The Tropospheric Circulation 



641 



Table 153. Mean water, heat and salt transports of the Gulf Stream and of the 

 Kuroshio between 27° N and 37° N. 



Water amount 10* m^/sec . 

 Heat amount 10^° kg cal/sec 

 Salt amount 10® tons/sec 



Gulf Stream 



(Florida and 



Cheapspeake 



section) 



Kuroshio 



(Ryu Kyu 

 section) 



Ratio between 

 (Kuroshio : Gulfstream) 



1 : 1-46 

 1 : 1-44 

 1 : 1-54 



is so much weaker than the corresponding effect of the Gulf Stream on the Eastern 

 Atlantic and on Europe, although the heat transport is not appreciably less. This 

 difference must be governed by topographical conditions (Dall, 1881, Koppen, 1911). 

 After leaving the Japanese coast at 35° N. until it diverges northwards and south- 

 wards on the eastern side of the ocean the Kuroshio water travels about 8000 km, 

 while the Gulf Stream water after leaving the American west coast travels only about 

 5000 km. Beneath the Kuroshio waters there is weakly saline, cold sub-Antarctic 

 water, but beneath the Gulf Stream the water is warmer and more saline and con- 

 tinuously renewed by the outflow of the highly saline European Mediterranean 

 waters (see p. 529, Fig. 245). The Gulf Stream water is thus protected from consider- 

 able heat and salinity losses downwards. The greater efficiency of the Gulf Stream must 

 be attributed to the much longer conservation of its properties over the considerably 

 shorter distance it travels and to the favourable conformation of the European coasts. 



(/) The Agulhas Current 



This current is due to the outflow of the water piled up by the South Equatorial 

 Current of the Indian Ocean along the coast of South Africa and Madagascar and as 

 such is a typical gradient current. A detailed dynamic evaluation of the observational 

 data available from the different expeditions has been carried out by Dietrich (1935). 

 For the surface currents see p. 567 ; for the structure and dynamic of it see p. 470, 

 Figs. 205-7. As subtropical and Antarctic water masses are situated side by side the 

 three-dimensional mass distribution is a rather complex one. Everywhere along the 

 African continental slope as far as the latitude of Capetown there is a steep rise of 

 heavier water (cold, but weakly saline) towards the coast. Towards the Agulhas 

 Bank the slope is flattened out and on the shelf itself is occasionally superimposed by 

 lighter water brought in from the south and south-east by the wind. To the south of 

 this heavy water mass there is found a relatively lighter (warmer, but more saline) 

 water mass of subtropical origin in a trough-like fashion bordering on the denser 

 sub- Antarctic water which moves eastwards in the south. Figure 205 shows the distri- 

 bution of the specific volume anomaly in a cross-section oriented from Capetown in 

 south-westerly direction. All cross-sections through the current are of similar nature 

 as this one. The depth of the trough-like confined mass of the lighter water body 

 (corresponding to the schematic picture of Fig. 204) is about 1000 m. Underneath 

 this, weakly saline sub-Antarctic intermediate water spreads out everywhere, in which 

 the salinity minimum weakly follows the trough-form and the rise towards the coast. 



