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. 



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