the usual iceberg population was absent.] In 

 1951-1952 a total of 23 icebergs passed 

 south of 48°N and in 1965-1966, 76. 



For many decades Ice Patrol and 

 others have struggled to understand what 

 causes the variability in the iceberg counts. 

 Most attention has focused on ocean and 

 atmospheric forcing (Davidson et al., 1986) 

 with special emphasis on the role of sea-ice 

 (Smith, 1931. Marko et al., 1994 and 

 Peterson et al., 2000). The number of 

 icebergs passing south of 48°N is well 

 correlated with sea-ice extent near 

 Newfoundland (Peterson et al., 2000). This 

 good correlation is not surprising because 

 extensive sea-ice protects icebergs from 

 destruction as they move southward. 

 Extensive sea-ice along the Labrador coast 

 may also inhibit icebergs from being driven 

 into shallow waters and grounded during 

 winter storms. 



The problem of understanding the 

 variability of the iceberg counts might be 

 getting more complicated. Thus far, most 

 studies have not considered the variability of 

 iceberg production at the Greenland glaciers 

 for two reasons. First, few detailed iceberg- 

 production data were available. Second, the 

 iceberg population arriving along the 

 Labrador and Newfoundland coasts is a 

 small fraction of the calf ice produced at the 

 Greenland glacial fronts. This leads to the 



implicit assumption that the glaciers were 

 producing a more-or-less constant and 

 extensive supply of icebergs to Baffin Bay 

 and the observed variability in Ice Patrol's 

 iceberg counts was due primarily to the 

 transport and deterioration processes farther 

 to the south. 



Recent research shows significant 

 changes are occurring in many of 

 Greenland's outlet glaciers. Mayer and 

 Herzfeld (2006) reported that in 1999 the 

 Jakobshavns Isbrae in West Greenland 

 entered a phase of rapid retreat and the 

 production of icebergs increased. This is one 

 of the fastest flowing ice streams in the world 

 and a major iceberg producer in West 

 Greenland. 



Moon and Joughin (2006) used 

 satellite images to study over 150 Greenland 

 outlet glaciers in 1992, 2000, and 2005 and 

 found an overall trend of retreat, with more 

 rapid retreat in 2000-2005. Finally, Rignot 

 and Kanagaratnam (2006) used satellite radar 

 measurements to document an enormous 

 increase in ice discharge from Greenland's 

 glaciers, with Jakobshavn Isbrae alone 

 increasing from 24 knrVyr in 1996 to 46 km' 

 ice/yr in 2005. These studies make it clear 

 that more, not fewer, icebergs are being 

 produced by Greenland's glaciers. 



References 



Bancroft, George P., (2006). Marine Weather Review - North Atlantic Area, January to April 

 2006. Mariners Weather Log, Vol. 50(2), August 2006. 



Canadian Ice Service, (2000). Sea-ice Climatic Atlas. East Coast of Canada, 1971-2000. Canadian 

 Ice Service, 373 Sussex Drive Block E-3, LaSalle Academy, Ottawa, ON, Canada K1A 

 0H3, 151 p. 



Canadian Ice Service, (2005). Seasonal Outlook, Gulf of St. Lawrence and East Newfoundland 

 Waters, Winter 2005-2006. Unpublished Manuscript, Canadian Ice Service, 373 Sussex 

 Drive, E-3, Ottawa, ON, Canada Kl A 0H3, 13 p. 



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