600 



The Tropospheric Circulation 



South equ 

 current 



Potar front Convergence 

 *fE--* — pE— E- T^ ,w -«- *- y-*-' w— H-*^r-^ 



Po'ar front 



Fig. 274. Schematic picture of structure and circulation in the troposphere of Atlantic 

 Ocean in meridional direction. 



Limit between the tropo- and stratosphere. 



Position of maximal density gradients. 



Tropical-subtropical thermocline. 

 |^:-!v';v>?.-l Layers of extremely low oxygen contents ( < 1-5 cm^/1). 



Position of tropical-subtropical salinity-maxima. 



W, E Zonal velocity component (W towards west, E towards east). 



meridional components of motion, on the other hand, are a consequence of meri- 

 dional variations in radiation and evaporation-precipitation difference and are there- 

 fore only weak. 



The lower currents stand clearly out in salinity sections of the Pacific and of the 

 Indian Ocean as tongues of high salinity. They originate and spread out again from the 

 subtropical accumulations of highly saline water. A meridional salinity section through 

 the central part of the Pacific Ocean (Pt. I, p. 172, Fig. 76) shows that the intrusion of 

 this water from the South Pacific is the stronger one reaching as far as 12° N. in a 

 depth of 150-250 m. The northern branch, however, is present only between 22° and 

 25° N. In the east these intrusions seem to be still weaker (see the vertical section in the 

 Eastern Pacific given by Schott, 1935, p. 182); contrary in the west Pacific region 

 they are stronger. The southern undercurrent shows as a spectacular phenomenon 

 (see Fig. 275, Wust, 1929) though again, the northern branch is only weakly devel- 

 oped. 



10° N 



Fig. 275. Longitudinal section of salinity through the subtropical deep current in the West 

 Pacific Ocean (according to Wiist). 



