DISCUSSION OF ICEBERG AND ENVIRONMENTAL CONDITIONS 

 1972 ICE SEASON 



In attempting to explain the environmental factors producing a 

 record season, both in longevity and number of icebergs, four major 

 conditions must be considered. First is the number of icebergs 

 available to drift south of 48°N latitude, second is the strength 

 and duration of the northwesterly wind component producing a drift 

 which transports the icebergs south, thirdly, the development of the 

 features of the Labrador Current, and finally, the reduced rate of 

 deterioration of the icebergs due to colder air and ,sea temperatures 

 and wave action inhibited by sea ice. 



The total number of icebergs counted during the pre-season flights 

 (194 in January, 360 in February) makes up but a small part of those 

 icebergs which drifted south of 48°N latitude. The January survey went 

 only as far north as Cape Dyer and the February flight extended to Cape 

 Chidley. Normally this is all that is necessary as the icebergs north 

 of Davis Strait rarely survive the 1000-mile drift without melting. 

 This ice season, as will next be discussed, was by no means normal. 



Figures 27a through 27e show the normal and the 1971/1972 surface 

 pressure patterns for November through August. During December a strong 

 low pressure system centered near the southeastern tip of Greenland 

 became clearly defined. Then for the next six consecutive months a 

 strong northwesterly wind anomaly persisted. These extrem^, excessive 

 conditions caused thousands of icebergs to drift out of Baffin Bay, 

 through Davis Strait and into the Labrador Current. This same 

 intensification created a mean southwesterly wind over the Grand Banks 

 by late February which remained until early July. Thus the majority 

 of icebergs were forced out of the influence of the Labrador Current 

 and drifted eastward into the somewhat warmer waters of the North 

 Atlantic Current. 



Examining each of figures 27a through 27e more closely, the November 

 Greenland High and a 4-mb positive anomaly lay over the northern half 

 of Greenland with the mean pressures from Labrador westward as much as 

 5 mb above normal. The Icelandic low was way out of position over the 

 Barents Sea (normally south of Denmark Strait) and 8 mb below normal. 

 A trough of low pressure extended southward from Baffin Bay through 

 the Labrador Sea into the waters well south of Newfoundland. Pressures 

 inside the trough ranged from 4 mb below normal near 40°N 55°W to 7 mb 

 above normal near the low pressure system west of Kap Farvel. 



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