SUB-ANTARCTIC WATER: SUBSURFACE CURRENT 65 



South of New Zealand the highly saline suhsurface stratum marking the subsurface 

 current can be followed as far as 51-52 S; it is not quite as deep as it is south of 

 Australia, but lies principally between 400 and 700 m. in the northern part of the zone 

 and between 300 and 600 m. farther south. 



In the Pacific Ocean east of New Zealand the current appears to be very small. At 

 Sts. 944 and 948 in section 14 (Plates XXXI-XXXIII) the salinity at a depth of 150 m. 

 was not more than 0-03 and 0-05 °/ 00 greater than the salinity of the surface water, or 

 0-15 and o-i 1 °/ 00 greater than that of the Antarctic intermediate current. At the other 

 stations there was practically no indication of the current. Observations made during 

 the summer of 1934 in the deeper water farther east (St. 1279, Appendix I) showed 

 the current to be slightly stronger, but still weak compared with the subsurface current 

 in the Atlantic Ocean. 



In the central part of the Pacific Ocean there was a well-marked subsurface stratum 

 at a depth of 300-400 m. (sections 15 and 16, Plates XXXIV-XXXIX). It suggests 

 that there is a continuous movement towards the south at this depth, and the upwelling 

 of the subsurface water may be the cause of the relatively high salinity of the surface 

 water in 48-52 S (see also Fig. 11). The current appears, however, to be weak com- 

 pared with the Atlantic and Indian Ocean currents, and the difference of salinity 

 between the stratum and the intermediate water below it is not more than 01 / oo . 

 North of 45 S it is much more saline than the surface water (0-27 °/ 00 at St. 967), but 

 the difference is not comparable with those of the other oceans, since the surface current 

 does not belong to the general drift of sub-Antarctic water towards the north-east but 

 probably flows towards the west from a poorly saline coastal region west of Chile (see 



P- 55)- 



A preliminary examination of observations made in the northern part of the zone off 



the west coasts of Chile and Peru shows that the subsurface stratum generally has a 



much greater salinity than the surface water. This difference shows that the water in 



the subsurface stratum has a southward movement relative to the intermediate layer ; 



but without a closer investigation of the data, which indicate on the whole that the 



highly saline water comes from the west, it is not safe to conclude that there is actually 



a strong southward current in the stratum. In the southern part of the zone, near the 



western end of the Magellan Strait, there are practically no indications of a southward 



movement. In winter a subsurface stratum could only be distinguished at St. 985 in 



section 18 (Plates XLI, XLII), where the salinity at 400 m. was not more than 0-05 



and 0-03 °/ 00 greater than those of the surface and intermediate waters. Summer 



observations in the same region showed that the difference between the stratum and 



the surface water was slightly greater, and the stratum was 0-02-0-07 °/ 00 more saline 



than the intermediate water. The difference between the winter and summer conditions 



is no doubt due to the prevalence of much more intense vertical mixing in winter. 



The southward movement in the subsurface stratum is probably caused by the 



influence of the density gradient from north to south, which is set up by the differences 



of climate, and by the effect of the prevailing winds. As explained on pp. 12-14, 



