15 



slight error in navigation could displace the contoured sur- 

 face the 500 or 600 feet necessary to bring the isothermal 

 lines into agreement. Third, the surface float used for 

 identification of the subsurface drogue cross was a 12"xl2 M x24 n 

 block of wood which presented a large surface area. The move- 

 ment of the upper water layer may have been such that the 

 track of the subsurface drogue was not the one it might have 

 followed had it been able to move freely. Even with these 

 possible sources of error, there is a remarkable correlation 

 between the drogue paths and the associated thermal gradients. 



It is because of this correlation that the effects of 

 temperature gradients are discussed below and that certain 

 conclusions regarding the circulation in Santa Monica Bay 

 are drawn from temperature distribution. 



Assuming now that water motion is related to a horizontal 

 temperature gradient, the rate of movement of the water 

 increases as the gradient becomes larger. If the gradient 

 were to act alone, the water would flow in the direction of 

 the gradient. Movement of water in the ocean, however, is 

 profoundly modified by an effect due to the rotation of the 

 earth (Coriolis force) and the result is a flow perpendicular 

 to the gradient, that is, parallel to the isotherms. This is 

 the reason, therefore, for the statement made above, for we 

 find that as a particle of water begins to flow down the 

 gradient, it is deflected to the right in the northern hemis- 

 phere so that the net result is a flow along isothermal lines 

 rather than across them. This deflecting reaction (force) is 

 a function of the sine of the latitude, acts at right angles 



