA JAPAN JAPAN CYPRUS LIBERIA UNKNOWN POLAND POLAND POLAND POLAND ISRAEL SST ICE REPORTS 1 2 1 1 1 8 1 1 1 1 44 Appendix B TIROS Oceanographic Drifter Tracks on the Grand Banks During the 1986 International Ice Patrol Season LT lain Anderson, USCG Introduction During the 1986 International Ice Patrol season, nine TIROS Oceanographic Drifting buoys were deployed in the Ice Patrol operating region. Three of the nine drifters were used exclusively for data gathering in conjunction with the IIP-1-86 cruise and these data are discussed in Appendix C. Of the six buoys used operation- ally, five were deployed by HC- 130 aircraft during regular ice re- connaissance flights. The sixth was deployed by USCGC EVER- GREEN as part of IIP-1-86 cruise and was not recovered so that its track could be used operationally. An oceanographic cruise was conducted using USCGC EVER- GREEN (WMEC 295) from 22 April until 22 May 1986. The primary objective of the cruise was to provide surface truth data for an airbome radar study of an oce- anic front south of Flemish Cap. The results of the cruise are discussed in Appendix C. The International Ice Patrol uses drifting buoys for real-time current information for weekly updates to the historical current field used in its iceberg drift model (Summy and Anderson, 1983 and Summy, 1982). Drifters are deployed for operational use in areas of high iceberg density and in areas of high variability in the current field to improve drift prediction. All of the drifters except drifter 4547 were deployed to monitor the variability of the Labrador Current. Drifter 4547 was deployed near the end of the Ice Patrol season in the area of the highest remaining iceberg concentration. All of the buoys deployed by Ice Patrol are three meters long and have a spar-shaped hull with a flotation collar. They are equipped with a sea surface temperature sensor, a drogue tension sensor, and a battery voltage monitor. The temperature sensor is located approximately one meter below the surface. Each drifter is deployed with a 2m by 10m window shade drogue attached to the drifter by a 50m tether. An average of nine positions per day was received from each opera- tional drifter with position accuracy of approximately 300m (Bessis, 1981) The positions and sensor data points are evenly distributed in time except for the period between OOZ and 04Z when virtually no data are received. This null data period is due to the orbits of the NOAA series satel- lites. As of 30 September 1986, no drifter remained transmitting in the Ice Patrol region (Table B-1). Two drifters (4542 and 4547) were recovered intentionally by Coast Guard cutters. Drifter 4557 was picked up by an unknown vessel. Drifter 4552 stopped transmitting 28 days after deployment. The remaining two drifters (4543 and 4549) are still drifting across the North Atlantic, providing data outside the Ice Patrol region. All air-launched buoys deployed properly except 4552. Its para- chute opened but the wooden frame holding the buoy broke apart in the air. Because of this the parachute did not cut free from the buoy after splashdown. The remainder of the air-dropped drifters deployed properly and the parachutes released from the drifter packages. The following section describes the data from the satellite-tracked buoys used by Ice Patrol during the 1986 iceberg season. It is not intended as an exhaustive data analysis. The data are archived at the International Ice Patrol, Avery Point, Groton, CT 06340. Buoy Trajectories The tracks of the operational buoys are discussed below in chronological order based on the deployment date. The numbers in parenthesis following dates are year dates (numbered sequentially from 1 January through 31 De- cember). 4543 Buoy 4543 was deployed on 26 March 1986 (85) from an HC-130 aircraft in the Flemish Pass at 46°59.3'N 47°19.6'W (Figure B- 1a). After deployment, it moved southwesterfy, following the bathymetry, with an average speed of 61 cm/s until it encoun- tered an oceanic front on 30 March (89). (This front was the focus of IIP-1-86 cruise and is dis- 45 Deployment No. of days Number Date Method Position Status in IIP AreaA'otai 4543 26 MAR C-130 46°59.3'N47°19.6'W Still transmitting 110/188 4542a 16 APR C-130 47°01.1'N47°19.7'W Recovered 3 MAY(1) 17/17 4542b 5 MAY EVERGREEN 46°58.2'N 47°18.5'W Recovered 17 MAY(1) 13/13 4557 12 MAY EVERGREEN 45°10.2'N47°18.8'W Recovered 14 JUL(2) 63/63 4549 16 MAY C-130 48°25.0'N 49°29.3'W Still transmitting 52/137 4552 30 MAY C-130 48°10.0'N48°55.0'W Stopped 27 JUN 28/28 4547 12JUN C-130 50°59.0'N 53°00.0'W Recovered 26 AUG (3) 75/75 Notes: (1) Recovered and /or redployed by USCGC EVERGREEN. (2) Picked up by an unknown vesse (3) Recovered by USCGC NORTHWIND. cussed in Appendix C.) It drifted in an easterly direction along ttie north side of the front at an aver- age speed of 12 cm/s until 9 April (99) when the temperature in- creased from about 0.8°C to 2.8°C in one day. Buoy 4543 accelerated to 47 cm/s from 9 April through 19 April (109). After 19 April, it moved in a northerly direction at 31 cm/s until it became entrained in an anticyclonic (warm core) eddy north of Flemish Cap on 8 May (128). Based on the buoy trajectory, the eddy was centered near 50°N 46°W and had no substantial translation. The ap- proximate diameter of the eddy as defined by the buoy track was 95 km. Buoy 4543 averaged 40 cm/s while completing five loops of the eddy. It departed the eddy on 25 June (175) and drifted north- easterly, passing east of 39°W (the eastern boundary of the Ice Patrol operations area) on 14 July (195). The drogue sensor indi- 46 cated the drogue remained at- tached throughout the period described atx3ve. As of 30 September 1986, buoy 4543 was still transmitting as it moved eastward across the North Atlan- tic. 4542 Buoy 4542 was used twice during 1986. The two deployments are referred to as 4542(a) and 4542(b). Buoy 4542(a) was deployed by an HC-130 on 16 April 1986 (106) in the Flemish Pass in position 47°01.1'N 47°19.7'W (Figure B- 1b). It drifted south with the Lab- rador Current at an average speed of 32 cnVs until 25 April (115) when it encountered an oceanic front. It drifted in an easterly di- rection at an average speed of 63 cm/s along the front until 30 April (120). On that date, 4542(a) turned northwest, still along the front, and drifted at 46 cm/s until recovered by USCGC EVER- GREEN on 3 May (123). Buoy 4542(b) was redeployed from EVERGREEN on 5 May 1986 (125) in the Flemish Pass in position 46°58.2'N47°18.5'W. It drifted south along the bathymetry at 37 cm/s until encountering the front again on 11 May (131). It then moved easterly along the front at an average speed of 53 cm/s until 13 May (133) when it turned north and slowed to 8 cm/s. Drifter 4542(b) was recovered by EVERGREEN on 17 May (137). The drogue remained attached to drifter 4542 throughout both deployments, and this fact was accurately reported by the drogue sensor. S/'W 55 50 45 40 J9U 45 - 40N Grand Banks • 50 :>^^ 52N 45 i + 4 ON 57W 55 50 45 40 3qw Figure B-la Drift trajectories of buoys 4543 and 4549, marked with Julian dates. 4557 Buoy 4557 was deployed in a warm core eddy (45°10.2'N 47°18.8'W (Figure B-1b)) on 12 May 1986 (132) from USCGC EV- ERGREEN as part of an oceano- graphic study. It remained in tfie eddy for three revolutions as the eddy migrated to the east at atxjut 4 km/day until 7 June (158). Based on the buoy track, the average diameter of the eddy was 70 km and within the eddy, drifter 4557 averaged 34 cm/s. Except for two short periods, the tempera- ture reported by drifter 4557 was about 12°C while in the eddy. In the first, a 24-hour period on 25 May, the temperature decreased to about 7°C and then returned to 12°C. The drifter motion was not affected, suggesting that the cold water encountered was only a surface feature. During the second, a 48-hour period begin- ning on 30 May, the temperature decreased to about 6°C and then returned to 12°C. The direction of the drifter was apparently unaf- fected but the average speed nearly doubled, to 65 cm/s. After leaving the warm core eddy on 7 June (158), 4557 moved eastward until 10 June (161) when it entered a cyclonic (cold core) eddy. In a 24 hour period, the temperature dropped from 12°C to 7°C. Drifter 4557 maintained its cyclonic motion until 23 June (174), completing two loops in the eddy. While in the cyclonic eddy, 4557's speed ranged from 1 1 cm/s to 133 cm/s, averaging 76 cm/s. Between 19 June (170) and 23 June (174), the temperature again rose to 12°C but the rtKition of the drifter did not change. The motion of 4557 between 23 June and 26 June (177) -was very sluggish with velocities averaging 12 cm/s and inconsistent direction. On 26 June, the temperature increased 47 57W 55 50 45 40 J9W 52N-J — .y / I 1 1 1 1—' — I 1 1 1— H 1 1 1 1 1 1 1 sjN 50 40N -■ 50 4S42b«4S42a \ 4 5 ■ ■'..-,:■:--::■, 4557- 132 M ^'} ]>192 162 • 15 57W 55 50 45 — I— 40 3qw 4 ON Figure B-1b Drift trajectories of by 2°C and 4557 was apparently caught in the North Atlantic Current and drifted towards the northeast at 45 cm/s. On 1 4 July (195), 4557 was picked up by an unknown vessel. The drogue sensor indicated the drogue was attached throughout its deploy- ment. 4549 Buoy 4549 was deployed from an HC-130 north of the Grand Banks on 16 May (136) in position 48°25.0'N 49°29.3'W (Figure B- 1a). It moved southward following the bathymetry at an average speed of 42 cm/s until it encoun- tered an oceanic front on 29 May (149). The average speed of drifter 4549 increased to 65 cm/s as it travelled along the front. On 4 June (155), drifter 4549 began a 48 buoys 4542 and 4557, marked with Julian dates. 4552 small cyclonic loop. The average speed of drifter 4549 during the loop was 31 cm/s. On 13 June (164), it accelerated to an average of 96 cnVs and began a large cyclonic loop. This motion contin- ued until 16 June (167). There was an increase from 7°C to 9°C when the motion stopped. The large cyclonic loop coincided temporally and spatially with the cyclonic eddy observed along the track of drifter 4557. Drifter 4549 moved to the north at an average speed of 30 cm/s until 19 June (170). It then accelerated to an average speed of 74 cm/s and drifted northeasterly, departing the Ice Patrol region on 27 June (178). The drogue sensor indicated the drogue was attached throughout its drift in the Ice Patrol region. As of 30 September 1986, the buoy was still transmitting. Buoy 4552 was deployed from an HC-130 north of the Grand Banks on 30 May 1986 (150) in position 48°10.0'N 48°55.0"W (Figure fl- ic). It drifted south with the Labrador Current approximately following the bathymetry at an average speed of 40 cm/s until 15 June (166). It then nearly re- versed direction and drifted in a northerly direction at about 25 cm/suntil27 June (178). No data were received after 27 June. There is no evidence in the data to suggest the reversal of direction was caused by the buoy being picked up by a vessel. The temperature sensor did not provide reliable data throughout the deployment. The drogue sensor indicated the drogue was attached throughout period \ 40N ■1 : 3 5 «■ -+- 1 1 r 52N 50 -- 45 -+- 4 ON 57U 55 50 45 40 39W Figure B-lc Drift trajectories of buoys 4547 and 4552, marked with Juiian dates. described above. The fact that the parachute did not cut free after the buoy entered the water means that the buoy also had a near- surface parachute drogue. It is likely that the parachute wrapped around the buoy hull as happened with a 1985 buoy (Anderson, 1985). Although the track of 4552 should be viewed with caution, the fact that the parachute remained attched to the buoy is probably not an important factor. 4547 Buoy 4547 was deployed from an HC-130 on 12 June 1986 (163) in the northwestern section of the Ice Patrol region in position 50°59.0'N 53°00.0'W (Figure B-lc). After its deployment, 4547 drifted north- east at 16 cm/s until 1 July (182). On 1 July, it moved south then east with the Labrador Current until about 9 August (221). On this date, the temperature in- creased from about 9°C to 1 1°C and drifter 4557 rrwved northeast and then southwest at 21 cm/s until its recovery by USCGC NORTHWIND on 26 August (238). The drogue sensor indicated the drogue became disconnected on the day after its deployment. When the buoy was recovered by NORTHWIND on 26 August 1986 (238) only about 10 meters of the tether still attached to the drifter. Inspection of the tether after recovery indicated the tether may have been cut. The prolonged low and inconsistent direction of the drift indicated early drogue loss during the deployment. This was another case where the drogue sensor reliably reported the drogue status. Discussion The tracks from this year's drifters illustrate the current variability of the Ice Patrol region. The pre- sense of the oceanic front south of the Flemish Cap greatly influenced the movement of all drifters coming through Flemish Pass. In past years, drifters moving south through Flemish Pass have gone as far south as 42°N (Anderson 1984 and 1985). This year the farthest south a drifter travelled was about 44°N (4552). This difference can be attributed directly to the front. 49 Buoy 4543 entered an anticyclonic eddy north of Flemish Cap. Eddies in this location have been observed in previous years (Anderson 1983 and 1985). This eddy and the front south of Flemish Cap were dominant sources of departure from the Ice Patrol normal current field during the 1986 season. The velocity distributions of the majority of this year's drifters are very similar except for the peaks at the high velocity end (greater than 100 cnrVs) of the distribution for buoys 4557 and 4549 (Figure B-2). Drifter 4549's high velocity peak was the result of its entrain- ment in the North Atlantic Current. The high peak of drifter 4557 coin- cided with the time it spent in a cyclonic eddy. The main peak of the distribution of drifter 4547 is shifted to the left towards a lower speed than the others. This shift in the peak coincide with the loss of the drogue from drifter 4547. Figure B-2 Frequency distribution of buoy drift veiocitles, by percent. 4547 4552 4542. 4542b =b.00 10 00 20 00 30 00 40 00 SO 00 60 00 VELOCITY CM/S 100 00 100- 4543 4549 4557 ■^b 00 40 00 SO 00 60. 00 VELOCITY CM/S I 00- 00 100- 50 Conclusion Ice Patrol has now been using satellite-tracked buoys for 5 years to provide near real-time current data for its iceberg drift prediction model. This year is a good example of the importance of this near real time input. Without weekly drifter data input, Ice Patrol would have been using historical mean currents to predict the mo- tion of icebergs. Using historical currents, icebergs in the Labrador Current would have been drifted south to 43°N. After modification by drifter data to the current field, icebergs in the Labrador Current were drifted south to only 45°N. The lack of drifter data could have resulted in a 190 km drift error. The drogue sensor appears to be providing more reliable data than in the past. All five recovered buoys (including those used exclusively for the cruise), verified the drogue sensor data, with four attached and one disconnected drogue. Ice Patrol plans to continue using drifting buoys for near real-time current data to update the histori- cal current field. In areas of high current variability, real-time data are essential to accurate drift pre- diction. Acknowledgements I am grateful to Dr. R. L. Pickett of the Naval Oceanographic Research and Development Activity and Dr. Brian Petrie of Bedford Institute of Oceanography for their comments on this manuscript. References Anderson, I., 1983. Oceanographic Conditions on the Grand Banks During the 1983 Ice Patrol Season. Appendix B, Report of the Interna- tional Ice Patrol Service in the North Atlantic. Bulletin No. 69, CG-188- 38. U. S. Coast Guard, Washington, DC 20593-7399, 73 pp. Anderson, I., 1984. Oceanographic Conditions on the Grand Banks During the 1984 Ice Patrol Season. Appendix B, Report of the Interna- tional Ice Patrol Service in the North Atlantic. Bulletin No. 70, CG-188- 39. U. S. Coast Guard, Washington, D.C. 20593-7399, 74 pp. Anderson, I., 1985. Oceanographic Conditions on the Grand Banks During the 1985 Ice Patrol Season. Appendix C, Report of the Interna- tional Ice Patrol Service in the North Atlantic. Bulletin No. 71 , CG-188- 40. U. S. Coast Guard, Washington, D.C. 20593-7399, 90 pp. Bessis, J. L, 1981. Operational Data Collection and Platfonn Location by Satellite. Remote Sensing of Environment, Vol II: p 93-1 11. Summy, A.D., 1982. Oceanographic Conditions on the Grand Banks During the 1982 Ice Patrol Season. Appendix B, Report of the Interna- tional Ice Patrol Service in the North Atlantic. Bulletin No. 68, CG-188- 37. U. S. Coast Guard, Washington, D.C. 20593-7399, 35 pp. Summy, A.D. and I. Anderson, 1983. Operational Uses of TIROS Oceanographic Drifters by International Ice Patrol (1978 - 1982). Pro- ceedings: 1983 Symposium on Buoy Technology, National Data Buoy Center. NSTL Station, MS 39529, pp. 246-250. 51 Appendix C Introduction In April and May 1986 Interna- tional Ice Patrol (IIP) conducted a study east of the Grand Banks of Newfoundland in which airtxjrne radar imagery of the sea surface was compared with surface-truth data. Sea surface roughness was mapped using a real aperture, X- Band, Side Looking Airborne Radar (Sl-AR) aboard an HC-130 aircraft; surface-truth measure- ments consisted of hydrographic measurements made from USCGC EVERGREEN (WMEC 295) and the trajectories of satellite-tracked drifting buoys. The primary goal of the experi- ment was to determine how well and how reliably the IIP SLAR could detect water-mass boun- dries. A knowledge of the location of the major boundries in the IIP operations area (40°-50°N, 39°- 57°W) is useful in predicting the motion of icebergs, an important part of MP's responsibility. The study focused on a warm core eddy spawned from, and interact- ing with the North Atlantic Current (NAC). No attempt is made to describe the dynamics of the eddy because the data are insufficient for such an effort. Indeed, neither the renfXJtely-sensed data nor the hydrographic data define the eddy txjundries completely and unambi- guously. Only from the drifting buoy data is it clear that the feature is an eddy. The treatment of the oceanographic data is undertaken solely to help under- stand the SLAR imagery. Observations of an Oceanic Front South of Flemish Pass Donald L. Murphy LT lain Anderson LTJG Neal B. Thayer 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° r2" J ;" mm I.I II ri tun iii| nil i 38° GRAND BANKS OF NEWFOUNDLAND §.. TAILOF THE "--. BANK mill mil mil iiiiiiiiiiiiiiiriiiiiiiiiiiiiiiiiiiiiiiiniiiiriiiiiiiiiiiiiiiiiiiiiiMiiiriiiiiiiii Figure C-1 Schematic of the major current systems near the Grand Banks of Newfoundland. The study area is shown by the shaded rectangie. Bacltground Circulation in the North Atlantic Ocean east of the Grand Banks of Newfoundland is dominated by two major currents (Figure C-1): the southward-flowing, cold and relatively fresh (<2°C and <34.3 ppt) Labrador Current (LC) and the northeastward-flowing warm and more saline (>12°C and >35.5 ppt) NAC. The mean dynamic height field is reasonably well mapped, due in large part to the efforts of IIP, which conducted routine hydrographic surveys of the region from 1934 to 1978, excepting the years of World War II. From these data, maps of monthly mean dynamic height relative to the 1000 dbar level for April through June were devel- oped by Soule (1964) and later updated by Scobie and Schultz (1976). Figure C-2, the mean dynamic topography for April, shows the narrow LC following along the eastern edge of the Grand Banks from Flemish Pass to the Tail of the Bank. The other months, May and June, show no 53 substantial departure from this distribution. Recognizing these similarities, IIP, in 1979, combined the rrronthly mean hydrographic fields and computed a single mean current field (Murray, 1979) for use in HP's numerical iceberg drift model. While the monthly mean dynamic topography represents the main features of the circulation, the averaging smooths out variations that may affect the circulation. For example, trajectories of satellite- tracked drifting buoys released in the LC (Anderson, 1983 and Anderson, 1984) suggest a much more complex flow pattern than the mean hydrography depicts. Figure C-3 summarizes the drift tracks of 17 buoys, deployed by IIP over a 10-year period (1976- 1986), that passed through the study area. Although the tracks show the LC clearly, the most striking feature of the plot is the variability in the flow field. A further indication of variability in the area is shown by the map of standard deviation of dynamic height of the individual hydro- graphic surveys from the April mean (Figure C-4). The pattern of fluctuations in the standard deviation suggests that meanders and eddies of the NAC are major features, particularly in the eastern and southern areas where the standard deviation reaches 15 dyn-cm. Little is known about the sizes and frequencies of NAC meanders or eddies in the study area, primarily because fog and clouds fre- 54 Figure C-2 Average dynamic topography for the month of April (from Scobie and Schuitz, 1976). 