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outward from Antarctica and gathers in a belt formed by the meeting 

 of southeasterly and northwesterly winds in the vicinity of the 60th 

 parallel. There is a close correspondence in the formation of this 

 belt of ice with that formed in the Arctic which follows down Davis 

 Strait and eastward off Greenland. In the Antarctic it is unusual for 

 sea ice to be more than 1 or 2 years old. The drift in both the Weddell 

 and Ross Seas carries the pack out into the open oceans in a little over 

 a year. 



In the Arctic, on the other hand, floes of great age are frequent. Ice 

 formed off the Siberian coast takes from 3 to 5 years to drift across the 

 polar basin and down the eastern coast of Greenland. Ice of this age, 

 therefore, becomes pressed and hummocked to a degree unknown in 

 ice formed in lower latitudes. The warmth of the Arctic summers also 

 has its effect and the result is worn-down, more or less even, floes of 

 great thickness known as "polar cap ice," During the summer, melt- 

 ing on the surface is considerable, as a rule about 2 feet, and pools of 



100 



90 



80 



12 70 



I 

 o 



z 



I 60 



50 



20 



Sept 



Apr 



May 



July 



Figure 4. — Course of thickness of ice formed in two typical sheltered harbors in the Nort-hern 

 Hemisphere at the latitudes indicated. 



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