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. 



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