Discussion of 1997 Ice Conditions 



Background 



This section presents a brief discussion 

 of the sea ice and iceberg distribution prior to 

 and during the 1 997 season. While IIP nnoni- 

 tors many environmental conditions near the 

 Grand Banks, by far the two most important 

 to iceberg population are the flow of the off- 

 shore branch of the Labrador Current and the 

 distribution of sea ice. 



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. Ice Patrol uses satellite 

 tracked drifters to monitor the variability in the 

 Labrador current. The tracks of the 13 drift- 

 ers used in 1997 are described in the Drifting 

 Buoy Atlas which is available upon request. 



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 may 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 1997 Season 



Figures 3 to 1 compare the sea ice edge 

 during the 1997 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 21 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 MP's model at 

 the indicated times. Numerals are given for 

 clarity for those one-degree squares where 

 six or more targets were located. 



The following is a discussion of the ice 

 conditions, comparing those ice conditions 

 observed and modeled in 1997 with the 

 twenty-year IIP climatological LAKI described 

 by Viekman and Baumer (1995). 



December through February 



Through December and January, sea ice 

 growth along the Labrador coast and in East 

 Newfoundland waters appeared to be slower 



13 



