General Theory of Ocean Currents in a Homogeneous Sea 



439 



for a comparison with those required by theory (see Fig. 189). The theoretical relation 

 is satisfied reasonably well, indeed, but the individual values are strongly scattered — 

 which in view of the possible sources of error is not surprising. With the wind direction 

 almost constant the coefficient of the ice resistance k computed from the "Maud" 

 values decreases from 5-75 to 1-21. In the "Deutschland" values the resistance function 



Fig. 190. Observed relation between wind and ice drift for a constant wind influence, but 

 for an increasing ice resistance. 



f{u) increases with increasing wind and drift velocities and in fact so, that a linear 

 function is obtained for/(w). For the ice resistance this gives 



f{u)u = au^. 

 It is thus approximately proportional to the square of the drift velocity. 



For the ice drift over the North Siberian Shelf Sverdrup found that the ice resis- 

 tance was directly proportional to the drift velocity. This difference can be explained 

 by the different nature of the ice cover in the two cases. Over the Siberian Shelf the 

 sea is covered throughout the year by a solid connected ice layer, about 3 m thick 

 (Pt, I, p. 273). In the Weddell Sea, on the other hand, the ice cover forms only through- 

 out the winter and also then is not nearly as thick as the Arctic drift ice. Furthermore, 

 in the Weddell Sea even in the winter there are frequent long open spaces in the ice 

 cover ("Wacken") so that even at low wind speeds the ice has a much greater freedom 

 for movement. 



Table 130. Relationship between wind and ice drift under quasi-stationary conditions 



{mean values) 



