416 MISCELLANEOUS STUDIES 



If, for example, there is a flow of the water, the rate of flow multiplied 

 by the temperature where the water enters a given element of volume 

 gives the rate at which the heat is carried into the volume. The rate 

 at which the heat leaves the volume, computed in the same way, 

 subtracted from the rate at which it enters gives the rate of change 

 of heat in the volume due to the corresponding ocean current, whether 

 horizontal or vertical. A term expressing this rate of change of heat 

 in the case of a horizontal current was added to the differential 

 equation, and the solution furnished a means of estimating the magni- 

 tude of horizontal currents from surface temperatures without con- 

 sidering the causes of the currents. 



Numerical applications of this formula to a region of the North 

 Pacific off the California coast and of the North Atlantic off the 

 African coast gave estimates of the horizontal flow in good agreement 

 with direct observations and with what would be expected from the 

 observed wind velocity. 



Conclusive evidence of the presence of currents directed upward 

 from the bottom along the California ccast which cause reduction in 

 temperature has been published before; but to test this conclusion 

 further it was assumed that the reduction of the temperature of the 

 coastal water was due entirely to the upwelling of deep water, and 

 the temperature distribution at depths exceeding 40 meters was 

 assumed to result from a flow of heat according to Fourier's well 

 known conductivity equation, in which a term expressing the rate of 

 loss of heat due to upwelling was added. The formal solution of this 

 equation contained certain physical constants whose evaluation re- 

 quired the observed monthly temperatures at a series of depths. Our 

 temperature data for a deep water region twenty miles offshore from 

 San Diego were sufficient for making approximate estimates of all of 

 the constants, of which the velocity of upwelling and the term corre- 

 sponding to conductivity are of special interest. The latter constant 

 depends largely upon the eddy motion, or alternating circulation, 

 which tends to mix the water and has been called eddy conductivity or 

 Mischungsintensitat, and was found in this case to be several thousand 

 times the laboratory value. In dealing with salinities the same 

 formula can be used; and a similar constant appears, which also 

 depends largely on the mixing motion of the water, and would be 

 expected to have practically the same value as that determined from 

 temperatures. Our salinitiy data, though not so complete as the 

 temperature data, confirmed this conclusion and gave approximately 



