Discussion of Ice and 

 Environmental Conditions 



Background 



The offshore branch of the Labrador Cur- 

 rent is the main mechanism transporting ice- 

 bergs south to the Grand Banks and the North 

 Atlantic shipping lanes (Figure 2). Its rela- 

 tively cold water keeps the deterioration of ice- 

 bergs to a minimum. 



Sea ice protects the icebergs from wave 

 action, the major agent in 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 edge retreats in the 

 spring, large numbers of icebergs will be left 

 behind in the vicinity of the Grand Banks. If 

 the time of retreat of the sea ice edge is de- 

 layed by below-normal air and sea surface 

 temperatures, the icebergs will be protected 

 from melt longer and be expected to survive 

 to drift farther south. In these cases a longer 

 than normal ice season can be expected. 

 Less southerly sea ice extent or above nor- 

 mal air and sea surface temperatures may 

 result in a shorter season. 



Sea ice can impede the transport of ice- 

 bergs. The degree depends on the concen- 

 tration of the sea ice and the size of the ice- 

 bergs. The greater the sea ice concentration, 

 the greater the effect on iceberg drift. The 

 larger the iceberg, the less sea ice affects its 

 drift. 



The 1996 Season 



Figures 3 to 1 compare the sea ice edge 

 during the 1996 ice year to the mean sea ice 

 edge. The mean sea ice edges were taken 

 from Cote (1989) and represent a 25 year 



average (1962-1987). The ice edge (sea ice 

 concentration > 1/10) is taken from the daily 

 Ice Analysis from the Ice Centre, Ottawa. 



Figures 11 to 19 show the Ice Patrol Lim- 

 its of All Known Ice (LAKI) and the daily sea 

 ice edge on the 1 5th and the last day of each 

 month during the ice season. The ice edge is 

 taken from the Ice Centre, Ottawa FICN2 daily 

 product. The edge plotted is a coarse numeric 

 representation of the daily Ice Analysis. These 

 figures show the distribution of all icebergs 

 and radar contacts tracked by HP's model at 

 the indicated times. Numerals are given for 

 clarity for those one-degree squares where 

 six or more targets are located. 



The following is a discussion of the ice 

 conditions, comparing those ice conditions 

 observed and modeled in 1996 with the 

 twenty-year IIP climatological LAKI described 

 by Viekman and Baumer (1995). 



December through March 



Through the period, sea ice growth along 

 the Labrador Coast and in East Newfound- 

 land waters appeared to be 2-4 weeks be- 

 hind normal (Figures 3-6). At the end of 

 March, 4 icebergs were south of 48°N and 

 the reported LAKI (Figure 12) fell between the 

 minimum and the 75 percentile climatological 

 LAKI for March 31. The 1996 Ice Patrol Sea- 

 son started on 15 March. 



April 



Throughout the month of April, the sea 

 ice rapidly melted and the edge receded to 

 the north and the Newfoundland-Labrador 

 coastlines. MP's LAKI was near the median 



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