processes. The first mentioned climatic factors and mixing processes 

 are especially responsible for some large scale density strati- 

 fications. With "large scale density stratification" in this sense 

 is meant, for example, the very weak vertical density gradient in 

 polar regions and the strong, significant vertical density gradient 

 in tropical regions, both taken as an average between the surface 

 and the bottom water. The vertical density stratification is an 

 important factor in the oceanic circulation, which, at least more 

 indirectly, may determine the wind driven circulation. This will 

 be shown by a simple model in the next two sections. 



V. A simple model of a stratified ocean 



Disregard at first the differences in the salinity distribution 

 and assume the temperature distribution as the main factor of the 

 density stratification. The vertical temperature distribution as 

 observed in the deeper layers of the oceans is to a certain degree 

 usually considered as the result of the oceanic circulation or the 

 "spreading" of water masses (G. Wust, 1935) • This is only partly 

 true, as shown by H.U. Sverdrup (1939). Stationary conditions which 

 appear on the average "gross" features to be rather similar to the 

 observed conditions in the ocean may exist even in the case where 

 the components u, v, w, of the oceanic circulation are zero; that 

 is, in an ocean completely at rest. 



Assume in the first step an ocean at rest. This "ocean" may 

 cover the whole earth, and only the sun's radiation (with zero de- 

 clination) may warm up the equatorial regions. The depth of the 

 ocean may be constant (= h meters). In this case, the resulting 

 temperature distribution will be symmetrical in the meridional di- 

 rection and equal in the zonal direction. Since u=v=w=Oby 



17 



