624 



The Tropospheric Circulation 



theory. By means of approximate calculations he was able to demonstrate that the 

 current leaving the Florida Strait will probably have a kinetic energy, so that already 

 half of this energy would be able to carry the water against frictional resistances of 

 various types exactly as far as a wind of 3 to 4 Beaufort could do blowing from the 

 Florida Strait until Cape Hatteras in the current direction. Over this section of the 

 current the theory should be able to make the most important characteristics of the 

 Gulf Stream understandable. However, for the section of the current from 60° to 20° W 

 conditions appear to be rather different, and in this section the initial velocity of the 

 water seems to be only of minor significance. Ekman therefore came to the conclusion 

 that for most of the ocean currents the theory is of limited usefulness only and can 

 be applied solely to very fast currents (such as the Florida Current and its immediate 

 continuation, see also, Thorade, 1938). The Rossby theory, due to its consequent 

 and careful style, had a very stimulating effect and has lead to a better understanding 

 of a number of phenomena displayed by the Gulf Stream between Cape Hatteras and 

 the Newfoundland Banks. 



A satisfactory theory of the Gulf Stream must take into account a further important 

 fact that has already been referred to by Dietrich (1937a). Determination of the mean 

 sea level along the North American coast from Florida in the south to Nova Scotia 

 in the north by means of precise trigonometric measurements has shown that the sea 

 level rises along this total route to the north with a mean slope of 13 cm in 1000 km. 

 The strongest slope occurs just north of Cape Hatteras (see Table 152 according to 

 An VERS, 1927 and Rappleye, 1932). 



The Gulf Stream thus shows an w/7H'(7r(/ motion along this section like the Caribbean 

 Current where according to Parr and Sverdrup (p. 607) there is a slope of about the 

 same magnitude. However, as it was shown by Dietrich, that the Gulf Stream in 

 contrast to the Caribbean Current does not show this slope when the physical sea level 



Table 152. Average Mean Water Along the North American East Coast. 

 (Zero point relative to Florida-Georgia) 



topography is calculated from the mass distribution along the continental slope. 

 Dietrich took the oxygen minimum layer as reference-level but recalculation for a 



