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Antarctic Bottom Water, characterized by high salinity 

 and high oxygen content, is generally believed to be formed 

 in association with sea ice (Gordon and Goldberg, 1970) . As 

 it cools, it moves down the continental shelf and spreads 

 northward along the bottom. The major area of Antarctic 

 Bottom Water formation may be the Weddell Sea and its greatest 

 influence is probably outside the Antarctic zone in the 

 Atlantic (Foster, 1976). The temperature gradient of this 

 water mass is dissipated eventually, and it again cycles 

 southward. 



Besides the meridional circulation patterns discussed 

 above. Southern Ocean waters have an equally important 

 longitudinal circulation pattern. A major driving force for 

 Southern Hemisphere currents are the east and west winds 

 generated by the high pressure zones over the Antarctic 

 continent surrounded by low pressure zones at about 65° S. 

 (Foster, 1976) . While winds near the continent are predominantly 

 easterly, those north of 60° S, are westerly. Major surface 

 movements follow these patterns, moving west near the continent 

 (East Wind Drift) and east to the north of 60° S. (West Wind 

 Drift) (Knox, 1970; Gordon, 1971). 



The East and West Wind Drift interface forms the Antarctic 

 Divergence, an area of upwelling (Knox, 1970; Kort, 1968). 

 At several points along the Divergence, gyres form in areas 

 of atmospheric cyclones. Beklemishev (1961) identified an 

 association between cyclone tracks and whale feeding grounds 

 (and therefore of krill) . The most clearly defined gyre is 

 that of the Weddell Sea (referred to as the Weddell Drift) . 

 Deacon (1976) pointed out that the maintenance of krill 

 stocks in the Atlantic sector may be contingent on this 

 circulation pattern. 



B. Ice Characteristics 



An important physical constituent of the Antarctic 

 marine ecosystem is ice. Ice originates from direct freezing 

 of the sea and from precipitation on the continent resulting 

 in glacier and ice shelf formation. Tabular icebergs calving 

 from ice shelves may have a considerable effect on the heat 

 budget of the Southern Ocean as they melt and subsequently 

 cool the immediate waters around them (Everson, 1977) . 



Equally important is sea ice which fluctuates between 

 approximately 4 and 22 million km^ between summer and 

 winter (Mackintosh, 1973) . Ice prevents wave action and 

 resultant turbulence, and acts as a light and thermal barrier 

 causing a marked seasonality in the sea and primary productivity 

 (Everson, 1977) . Sea ice comprising the circumpolar pack 

 ice zone is an important substrate for a variety of creatures, 

 notably seals and penguins. Seasonal fluctuations in pack 

 ice and its movements associated with wind drifts contribute 

 significantly to the distribution and movements of pack 

 ice fauna. 



