24 MARION AND GENERAL GREENE EXPEDITIONS 



described method of Jakhelln (1936). The difference in the values 

 thus found by the two methods seldom exceeded 15 percent of the net 

 transport, and this figure was considered immaterial. The net 

 volume of the current, figure 3, was 4.41 mVs X 10^ by graphic 

 method and 3.73 mVsXW by Jakhelln's method. It should of 

 course be borne in mind that Jakhelln's method (see also Werens- 

 kiold, 1935) gives results in terms of net volume or transport, and this, 

 for example where the two given stations span the boundary of op- 

 posing currents, furnishes information in comparative terms only. 

 Perhaps the best practice, although laborious, is, first, the construc- 

 tion of a velocity profile as earlier described, and, second, the com- 

 putation of the volume of the various currents by integrating to the 

 zero velocity lines as shown on the profile in accordance with the 

 Jakhelln method. The determination of the transport through the 

 several sections in the Labrador Sea the summer of 1931 have been 

 combined in a so-called transport map. (See fig. 4, p. 23.) Ekman 

 (1929) and Thorade (1933) have published similar maps for other 

 regions of the North Atlantic. 



It should be added that the construction of velocity profiles and 

 the planimeter determination of velocity areas and volumes there- 

 from is essential, wherever the average temperature of the separate 

 bands of currents and the rate of heat transport are desired. The 

 algebraic sum of the several products of velocity by cross-sectional 

 area by temperature represents the net rate of heat transfer through 

 the section. The average temperature has been obtained by dividing 

 this value for the rate of heat transfer by the net volume of flow. 

 The average temperature of the slope band of the West Greenland 

 Current in the Cape Farewell section A, figure 3, was 5.5° C. The 

 rate of heat transfer is expressed in million-cubic-meter-degrees, 

 centigrade-per-second. In the case of the slope band of the West 

 Greenland Current at Cape Farewell September 2-3, 1928, figure 3, 

 the rate of heat transfer was 17.5° C. mVsXlO^. 



In computing the volume of current (transport) from velocity 

 profiles, it is important that the profiles be drawn as accurately as 

 possible. The velocity profiles described and used in this report are 

 considered justifiable, if on no other basis than that they provide a 

 means of computing the average temperature of, and the rate of 

 heat transported by, ocean currents. 



The salinity of the sea is, of course, free from many of the in- 

 fluences that act upon the temperature. A quantitative determina- 

 tion of the rate of salt transport similar to the above-described 

 method of obtaining the rate of heat transport has been utilized as 

 shown on p. 77. 



