Discussion of Ice and 

 Environmentai Conditions 



Background 



The Labrador Current, aided by north- 

 westerly winds in winter, is the main mecha- 

 nism transporting icebergs south to the Grand 

 Banks. In addition, the relatively cold water of 

 the Labrador Current keeps the deterioration 

 of icebergs in transit to a minimum. 



The wind direction and intensity along 

 the Labrador and Newfoundland coasts has a 

 significant effect on iceberg drift. Icebergs can 

 be accelerated along or driven out of the main 

 flow of the Labrador Current (Figure 2). 

 Departure fromthe Labrador Current normally 

 slows their southerly drift and, in many cases, 

 speeds up their rate of deterioration. 



Sea ice protects the icebergs from wave 

 action, the major agent of iceberg deteriora- 

 tion. If sea ice extends to the south and over 

 the Grand Banks of Newfoundland, the ice- 

 bergs will be protected longer as they drift 

 south. When the sea ice retreats in the spring, 

 large numbers of icebergs will be left behind 

 on the Grand Banks. If this time of sea ice 

 retreat is delayed by below normal air tem- 

 peratures, the icebergs will be protected longer, 

 and a longer than normal ice season can be 

 expected. Less southerly sea ice extent or 

 above normal air temperatures may result in a 

 shorter season. Sea ice also acts to impede 

 the transport of icebergs. The degree de- 

 pends on the concentration of the sea ice and 

 the size of the iceberg. Thegreaterthesea ice 

 concentration the greaterthe affect on iceberg 

 drift. The larger the iceberg the less sea ice 

 affects its drift. Sea ice is itself an active 



medium, causing iceberg movement, continu- 

 ally moving toward the ice edge where melt 

 occurs. Icebergs in sea ice will eventually 

 reach open water unless grounded. 



The 1992 Season 



The sea ice information was derived 

 from the Thirty Day Ice Forecast for Northern 

 Canadian Waters published monthly by Ice 

 Centre Ottawa, Atmospheric Environment 

 Service (AES) of Canada, and information on 

 the mean sea ice extent was obtained from Ice 

 Limits Eastern Canadian Seaboard, Ice Cen- 

 tre Ottawa, Atmospheric Environment Ser- 

 vice, 1989. Figures 3 to 14 compare sea ice 

 extents during the 1 992 IIP year to mean sea 

 ice extents. Environmental information was 

 obtained from the Mariner's Weather Log and 

 AES Thirty Day Ice Forecasts. Figures 1 5 to 

 29 show the Limits of All Known Ice and the 

 sea ice edge for the 1 5th and 30th of each 

 month of the ice season. 



January and February 



Sea ice growth along the Labrador 

 Coast and in East Newfoundland was three to 

 four weeks ahead of normal (Figures 6 and 7). 

 The intensification of the usually weak Azores- 

 Bermuda High in conjunction with stronger 

 than normal Icelandic Low created a very 

 steep pressure gradient from the Grand Banks 

 to the Norwegian Sea. The winds over the 

 region were predominantly westerly. The mean 

 air temperatures were lower than normal, 

 approximately minus 6.0°C. 



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