50«N 48« 46" 44« 42»N 53»W 5r 49» 47* 1 1 — 45*W I I 1 r 1 — r 1000 m«f«rt ± _L 9JI.2 J L_ _L _L 50«N 48* 46* 44. 42»N 53»W 51' 49* 47* 45»W quently prevent mapping of the ocean's features by satellite infrared (IR) imagery. Using the sparse IR data available, Williams (1985) studied the eddy population east of the Grand Banks. He found that eddies are frequently seen near the Newfoundland Seamounts and Ridge. He suggested that eddy generation is caused by the rapid changes in Ixjttom topography, but there were insufficient data to form a com- plete history of an eddy. Although IR mapping is limited by fog and clouds, satellite and airtxjrne imaging radars, particu- larly the synthetic aperture radar (SAR) camed aboard SEASAT, are capable of all-weather detec- tion of oceanic features such as fronts and internal waves (Fu and Holt, 1982; Hayes.1981). Using 5 7° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 1 1 1 1 1 42° 41° 40° 39° 1 1 1 52°- 51°- ^ \ 50°- A ^\. 49°- ^^^M% •^' 48°- NFLD %^-:.:'"\i^^^Z; . , ...rv-,. 47°- •>^^imM ^^ Er Y flemish 46°- i&'&M GRAND 1 ^ vry BANKS j Hi/ i^^.A_ 45°- ^;""llllpi^ 44°- ^^LJ^ 43°- Wj^^S: 42°- \ ^^ i — ^^ # ( \i^ w? ^^ 41°- \ (n^^^jy^n*^ _^ Y 40°- 39°- oo ' Figure C-3 Trajectories of 17 satellite-tracl^ V/ 1004«. 60 so f Figure 4. February 1987 (from Mariner's Weather Log, 1987b). 17 Figures. March 1 987 (from Mariner's Weather Log, 1987b). 18 Figure 6. April 1987 (from Mariner's Weather Log, 1987c) . 19 Figure 7. May 1987 (from Mariner's Weather Log, 1987c) . 20 Figures. June 1987 (from Manner's Weather Log, 1987c). 21 Sea Level Pressure Monthly Mean (mb) July 1987 60 / Figure 9. July 1987 (from Mariner's Weather Log, 1988) . 22 Figure 10. August 1987 (from Mariner's Weather Log, 1988) . 23 \Ji3S^*'T^ ^"' vZH.'.;^vC-Y-^ .V .^ L s f ^-^■"-^^ ~T»^-.ri / / 1 a^\vy-^ Ki^M ^vA^^^l/^sfXyVr w ^^^ jfSv — / ^ — r- \^^^^^-4^ H^^'lTw^^ /r~-^>-^ JA \ / /^^ f^y^ <^^K '^W\\S\^y^ / ^Mdzo A j-A/ >Sf/ ,' /^"^Wa ' ^^^^f^'^v^'y^ ^**^ / V \\ /\^ x^^ / "VV — Lv5^^^f^5\ "vC^ Lju^^^>^ V J^s ^^^ ^KrM x:a. / y' \ m f;^Sri,.\ \ V / " s^ ^r--^ ZJ-'-V^ ^/ \ 1004^ vT\^ T\^0\ ^ LiowX^ K: 1 %*» ^ V Sea Level Pressure Monthly Mean (mb) September 1987 Figure 11. September 1 987 (from Mariner's Weather Log, 1988). 24 Ice Conditions 1987 Season The following discussion summarizes the sea ice and iceberg conditions along the Labrador and Newfoundland coasts and on the Grand Banks of Newfoundland for the 1987 ice year. The sea ice type and concentration information used in this discussion came from the Monthly Thirty Day Ice Forecast for Northern Canadian Waters published monthly by the Atmospheric Environment Service (AES) of Canada and the Southern Ice Limit published twice-monthly by the U.S. Navy-NOAA Joint Ice Center. Information on the maximum, mean, and minimum sea ice extent was obtained from Naval Oceanography Command, 1986. October 1986: Noseaice was seen south of 65°N in October, which is normally the case (Figure 12). There were no icebergs reported south of 52°N in October. November 1986: In mid- November, new, young, and thin first-year sea ice began to form in Ungava Bay, Hudson Strait, and Davis Strait (Fig- ure 13). The mean extent of sea ice in November is confined to the southern tip of Baffin Island with the maximum sea ice extent covering Hudson Strait, and Ungava Bay. Ice conditions in November 1986 were close to the maximum conditions. An unusually deep Icelandic Low (Mariner's Weather Log, 1987a) brought below normal temperatures to Labrador (Table 6) which enhanced the sea ice growth. There were 8 icebergs reported south of 52°N in November. December 1986: Aided by continued below normal tem- peratures (Table 6), the sea ice edge continued to be farther south than the mean and close to the maximum extent of sea ice. In mid-December, thin first- year, young and new sea ice were just north of the Strait of Belle Isle (Figure 14). Con- centrations were generally 8- 10 tenths. There were 9 icebergs reported south of 52°N in December; 5 of these icebergs were south of 48°N. January 1987: In mid- January, new and young sea ice were north of the Avalon Peninsula and along the eastern coast of Newfoundland (Figure 15). The Strait of Belle Isle was now ice covered with new and young sea ice. The sea ice again extended beyond the mean limits of sea ice, but did not extend to the maximum limits of sea ice extent. By the end of January, the sea ice growth and spread was 2-3 weeks ahead of normal (AES, 1987). This above average sea ice growth can again be attributed to below normal temperatures in Lab- rador and Newfoundland (Table 6). There were 5 icebergs reported south of 52°N in January; 2 of these were south of 48'="N. February 1987: By mid- February, a tongue of 9-10 tenths first-year sea ice extended along the Labrador coast, into the Strait of Belle Isle, and along the eastern coast of Newfoundland down to the Avalon Peninsula (Figure 16). Young, thin first-year, and first-year sea ice were west of Newfoundland with concentra- tions of 9-10 tenths. The extent of sea ice in February was close to the mean extent. The increase in temperatures to warmer than normal in Labrador and near normal on Newfoundland (Table 6) re- turned the sea ice extent to near normal. There were 14 icebergs observed south of 52°N in February; all of these icebergs were south of 48°N. 25 March 1987: The 1987 International Ice Patrol season opened on March 12. Figure 24 shows the iceberg distribu- tion at the beginning of the season. In mid-March, thin first-year sea ice advanced from the Avalon Peninsula south over the Grand Banks (Figure 17). The sea ice edge was again close to its mean extent. Towards the end of March, drastic changes in the sea ice extent occurred. Figure 26 shows the sea ice pushed off the Grand Banks with all the remaining sea ice confined to close to the east and south coast of Newfoundland. The iceberg distribution on March 30 showed a marked shift to the west compared to March 15 (Figure 25). Between March 15 and March 30, the prevail- ing winds were easterly (AES 1987), forcing the sea ice and icebergs westward. There were 57 new icebergs south of 52°N in March; 48 of these icebergs were south of 48°N. At the end of March, there were 25 icebergs on plot (Figure 26). April 1987: The unusual sea ice distribution created by the easterly winds at the end of March continued into April. There was no sea ice on the Grand Banks or the west coast of Newfoundland (Figure 18). The southern coast of New- foundland, usually ice free, had 9-10 tenths of sea ice. The extent of sea ice was still near average for April . The iceberg distribution on April 15 26 (Figure 27) only extended to 47°W. By April 30, the iceberg distribution extended to 43°W (Figure 28). There were 117 new icebergs south of 52°N; 76 of these were south of 48°N. There were 142 icebergs on plot at the end of April (Figure 28). May 1987: In mid-May, the southern and eastern coasts of Newfoundland became ice-free as the sea ice retreated north- ward (Figure 19). A large polynya (an area of open water surrounded by ice) formed along the Newfoundland and Labrador coasts between 50 and 55°N. This polynya was formed from southwesterly winds pushing the ice off-shore (AES, 1987). Above average temperatures on Newfoundland and southern Labrador had accelerated the sea ice retreat in these regions. As the sea ice retreated northward, large numbers of icebergs were released to drift southward. With 236 new icebergs south of 52°N, May was the heaviest month for new icebergs. Only 29 of these icebergs were south of 48°N. Only a few of these icebergs drifted with the Labrador Current through Flemish Pass. There were 158 icebergs on plot the end of May (Figure 30). June 1987: By mid-June, the ice edge had retreated to Goose Bay (Figure 20). This is the typical pattern of retreat in June (Naval Oceanographic Command, 1986). The number of new icebergs south of 52°N was again high in June. There were 215 new icebergs south of 52°N in June; 127 of these were south of 48°N. By mid- June, a large number of ice- bergs had drifted onto the Grand Banks (Figure 31). Most of these icebergs were gone by the end of June with most of the remaining icebergs north of 48°N (Figure 32). There were 64 icebergs on plot the end of June (Figure 32). July 19 87: The sea ice edge continued to retreat northward, but at a slower rate than normal. By mid-July, the sea ice edge has usually retreated to Baffin Island, with some sea ice also persisting in Ungava Bay. In mid-July 1987, however, the sea ice edge was still down along the Labrador Coast (Figure 21). The tem- peratures in July on Labrador were colder than normal (Table 6) and these cooler tempera- tures may have caused the sea ice edge to retreat slower than it would have normally. There were 25 new icebergs south of 52°N; 15 of these were south of 48°N. There were 10 icebergs on plot the end of July (Figure 34). The 1987 International Ice Patrol season was closed on July 31 ,1987. August 1987: The retreat of the sea ice edge to just north of Frobisher Bay in August left Hudson Strait and most of Davis Strait ice free (Figure 22). There were 57 icebergs re- ported south of 52°N in August: 2 of these were south of 48°N. September 1987: The only sea ice observed south of 65° N in September was near Fro- bisher Bay (Figure 23). 27 Figure 12. 65N 65W 60W 55W SOW 60N 55N SON 6SN — 60N — 55N — SON 60W 55W SOW — 4SN 4SW 28 Figure 13. 65N 65W 60W 55W SOW 60N 55N — SON 6SN — 60N — S5N — SON 60W SSW SOW — 4SN 4SW 29 Figure 14. 65N 65W 60W 55W SOW 60N 55N — SON 65N — 60N — SSN — SON 60W 55W SOW — 4SN 4SW 30 Figure 15. 65N 65W 60W 55W SOW 60N 55N — SON . 6SN — 60N — 55N SON 4SN 60W SSW SOW 4SW 31 Figure 16. 65N 65W 60W 55W SOW 60N 55N SON 6SN 60N 55N — SON 60W SSW SOW — 4SN 4SW 32 Figure 17. 65N 65W 60W 55W SOW 60N 55N SON 65N — 60N — SSN — SON 60W SSW SOW — 4SN 45W 33 Figure 18. 65N 65W 60W 55W SOW Greenland 60N 55N SON Sea Ice Conditions April 15,1987 3/1 0 or greater sea ice concentration (Redrawn from Joint Ice Center, 1987) 1 972—82 mean sea ice edge (Redrawn from Naval Oceanography Command, 1986) 65N 60N 55N SON 45N 60W S5W SOW 4SW 34 Figure 19. 65N 65W 60W 55W SOW 60N 55N SON 6SN 60N — SSN — SON 60 W 5SW SOW — 4SN 4SW 35 Figure 20. 65N 65W 60W 55W SOW 65N 60N 60N 55N — SON 60W S5W SOW 36 Figure 21. Figure 22. 65N 65W 60W 55W SOW 60N 55N SON 65N — SON SSN — SON 60W 5SW SOW — 4SN 4SW 38 Figure 23. 65N 65W 60W 55W SOW 60N 55N SON 6SN — 60N — 55N SON 3/10 or greater sea ice concentration (Redrawn from Joint Ice Center, 1987) 1 972—82 mean sea ice edge (Redrawn from Naval Oceanography Command, 1986) 60W 55W SOW — 4SN 4SW 39 Figure 24. Graphic Depiction of International Ice Patrol Plot for 1200 GMT March 12, 1987, Based on Observed and Forecast Conditions. 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° llllllll INI I Jll|lllll| I I I Illlllll|llllllll Ml I I III! I I 40°E 39°: :40' 39^^ 38°! 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 r 38° 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° N A Berg N M. Growler N X Radar Target / Contact Estimated limit of all known ice Estimated limit of sea ice 200 Meter bathymetric contour Where "N" Is The Number Of Designated Targets In A One Degree Rectangle 40 Figure 25. Graphic Depiction of International Ice Patrol Plot for 1200 GMT tAarch 15, 1 987, Based on Observed and Forecast Conditions. 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° rp" J 1 1 1 I I 1^1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 I 1 1 1 1 I p I 1 1 I j 1 1 1 1 1 I I r 1 1 1 1 I I 1 1 1 I I I 1 1 1 1 I n 1 1 1 I ) I 1 1 I 1 1 ) I _-o 38° 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 f 38*^ 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° N ▲ Berg N A Growler N X Radar Target / Contact Estimated limit of all known ice Estimated limit of sea ice 200 Meter bathymetric contour Where "N" Is The Number Of Designated Targets In A One Degree Rectangle 41 Figure 26. Graphic Depiction of International Ice Patrol Plot for 1200 GtATMarcf) 30. 1987, Based on Observed and Forecast Conditions. 57° 56° 55° 54° 53° 52° 51° 50° I I 1 1 I I 1 1 I I I I r 1 1 1 1 1 I r 1 1 1 1 1 1 1 1 I I 1 1 r 1 1 I ri 1 1 1 I 1 1 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° I I I 1 1 1 1 I r 1 1 1 1 I I 1 1 1 r 1 1 I I r I 1 1 I r i 1 1 1 i i r i 1 1 r 1 1 1 1 1 .' ' ' ' ' ' | (.po 40°: 39°: ~^-~i J— +~ -* y~ 51° E50° :49^ J48= = 47= E46° J45° :44° E43° E42° 41° E40' 39"= 38°1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 r 38= 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° N A Berg N Mk. Growler N X Radar Target / Contact Estimated limit of all known ice Estimated limit of sea ice 200 Meter bathymetric contour Where "N" Is The Number Of Designated Targets In A One Degree Rectangle 42 Figure 27. Graphic Depiction of International Ice Patrol Plot for 1200 GMT April 15, 1987, Based on Observed and Forecast Conditions. 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39= 38°l 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 r 38° 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° N A Berg N Mi Growler N X Radar Target / Contact Estimated limit of all known ice Estimated limit of sea ice 200 Meter bathymetric contour Where "N" Is The Number Of Designated Targets In A One Degree Rectangle 43 Figure 28. Graphic Depiction of International Ice Patrol Plot for 1200 GMT April 30, 1987. Based on Obsen/ed and Forecast Conditions. 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39 11 I I H I I I I I I I I I I I I I I I I I ] J I I I I I I I I I I I I I I I I I I I I I I I M I I [ I I I I I I I I I I I I I I I I I I I I M I I ■" > -J— 40°: 39°: -| — j 1 42° •j ( E41° : 40° ■I \ :39° 38°"l 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i I III I i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 r 38° :52° E51° E50° = 49° J48° E47° :46° 145° : 44° : 43° 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39' N A Berg N Jk, Growler N X Radar Target / Contact Estimated limit of all known ice Estimated limit of sea ice 200 Meter bathymetric contour Where "N" Is The Number Of Designated Targets In A One Degree Rectangle 44 Figure 29. Graphic Depiction of international Ice Patrol Plot for 1200 GMT May 15, 1987, Based on Obsen/ed and Fore- cast Conditions. 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° " I 1 1 1 1 I i; 1 1 1 I ; 1 1 1 1 1 1 ]'<"". M I 1 1 1 1 I r I I I 1 1 1 1 1 1 M 1 1 I I I r 1 1 1 I I I M I I I I (.po 40°= 39°E • 4X-X i i |.. 38° 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 r 38° E51° = 50° :49° = 48° = 47° = 46° = 45° :44° = 43° j42° E41° E40° = 39° 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° N A Berg N Jk. Growler N X Radar Target / Contact Estimated limit of all known ice Estimated limit of sea ice 200 Meter bathymetric contour Where "N" Is The Number Of Designated Targets In A One Degree Rectangle 45 Figure 30. Graphic Depiction of International Ice Patrol Plot for 1200 GMT May 30. 1987, Based on Observed and Fore- cast Conditions. 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39'= liiiiii I MjniMii II II I I III I III! I I III! I) I II II r| I Mill I mil I r | i n 1 1 1 i 1 1 1 i i 1 1 1 1 i 38°1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 J 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 r 38'^ 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° N ▲ Berg N A Growler N X Radar Target / Contact Estimated limit of all known ice Estimated limit of sea ice 200 Meter bathymetric contour Where "N" Is The Number Of Designated Targets In A One Degree Rectangle 46 Figure 31. Graphic Depiction of International Ice Patrol Plot for 1200 GMT June 15, 1987, Based on Observed and Fore- cast Conditions. 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° j^ I 1 1 1 I I in 1 1 I I 1 1 m I r | | i 1 1 1 1 1 " ' ' ' v "it i | 1 1 i ij | 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 i i ii 1 1 i] --q 42° 41 o: 40°i 39°E i i : X 38° 1 1 1 1 1 1 j 1 1 1 1 1 1 1 1 1 1 1 1 M 1 1 1 1 M 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 11 1 38° 51° £50° 49° 48° :47° :46° 45° :44° E43° :42° :41° :40° :39° 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39= N A Berg N M. Growler N X- Radar Target / Contact Where "N" Is The Number Of Designated Targets In A One Degree Rectangle Estimated limit of all known ice Estimated limit of sea ice 200 Meter bathymetric contour 47 Figure 32. Graphic Depiction of International Ice Patrol Plot for 1200 GMT June 30, 1987, Based on Observed and Fore- cast Conditions. 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39° )" llllllll MM Mirillllllllllllll I I MINI III I 11111111 I I III I) mil) II II I I 38°~l 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 r 38° 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° N ▲ Berg N M. Growler N X Radar Target / Contact Estimated limit of all known ice Estimated limit of sea ice 200 Meter bathymetric contour Where "N" Is The Number Of Designated Targets In A One Degree Rectangle 48 Figure 33. Graphic Depiction of Interrtational Ice Patrol Plot for 1200 GMT July 15, 1987, Based on Observed and Fore- cast Conditions. 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° )" I I 1 1 1 1 Iji 1 1 1 I I 1 1 1 11" I 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 1 1 1 r 1 1 1 1 1_ I I 1 1 1 1 1 1 M 1 1 1 1 1 1 I M I 1 1 n 1 1 f.^o 38° 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 r 38^^ 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° N A Berg N M. Growler N X Radar Target / Contact Estimated limit of all known ice Estimated limit of sea ice 200 Meter bathymetric contour Where "N" Is The Number Of Designated Targets In A One Degree Rectangle 49 Figure 34. Graphic Depiction of International Ice Patrol Plot for 1200 GMT July 30. 1987, Based on Observed and Fore- cast Conditions. 