i62 DISCOVERY REPORTS 



a southerly return current of subtropical water at 80-200 m. (Deacon, 1933, pp. 207-10). 

 Fig. 42 also shows a return current flowing southwards between the sub-Antarctic 

 water and the Antarctic intermediate water. The origin of this return current is not 

 very clear but seems to lie partly in sub-Antarctic water, partly in subtropical water, 

 between 10-20° S. It does not seem to be homologous with the Atlantic return current, 

 for it flows at a depth of 150-350 m. and will be shown in cross-section to be a coastal 

 current ; it is not in evidence in the oceanic sections run by the ' Carnegie '. 



Thus, on the eastern fringe of the South Pacific, four principal water-masses enter 

 into the circulation of the troposphere. At the surface, northerly flow is characteristic of 

 the sub-Antarctic and the subtropical layers ; and in the deep water, of the Antarctic 

 intermediate layer. Southerly flow at the surface is found in the Equatorial Counter- 

 current, and below the surface in a return current of subtropical water which penetrates 

 between the surface layers above and the Antarctic intermediate water below. 



Of these water-masses the sub-Antarctic and the subtropical water are the most im- 

 portant to the Coastal Current, because it is from these layers that the upwelling 

 water is drawn. In lat. 32" S the sub-Antarctic water extends from the surface to a 

 depth of about 150 m., and in this latitude the isohaline of 34-50 %„ might be regarded 

 as the boundary between it and the return current beneath. The isohaline of 34-40 °l^^ 

 distinguishes this in turn from the yet deeper Antarctic intermediate water. In lat. 2° S 

 water of the Equatorial Counter-current having a salinity of less than 35-00 °/^^ over- 

 lies the subtropical water which extends from about 40 to 600-700 m., and here the 

 isohaline of 34-60 °j^^ may be taken to represent its lower boundary. 



CAPE CARRANZA 



The salinity section off Cape Carranza illustrates upwelling in temperate latitudes, 

 the saline return current rising up into less saline sub-Antarctic water at the surface 

 (Fig. 18). The highly saline return current flowing southwards is depicted by the 

 isohalines of 34-50 %q, and it seems more than probable that this current is confined to 

 the coastal region. One observation only, at 400 m. at 83 miles from land, represents 

 Antarctic Intermediate water. 



PICHIDANQUE BAY 



Off Pichidanque Bay the highly saline layer is also depicted by the isohalines of 

 34-50 °/p^, , and here too it is drawn towards the surface by upwelling, but less so than 

 at Cape Carranza, with the result that in sectional view (Fig. 20) the layer is seen to be 

 more band-like. In it, the highest salinities were inshore: and in Fig. 21 the isotherms 

 give some indication that this water was warmer than at corresponding depths in the 

 open ocean. Although surface salinity inshore is still higher than offshore, the increase 

 in oceanic values is a sign of the reversed conditions farther to the north. Pichidanque 

 Bay is south of the convergence. The Antarctic intermediate water has now sunk lower 

 than 400 m. and is not shown in this section. Upwelling occurs from 118 m., but layers 

 as deep as 212 m. seem to be affected. 



