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WATER MASSES AND CURRENTS OF THE OCEANS 



of which (Maurstad's) has been adopted by the International Meteoro- 

 logical Organization. The classification of sea ice deals with forms 

 produced under different conditions of freezing, forms that are due to 

 the tearing apart and packing together of the ice under the action of 

 winds and tides and forms that result from disintegration and melting 



Fig. 62. Average northern limits of pack ice around the Antarctic Continent in 

 March and October (after Mackintosh and Herdman) and average northern Hmit of 

 icebergs according to British Admiralty Chart No. 1241. 



of the ice. The classification of icebergs is based on the shape of the 

 bergs, which depends partly upon the type of glacier from which they 

 originate and partly upon the processes of melting and destruction to 

 which they have been subjected. 



The great mass of sea ice around the Antarctic Continent is popularly 

 described by the somewhat loose term ''pack ice," by which is meant 

 drifting fields of close ice, consisting mainly of relatively flat ice floes, 