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° )" I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I M I I I I I I I I I I I M I I I I I I I I I I I M I I I --0 40°: 39°i :40° ■t t :39 38° 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 i 1 1 1 1 1 r 38° 57° 56° 55° 54° 53° 52° 51 ° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41 ° 40° 39° N A Berg N M. Growler N X Radar Target / Contact Where "N" Is The Number Of Designated Targets In A One Degree Rectangle Estimated limit of all known ice Estimated limit of sea ice 200 Meter bathymetric contour 50 Discussion of Ice and Environmental Conditions The number of icebergs that pass south of 48°N in the International Ice Patrol area is the measure by which the International Ice Patrol has judged the severity of each year since 1913 (Appendix B). With 318 icebergs south of 48°N, the severity of 1987 was below the 1913-1986 average (Appendix B). Since the number of icebergs calved each year by Greenland's glaciers is in excess of 10,000 (Knutson and Neill, 1978), a sufficient number of icebergs exist in Baffin Bay during any year. Therefore, annual fluctuations in the generation of Arctic icebergs are not a significant factor in the number of ice- bergs passing south of 48°N annually. The number of icebergs passing south of 48°N each season is determined by the supply of icebergs available to drift south onto the Grand Banks, as well as factors affecting iceberg transport (currents, winds, and sea ice) and the rate of iceberg deterio- ration (wave action, sea sur- face temperature, and sea ice). Sea ice impedes the transport of icebergs by winds and currents and protects icebergs from wave action, the major agent of iceberg deterio- ration. Although it slows current and wind transport of icebergs, sea ice is itself an active medium, for it is con- tinually moving toward the ice edge where melt occurs. Therefore, icebergs in sea ice will eventually reach open water unless grounded. The melting of sea ice itself is affected by snow cover (which slows melting) and air and sea water temperatures. As sea ice melt accelerates in the spring and early summer, trapped icebergs are rapidly released and are then subject to normal transport and deterioration. The Labrador Current, aided by northwesterly winds in winter, is the main mecha- nism transporting icebergs south to the Grand Banks. In addition to transporting ice- bergs south, the relatively cold waters of the Labrador current slow the deterioration of icebergs in transit. Sea ice conditions were above normal for the first part of the 1987 season. The sea ice edge was farther south than normal in December and January, and at its mean location in February. This would have the affect of pro- tecting the icebergs longer and releasing them farther south than normal. These ice condi- tions would normally lead to a season of average or above average iceberg severity. The AES/IIP pre- season surveys in January and February indicated an adequate supply of icebergs available to drift south onto the Grand Banks (Osmer and McRuer, 1987). Based on the sea ice conditions and availability of icebergs, International Ice Patrol was expecting an aver- age to above average season. The question of how and why the iceberg season develops as it does is always of interest to International Ice Patrol. This is particularly true when the season does not develop as expected, as happened in 1987. In February, the sea level pressure distribution indicated the mean flow pattern for the month was northeast- erly rather than northwest- erly. This would result in an unfavorable drift to the west, out of the Labrador Current and against the Labrador coast. The icebergs would get grounded or trapped in the many bays and inlets along the Labrador coast. The easterly winds in March pushed all the sea ice off the Grand Banks, and packed it against the Newfoundland coast. Again, the winds in March were unfavorable for iceberg drift. The icebergs were pushed out of the Labrador Current, and along the coasts of Labrador and Newfoundland. In summary, it ap- pears that in spite of adequate supply of icebergs and favor- able sea ice conditions, an average or above average 1987 iceberg season failed to occur because wind conditions were not favorable in February and March for the transport of icebergs south of 48°N. 51 References Alles, M.F., and M.A. Alfultis. A Mobile Oceanographic Data Collection System, International Ice Patrol Technical Report. In Press. Anderson, 1. Iceberg Deterioration Model, Report of the Inter- national Ice Patrol in the North Atlantic, 1983 Season. CG-1 88-38, U.S. Coast Guard, Washington D.C., 1983. Atmospheric Environment Service (AES), Thirty Day Ice Fore- cast for Northern Canadian Waters, January 1987. Atmospheric Environment Service (AES), Thirty Day Ice Fore- cast for Northern Canadian Waters, March 1987. Atmospheric Environment Service (AES), Thirty Day Ice Fore- cast for Northern Canadian Waters, May 1987. Knutson, K.N. and T.J. Neill, Report of the International Ice Patrol Service in the North Atlantic Ocean for the 1977 Season. CG-188-32. U.S. Coast Guard, Washington D.C.. 1978. Mariners Weather Log, Spring 1987, Vol. 31 , Number 2, 1987a. Mariners Weather Log. Summer 1987, Vol. 31. Number 3, 1987b. Mariners Weather Log, Fall 1987, Vol 31. Number 4, 1987c. Mariners Weather Log, Winter 1988, Vol. 32, Number 1. 1988. Murphy, D.L. and 1. Anderson. Evaluation of the International Ice Patrol Drift Model, Report of the International Ice Patrol in the North Atlantic. 1985 Season. CG-188- 40, U.S. Coast Guard, Washington D.C., 1985. Naval Oceanography Command, Sea Ice Climatic Atlas: Volume II Arctic East, 1986. Navy-NOAA Joint Ice Center, Naval Polar Oceanography Center, Southern Ice Limit, Published Bi-monthly, 1987. Osmer, S. R. and H. McRuer, 1987 Preseason Iceberg Survey ' and Season Prediction, Proc. Oceans '88, Oct. 1987, Halifax, N.S. 52 Acknowledgements Commander, International Ice Patrol acknowledges the assistance and information provided by the Atmospheric Envi- ronment Service (AES) of Environment Canada, the U.S. Naval Fleet Numerical Oceanography Center, U.S. Naval Eastern Oceanography Center, and the U.S. Coast Guard Research and Development Center. We extend our sincere appreciation to the staffs of the Canadian Coast Guard Radio Station St. John's, Newfoundland/ VON, Ice Operations St John's, Newfoundland, Air Traffic Control Gander, Newfoundland, Canadian Forces Gander and St. John's, Newfoundland, and the Gander Weather Office, and to the personnel of U.S. Coast Guard Air Station Elizabeth City, US Coast Guard Communications Station Boston, USCGC BITTER- SWEET, and USCGC TAMAROA for their excellent support during the 1987 International Ice Patrol season. It is also important to recognize the efforts of the per- sonnel at the International Ice Patrol: LCDR S. R. Osmer, LCDR W. E. Hanson, Dr. D. L. fi^urphy, LT I. Anderson, LT N. B. Thayer, LT M. A. Alfultis, MSTCS G. F. Wright, MSTC M. F. Alles, YN1 S. A. Cooper, MST1 P. O. Pelletier, MST1 M. G. Barrett, MST2 D. A. Hutchinson, MST2 D. D. Beebe, MST2 W. A. Henry, MST2 K. A. Austin, MST3 P. B. Reilley, and MST3 C. F. Weiller. 53 Appendix A List of Participating Vessels, 1987 VESSEL NAME FLAG SST ICE REPORTS ABITIBI MACADO FED. REP. OF GERMANY 4 ABTARTICO PORTUGAL 1 ACADIAN GAIL CANADA 1 ACADIAN TEMPEST CANADA 1 ADA GORTHON SWEDEN 3 AFRICAN EVERGREEN LIBERIA 1 AFRICAN GARDENIA LIBERIA 10 AGIATHALASSINI PANAMA 1 2 AIFANOURIOS LIBERIA 17 AKRANES ICELAND 1 ALBERRY SAUDI ARABIA 3 ALBRIGHT EXPLORER UNITED KINGDOM 1 ALBRIGHT PIONEER ALGERIAN UNITED KINGDOM 5 1 SWEDEN ALMARE SETTIMA ITALY 1 ALMESSILAH KUWAIT 16 2 AMERICANA ITALY 1 APOLLO UNITED KINGDOM 1 ARABELLA GREECE 1 ARCTIC CANADA 2 ARGUS TRAUCHER LIBERIA 9 3 ARKA UNKNOWN ARMERIA JAPAN 1 1 ASTOR ST. VINCENT THE GRENADINES 3 ATLANTIC NETHERLANDS 1 ATLANTIC AMITY UNITED KINGDOM 1 1 ATLANTIC LINK BAHAMAS 3 ATLSGA SWEDEN 1 BAFFIN CANADA 2 11 BALAO LIBERIA 7 1 BALTIC CYPRUS 7 BALTIC SUN NETHERLANDS 1 1 BARBER NARA SWEDEN 1 BARON PANAMA 1 BARTLE 1 1 CANADA 5 BELLE ETOILE MAURITUIS 1 BIENDIE LIBERIA t BIRDIE AUSTRALIA 5 BISHAH SAUDIA ARABIA 5 55 Appendix A VESSEL NAME BITTERSWEET BLUE PINE BOKA BOKHTARMA BONNY BRIDGEWATER BRITISH STEEL BROOMPARK CANMAR AMBASSADOR CANMAR (DART) EUROPE CANADIAN EXPLORER CAPETAN HALARIS CAPE BYRON CAPE ROGER CARMEN MARE CAST CARIBOU CAST HUSKEY CAST MUSKOX CAST OTTER CAST POLAR BEAR CAVELIER DELASSALLE CECELIA DESGAGNES CHARLOTTE BASTIAN CHIPPEWA CHERRY VALLEY CIECERO COASTAL CANADA CZANTORIA DAMODAR DR. A. BLOCK DANAU MARU DART AMERICA DART ATLANTIC DART BRITAIN DONNY DORTHE OLDENDORFF DUESSELDORF EXPRESS DUKE OF TOPSAIL DOZE VALE EASTERN UNICORN ECAREG LIRIA 56 FLAG SST USA 3 PANAMA JAPAN 4 PEOPLES REP. OF CHINA BAHAMAS 8 FED. REP. OF GERMANY UNITED KINGDOM UNITED KINGDOM CANADA BELGIUM UNITED KINGDOM UNKNOWN FED. REP. OF GERMANY CANADA GREECE 39 LIBERIA 1 UNITED KINGDOM UNITED KINGDOM UNITED KINGDOM LIBERIA 10 FRANCE CANADA FED. REP. OF GERMANY LIBERIA 1 USA CANADA CANADA POLAND 1 INDIA JAPAN PANAMA UNITED KINGDOM UNITED KINGDOM SWEDEN SINGAPORE FED. REP. OF GERMANY UNITED KINGDOM BRAZIL 8 PANAMA 7 SPAIN ICE REPORTS 1 2 2 1 1 8 4 1 1 1 1 2 2 1 1 4 1 1 3 1 2 4 4 4 1 1 2 2 1 1 4 2 1 7 1 Appendix A VESSEL NAME FLAG SST ICE REPORTS EDCO ^QYpj 1 EIRMNES LIBERIA 1 ENERCHEM FUSION CANADA 5 ENSORTFONAH BELGIUM 1 ESSICAMILLA SINGAPORE LIBERIA 1 2 ESSO PROVIDENCE EUROPEGASUS LIBERIA 1 EUTERPE CYPRUS 1 EVRYALOS GREECE 1 2 FAIR SPIRIT LIBERIA 3 FAI PHM LIBERIA 1 r f\LX^\Jv* FALKOFN SWEDEN 1 FEDERAL CALUMET SWEDEN 1 FEDERAL FUJI JAPAN 2 FEDERAL POLARIS JAPAN 1 FEDERAL ST. CLAIR LIBERIA 1 FINNARCTIS UNITED KINGDOM 1 FINN FALCON UNITED KINGDOM 12 FINNFIGHTER FINLAND 2 2 FINNPOLARIS UNITED KINGDOM 7 5 FINNSNES LIBERIA 1 FLAME CYPRUS 1 FREDJ. AGNICH CANADA 1 FROST CASTOR CYPRUS 1 FURIA LIBERIA 3 GALASSIA ITALY 15 GAUDREAU CANADA 1 GENERAL GARCIA PHILIPPINES 1 GENERAL VARGAS PHILIPPINES 1 GRAND COURT USSR 2 GRAND KNIGHT USSR 1 GRAND PRINCE UNKNOWN 1 GRENFELL CANADA 4 GROSEWATER CANADA 2 GULF HARVEST PANAMA 1 HANSEATIC PANAMA 1 HARITAS CYPRUS 5 HELENA OLDENDORFF PANAMA 2 HELLESPONT MARINER GREECE 1 HELLESPONT VALOUR GREECE 6 57 Appendix A VESSEL NAME FLAG SST ICE REPORTS HENRI TE' LLIER HEXMARRDO HIGH AEUT HOFSJOKULL HOLCAN MAAS HUAL TRAPPER HUBERT GAUCHER HUDSON ICE LACKENKY ICE TECHNO VENTURE IMPERIAL BEDFORD IMPERIAL QUEBEC INGRID GORTHON IRONMASTER IRVING OURS POLAIRE IRVING WOOD ISHIKARIMARU JACKMAN JESSIE STOVE JOHANNA SCHULTE JOKULFELL JUGOAGENT KANGUK KATTEGAT KAZIMIERZ PULASKI KHUDOYHNIK PAKHOMOV KHUDOYHNIK ROMAS KOELN EXPRESS KOLL BJORG KRISTINA LOGOS KRITI CORAL LABRADOC LACHENE LADY HIND LAKENBY LAKESTAR LAPPONIA LAURENCE H. GIANELLA CANADA UNITED KINGDOM SINGAPORE ICELAND URUGUAY PANAMA CANADA CANADA UNITED KINGDOM CANADA CANADA CANADA BAHAMAS PANAMA CANADA UNITED KINGDOM JAPAN CANADA SINGAPORE CYPRUS ICELAND UNKNOWN CANADA PHILIPPINES SUDAN USSR USSR FED. REP. OF GERMANY NORWAY USSR GREECE CANADA CANADA BELGIUM UNITED KINGDOM CYPRUS BAHAMAS UNKNOWN 10 11 3 1 1 4 4 1 1 5 2 2 2 2 1 3 16 4 1 6 3 3 1 2 1 1 1 4 2 o 11 1 3 1 2 2 2 1 1 1 1 58 Appendix A VESSEL NAME ■;■:-^^^^:-:-^^^^^^^^>^■.■.■.v.^■.-.•.■.■ LEBRAVE LECEDREN LECH LEERORT LEONARD J. COWLEY LIBERTY BELL VENTURE LIPNO LONE VENTURE LONG CHALLENGER LOTILA L ROCHETTE LUCIEN PAGUIN LUCKY MAN LUDOLFOLDENDORFF MAERSK SEBAROK MAHONE BAY MALOJA MANCHESTER CHALLENGE MANGA MARIA AUXILIDORA MARIA G L MARIN MARINE PACKER MASHUMARU MEDALLION MELA METRO STAR ML JET FLAG UNKNOWN CANADA AUSTRIA FED. REP. OF GERMANY UNKNOWN LIBERIA CZECHOSLAVIA CANADA LIBERIA BAHAMAS CANADA CANADA CYPRUS SINGAPORE SINGAPORE CANADA CYPRUS UNITED KINGDOM UNITED KINGDOM BRAZIL GREECE LIBERIA CANADA JAPAN DENMARK PANAMA CANADA YUGOSLAVIA SST ICE REPORTS 2 3 8 2 1 1 MOCHIZUKI JAPAN MOSILORE LIBERIA MT BONNY BAHAMAS MUO ST. VINCENT MUSKOX UNITED KINGDOM MYRSINIDI LIBERIA NADEZHDAOBUKHOVA USSR NARWHAL UNITED KINGDOM NELVANA LIBERIA NEMEMCHA ALGERIA NEPTUNE JADE SINGAPORE NORDHEIDI SINGAPORE NORDIC SUN LIBERIA 3 1 2 3 2 5 1 1 1 6 1 1 1 2 4 7 2 1 1 2 1 4 1 2 2 1 1 1 1 1 1 6 2 1 5 1 59 Appendix A VESSEL NAME FLAG SST ICE REPORTS nWBW^k SINGAPORE 2 NORD PACIFIC SINGAPORE 10 2 NORDSTAR SINGAPORE 3 NORLANDIA FED. REP. OF GERMANY 1 NORTHERN ENTERPRISE BERMUDA 1 NORTHERN PRINCESS CANADA 1 NORTHWIND USA 11 2 NORWIND NETHERLANDS 2 1 NOSAC LAKAYAMA LIBERIA 1 NURNBERG EXPRESS FED. REP. OF GERMANY 9 OKANAGAN CANADA 1 1 OLIVIA BRAZIL 1 ORIENTAL RUBY JAPAN 1 1 ORIENT PIONEER LIBERIA 1 ORLANDO LIBERIA 1 PENALARA FRANCE 2 2 PENNY LUCK UNKNOWN 1 PEONIA LIBERIA 2 PLACENTIA BAY CANADA 8 POLAR BEAR LIBERIA 2 PONIA HONDURAS 1 PRIMOSTEN YUGOSLAVIA 1 3 PRODUCT SPLENDOR UNITED KINGDOM 4 1 PROTECTEUR CANADA 6 PUHOS BAHAMAS 1 RAVIDAS INDIA 1 REED VOYAGER PANAMA 6 RIVER PRINCESS LIBERIA 1 1 ROBERT MAERSK DENMARK 3..-.::-.-..-.-...,.. 1 RODRIGOTORREABLA BRAZIL 7 ROVER USA 1 SAINT DIMITIRIOS LIBERIA 6 SAINT LAWRENCE PAKISTAN i SAINT VASSILLOS CYPRUS 1 SAMBURG USSR 2 SAM JOHN PIONEER PANAMA 1 SAMUEL L COBB USA 10 8 SANDNESS PANAMA 2 SANTA MALFALDO PORTUGAL 1 60 Appendix A VESSEL NAME FLAG SST ICE REPORT SEASTAR 2 CYPRUS 1 SELKIRK SETTLERR CANADA 1 SENTIS UNITED KINGDOM 3 SIR H. GILBERT CHILE 9 SIR ROBERT BOND CANADA 4 SKIDEGATE CANADA 10 SOREN TOUBRO INDIA 6 3 SOVETSK USSR 1 SPYROS A. LEMOS GREECE 1 STALWART USA 4 STARWORLD UNITED KINGDOM 1 STEFAN BATORY POLAND 4 STEFAN STARZYNSKI POLAND 2 STILLANOVA NETHERLANDS 1 STOLT CASTLE LIBERIA 2 STOLT CROWN LIBERIA 2 STOLT SAPPHIRE LIBERIA 4 2 STOLT SPAN LIBERIA 1 STOLT SYDNESS LIBERIA 3 STUTTGART EXPRESS FED. REP. OF GERMANY 1 SUMMIT LIBERIA 3 TAMAROA USA 5 1 TAVERN ER CANADA 1 TEAM FROSTA SINGAPORE 5 TEVERA CYPRUS 1 THAMES LIBERIA 1 TILIA GORTHOU SWEDEN 1 TOKI ARROW NORWAY 1 1 TORONTO BERMUDA 1 TRINITY BAY CANADA 4 UNDERWOOD USA 6 VADASTEINUR DENMARK 1 VALOR PHILIPPINES 1 VAYGACH USSR 1 VESALIUS BELGIUM 1 VICTORIUS PANAMA 2 VIKING OSPREY BAHAMAS 1 VIKTOR TKACHYOV USSR 2 VISHVA PALLAV INDIA 1 VOLOS LIBERIA 3 61 Appendix A I VESSEL NAME WESER HARBOUR WEST BRIDGE WILFRED TEMPLEMAN WINONA WOODLAND YAYAMARIA YOUNG SHINKO YUKOVA ZAGREB ZANDAM ZANDBERG ZAWRAT ZIEMIA LUBELSKA ZIEMIA OLSZTYNSKA ZIEMIA OPOLSKA ZIEMIA TARNOWSKA ZIM KEELUNG FLAG FED. REP. OF GERMANY LIBERIA CANADA LIBERIA CANADA CYPRUS JAPAN LIBERIA YUGOSLAVIA INDIA CANADA POLAND POLAND POLAND POLAND POLAND ISRAEL SST ICE REPORT 1 2 3 1 4 1 3 2 1 1 1 1 1 3 3 1 1 62 Appendix B Iceberg Populations South of 48° N Since 1900 LT Michael A. Alfultis, USCG Since its beginning, the International Ice Patrol has maintained an annual count ot the number ot icebergs cross- ing latitude 48°N. Each year the number ot icebergs south of 48°N is used by International Ice Patrol to gauge the potential threat to North Atlantic ship- ping, and, therefore, the opening and closing date of each Ice Patrol Season. Table B-1 provides a monthly breakdown of the estimated number of icebergs crossing 48°N each year since 1900. This updates the his- torical iceberg statistics last published in the 1977 Ice Patrol Bulletin No. 63. Table B-1 is in a slightly different format from that published previously. Recently, Interna- tional Ice Patrol began using as its ice year the period from October through September rather than the calendar year or the period September through August, as was done in the past. The data published in 1977 have been updated to reflect this, and the iceberg counts since 1977 added. The monthly counts are broken into four eras, 1900- 1912, 1913-1945, 1946- 1982, and 1983-1987. The first era is the pre-lnterna- tional Ice Patrol period when icebergs sighted by commercial shipping were reported to the U. S. Hydrograhic Office. During the next era, the Inter- national Ice Patrol estimated the iceberg distribution from surface observations made from U. S. Coast Guard cutters and commercial vessels tran- siting the area. Visual recon- naissance from aircraft became International Ice Patrol's primary method for iceberg detection during the third era. During the final era, the Side- Looking Airborne Radar (SLAR) provided International Ice Patrol with an all-weather capability to detect icebergs. Iceberg sightings provided by commercial shipping have been, and continue to be, an important source of informa- tion to International Ice Patrol. International Ice Patrol defines those ice years with less than 300 icebergs crossing 48°N as light or low ice years; those years with 300 to 600 icebergs crossing 48°N as average or intermedi- ate ice years; those years with 600 to 900 icebergs crossing 48 °N as heavy or severe ice years; and those ice years with more than 900 icebergs cross- ing 48°N as extreme ice years. Figure B-1 is a bar graph of icebergs crossing 48 N since 1912. The variability in the record is readily seen. The factors that determine this variability are the supply of icebergs available to drift onto the Grand Banks, those affect- ing iceberg transport (cur- rents, winds, and sea ice), and those affecting deterioration (wave action, sea surface temperature, and sea ice). These factors are often unpre- dictable. During the 1987 season, short term changes in the mean wind flow dramati- cally affected the iceberg distribution, and changed the character of an anticipated severe iceberg season to barely an average season (318 ice- bergs). 63 Table B-1. Iceberg Populations South of4ff'N Since 1900. ANNUAL ICE YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP TOTAL Pre-lnternatlonal Ice Patrol 1900 0 0 0 10 0 0 5 32 33 6 1 1 88 1901 1 0 0 1 0 0 4 13 29 22 6 5 81 1902 1 2 5 3 0 1 1 13 5 16 1 0 48 1903 1 0 0 0 2 400 166 151 52 23 7 0 802 1904 0 0 1 0 0 12 63 82 89 14 3 2 266 1905 0 0 0 3 2 168 373 109 100 50 9 8 822 1906 8 0 15 14 11 77 49 133 87 18 16 0 428 1907 0 0 0 0 1 11 162 248 138 64 11 0 635 1908 0 0 3 1 0 7 39 82 51 2 2 20 207 1909 15 3 0 0 55 147 134 321 181 121 45 19 1,041 1910 1 0 0 0 0 0 34 10 3 3 0 0 51 1911 0 0 0 0 8 41 112 72 77 21 40 3 374 1912 0 8 14 1 0 34 395 345 159 63 19 0 1,038 TOTAL 27 13 38 33 79 898 1,537 1.611 1,004 423 160 58 5,881 1900-1912 AVERAGE 2 1 3 2 6 69 118 124 77 32 12 4 452 1900-1912 Surface Patrol Vessels 1913 0 3 0 2 4 37 109 292 71 14 4 7 543 1914 0 6 4 1 41 32 27 419 71 22 46 52 721 1915 13 1 6 14 72 67 96 97 71 28 17 5 487 1916 0 1 0 0 0 0 0 25 29 0 0 0 55 1917 0 0 0 0 0 13 3 3 9 10 0 0 38 1918 0 0 0 0 0 12 23 26 37 27 34 22 181 1919 1 14 3 3 4 5 25 75 56 26 36 69 317 1920 2 12 4 6 43 20 5 211 86 18 5 18 430 1921 19 10 4 17 5 43 210 198 175 53 24 4 762 1922 10 1 6 0 3 35 71 245 83 21 11 6 492 1923 27 21 0 0 3 28 65 83 42 10 3 2 284 1924 0 0 0 3 0 6 2 0 0 0 0 0 11 1925 0 0 0 0 3 5 8 58 22 13 0 0 109 1926 0 0 0 0 3 15 58 168 85 4 6 2 341 1927 3 1 0 4 10 26 93 153 95 5 3 0 393 1928 0 0 0 0 0 14 156 190 87 55 5 0 507 1929 4 4 0 0 0 45 332 460 376 107 1 0 1,329 1930 0 18 12 14 116 87 89 101 62 3 1 1 504 1931 1 0 0 0 0 2 1 10 0 0 0 0 14 1932 0 0 0 0 1 43 321 90 58 1 0 0 514 1933 0 0 0 0 2 4 12 162 36 0 0 0 216 1934 0 0 0 1 0 0 245 228 87 14 1 0 576 64 Table B-1 (Continued). ANNUAL ICE YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP TOTAL 1935 0 0 0 0 0 46 177 501 134 11 3 0 872 1936 0 0 3 0 0 0 8 14 0 0 0 0 25 1937 0 0 0 20 53 121 124 137 14 1 0 0 470 1938 0 0 0 2 3 38 212 286 110 13 0 0 664 1939 0 0 0 0 0 22 173 471 150 28 6 0 850 1940 0 0 0 0 0 0 0 1 0 0 0 0 1 1941 0 1 0 0 0 0 1 1 0 0 0 0 3 1942 0 0 0 0 0 30 0 0 0 0 0 0 30 1943 0 0 0 0 0 25 90 298 270 150 7 0 840 1944 0 0 0 0 0 31 319 213 106 30 1 0 700 1945 0 0 0 0 6 352 253 256 92 109 15 0 1,083 TOTAL 80 93 42 87 372 1,204 3,308 5,472 2,514 773 229 188 14,362 1913-1945 AVERAGE 2 3 1 3 11 36 100 166 76 23 7 6 435 1913-1945 Visual Aircraft Reconnaissance 1946 0 0 0 0 2 67 98 168 88 7 0 0 430 1947 0 0 0 3 1 2 5 11 26 15 0 0 63 1948 0 0 0 0 0 60 210 185 68 0 0 0 523 1949 0 0 0 0 0 1 23 20 3 0 0 0 47 1950 0 0 0 0 12 61 183 135 58 7 0 1 457 1951 1 2 0 0 3 2 0 0 0 0 0 0 8 1952 0 0 1 0 0 0 12 2 0 0 0 0 15 1953 0 0 0 0 0 21 11 18 6 0 0 0 56 1954 0 0 0 1 16 47 165 65 16 2 0 0 312 1955 0 0 0 0 0 10 32 14 5 0 0 0 61 1956 0 0 0 0 0 9 13 34 21 3 0 0 80 1957 0 0 0 3 43 41 172 265 288 113 6 0 931 1958 0 0 0 0 0 0 0 0 0 1 0 0 1 1959 0 0 0 0 0 14 266 180 186 43 0 0 689 1960 0 2 3 3 0 0 41 161 44 4 0 0 258 1961 0 0 0 0 6 60 30 16 1 0 1 0 114 1962 1 0 1 0 0 14 72 21 10 3 0 0 122 1963 0 0 0 0 0 4 20 0 1 0 0 0 25 1964 0 0 0 0 3 88 225 19 28 5 1 0 369 1965 0 0 0 0 1 19 33 22 1 0 0 0 76 1966 0 0 0 0 0 0 0 0 0 0 0 0 0 1967 0 0 0 0 0 25 134 209 65 8 0 0 441 1968 0 0 0 0 0 0 104 44 60 14 4 4 230 1969 0 0 0 0 0 0 0 35 17 1 0 0 53 1970 0 0 0 0 0 0 5 2 70 8 ■ 0 0 85 65 Table B-1 (Continued). ANNUAL ICE YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP TOTAL 1971 0 0 0 0 0 31 4 20 7 11 0 0 73 1972 0 0 0 0 40 185 501 559 225 48 26 4 1,588 1973 0 0 6 54 110 134 212 159 151 19 1 0 846 1974 0 0 0 0 1 99 345 446 266 168 61 1 1,387 1975 0 0 0 0 24 41 10 20 5 0 0 0 100 1976 0 0 0 0 0 33 13 67 35 3 0 0 151 1977 0 0 0 0 3 7 12 0 0 0 0 0 22 1978 0 0 0 0 0 5 28 35 7 0 0 0 75 1979 0 0 0 0 5 20 81 34 9 3 0 0 152 1980 0 0 0 1 3 7 0 9 4 0 0 0 24 1981 0 0 0 0 0 48 10 5 0 0 0 0 63 1982 0 0 0 0 0 17 61 13 94 3 0 0 188 TOTAL 2 4 11 65 273 1,172 3,131 2,993 1,865 489 100 10 10,115 1946-1982 AVERAGE 0 0 0 2 7 32 85 81 50 13 3 0 273 1946-1982 Aircraft SLAR Reconnaissance 1983 0 0 2 9 165 124 339 465 168 76 4 0 1.352 1984 0 0 0 0 0 101 953 484 227 335 93 9 2,202 1985 3 11 7 2 57 129 208 205 247 123 39 32 1,063 1986 0 0 0 0 3 40 60 59 24 18 0 0 204 1987 0 0 5 2 14 48 76 29 127 15 2 0 318 TOTAL 3 11 14 13 239 442 1,636 1,242 793 567 138 41 5,139 1983-1987 AVERAGE 0 2 3 3 48 88 327 248 159 113 28 8 1,027 1983-1987 TOTAL 112 121 105 198 963 3,716 9,612 11,318 6,176 2,252 627 297 35,497 1900-1987 AVERAGE 1 1 1 2 11 42 109 129 70 26 7 3 403 1900-1987 TOTAL 85 108 67 165 884 2,818 8,075 9,707 5,712 1,829 467 239 29,616 1913-1987 AVERAGE 1 1 1 2 12 38 108 129 69 24 6 3 395 1913-1987 66 Figure B- 1. ti\nSS8«rnaj|(dl|-e86l' I — S86t ■0861- -gz6i. 1^ GO I CM Oi o 00 ■0Z6I. 9961 0961 3 O CO (0 O) JD o eoues9|euuooej 6jeqeo| J0| UEJSJts |o esn lajy g^ei '^ 2AMAOl«ips|cuiBdON ■9S61 0S6I. ■0^61 o CO 0) CO I — st'et i= CO 0) o 0 E 3 8 M2C.e9 NOZoOe .