features of the steady oceanic circulation again. 



In the present report it will be shown that the depth of the 

 wind induced oceanic circulation plays a significant role in the 

 hydrodynamic analysis of the problem. A more realistic model of 

 the wind driven circulation of the North Atlantic Ocean will be 

 treated by numerical integration of the basic differential equa- 

 tions in a subsequent report. 



III. The differential equation of horizontal mass transport 



Rectangular coordinates may be assumed for a first simplified 

 model. Let the y-axis point northward, the x-axis eastward, and 

 the z-axis vertically upwards from the undisturbed sea surface which 

 coincides with a level surface. The boundaries of the ocean model 

 may be considered as vertical walls, which at first approximation 

 would account for the continental slope. Besides these latera l 

 boundarie s the lower boundar y of the current system has to be fixed. 



It is known that in equatorial regions the layer of no motion 

 ("zero layer") for the wind driven circulation is found in about 

 200-300 m of depth, and it increases with increasing latitude to 

 approximately 1500 m in 45°-50°N. (The depth of this "zero layer" 

 should not be confused with the depth of the layer of frictional 

 influence.) There is much evidence for this fact, and it has been 

 assumed by most oceanographers that there is a continuous change 

 of this "level of no motion" between low and high latitudes. Much 

 support of this point of view has been given by A. Defant (1941) 

 in his extensive analysis of the Atlantic circulation, where inter- 

 esting details of the layer of no motion have been revealed. 



The "zero layer" of the oceanic circulation in the wind affected 

 surface and subsurface layers may be considered as the lowj^oundary. 



7 



