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 to maintain turbulence must be greater than 1.4x10 sec Multi- 



5 

 plying this by the depth of the ocean, 4x10 cm, yields a value of 



560 cm/sec for the change in velocity of the top relative to the bottom, 

 exclusive of the sharp drops occurring in the boundary layers^ Tidal 

 Currents are of the order of 10 cn^/sec and wind induced velocities 

 rarely exceed 30 cm/sec. Consequently it is doubtful that wind or tide 

 could produce vertical turbulent fluctuations in the deep ocean, if Town- 

 send' s criterion is applicable. It should be noted that the largest 



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 gradients in the Gulf Stream are only about 5x10 sec 



Eddy Diffusivity 



A turbulent fluid can transport properties such as momentum or 

 temperature at a much higher rate than a non-turbulent liquid as a result 

 of the eddy motion. Measured values of the eddy viscosity for momentum 

 transport or eddy diffusion for the transport of impurities can be used 

 to get a measure of the associated turbulent velocities. 



Eddy diffusion coefficients have been obtained at various locations 

 in the ocean (S, 481) by measurements of changes in temperature, salinity, 

 concentration of dissolved gases, etc; eddy viscosity measurements, which 

 represent momentum transport, are generally based on relations assumed to 

 exist in the velocity field being studied. In a horizontal direction 

 both types of coefficient are approximately equal, but in the vertical 

 direction the viscosity coefficient is ten or more times larger than the 

 diffusion coefficient. A given coefficient changes in going from the 

 vertical to the horizontal direction by the staggering factor of about one 

 million. 



Both coefficients result from a mass transport and they can have equal c.g.s. 

 numerical values because water conveniently has unit specific heat (S92). 



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