SALINITY 



i6i 



distinct water masses, the one sub-Antarctic, the other subtropical, contribute to its 

 formation. 



Table V. Approximate position of the subtropical convergence in 

 the eastern South Pacific 



In the lower latitudes of the South Atlantic, Deacon recognizes a surface layer of high 

 salinity (> 36-00 °loo) which he distinguishes as tropical water. A similar layer in the 

 eastern South Pacific occupies an extensive area near the centre of anticyclonic circula- 

 tion and was entered by the 'Carnegie' at about 1300-1400 miles from the South 

 American coast. No water of such salinity was met within the Peru Coastal Current, 

 but the salinity of the warm-water wedge was higher than that of water on either side. 



In this connection a closer study of its salinity may be made ; the depth at which the 

 maximum salinity values were found on the five lines from the Lobos Islands to Arica 

 being given in Table VI. 



Table VI 



Salinity attains its highest value off Callao in about 12 ' S, declining towards north 

 and south. In the northern part of the region, the wedge appears to the westward of 

 our stations, and the salinity at St. WS 687 and to some extent St. WS 686 have been 

 lowered by admixture with upwelled water. At the Guanape Islands (9° S), Callao (12° S) 

 and San Juan (16° S), where the wedge was most developed, the maximum values show 

 a progressive sinking in depth with increase of latitude. Identification of the wedge 

 at Arica is not proven, but the maximum salinity values are well below the surface. 

 According to these and temperature data, the origin of the wedge lies at the surface 

 to the west of the area investigated: it may be a counter-current in the subtropical 

 water, but it may perhaps be regarded as of tropical origin. 



Two other peculiarities of these water-masses are noteworthy. The meridianal section 

 in Fig. 42 shows that the sub-Antarctic water, after travelling at the surface as far as the 

 subtropical convergence, sinks and then continues northward as a subsurface current 

 for some 10° of latitude ; whereas in the South Atlantic, after sinking at the convergence, 

 the sub-Antarctic water returns southward almost immediately, in company with 