^_ eiep 01 Bieq isoiuujeiivios " pei4S|iq«lse dll ,^_ o CVJ 8 lO ■see I. ■oeet S26I. 0361 s6jeq90|iOJ9qLunN 67 Appendix C 1987 International Ice Patrol Drifting Buoy Program Donald L Murphy LT Neal B. Thayer, USCG INTRODUCTION This report documents the operational portion of the 1987 drifting buoy program of the International Ice Patrol. The program, which began in 1976, supports Ice Patrol operations and research. Eighteen separate buoy deploy- ments were made in 1987. Of these, nine were launched from Ice Patrol reconnaissance aircraft and the data used primarily for operational purposes (Summy and Anderson, 1983 and Summy, 1982). The remainder were de- ployments from U.S. Coast Guard vessels conducting Ice Patrol research cmises. Most of the latter were drift tracks of short duration, with the buoy being recovered at the end of each experiment. Two of the aircraft- deployed buoys were launched by Ice Patrol off northern Labra- dor as part of a Canadian Atmos- pheric Environment Service (AES) test of their iceBerg Analysis and Prediction System (BAPS). Ice Patrol sponsored two oceano- graphic research cmises in 1987. The first, (IIP 87-1) from 27 April to 20 May, was conducted at)oard USCGC BITTERSWEET (WLB 389). The objective of IIP 87-1 was to investigate the ability of HP's side-looking airt)orne radar (SLAR) to detect warm-core eddies. Six separate buoy deployments were made during this research. Of these, two buoys were not recovered at the end of the experiment, and their data were used for operational purposes. The buoy tracks during the cruise period are discussed in Appendix D of this Bulletin. The second 1987 Ice Patrol research cruise (IIP 87-2) was an iceberg drift and deterioration study conducted aboard USCGC TAMAROA (WMEC 166). from 8 June to 27 June. TAMAROA deployed three buoys, all of which were recovered at the end of the experiment. The results of this cruise are discussed in Appendix With the exception of the buoys deployed solely for research. Ice Patrol enters all of its buoy data onto the Global Telecommunica- tions System (GTS). Although Ice Patrol is directly interested in sea surface temperature and position data only when the buoys are within its operations area, the buoys frequently leave the area and move eastward across the North Atlantic. Tracking the buoys eastward serves the dual purpose of providing useful oceanographic data to the world oceanographic community and providing the opportunity to recover a buoy when it beaches or crosses the path of a ship willing to recover it. Approxi- mately one buoy per year is recovered and returned to Ice Patrol for reuse. All of the buoys used in 1987 had a 3 meter long spar hull with a 1 meter diameter flotation collar. Each buoy was equipped with a 2 by 10 meter window-shade drogue attached to the buoy with a 50 meter tether of 1/2" (1 .3 cm) nylon. The center of the drogue was at 58 m. In addition, each buoy had a temperature sensor mounted approximately 1 m below the waterline, a drogue tension monitor, and a battery voltage monitor. The sea surface temperature is accurate to approximately 1°C. The drogue sensor data should be viewed with some caution. Although recent experience (Anderson, 1986) suggests that the sensor reliably reports drogue status, it sometimes fails. In some cases the buoy's drift track can provide evidence of drogue separation. For example, an abrupt increase in variability with a period of several days might suggest that the drogue has detached and the buoy drift is being affected by the wind and wind-driven currents. However, short of relocating and recovering the buoy, there is no way to know with certainty that the drogue remained attached for the period of interest. The data from the buoys are acquired and processed by Service ARGOS. Ice Patrol queries and stores the data files once daily. Table C-1 summarizes the 18 buoy deployments in 1987. This table reflects the status of all the buoys as of 31 December 1987. 69 Table C-1. Summary of the 18 buoy deployments in 1987. This Table reflects the status of all buoys as of 31 December 1987. Buoy Date Deployment Deployment Recovered/Stopped ID Deployed Platform Position Transmitting 14511 a 07 MAY BITTERSWEET 43'»59'N 48*'09*W 1 1 MAY (1) 4511b 17 MAY BITTERSWEET 43°13"N 47°43'W ACTIVE 4528 15 AUG HC-130 60°00'N 61<'43*W ACTIVE 4536 07 MAY BITTERSWEET 43°39'N48°12'W 09 DEC |4545a 04 MAR HC-130 47°48'N 48<'45*W 05 MAY (2) 4545b 05 MAY BITTERSWEET 45°14'N 48°46'W 11 MAY 114545c 17 MAY BITTERSWEET 44*40'N 49*00*W 20 MAY 4545d 15JUN TAMAROA 51°06'N53°28'W 19JUN 4547a ^'" 07 MAY BITTERSWEET 44"'10'N48"*10'W 11 MAY 4547b 15JUN TAMAROA 51°06'N53°28'W 20JUN 4553 25JUN HC-130 ,,,^,^^ 52''44'N SrSS'VJ ACTIVE 4554 25 MAR HC-130 50°00'N 50°40'W 28 MAY 4555 25 MAR HC-130 , 48''20'N 48°26-W 03 JUL 4556 14 APR HC-130 48°20'N49°19'W 19JUN 4558 14JUN TAMAROA 5ri4'N53^20'W 20JUN 4559 06JUN HC-130 49°40'N 50°52'W 06 AUG (3) : 4560 06 MAY HC-130 49*00'N 50<^36*W 1 Wlmi ACTIVE 4562 15 AUG HC-130 59°13'N60°18'W ACTIVE Notes: (1) A letter behind a buoy number indicates that the buoy was deployed more than once during the year. (2) Buoy 4545 was recovered by USCGC BITTERSWEET on 5 May at position 45°42' N, 49°2rw. The missing drogue was replaced and the buoy redeployed on 5 May. (3) Buoy 4559 was picked up by an unknown vessel on 6 August. The buoy track from that point headed toward Europe at approximately 12 knots. 70 BUOY DEPLOYMENT FROM AIRCRAFT Ice Patrol has deployed satellite- tracked buoys from HC-130's since 1979. The buoy is strapped into an air-deployment package and launched out the rear door of an HC-130 flying at an altitude of 500 feet (150 m) at 150 knots (77 m/s). The air-deployment package consists of a wooden pallet and a parachute, both of which separate from the buoy after it enters the water. The parachute riser is cut by a cable- cutter that is activated by a battery that energizes when immersed in salt water. The pallet separates when salt tablets dissolve and release straps holding the buoy to the pallet. The buoy then floats free and the drogue falls free and unfurls. Nine buoys were air-deployed in 1987. Of these, three pallets (4528. 4553, and 4559) failed upon entry into the HC-130"s airstream. When this occurs, the buoy and drogue usually survive intact, but frequently the wires to the parachute cutter break. This means that the parachute re- mains attached to the buoy hull and can act as a near-surface drogue. Aerial inspections and shipboard recoveries of buoys have shown that the parachutes collapse and become entangled with the buoy hull or the upper part of the drogue tether. It is not likely that these failures contami- nated the drift data significantly. BUOY DEPLOYMENT STRATEGY It is not possible to obtain ade- quate temporal and spatial coverage of the Ice Patrol opera- tions area (40-52N, 39-57W) over a 5 or 6-month period with a few (< 12 ) buoys. As a result, the buoy deployment strategy fo- cuses on the current that is the major conduit of icebergs into the North Atlantic shipping lanes, the southward-flowing off-shore branch of the Labrador Current. The goal is to monitor this current for the entire ice season by keeping one or two buoys in it at all times. With two exceptions (451 1 and 4536), all of the 1987 buoys were deployed in the Labrador Current. The two exceptions were deployed in and near a warm-core eddy that was affecting the flow of the Labrador Current near 44°N. No buoys entered, nor were any deployed, in the inshore branch of the Lab- rador Current. Previous attempts at deployments in this near-shore region resulted in short drift tracks because the buoys became entangled in fishing gear and were recovered by fishermen. DATA PROCESSING l^/lost of Ice Patrol's buoy position data fall within the standard location accuracy (LeTran and Liabet, 1 987) provided by Service ARGOS. The data are reported to 0.001 ° of latitude and longi- tude, which far exceeds this standard location accuracy. For 46°N. the center latitude of the Ice Patrol operations area, the positions are accurate to 0.003° of latitude and 0.005° of longi- tude. The raw position data are unevenly-spaced in time, with virtually no data from the period from OOZ to 004Z each day. This null period is due to the orbits of the NCAA satellites. Approxi- mately 10 fixes are determined each day for each of the buoys. Although the data are relatively noise free, all records are scanned before processing to ensure quality control. First, duplicate positions and positions with time separations of 30 minutes or less are deleted. Then, positions < 700 m from adjacent positions are deleted, unless the deletion results in a time separation of 4 or more hours. The error-free position data are then fitted to a cubic spline curve to arrive at an evenly-spaced record with an interval of 3 hours. This process results in a slight reduction in the number of fixes per day (from 10 to 8). Next, the position records are filtered using a low-pass cosine filter with a cut- off of 1.16 X 10-5 Hz (one cycle per day). This filter removes most tidal and inertial effects. Finally, the buoy drift speeds are calculated at three-hour intervals using a two-point backward differencing scheme. Most of the trajectory plots presented in this report are from the filtered records. Also pre- sented for each buoy is a plot of 71 BUOY 4545 1000m 42N + + 55W + 47W Figure C- 1. Trajectory of Buoy 4545. the time history of the U (east is positive) and V (north is positive) components of velocity from the filtered records. Finally, a time history of the raw sea surface temperature data is plotted for each buoy. The dates used in all of the plots are year-dates, which are numbered sequentially from January 1 . In the text, the year- dates are included parentheti- cally. BUOY TRAJECTORIES In the following sections each buoy trajectory is discussed separately, presented in chrono- logical order by deployment date. Only the operational buoys are discussed. This includes two buoys that were deployed from 72 BITTERSWEET and allowed to drift free at the end of the experi- ment and two buoys purchased by, and deployed for, AES. Buoys 4547 and 4558 were used only during the research cruises. Their data are reported in Appen- dices D and E. The intent of the following discus- sions is to summarize each buoy's performance and the data that it contributed to Ice Patrol operations. It is not intended to be an exhaustive data analysis. The buoy data from the area east of 39°W, the eastern boundary of the Ice Patrol operations area, are not presented. All of the data from the IIP drifting buoy program are archived at the IIP office in Groton, Connecticut. FLEMISH CAP BUOY 4545 Buoy 4545 (Figure C-1 , C-2) was deployed and recovered four times in 1987 (Table C-1), but only one deployment was for operational use. On 4 March (63) it was air- deployed at 47-45N, 48-45W. It provided position and temperature data for 63 days until it was recov- ered on 5 May (125) at 46-42N, 49-21 W by USCGC BITTER- SWEET during IIP 87-1 . During the entire period, the drogue sensor showed that the drogue remained attached; however, when the buoy was recovered only the 50 m nylon drogue tether and the chain bridle that supports the drogue were attached to the buoy. The chain was badly abraided, suggesting that it had dragged across the bottom. The position data presented and discussed in this section are the raw data, not filtered. The record was short and the data return from the buoy immediately after its deployment • was poor (2-3 fixes per day) so much of the interesting data would be lost filling the filter. Buoy 4545 was deployed near the 200 m isobath. During the first 48 hours after deployment, it moved onto the Grand Banks and made an anticyclonic loop with a diameter of about 35 km. Typical buoy speeds during this period were 30-40 cm/s. For the next 1 0 days (7-16 March, 66-75) it moved southward through Flemish Pass, near and parallel to the 200 m isobath. Buoy speeds during this period were 40-50 cm/s and the temperature changed little (-0.8 to -1.4°C). On 16 f^arch (75), 4545 started to move northwestward onto the continental shelf. By 8 April (98) the buoy had moved into a region where it is likely that the drogue was dragging on the bottom, so the drift data after this date are of little use. The surface tempera- ture continued to increase slowly but persistently. The surface temperature when the buoy was recovered was 3.3°C. a;: - c/5 O • 82 - i; BUOY 4545 1987 TEMP^ '.2Z>- 53 133 93 :e3 : YCAnOATE V-COMP, •J3 :l'3 ::3 YEAR DATE Figure C-2. Temperature, U and V velocity components for buoy 4545. 73 50H/ BUOY 4554 ' rVv ^ ^ , V v^ xlv H 46N / 0^ '* ^"^vi?-i ^ / ( 42N VJ + + + 55W 47W Ffgure C-3. Trajectory of Buoy 4554. 74 BUOY 4554 Buoy 4554 (Figure C-3, C-4) was air-deployed at 50-OON, 50-40W on 25 March (84). It transmitted position and temperature data for 65 days, failing on 28 May (148). The buoy's battery voltage and the number of fixes per day were normal until failure. The drogue remained attached during the entire drift period. After its deployment, 4554 moved southeastward, approximately following the 1000 m isobath. Over this period, the filtered buoy speeds varied over the range of 5 to 30 cm/s. The temperature record is unremarkable, with a slow increase in temperature of from 0 to 6°C over the 65 days (0.1°C/day) of the buoy's life. At Sackville Spur, 4554 turned to the northeast, after which it made an anticyclonic loop (-50 km di- ameter). It failed shortly thereafter. BUOY 4554 1987 TEMP. o IS IE M 12 le e 6 4 2 - a -2 _i_ _i_ as 9S ME I2S YEAR DATE 136 156 CO i o laB r- U-COMP, \00 - 88 - 68 - 48 - 20 8 -20 La^H/ ^/^^^--A /V^ 7 ^^ -y vx ^ -40 ^ -68 - -90 - -100 -120 1 1 1 1 1 1 1 86 128- 100- 80 60 48 20 O -^^ -40 - -E0 - -88 -100- -i2e 86 18E 116 126 YEAR DATE 136 156 cn V-COMP. 96 116 126 YEAR DATE 136 156 Figure C-4. Temperature, U and V velocity comporients for buoy 4554. 75 42N + 117 + 55W + 47W + 39W Figure C-5. Trajectory of Buoy 4555. BUOY 4555 Buoy 4555 (Figure C-5, C-6) was air-deployed at 48-20N, 48-26 W on 25 March (84). It remained in the Ice Patrol operations area for 91 days, passing east of 39°W on 23 June (1 74). The drogue remained attached to the buoy for the entire 91 -day drift period, de- taching on 29 June (180). Shortly thereafter (3 July, 184), 4555 was recovered by an unknown vessel at 46-28°N, 37-06°W and taken in the direction of Europe. 76 After deployment, 4555 moved southeastward and then south- ward through Flemish Pass, approximately following the 200 m isobath. During this 25-day period, from 25 March to 19 April (84-109), the temperature in- creased slowly from -1 .4 to 1 .4°C and the speed varied widely (10-50 cm/s). At approximately 44''N, the trajectory of 4555 changed abruptly under the influence of a warm-core eddy centered at 43-30N, 48-10W. The buoy slowed, reversed direction, and then moved eastward and southward, tracing an anticyclonic path approximately one-half the way around the boundary of the eddy. This occurred over a 6-day period, during which the buoy moved at speeds of 50-70 cm/s. During the period that 4555 was moving around the outside of the eddy, the temperature record shows a considerable variability over the range from 0.8 to 13°C, suggesting that the buoy was TEMP. BUOY 4555 1987 166 see U-COMP. 186 196 ME 156 YEAR DATE 166 196 aes Figure C-6. Temperature, U and V velocity components for tjuoy 4555. 77 :'y ' ■'■:\7 r> 50N/ BUOY 4556 ■ 167 +Y y^^A^ \ 1 cA ^5 il59-C J J''/^ /"..•"'Ay 46N vi 120 ^Sn,( ^125 ::> 42N ^S:;^:^ + + + + 55W 47W 39W F/gure C-7. Trajectory of Buoy 4556. close to the eddy's boundary. It is likely that the drogue (~58 m) remained in the cold, subsurface core of the Labrador Current while the temperature sensor at the surface was moving through surface waters of various tem- peratures near the eddy's bound- ary. The track of 4555 after it left the vicinity of the eddy was generally northeastward, with wide fluctua- tions in the filtered speeds. The temperature record shows that 78 the buoy remained in waters greater than 8°C, with most of the readings in the range of 12-14°C. The buoy's subsequent movement is complex, with evidence of eddies and meanders associated with the North Atlantic Current, particularly in the area east of Flemish Cap. BUOY 4556 Buoy 4556 (Figure C-7, C-8) was deployed from an aircraft on 14 April (104) at 48-20. IN, 49-19.8W. it remained in the Ice Patrol operation area for 63 days, passing east of 39°W on 1 6 June (167). Three days later (170), the buoy stopped transmitting, al- though there was no prior indica- tion of a reduction in the buoy's battery voltage or the number of fixes per day. The drogue indicator showed that the drogue detached on 31 May (151). thus it remained attached to the buoy for 48 days. After its deployment, the buoy moved southward through the Flemish Pass and along the eastern edge of the Grand Banks, approximately following the 1000 m isobath. During this period (14-20 April, 104-120), the average speed was 30-45 cm/s and the sea surface temperature increased slightly from -1 .4°C to 0.6°C. On 30 April (120), 4556 began to move rapidly (50-70 cnn/s) to the east, north of the warm core eddy that was surveyed during IIP 87-1 . This eastward motion of a buoy deployed in the Labrador Current and encountering a warm core eddy near the eastern edge of the Grand Banks is similar to that ob- served in 1986 (Murphy et al, 1986). The buoy's motion around the eddy suggests that a portion of the Labrador Current left the eastern edge of the Grand Banks at approximately 44-1 ON and traced a path partially around the eddy. Buoy 4556's temperature record, which showed a slow in- crease in temperature (0.6 to 2.0°C), suggests that it did not enter the eddy, instead remaining in the Labrador Current. On 4 May (124), 4556 started a general northeastward drift, which is typical of many IIP buoys that become entrained in the North Atlantic Current. Over the next twelve days the temperature in- creased 8°C (2-1 0°C). This period is also remarkable in that the buoy's trajectory shows that it became entrained in a small (< 40 km in diameter) cyclonic eddy that was propagating north- eastward and apparently decreas- ing in size. The trajectory shows that the buoy made three circuits of the eddy while the eddy moved northeastward at about 5 km/day. BUOY 4556 1987 TEMP. 188 HE 126 13B M6 YEAR DATE 136 176 U-COMP 176 106 126 136 146 YEAR DATE 1S6 166 176 Figure C-8. Temperature, U and V velocity components for buoy 4556. 79 Figure C-9. Trajectory of Buoy 4560. The temperature record during the period that 4556 was moving in the anticyclonic eddy (125-146) cannot be easily explained. First, the temperature increased from 2-1 0°C, then it decreased rapidly to 5-6°C. It is possible that the low temperature recordings from 19 May to 8 June (139-159) are the result of a sensor malfunction. However, other than the loss of the drogue on 30 May (150), there is no evidence of a buoy malfunction. 80 On 8 June (159) the temperature record shows an increase from 8.2 to 1 1 .8°C on successive satellite passes (about three hours apart). Eight days later (167), 4556 crossed east of 39°W. On 19 June (170), 66 days after its deployment, 4556 stopped transmitting. Buoy 4556 was recovered by the Irish Navy and returned to Ice Patrol in August 1988. It was severely damaged and could not be returned to service. BUOY 4560 Buoy 4560 (Figure C-9, 0-10) was air-deployed on 6 May (126) at 49-OON, 50-36W. It provided data in the Ice Patrol operations area for 73 days, passing east of 39''Won17July(198). The drogue remained attached for the entire period, detaching on 17 October (290) 1 75 days after deployment. The buoy continued to transmit data for the remainder of the calendar year. BUOY 4560 1987 128 138 148 1S8 168 178 188 198 YEAR DATE aea S\B 23B U-COMP -ize 128 -12*- 128 138 ua 158 168 178 188 1S8 YEAR DATE 2B8 218 228 238 248 V-COMP. 138 148 1S8 168 178 188 198 YEAR DATE 208 218 236 248 Figure C- 10. Temperature, U and V velocity components for buoy 4560. 