the experiment illustrated that 

 iceberg shape and size cannot be 

 readily measured. In patrolling 

 the southern, southeastern, and 

 southwestern limits of the Grand 

 Banks with SLAR during 1983 

 and 1 984, the iceberg detection 

 capability has improved greatly 

 (see Appendix C) over prior visual 

 search years. SLAR has provided 

 a more efficient Ice Patrol, since 

 visual reconnaisance flights were 

 conducted only 50% of the time, 

 covering much smaller search 

 areas with visibility partially 

 obscured by fog or low clouds. 

 Since the SLAR capability of 

 detecting and identifying 

 icebergs is unknown for more 

 severe weather conditions, future 

 experiments will need to be 

 conducted. 



Since the numberof icebergs 

 calved each year by Greenland's 

 glaciers is in excess of 1 0,000 

 (Knutson, 1978), a sufficient 

 numberof icebergs exist in Baffin 

 Bay during any year. Therefore, 

 annual fluctuations in the 

 generation of Arctic Icebergs is 

 not a significant factor in the 

 numberof icebergs passing 

 south of 48°N annually. The 

 factors that determine the 

 numberof icebergs passing 

 south of 48°N each season can 

 be divided into those affecting 

 iceberg transport (currents, 

 winds, and sea ice) and those 

 affecting iceberg deterioration 

 (wave action, sea surface 

 temperature, and sea ice). 



Sea ice acts to impede the 

 transport of icebergs by winds 

 and currents and also protects 

 icebergs from wave action, the 

 major agent of iceberg 

 deterioration. Although it slows 

 current and wind transport of 

 icebergs, sea ice is itself an active 



medium, for it is continually 

 moving toward the ice edge 

 where melt occurs. Therefore, 

 icebergs in sea ice will eventually 

 reach open water unless 

 grounded. The melting of sea ice 

 itself is affected by snow cover 

 (which slows melting) and air and 

 seawaterte mperat u res . As sea 

 ice melt accelerates in the spring 

 and early summer, trapped 

 icebergs are rapidly released and 

 then become subject to normal 

 transport and deterioration. 



Under the influence of northerly 

 winds over Davis Strait and the 

 Labrador Sea, a large numberof 

 icebergs entered the 

 International Ice Patrol area in 

 April, making it the heaviest 

 iceberg month of the 1 984 

 season. Light westerly flow 

 during May, which did little to 

 assist the southward transport of 

 icebergs, and the persistance of 

 sea ice off Newfoundland and 

 Labrador througfxjut the month 

 resulted in a reduced numberof 

 icebergs entering open water. 

 The sea ice remained south of 

 52°N until mid-June, retarding 

 iceberg drift and preserving the 

 icebergs longer than normal (see 

 SST chart for June 1 984 in 

 Appendix B). 



During late June and early July, 

 the sea ice retreated dramatically 

 and the number of icebergs 

 south of 48°N significantly 

 increased in July. The sharp 

 decrease in the number of 

 icebergs in August and 

 September was the result of the 

 increase in air temperatures 

 (Table 5) and the warming of 

 surface waters on the Grand 

 Banks, both of which accelerated 

 iceberg melt. 



References 



Rossiter, J.R., L.D. Arsenault, 

 A.L. Gray, E.V. Guy, D.J. Lapp, 

 R.O. Ramseier, E. Wedler, 

 (1984); Detection of Icebergs by 

 Airtwrne Imaging Radars, 

 Proceedings of the 9th Canadian 

 Symposium on Remote Sensing, 

 St. John's, Newfoundland 



Knutson, K.N. and T.J. Neill, 

 (1978); Report of the 

 International Ice Patrol Service in 

 the North Atlantic Ocean forthe 

 1 977 Season, CG-188-32, U.S. 

 Coast Guard, Washington, DC. 



Acknowledgements 



Commander, International Ice 

 Patrol acknowledges the 

 assistance and information 

 provided by the Canadian 

 Department of the Environment, 

 the U.S. National Weather 

 Service, the U.S. Naval Weather 

 Service, and the U.S. Coast 

 Guard Research and 

 Development Center. 



We extend our sincere 

 appreciation to the staffs of the 

 Canadian Coast Guard Radio 

 Station St. John's, 

 NewfoundlandA/ON and the 

 Gander Weather Office and to the 

 personnel of U.S. Coast Guard Air 

 Station Elizabeth City and the 

 USCGC HORNBEAf^ for their 

 excellent support during the 

 1984 International Ice Patrol 

 season. 



46 



