WATER MASSES AND CURRENTS OF THE OCEANS 185 



Tropical Convergence and rising motion takes place at the northern 

 boundary of the countercurrent. The data from the Atlantic Ocean 

 indicate the existence of these cells, and the Carnegie section across the 

 Pacific Countercurrent (fig. 52, p. 194) demonstrates their presence con- 

 vincingly. As a consequence of these transverse circulations the northern 

 boundary of the countercurrent and of the Equator represent lines of 

 divergence, whereas the southern boundary of the countercurrent is a line 

 of convergence, and individual water masses carried by the different 

 currents follow complicated spiral-like trajectories. 



In summer, when the countercurrent is best developed, the effect of the 

 divergence at the Equator appears on the charts of surface temperatures 

 as a tongue of low temperature, but no effect of the divergence at the 

 northern boundary of the countercurrent is visible (chart 1). 



Currents of the South Atlantic Ocean 



The most outstanding current of the South Atlantic Ocean is the 

 Benguela Current, which flows north along the west coast of South Africa 

 and is particularly conspicuous between the south point of Africa and 

 latitude 17° to 18°S. In agreement with the dynamics of currents in the 

 Southern Hemisphere the denser water of low temperature is found on the 

 right-hand side of the current — that is, close to the African coast. Under 

 the influence of the prevailing southerly and southeasterly winds the 

 surface layers are carried away from the coast, and upwelling of water 

 from moderate depths takes place in most seasons of the year. As a 

 consequence of this upwelling a band of water of low temperature and of 

 relatively low salinity is found along the coast extending out to a distance 

 of approximately 200 km. 



Proceeding toward the Equator, the Benguela Current gradually 

 leaves the coast and continues as the northern portion of the South 

 Equatorial Current, which flows toward the west across the Atlantic 

 Ocean between latitudes 0° and 20°S. In the charts which show the dis- 

 tribution of surface temperatures, the tongue of low temperature along 

 the Equator is due not only to the cold waters of the Benguela Current, 

 but also to the divergence along the Equator. The South Equatorial 

 Current partly crosses the Equator, continuing into the North Atlantic 

 Ocean, and it partly turns to the left and flows south along the South 

 American coast, where it shows up as a tongue of water of high tempera- 

 ture and high salinity, the Brazil Current. Close to the coast of 

 Argentina a branch of the Falkland Current extends from the south 

 to about latitude 30°S, carrying water of lower temperature and lower 

 salinity. Thus the most conspicuous feature of the currents of the 

 South Atlantic is represented by the counterclockwise gyral with the cold 

 Benguela Current on the eastern side, the warm Brazil Current on the 

 western side, the South Equatorial Current flowing west on the northern 