81 During the first 14 days following its deployment (6-20 May,126- 140), 4560 nx)ved southeast- ward to the northern part of Flemish Pass. During this period the buoy's speed varied over the range 25-40 cm/s while the tem- perature increased slightly (1-3°C). The southward motion through Flemish Pass approxi- mately followed the 1000 m isobath. The buoy speed through Flemish Pass varied from 20-35 cm/s, while the temperature remained about 2-3°C. After departing Flemish Pass, 4560 left the slope and moved slowly (< 20 cm/s) southeast- ward. During this period the temperature changed little. The buoy trajectory in the region south of Flemish Cap is complex. Buoy 4560 remained in this region for 31 days (9 June-10 July,160-191), during which the surface temperature increased from 8 to 12°C. On 10 July (191), 4560 began a rapid and persistent movement northeastward with speeds varying over the range of 65-135 cm/s. During this period the surface temperature in- creased rapidly, from 12 to 16°C. BUOY 4536 Buoy 4536 (Figure C-1 1 , C-1 2) was deployed from BITTER- SWEET at 43-39N, 48-1 2W on 7 May (127) in a warm-core eddy. It provided data in the Ice Patrol operations area for 152 days, passing east of 39°W on 5 October (278). The drogue sensor indicated an early drogue failure, with detachment occurring on 20 May (140), 14 days after deployment. The buoy ceased transmitting on 9 December (343). Buoy 4536 remained in the eddy for only 3 days. The data from that period are presented in Appendix D. The departure of 4536 from the eddy was marked by an abnjpt decrease in surface temperature (10.2 to 7.8°C in about 5 hours) and a persistent movement to the east. Over this 5-day period, 11-15 May (131- 135), the buoy accelerated form 40 to 1 10 cm/s and the surface temperature increased from 6 to over13°C. This motion and temperature increase suggest 4536 entered the North Atlantic Current. During the next 34 days (17 May - 20 June, 137-171) 4536 remained in the region directly south of Flemish Cap. The buoy's trajec- tory in this area is complex, with three anticyclonic and one cyclonic loop. At times 4536 moved at over 60 cm/s. The surface temperature varied form 8-1 2°C. These data suggest an area characterized by North Atlantic Current meanders and eddies. Over the next 6 days (20-25 June, 171-176), 4536 moved rapidly (70-125 cm/s) eastward and then northward. The tem- perature over the period re- mained within 10-1 3°C. Forthe remainder of its period in the Ice Patrol operations area (26 June - 5 October, 1 77-278) 4536 re- mained north of Flemish Cap. The trajectory is complex but it suggests that the flow in the region was dominated by North Atlantic Current meanders. The temperature varied over the range of 13-18°C. 82 '.•y ' \ 'x\^<'^^K^ A^- \ mLV ' '''^''ly.r l It Lj W '''r> ^ r\\ X 'W^A{ ■^\f\> '^'v^ /7 x^n^ vjl^ f 9^*\ /V iS ^^ ^^^ j/ ( ^^ ^^^ ^ • '.: • • /. .v.* '•. *-r\ii a/ A ^ *»■ k y V ij ^ ^"•^s,^^ 1 .^^ ^ ^b (• •'*'/ )1( y*— -171 140 Vl^ J lil 42N ^ V • '■•'■7 ' ^ BUOY 4553 ■s 46N + \ ^\^ 1 y 237 42N + + 58W + sow + 42W F/gure C- 1 7. Trajectory of Buoy 4553 approximately one-half of the 100-day period, detaching on 12 August (224). Buoy 4553's southeastward motion after deployment almost exactly traces the 1000 m isobath down to 46°N, including the movement southward through Flemish Pass. While moving southward through Flemish Pass, 4553 recorded a 5.2°C increase in temperature over a 21 -day period (-.25 deg/day). During this period the buoy's speed varied from near zero to 30 cm/s. It is also during this period that the drogue sensor showed drogue detachment. The detach- ment of the drogue added no noise to the position record, as might be expected due to wind effects on the above-water portion of the buoy hull. On 15 August (227) at approxi- mately 46°N, 4553 began an eastward motion south of Flemish Cap. During the next 1 0 days the temperature continued to in- crease until it reached at)out 15°C on 25 August (237), while the buoy moved persistently east- ward at 15-35 cm/s. At this point the temperature leveled off and remained within 2°C of 15°C for the remainder of the drift period in the Ice Patrol operations area. At the same time, 25 August (237), the buoy's movement changed substantially. Figure C-1 8 shows that on this date 4553 entered a region east of Flemish Cap where the flow was vigorous, apparently dominated by eddies and mean- ders of the North Atlantic Current. 89 in i o BUOY 4553 1987 TEMP, lee 338 246 YEAR DATE 25B 268 278 288 298 U-COMP 1B8 138 228 238 248 YEAR DATE 258 268 278 288 298 V-COMP. Figure C- 18. Temperature, U and V velocity components for buoy 4553. 90 BUOY 4562 Buoy 4562 (Figure C-19, C-20) was launched from an aircraft on 15 August (227) at 59-1 3N, 60-1 8W. It entered the Ice Patrol operations area on 26 November (330) when it passed south of 52°N and transmitted data throughout the remainder of 1987. The drogue sensor indicated drogue detachment on 24 October (297), 70 days after the buoy's de- ployment. For the first 28 days (15 August- 1 1 September (227-254)) after its deployment, 4562 moved to the southeast, mostly between the 200 m and 1000 m isobaths. The speeds were in the range of 20 to 55 cm/s, while the temperature remained nearly constant (4-5°C). On 13 September (256), 4562 moved onto Hamilton Bank into water that was too shallow for the buoy's drogue. It remained in that vicinity for about 57 days, during which it moved slowly, with fre- quent direction changes. About halfway through this period (3 October (276)) the temperature record shows an abmpt decrease in temperature (3°C over 18 hours). The remainder of 4562's south- ward movement occurred well inside the 1000 m isobath (3 days). The buoy speeds varied widely (0 to 35 cm/s), while the temperature decreases slowly but persistently from 3°C to 0°C. 91 Figure C- 19. Trajectory of Buoy 4562. 92 o le 16 14 12 la B 6 4 2 BUOY 4562 1987 TEMP. ;;V'vA^>-^-'-v^''''^^^ 0 _____ — — en o -12E 231 231 241 251 261 271 281 291 301 311 321 331 34 1 YEAR DATE 35 1 120- 100- 80 - 60 - 40 - 20 I- O -20 - -40 I- -60 - -80 |- -100I- -120*—^ 231 i20r 100I- 80 - S0 - 40 - -20 ^- -40 I- -G0 |- -80 f- -I00J- U-COMP. 24 1 251 261 271 281 291 301 YEAR DATE V-COMP. 311 321 331 341 351 24 1 251 261 271 281 231 301 311 321 331 341 351 Figure C-20. Temperature, U and V velocity components for buoy 4562. 93 BUOY 4528 Buoy 4528 (Figure C-21, C-22) was deployed from an aircraft at 60-OON, 61 -43W on 1 5 August (227), after the close of the 1987 iceberg season. Due to a data formatting error, no data regard- ing the status of the drogue were received from the ARGOS processing center. Buoy 4528 transmitted data throughout the remainder of 1987. It entered the Ice Patrol operations area on 13 October (286) when it crossed south of 52°N. Buoy 4528 was deployed near the 200m isobath, which it then followed southward to approxi- mately 55°N. Along this track, the buoy's speed varied over the range of 20-30 cnVs. However, there was one 5-day period (1-5 September, 244-248) during which it slowed to about 1 0 cm/s. This occurred between Sagiek and Main Banks, where the buoy made a small westward excur- sion. The temperature record during the period, between launch and 55°N, is unremarkable, with a slow increase from 1 to 6°C. After passing south of 55°N (25 September, 268), 4528 followed the 1 000 m isobath for the next 50 days, during which period it moved southward then eastward to a region directly north of Flemish Pass. During this period, the buoy's speed varied mostly over the range of 20-45 cnVs, with two brief periods of slower motion. The temperature record is remarkably constant during the southward motion, but when 4528 began its eastward motion (6 November, 310) the temperature increased rapidly from 3.5 to 6°C. Buoy 4528 continued its eastward motion, moving to the north of Flemish Cap. Its subsequent rTX)tion is complex. First it moved around Flemish Cap, approxi- mately following the 1 000 m isobath. Then it apparently became entrained in the North Atlantic Current, as indicated by an abrupt eastward (2 December, 336) then northward motion. Dur- ing the first part of the period the temperature increased slowly from 6 to 8.5°C, then during a 28- hour period (8-9 December, 342- 343) the temperature increased by nearly 8°C. Over the same period the buoy's speed in- creased from 50 to 85 cm/s. This indicates that the buoy had entered a portion of the North Atlantic Current dominated by meanders and eddies. 94 60W SON 55N SOW Figure C-21. Trajectory of Buoy 4528. 95 BUOY 4528 1987 18 - IB [- 14 h 12 h o '0 o e U G ^ 4 i( TEMP. u/^ -W^: l-V^ l/N -2 231 2'11 251 2S: 271 28! 291 30: YEAR DATE 31! 32 : 33 : 34 1 351 U-COMP. -6C - -BC - - •. 23- :23'- 23: _l I I l_ 25: 26: 2?: 29 : 29: 3c: YEAR DATE 3:: 32: 33: 3-;: 3b: Figure C-22. Temperature, U and V velocity components for buoy 4528. 96 SUMMARY AND CONCLUSIONS In 1987 the data return from the buoys was good. The average length of time that a buoy trans- mitted data from the Ice Patrol operations area was 78 days. According to the drogue sensor data, the average drogue life span was somewhat shorter (70 days), but its survival is well- matched to the requirement that it remain attached during the period the buoy drift is used for opera- tions. Most buoys transmit data far longer than the 78 days they spend in the Ice Patrol operations area. Five continued to transmit for the re- mainder of the calendar year. Three buoys were recovered be- fore leaving the area, one by an Ice Patrol research vessel (for rede- ployment), and two by unknown vessels. Two buoys suffered pre- mature failures, after 65 days and 67 days. It is possible that they were recovered by unknown ves- sels, but their fate remains uncer- tain. The 1 987 buoy program did an excellent job of monitoring the Labrador Current, particularly from Flemish Pass southward. The trajectories showed strong bathymetric steering of the current, with most buoys following the continental slope (200-1000 m) southward through Flemish Pass. Substantial temporal variability in the Labrador Current is also evident in the data. Early in the iceberg season (April - May), two buoys (4555 and 4556) left the slope at 44° and moved rapidly to the east, north of a warm-core eddy at the shelf edge. A similar event occurred in 1986 (Ander- son, 1986). Later in the season (July), the track of 4559 suggests that neither the eddy nor any North Atlantic Current meanders were significant factors in the southward movement of the Labrador Current along the slope. After departing Flemish Pass, buoy 4559 moved to the region south of Tail of the Bank ( 41- 50N) in 14 days. This is the most dangerous flow pattern in terms of icebergs moving into the North Atlantic shipping lanes. However, it occurred in July when no icebergs were moving southward through Flemish Pass. Had Ice Patrol relied solely on its historical current data base, which is based on many years of hydrographic data and is time-invarient (Mur- ray, 1979), there would have been no recognition of this observed temporal variability of the Labrador Current. The 1987 drifting buoy data suggest that the Labrador Current speeds in Ice Patrol historical current data base for the region south of Flemish Pass are too high. [During the iceberg season IIP operations center personnel had to reposition many resighted icebergs upstream from where the drift model had predicted.] Six buoys passed southward through Flemish Pass, three of which continued their southward movement along the continental slope well south of the pass. In the data base, typical Labrador Cun-ent speeds in the area along the slope from 44-46°N are 90- 1 1 0 cm/s. None of the 1 987 buoys recorded speeds as high as this, even for short periods (3 hr). Buoy 4559, which moved from the pass the the Tail of the Bank, recorded the highest speeds, but most were in the 40- 60 cm/s range. Ice Patrol has undertaken a program that will make use of all available drifter data to investigate the accuracy of its historical data base. In the regions where sufficient data exist, the data base will be modified to reflect these observa- tions. No current data were collected on the Grand Bank or in the inshore branch of the Labrador Current in 1987. The distribution of icebergs for this year shows that this is a problem that needs to be ad- dressed. Many icebergs were sighted along the Newfoundland Coast and directly south of the island, a region where the Ice Patrol data base is particulariy poor. Little attention has been given to this region. A new generation of smaller, less expensive satellite-tracked buoys is now available. Ice Patrol has been evaluating these buoys and expects to integrate them into the buoy program within the next few years. They will be particularly 97 useful on the continental shelf and in the near-shore areas where there is a greater risk of unauthorized recovery. They are smaller, more difficult to see, and less of a financial loss when they are recovered by unknown vessels. REFERENCES Anderson, 1, 1986. TIROS Oceanographic Drifter Tracks on the Grand Banks During the 1986 International Ice Patrol Season. Appendix B, Report of the International Ice Patrol in the North Atlantic Ocean , Season of 1986, (CG- 188-41), Bulletin No. 72. International Ice Patrol, Avery Point, Groton, CT 06340-6096, U.S.A. Le Tran, P.Y. and R. Liaubet, 1987. Location: Matching Service To User Needs ARGOS Newsletter No. 30, July 1987. Service ARGOS Inc., 1801 McCormick Drive, Suite 10, Landover, MD 20785 (USA). Murray, J.J. , 1979. Oceanographic Conditions. Appendix B, Report of the International Ice Patrol Service in the North Atlantic Ocean, Season of 1979 (CG-1 88-34), Bulletin No. 65. International Ice Patrol, Avery Point, Groton, CT 06340-6096, U.S.A. Murphy, D.L., I. Anderson, and N.B. Thayer, 1986. Observations of an Oceanic Front South of Flemish Pass. Appendix C, Report of the International Ice Patrol in the North Atlantic Ocean, Season of 1986 (CG-1 88-41). Bulletin No. 72 . International Ice Patrol, Avery Point, Groton, CT 06340-6096. U.S.A. Summy, A.D.; "Oceanographic Conditions on the Grand Banks During the 1982 Ice Patrol Season"; Appendix B, Report of the International Ice Patrol Service in the North Atlantic, Season of 1982 (CG-1 88-37) Bulletin No. 68. international Ice Patrol, Avery Point, Groton, CT 06340-6096, U.S.A. Summy, A.D. and I. Anderson; "Operational Uses of TIROS Oceanographic Drifters by International Ice Patrol (1978 - 1982)", Proceedings 1983 Symposium on Buoy Technology^ Marine Technology Society, Gulf Coast Section, pp. 246-250. 98 (Appendix D Observations of a Warm-Core Eddy Near the Grand Banks of Newfoundland INTRODUCTION In April - May 1987, the Interna- tional Ice Patrol conducted a surface hydrographic and remote sensing study of a warm core eddy near the eastern edge of the Grand Banks of Newfoundland (Figure D-1). The surface vessel was USCGC BITTERSWEET (WLB 389). The primary objective of the study was to improve Ice Patrol's ability to interpret images of the ocean's surface made with its side-looking airborne radar (SLAR). Imaging radars map the sea surface roughness primarily through Bragg scattering (Robin- son, 1985), which for the 3 cm wavelength and incidence angles (45° to 87°) of the Ice Patrol SLAR, results in a sensitivity to wavelengths of 2 cm. These waves are in the capillary-gravity part of the spectrum, thus they are influenced by molecular viscosity, which is a function of sea surface temperature and salinity. The physics of radar returns from the sea surface is receiving increased research attention (see for ex- ample, Phillips, 1988 and Donelan and Pierson, 1987) mostly be- cause radar is used to measure oceanic wind distributions. Ice Patrol is interested in using radar images of the sea surface to map the major water-mass boundaries within its operations area. A previous study (fwlurphy et al, 1986 and Thayer and Murphy, 1987) showed that the SLAR mapped the location of sharp surface thermal gradients that marked the boundary between a warm-core eddy and the Labrador Current. They found that the warm surface-water within the eddy was always marked by a stronger radar return than the surrounding cooler water. How- ever, they were unable to map the entire boundary around the eddy. A likely explanation of this obser- vation is that their flight patterns permitted only two look angles (with respect to the wind) at the eddy boundary and these were reciprocals of each other. This means that along some portions of the eddy's boundary, the radar was looking along the Bragg wave field rather than into it. This reduces the intensity of the radar return from within the eddy and makes the location of the thermal front difficult to determine. One of the goals of the 1987 experiment was to improve on the previous experimental design by including four look angles at the eddy in hopes of defining the entire boundary of the feature. In addition, the 1987 experiment provided an opportunity to conduct the surveys under different environmental conditions than those encountered in 1986. The intent of this report is to describe the experiment that was conducted in 1987 and to present some of the preliminary results. None of the SLAR data are available for presentation at this time, but a portion of the surface- truth data is. This presentation, made before a thorough analysis Donald L. Murphy is completed, is nonetheless worthwhile because it helps understand the oceanographic conditions in the Ice Patrol opera- tions area during 1987. The eddy studied during IIP-87-1 dominated the circulation near the southeast- ern edge of the Grand Banks early in the season OBSERVATIONAL PROGRAM The study site was chosen prior to BITTERSWEET's departure from port based on a satellite infrared image obtained from the National Marine Fisheries Service (NMFS) laboratory at Narragansett, Rhode Island. It showed a warm-core eddy near the eastern slope of the Grand Bank at about 44°N. In addition, data from Ice Patrol operational drifting buoys showed apparent eastward movement in the Labrador Current north of the eddy. Hence, the region had waters of the cold and relatively fresh (< 2°C and < 34.3 ppt) Labrador Current and the warm and more saline (> 12°C and > 35.5 ppt) North Atlantic Current in close proximity. The substantial surface temperature gradients presented a good location to test the SLAR. Hydrographic Survey The hydrographic survey was divided into two phases, the first during 5-10 May and the second from 16-20 May. The objective was to survey the eddy and its surroundings twice, in an attempt to describe the evolution of the feature over the entire three-week 99 46 N GRAND BANKS OF NEWFOUNDLAND STUDY AREA 42 N + V^" 40 N + + 55 W + 51 W + 47 W + 43 W Figure D-1. Schematic of the major current systems near the Grand Banks of Newfoundland. The study area is shown by the shaded rectangle. 