Ice and Environmental Conditions During 

 the 1998 Iceberg Season 



1998 Iceberg Season 



Many factors combine to shape the 

 severity of an iceberg season in the 

 western North Atlantic Ocean. They may 

 be divided into three main categories. First 

 are those factors affecting the supply of 

 icebergs to the southern Labrador coast, 

 including calf ice production at the various 

 glaciers and deterioration processes in 

 Baffin Bay that might destroy the icebergs 

 before they reach the shipping lanes. The 

 second category includes factors relating 

 to the mechanisms that destroy icebergs in 

 east Newfoundland waters, such as the 

 duration and areal extent of the sea-ice 

 cover, air and sea surface temperature 

 (SST), and storm tracks. The final 

 category includes those factors relating to 

 the movement of icebergs once they reach 

 the vicinity of the Grand Banks of 

 Newfoundland, primarily the ocean 

 currents in the region, and to a lesser 

 extent, winds. 



Since there is no routine monitoring of calf 

 ice production or iceberg destruction in 

 Baffin Bay, the following discussion 

 focuses on the second and third 

 categories. This discussion draws from 

 several sources, including the Seasonal 

 Summary for Eastern Canadian Waters, 

 Winter 1997-1998 (Canadian Ice Service, 

 1998); sea-ice analyses provided by 

 Canadian Ice Service (CIS) and the United 

 States National Ice Center (NIC); and the 

 Integrated Global Ocean Services System 

 Products (IGOSS) SST Anomaly (Climate 

 Data Library, International Research 

 Institute for climate prediction at Lamont- 

 Doherty Earth Observatory of Columbia 

 University); and, finally, summaries of the 

 iceberg data collected by Ice Patrol. It is 

 useful to compare the 1997-1998 sea-ice 



and iceberg observations to the historical 

 record to emphasize departures from 

 normal. For sea ice, Cote (1989) provides 

 maximum, median and minimum extent of 

 sea-ice cover along the eastern Canadian 

 seaboard at weekly intervals from mid- 

 November through the end of July. The 

 maps are based on a 25-year record 

 beginning in 1962. Viekman and Baumer 

 (1995) present an iceberg limits 

 climatology from mid-March to 30 July 

 based on 21 years of Ice Patrol 

 observations from 1975 through 1995. 

 They provide the extreme, median, and 

 minimum extent of the limits of all known 

 ice (LAKI) for the period, as well as two 

 intermediate extents, the 25 th and 75 lh 

 percentiles. The 75 th percentile means 

 that, for the 21 -year period, 75% of the 

 limits for a particular date extended beyond 

 the 75 th percentile limit. 



December 1997 through February 1998 



Sea-ice development along the 

 Labrador coast was near normal in 

 December 1997 and January 1998, but 

 warmer-than-normal air temperatures in 

 the second half of February resulted in 

 southern and eastern ice edges that were 

 less extensive than normal at the end of 

 month. The SST along the southern 

 Labrador and northeast Newfoundland 

 coasts was near normal, except near the 

 Strait of Belle Isle where it was about 1° C 

 colder than normal. In east Newfoundland 

 waters, the January southern and eastern 

 ice extents were near normal. The Strait of 

 Belle Isle was closed for navigation in mid- 

 January. A series of storms during the last 

 two weeks of February caused a reduction 

 in the eastward extent of the ice edge in 

 east Newfoundland waters The 1998 

 iceberg season began on February 13, 



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