Discussion of Ice and 

 Environmental Conditions 



Background The 1993 Season 



The Labrador Current is the main 

 mechanism transporting icebergs south to the 

 Grand Banks. Its relatively cold water 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 from the 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 airtemperatures may result in a 

 shorter season. 



Sea ice can impede the transport of 

 icebergs. The degree depends on the con- 

 centration of the sea ice and the size of the 

 iceberg. The greater the sea ice concentra- 

 tion, the greaterthe affect on iceberg drift. The 

 larger the iceberg, the less sea ice affects its 

 drift. 



Figures 3 to 14 compare the sea ice 

 edge during the 1 993 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 /1 0) is taken from the daily 

 Ice Analysis from Ice Centre Ottawa. 



Figures 15 to 29 show the Ice Patrol 

 Limits of All Known Ice (LAKI) and the daily 

 sea ice edge on the 1 5th and 30th 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 daily Ice Analysis. These 

 figures show the distribution of all icebergs 

 and radar contacts tracked by HP's model at 

 the given times. Numerals are given forclarity 

 for those one-degree squares where six or 

 more targets are located. 



The following is a discussion of the 

 environmental conditions (the meteorological 

 and sea ice information is taken from the Ice 

 Centre Ottawa Thirty Day Ice Forcast for North- 

 ern Canadian Waters): 



December 



The mean airtemperatures were about 

 2-4°C below normal along the Labrador Coast 

 and in East Newfoundland waters. This was 

 due to a persisting northwesterly flow. The 

 sea ice growth in the East Newfoundland 

 waters was about four weeks ahead of normal 

 (Figure 5). There were 16 icebergs crossing 

 48°N in December. 



January and February 



Sea ice growth along the Labrador 

 Coast and in East Newfoundland waters was 

 three months ahead of normal (By January, 

 the southern limit of the sea ice was farther 



13 