100 study period. In particular, a knowledge of the movement of the thermal fronts over the period of the SLAR surveys is essential when the images are compared to the surface data. The length of each hydrographic phase was limited to no more than 6 days due to the short endurance of the survey vessel. Phase one consisted of 50 CTD (conductivity, temperature, and depth) stations and 70 XBT sta- tions. This phase consisted of six hydrographic lines, four oriented north-south and two east-west, and one XBT line, a diagonal. The CTD station spacing along the hydrographic lines was 18 km (10 nm), with an XBT cast taken half way between the CTD stations. The station spacing along the XBT line was 9 km (5 nm). The CTD casts were taken to about 1 000 m or to within 50 m of the bottom at stations shallower than 1000 m. To verify CTD results, deep quality control samples were taken at most stations using a Nansen bottle with reversing thermometers. XBT stations were made with T-4 XBT's, which provide a tempera- ture profile to 450 m. High winds and seas further constricted the time available for sampling during phase two. BITTERSWEET was unable to complete the oFiginally-planned 45 station star pattern, and com- pleted 38 CTD stations and 48 XBT deployments. As in phase one, CTD station spacing was 18 km (10 nm) and XBT casts were conducted about halfway between the CTD stations. This research cmise marked the first operational use of Ice Patrol's f^obile Oceanography Laboratory (MOL). BITTERSWEET is a buoy tender with no special equipment for oceanographic sampling, thus all sampling and analysis equip- ment had to be brought aboard for the cruise and removed after its completion. The MOL consists of a 4.2 X 2.4 X 2.4 m (14 X 8 X 8 ft) steel shipping container, which was attached to brackets welded to BITTER- SWEET's buoy deck. The interior of the MOL is fitted with desks and equipment racks containing the computers that retrieve and store data from the CTD and XBT systems, as well as a global positioning system (GPS) receiver. An electrically-powered, portable oceanographic winch with about 2000 m of 1/4" (0.6 cm) armored hydrographic cable was chained to the buoy deck. The final compo- nent of the sampling system was a portable hydrographic platform with a hydraulically operated A- frame, which was placed in the buoy port. All of this equipment can be installed in one day and removed in about four hours. Drifting Buoys The drifts of satellite-tracked buoys were used to determine the current speed and direction in the study area. The buoys were 3 meter long spars with a 2 X 10 meter window-shade drogue attached at the end of a 50 meter tether. The accuracy of the position data is about 350 m. The buoys were fitted with temperature sensors (accuracy ~1°C) mounted approximately 1 m below the buoy's waterline. Each buoy received about 8 fixes per day. Eight drift tracks are used for this study. Of these, two are from operational buoys deployed in the Labrador Current well north of the study area by Ice Patrol's recon- naissance aircraft (HC-1 30). They moved southward along the eastern edge of the Grand Banks (Murphy and Thayer, 1987) and passed through the study area shortly before BITTERSWEET arrived on scene. The remaining drift tracks are from buoys de- ployed from BITTERSWEET, most of which were recovered after the experiment concluded. SLAR Surveys Four SLAR surveys, on 2, 6, 14 and 20 May, mapped the features in the study area. On two dates (15, 18 May) portions of the study area were mapped during routine iceberg patrols. The Ice Patrol SLAR is an X-band (3 cm wave- length), real-aperture radar that produces a continuous 9" (23 cm) analog image on film. When the 101 aircraft is flown at 8000 ft (2440 m), the radar maps a 50 km wide swath on each side of the aircraft with a blind spot 5 km wide directly under the aircraft. Both antennas are vertically polarized. Several different flight patterns were used during the survey. The intent of the various patterns was to obtain several different direc- tions of look relative to the wind, in addition to looking at the thermal fronts from various ranges. RESULTS The following sections describe some of the data that constitute the surtace-truth for the SLAR interpretation experiment. The radar data are currently being analyzed. The surface-truth data presented here are limited to the first phase because it is the more complete of the two data sets and the first to be analyzed. Hydrography Figure D-2 shows the surface temperature on the first phase hydrography. A small, warm-core eddy, centered at 43-50N, 48-20W and with a diameter of about 65 km dominates the temperature field in survey area. North of the eddy is cold water (< 3°C) of Labrador Current origin, while warm water (> 12°C) from the North Atlantic Current is evident in the southeastern part of the study area. Although it appears from the surface temperature distribution that the eddy was separate from the North Atlantic Current, their proximity makes it likely that they were interacting. The greatest surface temperature gradient, about 8°C, is located at the northern boundary between the eddy and the Labrador Cur- rent. Over an 18 km distance, the surface temperature changes from less than 3°C to greater than 10°C. It is in this region that the SLAR is most likely to detect a difference in radar return. A vertical temperature section (Figure D-3) along the center of the 5 north-south transects (A-B on Figure D-2) shows that the 10°C isotherm extends to about 160 m. It also shows the locations where three of the drifting buoys were deployed. Buoy 4536 was deployed in 13°C water near the center of the eddy. Buoy 4547 was deployed in 3-4°C water north of the eddy. Finally, buoy 451 1 was deployed near the eddy's northern edge. The center of the drogues for all of the buoys is at ~ 58 m. 102 SEA SURFACE TEMPERATURE (deg C) 49-00 W + 44-30 N + 44-00 N + 43-30 N 47-00 W Figure D-2. Distribution of sea surface temperature based on tlie first ptiase (5-10 May) tiydrographic survey. 103 a w w Hi cc a 500- 1000- TEMPERATURE (deg C) Figure D-3. Vertical distribution of temperature along transect marked A-B in Figure D-2. Drifters The drifter data are presented in two plots. The first (Figure D-4) presents trajectories of 4555 and 4556, both of which were Ice Patrol operational drifters de- ployed in the Labrador Current north of Flemish Pass. Buoy 4555 arrived in the study area on 20 April, approximately two weeks before the start of the hydrographic survey. Over the next 6 days it traced an anticy- clonic path approximately one-half the way around the eddy's bound- 104 ary. The buoy speeds over this period varied over the range of SO- TO cm/s, while the temperature varied over the range from 0.8 to 13°C, suggesting that the buoy was close to the eddy's boundary. On 30 April, 4556 entered the study area. Like 4555, buoy 4556 moved rapidly (50-70 cm/s) to the east, north of the eddy. However, buoy 4556's temperature record was quite different, with a slow increase from 0.6 to 2.0°C over the period during which it re- mained in the area. Figure D-5 presents the drifter data from the four buoys deployed by BITTERSWEET. They are plotted on a map of the surface dynamic topography (relative to 1000 db) calculated from the first phase (5-10 May) hydrographic survey. The buoy tracks are for the same period as the survey. Both the dynamic topography and 4536's drift track suggest that the eddy was interacting with the North Atlantic Current. Buoy 4556 did not complete one entire circuit around the eddy before it departed to the east and left the study area. 4G N + / / i 45.5 N /y + 45 N + <: JS / 44.5 N * ) T + ^ iX 1 1 20 L + . 44 N J ^V *-^s . + X \ X. BUOY 4556 / 43.5 N + BUOY 4555 J \ 124 / 43 N ) 117'^ I + p^ \ + + + ' + + 1/^ r 49.5 W 48.5 W 4?. 5 W 46.5 W 45.5 W Figure D-4 Trajectories of 4555 and 4556, both of which were deployed north of Flemish Pass. The track of 4547 is remarkable in that shortly after deployment it moved southward and eventually intersected the path of 451 1 . The drifter tracks are in general agreement with the surface dynamic topography. CONCLUSIONS The data presented here show a small, warm-core eddy centered at 43-50N, 48-20W and interacting with the North Atlantic Current. Although the detailed dynamics of the eddy cannot be resolved by the coarse sampling scheme, its effect on the Labrador Current is clear. During the period that the eddy was close to the continental slope (April-May), a portion of the Labrador Current departed tlie slope and moved to the east at about 44°N. The tracks of 4555 and 4556, which were deployed in the Labrador Current but moved eastward off the slope at 44°N, are consistent with the existence of an eddy at this location. The eddy had alnajor influence on the Labrador Current as early as 20 April, and perhaps before. 105 49-00 W BUOY LAUNCH POSITIONS 4536 48-00 W 44-30 N 4-00 N 43-30 N 47-00 W Figure D-5. Trajectories of four buoys (451 1, 4536, 4545. and 4547) plotted on a map of the surface dynamic topograptiy (witti respect to WOOdb) based on tt)e first ptiase tiydrographic survey. 106 ACKNOWLEDGEMENTS REFERENCES Sincere appreciation is extended to the Marine Science Technicians of International ice Patrol who collected and are currently analyz- ing the data from the experiment described herein. Without their efforts this work could not have been accomplished. The officers and crews of USCGC BITTERSWEET (WLB 389) and CG 1503 and CG 1504, both of Coast Guard Air Station Elizabeth City, North Carolina enthusiasti- cally supported ice Patrol's research. Their efforts are greatly appreciated. Donelan, M. A. and W. J. Pierson, Jr., 1987. Radar Scattering and Equilibrium Ranges on Wind-Generated Waves With Application To Scatterometry. Journal of Geophysical Research, Vol 92 (C5): 4971-5029. Mutphy, D. L., I. Anderson, and N. B. Thayer, 1986. Observations of an Oceanic Front South of Flemish Pass. Appendix C, Report of the International Ice Patrol in the North Atlantic Ocean, Season of 1986 (CG-1 88-41), Bulletin No. 72. International Ice Patrol, Avery Point, Groton, Connecticut 06340 U.S.A. Murphy, D. L. and N. B. Thayer, 1987. 1987 International Ice Patrol Drifting Buoy Program. Appendix C, Report of the International Ice Patrol in the North Atlantic Ocean, Season of 1987 (CG-1 88- 42), Bulletin No. 73. International Ice Patrol, Avery Point, Groton, Connecticut 06340 U. S. A. Phillips, O. M., 1988. Radar Returns From The Sea Surface - Bragg Scattering And Breaking Waves. Journal of Physical Oceanog- raphy, ^/o\^8■.^065-^074. Thayer, N. B. and D. L. Murphy, 1988. SLAR Observations of Ocean Fronts East of the Grand Banks of Newfoundland. Proceedings of the 1 1th Canadian Symposium on Remote Sensing, Univer- sity of Waterloo, Waterloo, Ontario, Canada N2L 3G1 . (In press). Robinson, I. S., 1985. Satellite Oceanography: An Introduction for Oceanographers and Remote Sensing Scientists. West Sussex, England: Norwood Limited. 455 pp. 107 Appendix E Operational Forecasting Concerns Regarding Iceberg Deterioration LCDR Walter E. Hanson Jr., USCG INTRODUCTION Since 1971, the International Ice Patrol (HP) has used computer- based drift prediction models to help evaluate the extent of the iceberg danger to North Atlantic shipping in the vicinity of the Grand Banks of Nev\rfoundland. A dynamic model began operational use in 1979 (Mountain, 1980). This model, along with a paramet- ric iceberg deterioration model which began operational use in 1983 (Anderson, 1983), has grown in importance as iceberg recon- naissance has gone to an every other weel< schedule. During the peak of the iceberg season, April through June, the iceberg danger covers a large area, requiring reconnaissance missions to concentrate on patrolling the limits. Often icebergs go several weeks before being resighted. Resighting icebergs depends heavily on these models effec- tively predicting drift and deteriora- tion rates. These predictions are also routinely used to set the limit of all known ice, as reported in the IIP bulletins. As evidenced by the many years of safe passage by trans-Atlantic shipping, the IIP seems to have some skill in determining the extent of the ice danger. (To assess the model's predictions there is a need for accurate data to represent the initial iceberg, interim iceberg, and environmental conditions.) Iceberg drift predic- tion is highly dependent upon iceberg mass (size and shape). Consequently, the ability to accu- rately predict changes in iceberg size for the majority of icebergs, which are infrequently resighted, becomes very important. Between 1983 and 1985, the IIP studied the drift and deterioration of four icebergs. Although no firm conclusions could be drawn from such a small data set, which rep- resented an average drift of 4.5 days, the prediction models did fairly well hindcasting the drift and deterioration when observations were used as inputs (Anderson, 1985). A similar study was per- formed, using U. S. Coast Guard iceberg data, for the Atmospheric Environment Service of Canada (El-Tahanetal, 1987). The results were mixed. Thus in June 1987, the IIP conducted another cruise to collect similar data for a cluster of icebergs. The objectives of this study were to compare iceberg deterioration predictions derived from environ- mental data collected in situ to inputs available from operational data centers. These latter inputs were divided between global and regional scale products. BACKGROUND The iceberg deterioration model used by the IIP provides its watch officers with a daily estimate of the "melt" status of each iceberg entered in the drift model. The computer-based application (Anderson, 1983), which com- putes the melt rate, is derived from White, et al 1980. The model sums the effects of the following processes which are depicted in order of importance in Figure E-1 : • solar radiation; • buoyant heat convection; • heat convection caused by iceberg nrwvement relative to the water mass (forced heat convection); and • waterline wave erosion, followed by calving of the resultant ice overhang. Based on the 1980 report, warm air heat convection is considered insignificant and not calculated. The report also identified other iceberg deterioration processes; however, they were only partially addressed and difficult to quantify. Consequently those processes are not rTX)delled. The model calculates melt in terms of length instead of mass. This measure of melt accommo- dates HP's operational proce- dures, in which nearly all iceberg dimensions are reported by size categories. These categories are based primarily on the maximum observed length of the iceberg. 109 \ / / \ Relative velocity (cm/sec) ■TiO m I--- 50m I; 20 m Relative temperature ('C) 0 12 3 4 5 6 40 m 100 m Figure E-1. Modelled Iceberg Deterioration Processes. This figure depicts four processes used by ttie IIP deterioration model to "melt" icebergs. Ttie four processes, whicti are labelled in order of importance are: (1) wave erosion; (2) forced tieat convection; (3) buoyant heat convection; and (4) solar radiation. The figure also identifies the variable environmental terms used to model each process and their influence on "melt" for the icebergs studied by IIP. These terms are: relative velocity; wave height; wave period; and relative temperature. Other terms used to model iceberg "melt" are: cloud cover, which is constant; and maximum waterline length of the iceberg. 110 1987 DATA COLLECTION EFFORT This study collected data on six medium to small icebergs for a period ranging from 2.1 to 6.3 days. The icebergs were studied as they drifted south with the Labrador Current on the northeast Newfoundland Shelf (centered around position 50-45°N, 53- 30° W); see Figure E-2. The study was conducted between 15 and 21 June 1987 using the USCGC TAMAROA, a 68m (205 ft) U. S. Coast Guard cutter. Iceberg above water dimensions were taken during daylight using a camera and reticulated laser rangefinder. Iceberg shape and size were calculated from photo- graphic images scaled according to rangefinder measurements. This required a 360 degree look at each iceberg; measuring and photographing all prominent faces. Measurements were accurate to +/- 8% of the observed dimen- sions. No underwater iceberg dimensions were measured. The rangefinder-derived distances were used with visual bearings to fix the icebergs' positions during daylight. At night, radar bearings and ranges were used. The cutter used LORAN-C and SATNAV to fix its position. Positional accu- racy for iceberg positions was esti- mated (by summing system errors) to be +/- 750m. Table E-1 summarizes the observed dimen- sions and estimated drift of the icebergs. Hourly environmental observations included: air and sea surface temperature, cloud cover, and wind (at 22.3m). Sea surface temperature was taken by bucket thermometer (error was +/- 0.1°C); wind was measured by the ship's anemometer. Wave height, period and direction were visually esti- mated every six hours. Visual wave observations were estimated to have an error of +/- 0.5m for wave height; and +/- 2sec for period. Surface currents were inferred from the drift of two satellite-tracked drifters (FGGE- hulled), which had window-shade (2m X 1 0m) drogues. Both drifters were deployed at the same time near the center of the cluster. One was drogued near the surface (center of the drogue: 8m deep), while the other was drogued at 58m, at the core of the Labrador Current. Temperature vs. depth profiles were taken in the vicinity of each iceberg and transects were made at the beginning and end of the study to determine iceberg drift in relation to the 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39' 52°: 38 ' ' "" I cpo :51° 150° 48° 47° 46° E45° j44° :43° 42° 41° 40° E39° - denotes the mean position of the Labrador Current - defines the June 1 987 study area lllllllllllllfllllllllllllllllllllllllllllllllllllllllllllllMIIIIIIMIMIIIIIIIIIIIIIIIIIIIIIIIMIfllll 57° 56° 55° 54° 53° 52° 51° 50° 49° 48° 47° 46° 45° 44° 43° 42° 41° 40° 39 38° Figure E-2. International Ice Patrol Study Area. This figure depicts the area in which iceberg drift and deterioration is operationally modelled by IIP. The 200m bathymetric contour is shown to describe the Grand Banks of Newfoundland and Flemish Cap. 111 Table E-1: Observed Size, Shape, and Estimated Drift of Icebergs. Maximum Dimensions (in meters) Elapsed Days Length Height Interpolated 12-hourly Shape Speed (cm/sec) Direction (T) <;^s*».^^^^ J^-^-«»i>-<;-S«A¥J>S.*.* <»sps>SV;^txs^*KS- •. %«.■■ ..IJI,. Tr"""*"^^"mage(l Berg #620 ^^B" 0.0 0.6 0.9 1.1 1.7 36 11 Domed 2.6 3.1 s\'^ '''^*^"''W"'"ii •.■^'W:K■'w^■o■^on■5l&^^%^^^»N'v.^^■J^ ¥^^»^«^v^>»^it»n^ ^|^ft■*»«w^»y■w^ ^■>■'^'•^■*^,'^^■•'*^^^^•.^^•. *■%•••. \sX'\Ns«iWs\S'.\^ >.■«>>■«. \NsS 19 18 ss^^^^- ■>\^&>j- ■■ x*- ^\::^!i^«t^^•xs:;«^\*:^:\l■''^^'■• "^SSSS^-^^^V^* fl"^^- "^^^Tlnnaded 4.0 4.6 4.8 52 27 Pinnacled •^ ^^^V^'^^X* 45 32 46 ^8 24 \v»>'^"-^\'*» V. j«^ "^ ■^'W^ys. i^^JWN- ■■ ■'■^»«ij$» "^J^vjn*. "W-^ w 7 Pmnacled Berg #744 — :-- 0.0 0.1 ^^ 0.6 0.8 f.l" 1.6 'Demed \ SSSV%VSS%VX.VA V 77 2.1 45 231 s s s \ \s 201 ^09 1§6 171 165 193 127 %s AS^ ■V.-Cv> s%-q}«S^'<>'^^'v>. ■i % ■■ s --WvNV ■■ '■%■• 6 20 295 295 18 Pinnacled 8 229 ^^.^e^llPHIII... 37 140 138 112 Table E-1 (Continued). Elapsed Days Maximum Dimensions (in meters) Length Height Shape Interpolated 12-hourly Speed Direction (cm/sec) ( T) Berg #747 24 24 ^ 15 ■SK<^\\v<^^v;^X■;■;■;^X^\\S■^\S^^\^\■Ws'>^\\^\\^^ 1.7 2.0 2.5 2.9 3:0 3.5 4.5 5w5 6.0 6.5 Berg #784 0.0 0.8 1.3 1.8 2.0 2.3 2.8 3.0 3.3 3.8 4.3 4.8 4.9 96 86 115 96 89 107 112 117 113 25 28 22 23 .xgg:::.::::..:.:.:,:.:«.M.....x.: 27 31 43 24 43 33 Wedged Wedged Wedged Pinnacled w>rw>MWW'>»> :-:'K-i'X4«>Ait'>>x;;-: Pinnacled ■«K^*.■^v.^''^ ^^ ' Pinnacled Pinnacled Pinnacled Pinnacled Pinnacled Pinnacled 16 13 = 33 41 32 '^' 23 21 •••• ■^•6 Pinnacled 14 Pinnaded ■■■"™^^^-^^-*^^--^^ 33 23 234 183 150 146 154 142 XSSSSStSSS 107 065 118 131 121 274 275 ,.sS) s^-i 28 153 36 3*8 44 168 11 38 178 35 182 21 185 4 147 113 Table E-1 (Continued). Elapsed Days Maximum Dimensions (in meters) Length Height Shape Interpolated 12-hourly Speed Direction (cm/sec) ( T) 0.0 0.4 97 37 Pinnacled ^""'"ie™^^^'^ 355 0.8 . 94 32 Drydopk,;,,,, 0.9 12 293 1.9 92 30 Drydock 21 191 "^'^ 35 169 2.8 .^^^.x„_...^.