APPENDIX B 



REMOTE SENSING AS IT APPLIES TO THE INTERNATIONAL ICE PATROL 



CDR A. D. Super, USCG 

 LTJG S. R. Osmer, USCG 



Icebergs calve from the major glaciers of 

 Greenland. As many as 10,000 are produced 

 each year. Although exposed to open sea and 

 warmer water in the summer and fall, these bergs 

 become trapped in and protected by sea ice dur- 

 ing the remainder of the year. Those that sur- 

 vive, travel with the pack ice from Baffin Bay to 

 the western Labrador Sea and start to arrive off 

 the Newfoundland coast in January and Feb- 

 ruary. The bergs exit the sea ice to the south 

 and east, continuing their drift until they even- 

 tually melt in the warmer North Atlantic water. 

 As the pack ice recedes in late spring, bergs con- 

 tinue to survive south of latitude 48°N until mid 

 to late summer when warmer water and open seas 

 normally deteriorate them before they can reach 

 the main shipping routes. The annual average 

 number of bergs crossing latitude 48°N to menace 

 shipping since WWII is 318, although season 

 severities have varied from 1587 bergs in 1972 

 and 1387 in 1974 to in 1966 and 1 in 1958. 



The Grand Banks and its approaches are 

 uniquely hazardous to shipping for a number of 

 reasons. Foremost of these are : the high density 

 of shipping, extremely rich fishing grounds, great 

 frequency of bad weather and poor visibility, and 

 the intrusion of pack ice and icebergs. The 

 shortest routes between the major ports of North 

 America and Europe pass through this area. The 

 interchange of the cold, southward flowing Lab- 

 rador Current with the warm North Atlantic 

 extension of the Gulf Stream fosters both a 

 nutrient rich fishing ground and a great profu- 

 sion of fog. Additionally, North American 

 storm tracks usually cross this area. 



There are two possible approaches to make the 

 area safer for shipping. They are: (1) elimina- 

 tion of the hazards and (2) location of the haz- 



ards with wide dissemination of location 

 information so that they may be avoided. In 

 attempts to destroy bergs, Ice Patrol has carried 

 out a number of experiments including gunfire, 

 demolition mines, high explosive bombs, thermite, 

 bombs, and carbon black without significant suc- 

 cess. Destruction of the bergs is not feasible. 

 Thus, Ice Patrol collects iceberg location infor- 

 mation and disseminates warning information to 

 shipping as widely as possible. 



One might presume that, with modern surface 

 radar, ships could detect and avoid icebergs. 

 Aside from human errors of nondetection this is 

 found to be untrue. In 1959 an extensive study 

 of ice detection by radar was completed. This 

 work determined the behavior of floating ice to 

 electromagnetic radiation and assessed the ef- 

 ficiency of radar in providing reliable informa- 

 tion for safe navigation through potential ice 

 areas. A summary of the results are: 



1. Ice typical of that in icebergs on the Grand 

 Banks has a reflection coefficient of approximately 

 0.33 and reflects radar waves 60 times less than a 

 steel ship of equivalent cross sectional area. 



2. The maximum range of radar contact is 

 proportional to the fourth root of the physical 

 cross-sectional area of icebergs. A statistical re- 

 lation derived from 152 observations shows that 

 growlers (above water area of less than 1x6 

 meters) normally cannot be detected at ranges 

 over 4 miles. 



3. The Grand Banks and continguous areas of 

 the North Atlantic exhibit conditions of sub- 

 normal radar propagation during the spring 

 months when fog and ice hazards are most 

 prevalent. 



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