All-101 73 



Since we have been unable to arrive at a useful solu- 

 tion for the non-steady ocean circulation without assuming 

 negligible velocities in the bottom layer, we have no assurance 

 that our analysis is valid* Reliable observational data which 

 might guide us in this matter are not available. We may per- 

 haps gain a little more confidence in the results of this inves- 

 tigation by the following considerations. 



For the formulation of Problem 1 it was assumed that 

 the velocities, and hence the horizontal pressure gradient, 

 vanish in the bottom layer. This, together with the hydrostatic 

 pressure lav;, immediately led to the conclusion that the thermo- 

 cline responds instantaneously to any motion of the free surface. 

 Naturally, this can hold, if at all, only for sufficiently 

 slowly varying circulation* 



Some investigators are of the opinion that the very 

 opposite situation actually exists, i.e., the thermocline re- 

 mains essentially fixed and does not respond to wind variations 

 of, say, seasonal or annual periods. This is perhaps a more 

 reasonable assumption because it is based on the idea that the 

 frequency of wind variation is much greater than the important 

 frequencies of free oscillations of the bottom layer. 



Let us assume, therefore, that the shape of the thermo- 

 cline remains roughly fixed in such a manner as to result in a 

 vanishing time-average horizontal pressure gradient in the 

 bottom layer. That is to say, the thermocline adjusts itself 

 to the mean wind distribution so as to give zero pressure 