*™.......w..._--^^^^^^^^^^^ ^ rydock '^" " ' 11 2.9^^^^^^^^^^^^,^^^^^^^^^^^^^^^^^ >^^^^x■vv•^;vXv^ivivivXvKv;%-;-Kv>x:^i^>>^^^^>K<^>>>>>^^ 21 308 114 Labrador Current. The measure- ments were made to a depth of about 300m using T-4 expendable BathyThermographs (XBT). Having only one observation platform to monitor the drift and deterioration of six icebergs, which were within a circle of approxi- mately 55km radius, made both compiling environmental factors affecting each iceberg and verify- ing iceberg identity difficult. The distance between the cutter and each iceberg determined the applicability of environmental observations. Table E-2 summa- rizes the distances between observations and icebergs. The average distance wave data were collected from each iceberg was 48km; wind and weather data, 61km; and sea temperature data, 7km. These distances were computed from the interpolated positions of each iceberg for OOOOZ and 1200Z as derived from a cubic spline. The spatial separation of the wind and wave observations is much smaller than the 250km data grid- spacing on which global environ- mental products are prepared by FLENUMOCEANCEN for IIP use (COMNAVOCEANCOM, 1986). Because the study area was at least 105km offshore, the wind and wave fields were assumed to be spatially uniform. In mapping the sea surface temperature, the icebergs were in a tongue-like feature of cold water which protruded southeastward. The feature, which measured about 1 8km across, complicated the data analysis, since the temperature field could not be assumed uniform. As a compro- mise, only observations within 9km of an iceberg's position were accepted. Because of this restric- tion and having only one observa- tion platform, the data sets for some icebergs were incomplete. The temperature values necessary to model deterioration were linearly interpolated from these data sets. Table E-2: Distance of Observations from Individual Icebergs. Type of Data Collected Distance (ir km) From Iceberg Wind Min Max Avg Berg# 620 3 104 49 744 9 71 45 747 ■ -.;.»»y.uA>ji>\ :-:;:■ 121 69 784 1 136 60 785 1 111 52 787 13 103 49 Sea Surface Temperature Min Max Avg Berg# 620 3 15 7 744 3 14 9 747 1 11 7 784 0 16 9 785 1 7 :,,.,.^,, .. 787 4 9 6 Wave Mm Max Avg Berg# 620 14 53 31 744 1 76 52 747 73 127 106 784 1 ' ^ 31 16 785 4^^^^ ^^;^-^^*^ 61 17 787 11 107 65 115 THE ICEBERGS STUDIED Six non-tabular icebergs were studied. Five were classified medium in size; one was small (#620). Most icebergs did not deteriorate enough to change size. The numbers (e.g. #620) refer to the sequential numbering system that IIP uses to identify individual icebergs during the course of the ice season. These are the same numbers used in archived IIP iceberg data at the World Data Center for Giaciology, Boulder, Colorado. Although the icebergs did not change size category during the course of the study, all were deteriorating rapidly. Because of the recurring presence of growlers and bergy bits in the vicinity of all icebergs except #620 and #744, calving was assumed to be a major factor in the cluster's deterioration. Table E-3 describes the amount of calved ice in the vicinity of each iceberg during daily sizing measurements. The study could not document all calving for any one iceberg since no iceberg was observed around- the-clock. However, two events were documented: iceberg #784 on 19 June; and #747 on 21 June. Because of the warm water (greater than 3°C), the brash melted between daily observa- tions. Bergy bits and growlers which did not fully melt between observations were tracked (in one case up to 18 hours), to keep calving statistics for the cluster from being inflated. Only icebergs #785 and #787 appeared stable throughout the study period. Stability in this context meant that the iceberg length and height constantly decreased. Figure E-3 describes the areal dimensions for these icebergs at the beginning and end of the study period. Most of the icebergs changed shape during the study, probably from rolling. Iceberg #784 rolled while the cutter was nearby on 19 June. In this case, the rolling caused height to double although length in- creased insignificantly (5%). Table E-3. Total Amount of Calved Ice Observed Daily in the Vicinity of Icebergs. Iceberg # Date (June) 620 744 747 784 785 787 ""'^'IT"''''''''''^'^^'' ' ' 0 fog fog fog -.^vw.»;.>;.V".ji»v.>^^>;.>:. brash s%^;. jvy.s;.;i^«.^'.«.\;.;.%vv;.;,;.;.;.' .;.■,■ {7 0 brash brash 4G-H1B 0 0 brash 4G 3G-H1B ; i^-"'" 6 - ■""8G+1B 3G ■5G-H2B '' 19 0 1G+1B 5G - 1G ^^^^mmmmmmmmmmmmmmmmm - 0 2B fog " 21 - - 5G - - - fog - observations obscured by dense fog (-) - no observation made during 24-hour period G - growler, which is less than 1m high and/or 5m long B - bergy bit, which is larger than a growler, but less than 5m high and/or 15m long 116 E-3a. 180' E-3C. 180° E-3b. ^70' E-3d. Figure E-3. Areal Dimensions of Icebergs. Ttiese figures describe the major faces of two medium-sized, non-tabular icebergs studied during June 1987. The initial and final dimensions of each iceberg are presented. The scale is the same for all figures (1 unit = 3. 1m (10 ft)). The orientation of each face to true North is also shown. The faces depicted in the initial and final sizing are dissimilar Figure E-3a. depicts the inital dimensions of iceberg #785 (maximum height = 37m, maximum length = 97m); Figure E-3b shows the same iceberg 4.8 days later (maximum height = 7m, maximum length = 71 m). Figure E-3c depicts the initial dimensions of iceberg #787 (maximum height = 34m, maximum length = 81m); '-■v.Mrfl E-3d shows the same iceberg 3. 1 days later (maximum height = 23m maximum length = 59m). 117 THE WATER COLUMN The cluster of icebergs was in a tongue of tfie Labrador Current as evidenced from botfi sea surface temperatures and the XBT profiles (see Figure E-4). The tongue of Labrador water had a cold (-1°C) core at 60m, below a shallow thermocline at 40m. Surface temperatures ranged between 3.4 and 7.6°C. Temperatures of -1°C or colder, that would preclude melt (White et al, 1980), existed from 40m to 90m in the eastern portion of the study area, and from 40m to 1 60m in the western portion. XBT casts taken in the vicinity (within 28km) and within 6 hours of the OOOOZ interpolated iceberg's positions were used to estimate the average heat available in the water column to melt the iceberg. When there was no XBT cast near a particular iceberg within six hours of OOOOZ, the temperature informa- tion was calculated by linearly interpolating in time. The water temperature, relative to -1°C, was averaged over 10m intervals over the estimated draft of the iceberg. Iceberg draft was estimated as 3.95 times the average sail height observed during the study (Robe, 1975). 118 From analyzing temperature profiles taken about four days apart, this tongue of the Labrador Current had advected south 74km. The advection of the cold core at 60m agrees well with the deep- drogued drifter. Its drift indicated a predominantly southerly flow (186°T at 21cm/sec) for 4 days (from 15 June/OOOOZ through 19 June/OOOOZ), then an easterly flow (1 12°T at 12cm/sec) for the last 1 .5 days of drift. The west- ward displacement of the thermal field above the thermocline agreed well with the shallow-drogued drifter. From 15 June/OOOOZ to 17 June/1 600Z the drift was 193°T at 27cm/sec. From 17 June/1 600Z until recovered on 20 June/1 243Z, the drifter showed a steady deceleration, averaging 206°T at 9cm/sec. Figure E-5 summarizes the drifts of all icebergs and drifters and shows the XBT transects used to describe the thermal characteristics of the water column. All of the drifters recorded sea temperature at 1m depth between 3 and 5°C, which agreed well with the bucket thermometer measurements. DETERIORATION MODEL EVALUATION CRITERIA The deterioration processes were evaluated based on observations compiled for the four medium, non- tabular icebergs #747, #734, #785, and #787 which had estimated drafts from 98 to 1 46m. This cluster was studied for 5 days. Based on in situ temperature, icebergs #747 and #787 had insignificant melt from convective processes below 40m depth. Therefore the buoyant and forced heat convection contributions below 40m depth were calculated and evaluated for only icebergs #784 and #785. 96 9p 9d S8 5'f0^^~" E-4C. E-4b. E-4d. Figure E-4. Thermal Structure of tfie Water Columr}. These figures depict the thermal structure along four expendable BathyThermograph transects taken during the IIP June 1987 study. These transects were nearly orthogonal to the flow of the Labrador Current. The XBT positions are noted by cast numbers along the top of each figure. The geographic positions of the transects are shown in Figure E-5. Figure E-4a depicts transect A1, which was measured between 0645Z June 15 and 0631 Z June 16. Figure E-4b depicts transect 81, which was measured between 1949ZJune 14 and 0151Z June 16. Figures E-4c and E-4d represent transects taken about 4 days-later approximately 74km downstream from the A 1 and 31 transects. Figure E-4c depicts transect A2, which was measured between 081 9Z June 19 and 1234Z June 20. Figure E-4d depicts transect 32, which was measured between 0429Z and 2008Z June 19. 119 sj'oc tt ^ bl'oo # 747 A \ 5000 vj \ . E-5a. E-5b. 52°00 « «- 1 SHAl tow CEtP rSlFTCR ,Ri 0^ _ - B2 500c » J» -3 ' . 1 54 00 53° 30 E-5C. tt620 0 XBT CAST 15 JUNE • 16 JUNE D 17JUNE ■ 18 JUNE ^ 19 JUNE ^ 20 JUNE * 21 JUNE Figure E-5. Iceberg and Bathythermograph (XBT) Position Data. Figures E-5a and E-5b show the interpolated OOOOZ positions for the six icebergs studied during June 1987. The icebergs in Figure E-5a were used to evaluate the deterioration model; the icebergs in Figure E-5b were not. Figure E-5c shows the interpolated OOOOZ positions for the shallow and deep-drogued drifters and the positions of the four XBT transects described in Fiaure E-4 120 The rest of this paper evaluates modelled iceberg deterioration by examining environmental terms used in the formulae. The envi- ronmental assumptions regarding each melt process are also re- viewed. Building on White's research (White et al, 1980), various observed thermal and velocity parameters are independ- ently compared to determine which of each best represent the terms in the formulae. Using Anderson's operational computer model (Anderson, 1983), melt estimates are calculated from operational data center inputs. Figure E-6 depicts the contribution of each deterioration process to illustrate its relative importance and the changes in contribution caused by using different parame- ters to represent terms in formu- lae. The implications of error estimates for various model inputs on IIP operations are then dis- cussed. WARM AIR CONVECTION Melt from warm air convection is ignored in the model. For March through mid-May, no melt is estimated for air convection. For July through September, the average melt is estimated at Scm/day, assuming an average daily air temperature of 1 0°C and average wind of 37km/hr. The daily average air temperature warmed during the study period from 6°C on 1 5 June to 8°C on 21 June. The average wind speed for the study period was 33km/hr. Warm air heat convection was estimated at 4cm/day. Climatological average air tem- peratures for the IIP region could be used to make monthly melt estimates. Likewise, daily global- scale air temperature values could be requested from an operational data center; however, this level of effort for a relatively insignificant deterioration process seems impractical for operational fore- casting purposes. SOLAR RADIATION The modelled melt due to solar radiation is fixed at 2cm/day, which represents the minimum melt rate for the period March through August (Anderson, 1983). The model assumes cloudy conditions. The daylight (0800Z to 2400Z) was obscured (100%) by cloud cover or fog every day of the study except for the afternoon of 17 June and rrwming of 19 June. For those half day periods the skies were partly (averaged 50%) cloudy. Assuming a 35% albedo for an iceberg, the average melt rate for the June study period was 4cm/ day (White et al, 1980). The model could be adapted to the monthly melt estimates derived by White, although the benefit would be minimal. Like- wise, global-scale radiation estimates could be requested from operational data centers (COMNA- VOCEANCOM, 1986); however, the level of effort to identify those periods of clear skies would only provide an additional melt of 2cm/day. Again this level of effort for a relatively insignificant deterioration process seems impractical for operational forecasting purposes. WATER TEMPERATURE The model uses sea surface temperature to estimate both buoyant and forced convection contributions to iceberg melt. The melts due to buoyant and forced convection were computed as a function of observed sea surface temperature (T^) and as a func- tion of the in-situ temperature of the water column integrated over the estimated draft of the iceberg (fTo)- Buoyant Vertical Convection Buoyant convection is considered solely dependent upon the "rela- tive" temperature between a near vertical wall of ice and the water column. The cluster's average daily melt due to buoyant convec- tion using Jt, was estimated at 2cm/day with average values for individual icebergs ranging from 1 cm/day (#787) to Scm/day (#785). The melt rate as a func- tion of Tg averaged 7cm/day greater; with daily differences ranging from +3cm/day (#787/21 June) to -f-1 IcnVday (#747/20 June). These differences were associated with surface tempera- tures which were approximately 1 .5°C warmer than the averaged temperature for the first ten meters of the water column. 121 PROCESS (PARAMETERS USED) WARM AIR CONVECTION SOLAR RADIATION BUOYANT CONVECTION (/X) BUOYANT CONVECTION (To) FORCED CONVECTION (/To, Vsfc ) FORCED CONVECTION (X, Vsfc ) FORCED CONVECTION (To. Vdeep) FORCED CONVECTION (X, Vh.st) WAVE EROSION (To, Ho, ^g) WAVE EROSION (Tg, Hg, Pg) WAVE EROSION (Tr, Hr, Pq) 10 1 0'j -1 -^ o," 1 1 1 1 1 1 . 1 : :|;i; i' I'M:,! : 1 : II i , : 1 : ' 1 .... : 1 : : 1 : ■ ■ ; 1 ■ i: ' ' 1 ■ ; '^ ( ' ■ i 1 , , ; \ f <:'• i i 1 ■ 1 i 1 ■ • ■i 1 iiNi :l ' i lii! _ X-i — K : 1 1 1 1 ll i . , 1 } ; i lii 1 , ...^ 1 : : i ; ! i 1 : , 1 . 1 i ■ ) ' ■ • 1 - ■ -LlL ■ ■ i i ■ 1 ' ■ ' ■ Mil Mil ■ i 1 "* " 1 ! ■ : i !M ' ' 1 1 1 1 1 i i : i ■ l"^ i i 1 ! I ' ' i M i i M-! ■ I 1 i ■ i ; i 1 M i 1 • ■ : ill 1 1 ■ 1 ■ i ■ 1 1 1 ' ■ ^^ l; 1 ' ■ ■ ! 1 i : r I: ; Figure E-6. COMPARISON OF ICEBERG DETERIORATION PROCESSES. This figure graphically de- scribes both the significance of each process and the affects that different parameters have on the "melt" contribution for these processes. The "melt" contributions, which are denoted by a (•), are the five-day average for a cluster of four medium-sized, non-tabular icebergs. An (X) denotes the minimum and maxi- mum five-day average for an individual iceberg. A (I) denotes the minimum and maximum daily "melt" for an individual iceberg. = Observed sea surface temperature = In situ temperature as a function of depth = Global-scale sea surface temperature product = Regional-scale sea surface temperature product = Observed significant wave height = Global-scale significant wave height = Regional-scale significant wave height = Global scale primary wave period product = Differential velocity between iceberg and surface-drogued drifter V(deep) = Differential velocity between iceberg and deep-drogued drifter V(hist) = Differential velocity between iceberg and historical current field K Ho Ha H. Pa V(sfc) 122 Forced Heat Convection Forced convection is primarily dependent upon the relative temperature between iceberg and the water flowing past the iceberg. The cluster's average daily melt due to forced convection usingjl^, was approximately IScnVday with average values for individual icebergs ranging from 12cnVday (#787) to 21 cm/day (#785). The melt rate as a function of T^ averaged 47cm/day greater; with daily differences ranging from +17cm/day (#784/20 June) to +69cm/day (both #747 and #784 on 18 June). These differences were associated with surface temperatures which were about 0.9°C warmer than the averaged temperature for the first ten meters of the water column. Combined Effect in Using Sea Surface Temperature By using sea surface temperature to derive the relative temperature term, the waterline loss could be overestimated by 20 to 80cm/day. This error represents summer conditions (surface warming). Errors for the period f^arch through mid-May should be significantly smaller. Although the error associated with summer sea surface temperatures appears significant, it is an order of magni- tude less than the sum of all modelled deterioration processes. Subsurface temperature values can be requested from operational data centers; however, the quality of the analyses are highly depend- ent upon the availability of bathythermograph data. More daily observations occur in the IIP region for surface than for subsur- face temperature. Additionally, the thermal stmcture of the water column depicted by data center products often have an accuracy no better than the temperature differences between surface and near surface values (Clancy et al, 1987). Using a subsurface temperature profile would mean substituting a known small bias in melt rate for errors which could vary as described. It would also mean a two- to four-fold increase in data input. For these reasons, IIP could not justify requesting and using subsurface temperature fields from operational data centers. RELATIVE VELOCITY Forced convection is also a function of relative velocity be- tween the iceberg and the sur- rounding water column. The model equates relative velocity to the difference between iceberg drift and the IIP historical current in the iceberg's vicinity. The wind- induced component of the current is ignored. Melt rates for forced convection using relative velocities derived from different current inputs were compared. The shallow-drogued drifter was assumed to represent the velocity of the water mass between the surface and the 40m thermocline, that portion of the water column which contributed most to iceberg deterioration. The relative velocity between each iceberg and the following were cal- culated as inputs to the model: shallow- and deep- drogued drifters, and the MP's "master historical current field velocity, which for the entire study area was 160°Tat 23cm/sec. The deep-drogued drifter represents real-time current data which, when available, is used to "modify" the historical current. (Summy et al, 1983) Sea surface temperature was used to compute the relative temperature term. The melt rates derived using the deep-drogued drifter and "master" current as inputs were compared to the melt rate derived from the shallow- drogued drifter input. The average daily melt due to forced convection, using iceberg drift relative to the shallow- drogued drifter, was estimated at 59cm/day with average values for individual icebergs ranging from 55cnVday (#785) to 62cm/day (#747). The melt rate as a func- tion of iceberg drift relative to the deep-drogued drifter ranged from 25cm/day slower (#747/19 June) to 38cm/day faster (#784/20 June). Using the "master histori- cal current, the melt rate ranged from 53cm/day slower (#747/19 June) to 63cnrVday faster (#784/20 June). These differences in melt equated to velocity differences between the shallow.-drogued drifter and the deep-drogued drifter (i.e. the "modified"' current) and between the shallow-drogued drifter and the "master current of +/- 9cm/sec 123 _iL.