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Pack ice drifts with the wind and tide, nsually to the left of the trne 

 wind in the Southern Hemisphere, and to the right in the Northern 

 Hemisphere. The speed of drift may not depend entirely upon the 

 strength of the wind, since it is influenced greatly by the presence or 

 absence of open water in the direction of the drift, even though the 

 open water is somewhat distant. 



Xeglecting the resistance of the ice, Ekman's theory of wind drift 

 calls for the ice to drift 45° from the wind direction. Observations 

 show that the actual drift is about 30° from the wind direction on the 

 average, or very nearly parallel to the isobars on a weather map. In 

 winter, when the ice is more closely packed and offers more resistance, 

 its drift deviates less from the wind direction than in summer, and 

 tidal influences become more important. 



The speed of drift of pack ice can be fairly closely determined from 

 the wind speed. Observed average speeds of drift of ice in the 

 Northern Hemisphere range from 1.4 percent of the wind speed in 

 April to 2.4 percent of the wind speed in September. 



There is a northward tendency in the drift of Antarctic ice, on which 

 the left-hand component due to the earth's rotation is superimposed. 

 The pack therefore travels westward and northwestward around the 

 continent, and into and around the Weddell Sea in a clockwise 

 direction. 



The general circulation of the ice of the Arctic Ocean is determined 

 by the direction of the ocean currents, which are the result of two chief 

 factors : the circulation of the atmosphere above the polar basin and 

 the surrounding adjacent seas, and the influx into the polar basin of 

 water of oceanic and river origin, with a compensatory outflow of the 

 water from the polar basin. 



Above the central part of the polar basin, the cap of cold air has an 

 anticyclonic (clockwise) movement which causes a movement of the 

 polar cap ice in the same direction. Because of the deflecting influ- 

 ences of the eartli's rotation, all movements in the Northern Hemis- 

 phere tend to incline to the right. 



The ice moves slowly under the action of wind and current toward 

 the opening between Norway and Greenland. The speed of the cur- 

 rent increases as it approaches the opening, particularly its western 

 mouth between Svalbard and Greenland, and great masses of ice (the 

 storis) are carried swiftly southward along the east coast of Greenland. 

 The ice that floats southward, east of Svalbard, soon melts in the warm 

 waters derived from the Gulf Stream. 



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