is replaced by A H V \|/ in Monk's notation. 



Before an evaluation of equation (11) several important factors 

 involved in the model have to be discussed and to be fixed. This 

 is concerned with D as a function of x and y, with the wind stress 

 at the sea surface and with the effective friction coefficient, 

 r, in the water as defined before. 



IV. T he "zero-layer" in the Atlantic Ocean 



A successful attempt to determine the depth of the zero layer 

 (layer of no motion) in the Atlantic Ocean was made by A. Defant 

 (1941). When comparing the differences in the dynamic depth of 

 given pressure surfaces between adjacent oceanographic stations, 

 it was found that in certain levels this difference was almost 

 constant over a rather large depth interval. This would mean that 

 either the whole body of water throughout this depth interval 

 (sometimes with a thickness of 500-800 meters) has a constant velo- 

 city in the vertical direction, or that this layer is absolutely 

 at rest. 



Defant's analysis of the North and South Atlantic Ocean has 

 shown that it is much more plausible to assume that this layer is 

 absolutely at rest, than that it is in relative motion to some 

 other "reference level" in the body of water. Defant assumed the 

 average depth of this layer to be the "level of no motion" for his 

 dynamical computations. This hypothetical level of no motion was 

 traced throughout the whole North and South Atlantic, and it was 

 found that it composes without any constraint to a closed layer 

 of varying thickness. This fact and others as pointed out by 

 Defant may serve to strengthen our confidence in Defant's analysis 



12 



