172 WATER MASSES AND CURRENTS OF THE OCEANS 



the transport of water of temperature higher than 7° between a number of 

 selected stations north of lat. 20°N, and adjusting the figures in order to 

 take the continuity of the system into account. To the northwest of a 

 Une that can be drawn roughly between the Straits of Florida and the 

 English Channel it has been assumed that the 2000-decibar surface could 

 be taken as a surface of no motion, but to the southeast of that line it has 

 been assumed in general that the 7°-isothermal surface was a surface 

 of no motion. This treatment was necessary because the condition of 

 continuity has to be satisfied and because a reversal of the direction of 

 flow appears to take place below the 7°-isothermal surface over large parts 

 of the southeastern area. It is not claimed that the picture in fig. 42 is 

 accurate in details, but it is believed that it gives an approximately 

 correct idea of the circulation of the upper water within the greater 

 part of the North Atlantic Ocean. 



The representation shows the Florida Current and the Gulf Stream 

 as the only well-defined currents of the Atlantic Ocean. It also shows 

 that the greater amount of the waters of the Gulf Stream turns south 

 before reaching the Azores and circulates around the Sargasso Sea. 



In the figure the areas are shaded in which the average surface temper- 

 ature is higher than the general average for that latitude. Thus the 

 shaded portions represent the areas with positive temperature anomalies 

 as referred to the average temperatures along parallels of latitude in the 

 Atlantic Ocean, and the unshaded portions represent the areas of nega- 

 tive temperature anomalies. As should be expected, water that is 

 transported from lower to higher latitudes is warm, whereas water that 

 is transported from higher to lower latitudes is cold. If the velocity 

 distribution within the different branches of the currents were known, 

 it would be possible to compute the net amounts of heat that are given 

 off or taken up by the ocean currents, but so far such calculations must 

 be made on an entirely different basis (p. 229). 



Another characteristic of the system of currents is brought out by a 

 comparison between the transports and the temperatures off Chesapeake 

 Bay and to the north of the Azores (fig. 41). The Gulf Stream off 

 Chesapeake Bay transports large volumes of water of temperatures above 

 16°, but the North Atlantic Current to the north of the Azores carries 

 only small amounts of water as warm as that. This apparent reduction in 

 temperature must be due to the fact that the warmer waters of the upper 

 layers have been carried south before reaching the Azores, whereas the 

 somewhat colder waters at greater depths have risen and continued 

 toward the east. 



As will be shown (p. 186), 6 million mVsec of South Atlantic Upper 

 Water enter the North Atlantic Ocean along the coast of South America. 

 Correspondingly, 6 million mVsec of North Atlantic Water sink in 

 different localities and return to the South Atlantic as a deep-water 