-^_&, and +/- 16cm/sec respectively. In comparing the melts due to forced convection between the "master" and "modified" currents, the real- time input serves to reduce the daily differences for each iceberg by nearly half. The meteorologi- cal conditions during the study also helped to reduce the daily differences in melt between using the shallow- and deep-drogued drifter velocities. Rapid changes in the weather prevented wind direction from remaining constant (within a 60° arc of the compass) for periods longer than 27 hours; wind shifts averaged every 12 hours. Consequently, the sum of the differences for each iceberg never exceeded +1- 70cm for the study period, or an averaged error of +/- 21 cm/day. These statistics probably repre- sent the minimum errors. In the IIP region 5- to 7-day wind events occur. An effort to control the growth of these errors may be ap- propriate. Wind-induced compo- nents of the current could be extracted from the dynamic iceberg drift model and substi- tuted for the existing input. This is perceived to be a nnoderate level of effort for the IIP. WAVE EROSION: GLOBAL VS REGIONAL SCALE PRODUCTS Wave erosion, which is induced by heat convection from the turbulent maximum orbital velocity caused by the wave field sur- rounding the iceberg, is computed by the model. This convection is 124 proportional to wave height (H) times relative temperature (T), and inversely proportional to wave period (P). The model assumes the effects of the wave field are non-directional, implying that the iceberg is melted uniformly from all directions (White et al, 1980). This assumption probably overes- timates melt due to wave erosion. Regardless, its melt contribution is up to ten times greater than melt by forced convection, and around 100 times greater than buoyant convection. The applicability and accuracy of the environmental parameters used to model wave erosion thus greatly affect the daily melt rate estimated by the model. The model computes T from sea surface temperature. Significant wave height and a primary wave period, which is that period associated with peak energy observed in the full wave spec- trum, are currently used by the model for H and P respectively. Sea surface temperature is as- sumed to be the best parameter from which the relative tempera- ture term for wave erosion is calculated, and it is readily avail- able from data centers. Data center products representing H are significant wave height, sea height, or swell height, and products representing P are peal< periods for the full, sea, or swell energy spectra (Clancy, 1987). When the model was implemented in 1983, the wave parameters currently used were the only ones available. Table E-4 shows the differences between our observations and those analysis values produced by operational data centers: U. S. Navy Fleet Numerical Oceanogra- phy Center, Monterey, CA (FLE- NUMOCEANCEN); and Canadian Forces Meteorological and Oceanographic Center, Halifax, Nova Scotia (METOC). The global-scale (250km grid-spacing) analyses were produced by FLE- NUMOCEANCEN using its computerized Expanded Ocean Thermal Structure (EOTS) analysis and Global Spectral Ocean Wave Model (GSOWM) (COMNAVO- CEANCOM, 1986). The regional- scale (estimated from 50 to 1 00km grid-spacing) analyses were produced by METOC Halifax. METOC depends on human interpretation of surface thermal observations and uses a paramet- ric ocean-wave model (MacDonald et al, 1987) which is qualitatively blended with ship observations. All data center values were interpo- lated to each iceberg's OOOOZ position. All values are for OOOOZ, except for the METOC sea state analyses, which were analyzed at 1800Z. The METOC 1800Z sea state analysis normally contains more ship observations than the METOC OOOOZ analysis, thereby improving the quality of the 1800Z analysis. FLENUMOCEANCEN and METOC sea surface temperature products differed. The FLE- NUMOCEANCEN-produced temperatures averaged 1.3°C colder than the observed values for the cluster; the METOC-produced temperatures were 0.6°C colder. Averaged differences between ob- servations and FLENUMOCEAN- CEN products for individual icebergs ranged from 1 .9°C (#784) to0.6°C (#785) colder. The differences listed in Table E-4 which are greater than the re- ported system error are due to the presence of sub-scalar thermal features. In this case, iceberg #747 and #784 had crossed the surface thermal front between the colder Labrador water and the warmer Newfoundland Shelf water. Little difference existed between the wave height products by FLE- NUMOCEANCEN and METOC. The FLENUMOCEANCEN- produced wave heights averaged 0.9m higher than the observed height for the cluster; the METOC- produced height was 0.8m higher. Daily differences between ob- served and predicted wave heights for individual icebergs ranged: from 0.3m (all/17 June) to 1 .5m (#785/20 JUNE) for FLE- NUMOCEANCEN products; and from 0.2m (ail 19 June) to 1.2m (all/18 June) for METOC products. The wave period differences in Table E-4 which exceeded system error may be based partly on the limitations of visual observations and the expertise of each ob- server. The cluster's average daily melt due to wave erosion using ob- served values was estimated at 379cm/day with average values for individual icebergs ranging from 330cnfVday (#785) to 408 cm/day (#747). The cluster's average daily melt rate using FLE- NUMOCEANCEN (global-scale) products averaged 152cm/day faster. Individual icebergs' average melt ranged from 144cm/day (#784) to 200cm/day (#785) faster. The cluster's average daily melt using METOC (regional-scale) products aver- aged 195cm/day faster. Individual iceberg's average melt ranged from 149cnfVday (#785) to 218crTVday (#787) faster. Table E-4. Average Difference Between Data Center Products and Observations. OBSERVED - FLENUMOCEANCEN OBSERVED - MtlOC Date #of SSI WaveHT Wave PD SST Wave HT OOOOZ Icebergs (°C) (m) (sec) (°C) (m) 15JUN 2 +1.1 '1.2 :::i:,::::.,,,-8 (2) ,,,,,,,,^,,^.^^^_ +0.5 „.:.:._ -0.9 16JUN 5 +0.7 -0.9 -5 (5) +1.0 -0.6 1 17JUN 5 +0.3 -0.3 -5 (5) +0.5 -0.6 18JUN 6 -•-1.0 -0.9 -4 +0.2 -1.2 19JUN 5 +1.5(2) * -0.9 -2 -0.1 -0.3 20JUN 4 +1.8(2) -1.2 -4 (1) +0.2 -0.9 21 JUN .J™. -j-2.5 (2) -0.6 -2 +0.7 -1.2 *Note: Numbers in parentheses indicate number of times a value was outside the following error bounds: SST +/- 1.6°C Wave Height +/- 1.8 m Wave Period +/- 4 sec 125 The higher melt estimate derived from using either FLE- NUMOCEANCEN or METOC products was a function of their higher wave height analyses. The melt estimate using FLENUM- OCEANCEN products appeared better than METOC because the underestimation of the tempera- ture analyses offset the overesti- mation in the wave height analy- ses. The model's sensitivity to wave height makes that term just as important as the temperature term. The significant overestimation of wave erosion justifies IIP seeking better temperature and wave data from operational data centers. Regional-scale temperature analyses are available and could reduce the variable error associ- ated with features (i.e. the Labra- dor Current) which are sub-sealer to the analysis grid. Unfortu- nately, no digital product is presently available for regional- scale wave analyses. However, the global-scale sea height and associated peak period may reduce the bias evident in the global-scale significant wave height data. Any shift to new inputs should be evaluated by IIP to determine the combined effect of input errors before their final acceptance for operational use. SUMMARY Table E-5 summarizes the dete- rioration processes examined by this paper. For this ensemble of medium-sized, non-tabular- shaped icebergs, a daily melt rate was estimated by the model to be 4.0 m/day. Using FLENUM- OCEANCEN products, the melt rate was overestimated by 1 .7 m/day. METOC products overestimated the melt by 2.2 m/day. These melt estimates are of the same magnitude as the iceberg sizing error. Because of the short duration of the study, no firm conclusions could be drawn from the observed iceberg meas- urements. Icebergs #785 and #787, which were the only ice- bergs to constantly decrease in length and height throughout the study period, appeared to have melted faster than the predictions based on the optimum, observed environmental parameters. Melt predictions based on data center products were within measure- ment error bounds. Sea surface temperature appears to be a suitable input for calculat- ing the relative temperature term. In this study the use of sea surface temperature to solely rep- resent the relative temperature temri vice using temperature versus depth to represent the term for buoyant and forced convection, caused the melt rate to be overes- timated by 12%. Global-scale thermal products cannot ade- quately represent the Labrador Current. Regional-scale tempera- ture products currently available can improve the resolution of the temperature data. Oversimplification by IIP of methods used to derive the relative velocity between icebergs and the surrounding water contrib- uted to an error of up to 1 6% of total melt. Because the wind- induced component of the ocean surface layer (between the surface and 50m depth) is computed in the IIP iceberg drift model, this velocity component could be added to the "rrxjdif led" or histori- cal surface current. The resultant current value could then be used to compute relative velocity to reduce the magnitude of this error. Wave height overestimation causes daily melt to be overesti- mated. This significant (about 38% of total melt) error in deter- mining the wave erosion contribu- tion probably compensates for the nxjdel's inability to represent all deterioration processes. New wave products that have recently become available should improve the melt estimate due to wave erosion. The iceberg sizing method and study time constraints made comparisons of model estimations to observed lengths inconclusive. Either a better method must be used in future studies or studies must be extended over much longer periods (14-21 days). Given the potential for errors asso- ciated with operational reconnais- sance, which depends heavily on arbitrary size classifications, and the inability to model all deteriora- tion processes, the IIP policy to require icebergs to deteriorate 175% of their original length is prudent. 126 Table E-5: Average Melt Rate for Various Inputs. MODEL TERMS Relative Temperature Relative Velocity Wave Height Wave Period DETERIORATION PROCESSES Warm Air Convection Solar Radiation Buoyant Radiation Forced Convection Wave Erosion Total Average Melt PARAMETERS USED Tt T T T T Jo O O G R V{sfc) V(sfc) V(deep) V(sfc) V(sfc) H^ H^ H^ H H MELT RATE fcm/dav^ USING ABOVE PARAMETERS 4 4 2 15 379 404 4 4 9 62 379 458 4 4 9 6-122 379 402-520 2 0 6 33 531 572 T G T R p V(sfc) V(deep) = Observed sea surface temperature = In situ temperature as a function of depth = Global-scale sea surface temperature product = Regional-scale sea surface temperature product = Observed significant wave height = Global-scale significant wave height = Regional-scale significant wave height = Global-scale primary wave period product = Differential velocity between iceberg and surface-drogued drifter = Differential velocity between iceberg and deep-drogued drifter 2 0 8 41 574 625 127 REFERENCES ANDERSON, I., 1983. Iceberg Deterioration Model. Reportofthe International Ice Patrol in the North Atlantic Ocean, Season of 1983, (CG-1 88-38), p 67-73. ANDERSON, I., 1985. Oceanographic Conditions On The Grand Banks During The 1985 IIP Season. Reportofthe International Ice Patrol in the North Atlantic Ocean, Season of 1985, (CG-1 88-40). p 56-67. CLANCY, R. M., B. L. SAMUELS, and K. D. POLLACK, 1987. Technical Description Of The Optimum Thermal Interpolation System (OTIS): A Model For Oceanographic Data Assimilation. Fleet Numerical Oceanography Center Tech Note 422-86-02, 22 May 1987. pp 1 10. CLANCY, R. M., 1987. Real-Time Applied Oceanography At The Navy's Global Center. Marine Technology Society Journal, Vol 21, No 4, December 1987, p 33-46. EL-TAHAN, M., S. VENKATESH, and H. EL-TAHAN, 1987. Validation and Quantitative Assesment Of The Deterioration Mechanisms Of Arctic Icebergs. Journal of Offshore Mechanics and Arctic Engineering, Febmary 1987, Vol 109, p 102-108. MACDONALD, K. A., and S. CLODMAN, 1987. The AES Parametric Ocean-Wave Forecast System. Proceedings of the International Workshop on Wave Hindcasting Forecasting. Report 065. Environmental Studies Revolving Funds, atawa,pp 119-132. MOUNTAIN, D. G., 1980. On Predicting Iceberg Drift. Cold Region Science and Technology, Vol I (3/4), p 273-282. ROBE, R. 0., 1975. Height To Drift Ratios Of Icebergs. Proceedings of the Third International Conference on Port and Ocean Engineering Under Arctic Conditions, 11-15 August 1975, Vol I, p 407-415. SUMMY, A. D. and I. ANDERSON, 1983. Operational Uses Of TIROS Oceanographic Drifters By the International Ice Patrol (1978-1982). Proceedings 1983 Symposium On Buoy Technology, 27-29 April 1983, p 246-250. WHITE, F. M., M. L. SPAULDING, and L. GOMINHO, 1980. Theoreti cal Estimates Of The Various Mechanisms Involved In Iceberg Deterioration In The Open Ocean Environment. Report CG-D-62-80, U. S. Coast Guard Research and Development Center, Groton, Connecticut 06340-6096, pp126. Numerical Environmental Products Manual, Vol II, August 1986 Prepared under authority of Commander, Naval Oceanography Command, Stennis Space Center, Mississippi 39525, pp 200. 128 Appendix F Evaluation of Shipboard Visual Estimation of Iceberg Size LCDR Walter E. Hanson, USCG INTRODUCTION During 1987, approximately 21 per cent of all sightings entered into the International Ice Patrol (IIP) computer were from visual ship observations. Shipping has each year contributed a significant number of visual sightings. Many studies have assessed the ability of ships to detect icebergs, primarily by radar (Budinger, 1960; Ryan et al, 1985; and Harvey et al, 1986). However, little information is known about the sizing accu- racy of visual sightings. Conse- quently, the 1987 iceberg IIP iceberg deterioration study, described in Appendix E, pre- sented an opportunity to evaluate the ability of shipboard observers to visually estimate iceberg size. This study evaluates visual sizing efforts which had neither the aid of visual cues (i.e. an object in close proximity for size comparison) nor the aid of stadimeter or sextant. This sizing technique may mirror that of the shipping community. The icebergs studied by IIP were primarily medium-sized, non- tabular shaped. This category of iceberg seems to be the most often sighted by shipping. BACKGROUND The IIP uses iceberg size and shape in sighting reports to predict their drift and deterioration. For operational purposes, only seven different categories of icebergs are modelled (Mountain, 1980). They are: " Growler ° Small, Non-Tabular ° Small, Tabular ° Medium, Non-Tabular ° Medium, Tabular ° Large, Non-Tabular ° Large, Tabular Drift and deterioration predictions are computed twice daily using computerized models. Iceberg size is used differently by the two models. In the drift model, the size and shape parameters together select one of seven profiles. Each profile is a different cross-sectional representation of above-surface and sub-surface area. The profile represents the average dimen- sions for icebergs in that size and shape category. The iceberg is drifted based on the forces acting upon the profile. The profile is not changed until a new size and/or shape is specified. In the deterioration model, the size and shape parameters together select one of seven waterline lengths. The model calculates "melt" in terms of length instead of mass. Each of the seven lengths is assumed to be the maximum value for the particular size and shape category. Environmental conditions and waterline length are then used as inputs for the daily "melt" of the iceberg. DATA COLLECTION The USCGC TAMAROA, a 68 m (205 ft) U. S. Coast Guard cutter, was used for the 6.3 day study. Visual obsen/ations were made from the bridge wing; height of eye was 10.8 m. Two IIP ice observ- ers, who each had at least two years of aerial iceberg reconnais- sance experience, made the observations. Iceberg above the waterline dimensions were measured during daylight (from 0800Z to 2400Z) in al! weather and light conditions. Table F-1 shows the hours when iceberg sizing occurred. Iceberg shape and size were both esti- mated by the ice observers and calculated from photographic images scaled according to rangefinder measurements. This required a 360 degree look at each iceberg; measuring and photographing all prominent faces. Measurements were accurate to +/- 8% of the observed dimen- sions; see Table F-1. The cutter circled each iceberg twice; once to identify the promi- nent faces; and during the second pass, to make measurements. When perpendicular to each face the true bearing and laser-derived distance to it were recorded, a 129 Table F-1. TIMES OF ICEBERG SIZING MEASURMENTS. Dates and times to the nearest hour when icebergs were sized are listed. Iceberg numbers refer to the sequential numbering system that IIP uses to track individual icebergs during the course of the ice season. ICEBERG # 620 747 744 784 785 787 DATE^IME 14 June 22Z - - - - ♦ 15 19Z 00Z/21Z 23Z 16Z 08Z - 16 15Z 17Z 19Z 13Z 09Z - 17 20Z 21Z 23Z 17Z 12Z 16Z 18 22Z ' ■ ■ .'■**.-. - 16Z 11Z 18Z 19 18Z ''"^'^S™''™ - 10Z - 08Z 20 - - - 13Z 09Z 18Z 21 - 00Z/08Z - - - - photograph taken, and the scalar dimensions recorded. (Scalar dimensions were converted to length and height after all the field work was completed.) At the end of the second pass, the ice observers collectively estimated the iceberg's maximum height and length. No visual cue, like a ship's boat or another vessel, was available to help size the iceberg; only the horizon, when weather permitted. Neither stadimeters nor sextants were used. Iceberg size measurements were conducted within 1900 m of each iceberg; distances for each observation are listed in Table F-2. These distances were dependent upon weather and the ability to view/measure the entire face of the iceberg through the reticulated binoculars. 130 STUDY FINDINGS Thirty-one visual estimations of both height and length were compared to measured dimen- sions. The results indicated that the trained observer tended to underestimate both length and height. All but one of the visually-esti- mated lengths were less than the measured length; see Figure F-1 a. For this set, a linear regression indicated the estimated length was about 56 per cent of the measured length. The data set's linear correlation was 0.72. The observers better estimated height. All but seven of the visually-estimated heights were less than the measured height; see Figure F-1 b. For this set, the regression indicated the estimated height was about 66 per cent of the measured height. The correla- tion was 0.81. CONCLUSIONS Visual observations made close to medium-sized, non-tabular icebergs without the aid of meas- urement devices (i.e. stadimeters, sextants, or reference objects) may underestimate their size. Therefore, if an iceberg appears on the txjrder between two size categories, the IIP recommends assigning the iceberg to the larger of the two size categories. Given the difficulty in properly estimating size, IIP encourages the use of all measurement devices at one's disposal. Table F-2. DISTANCE AT WHICH ICEBERG SIZING MEASUREMENT MADE. The beginning and ending distance in meters from the iceberg are listed. ICEBERG* 620 747 744 784 785 787 DATEATIME .i::V:i4,.:::JUnem:»:::::» j«f»i« -;■;■:■:■:■:■"•:■:■:■:■:■:•:«■ . -^^^, „ ^■SKSS^\.'»WS«W 15 490-310 1880-1160 300-260 51 7-390 960-710 - 'l6 580-380 1280-930 1130-710 1350-690 1210-990 780-550 1270-990 1350-980 1060-870 720-550 1190-940 1070-700 17 18 19 1040-750 1370-580 ai#-l50 1340-1050 1450-810 1020-860 1230-710 700-540 -il 20 - 1430-870 790-570 560-420 21 ------ -■™-- .1360-860 ... 1780-570 :«»>>:.>:««.»:.x«x^^^^^^ :-:-,,:.,y,,,>,.,y.<:.:.,,,^^ JOO I 300 z 200 10C-- F-1a. Y = 0.56x-I1.7 R= 0.72 IDEAL (Y = X ) TOO 200 MEASURED LENGTH (ft) 300 400 v= 0.66x'117 R= 0.81 F-1b. IDEAL ( Y = X ) -y 100 MEASURED LENGTH ((t) Figure F-1. VISUAL ESTIMATION VS. ACTUAL MEASUREMENTS. These scatter diagrams show the esti- mated and the measured dimensions of icebergs sized during the IIP June 1987 iceberg deterioration study. The linear regression is the solid line; its equation (in which Y = estimated feet and X = measured feet) and its correla- tion coefficient are in the upper lefthand corner. The ideal condition (estimated = measured) is shown by the dashed line. Figure F-1 a compares estimated vs measured lengths; Figure F-1 b compares heights. 131 REFERENCES Budinger, T. F., 1960. Iceberg Detection by Radar. International Ice Observation And Ice Patrol Sen/ice In The North Atlantic Ocean, Season of 1959, Bulletin No. 45, p 49-97. Ryan, J. P., M. J. Harvey, and A. Kent, 1985. Assessment Of Marine Radars For The Detection Of Ice And Icebergs. Environmental Studies Revolving Funds Report 008, Ottawa pp 127. Harvey, M. J. and J. P. Ryan, 1986. Further Studies On The Assess- ment Of Marine Radars For The Detection Of Icebergs. Environ- mental Studies Revolving Funds Report 035, Ottawa pp 82. Mountain, D. G., 1980. On Predicting Iceberg Drift. Cold Region Science And Technology, Vol I (3/4) p 273-282. S. 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