which is closer to the facts observed in nature. Actually, as we have seen, individual floes, 

 experiencing constant collisions, gradually assume a more or less regular oval shape. 



For simplicity's sake, I propose that at the moment the wind begins to act on the floe only two 

 forces are operative: the motive force of the wind F and the hydrodynamic resistance R (figure 

 141). These forces are opposite in direction, and are applied to the corresponding centers of the 

 lateral surfaces of the floe. In the general case, they are applied at an angle to the surfaces. 



Dividing each of these two forces into their components, one perpendicular and the other 

 parallel to the lateral surface of the floe and neglecting the influence of the forces slipping along 

 the lateral surfaces of the floe, we get a pair of forces that strive to rotate the floe such that the 

 wind pressure and the resistance of the water will be parallel to the minor axis of the floe. * 



For the same reason, a ship with its motor stopped stands broadside to the wind. 



Figure 141. The rotation of an elliptical ice floe 

 due to wind action. 



Thus, when the wind begins, at first, each floe rotates and then begins to move. 

 LITERATURE: 56, 59, 62, 77, 86, 94, 117, 127, 171. 



Section 140. The Drift of Scattered Ice 



The drift of scattered ice depends on the concentration of such ice and accordingly can 

 approximate the drift of close pack ice (in which the form of the individual floes is unimportant) or 

 the drift of an isolated floe (in which the form plays a very distinct role). 



As we have seen, floes of various sizes drift at various speeds and at various angles to the 

 wind even when their external form is identical. The motions of individual floes which differ 

 sharply in size and shape differ even more. This greatly complicates the investigation of the drift 

 of more or less scattered ice, where one must consider the collisions of floes. 



Sverdrup, in analyzing his observations of the wind drift of ice in the East Siberian Sea 

 during the expedition on the Maud (1922 to 1924) and the observations of Brennecke in the Weddell 

 Sea (1911 to 1912), concluded that the following forces determine the speed and direction of ice 

 drift after the motion has become steady: 



1. The friction between air and ice direction with the wind. 



*If the forces were parallel to the major axis of the floe, the equilibrium would not be 

 stable. 



386 



