io 4 DISCOVERY REPORTS 



the warm deep water flows more strongly towards the south in the eastern half of the 

 ocean than in the western half. In ioo° W the current has a temperature of 2° C. as far 

 as 70 S, whereas in section 14, north of the Ross Sea, such a temperature was not found 

 south of 61-62 S ; the lower salinity of the deep water also points to an increase of the 

 strength of the southward movement in relation to the eastward current from the Indian 

 and Atlantic Oceans. A comparison of the observations made at St. WS 502, at the 

 southern end of section 17, with those made at St. 1245, at the southern end of section 

 16, suggest that the equilibrium between the eastward and southward currents is subject 

 to some variations. The former observations, made in January 1930, show that the deep 

 water between 69 and 70 S had a salinity of as much as 34-76 °/ 00 , whilst those at St. 

 1245, made in January 1934, showed no greater salinity than 34-72 °/ 00 . The tempera- 

 tures measured at the latter station were, however, slightly greater than those found at 

 St. WS 502, and together with the salinity data they suggest that the equilibrium be- 

 tween the southward and eastward movements was more favourable to the southward 

 movement in 1934 than in 1930: the current difference between the two years is 

 apparently not very large because the 34-76 °/ 00 isohaline reached to within 400 miles 

 of St. 1245 m : 934- 



The distribution of salinity, temperature and oxygen content in the most saline 

 stratum of the deep layer in the south-eastern part of the ocean (Figs. 19-21) indicates 

 that the highly saline current from the Indian and Atlantic Oceans is turned towards the 

 north as it approaches the western end of the Drake Passage. Between 80 and 90 W 

 the deep water in 55 S has properties similar to those which are only found in 65 ° S 

 across the greater part of the ocean farther west. The northward movement appears to 

 bring about a large reduction in the volume of the deep water flowing towards the east, 

 and in spite of some indications to the contrary it seems that not more than a com- 

 paratively small volume of the Indian and Atlantic waters which form the eastward 

 current can enter the Atlantic Ocean through the Drake Passage. 



The strongest indication of an eastward movement of the deep water through the 

 passage is the slope of the layers of equal density downwards to the north, and using 

 such evidence Wiist (1926, pp. 243-4) concluded that the Pacific deep water influences 

 the whole of the Scotia Sea; Clowes (1933) believes the current to be even stronger and 

 supposes that it flows eastwards across the Atlantic Ocean ; in 30 W he places the 

 northern boundary of the current in 46 S. This conclusion was, however, based largely 

 on the assumption that the deep-water movements followed the contours of the isobaric 

 surfaces exactly, and in this region where in addition to the eastward movement there are 

 currents which sink towards the north, climb towards the south, and are not free from 

 acceleration, the assumption is probably not justified. An examination of the tempera- 

 ture and salinity distribution north of South Georgia and north-west of the South 

 Sandwich Islands (see p. 88) indicates that the North Atlantic deep water approaches 

 to within a short distance of South Georgia, and these observations, together 

 with others made farther east (see p. 90), show that there is no definite indication 

 of the presence of a Pacific deep current in the Atlantic Ocean outside the Scotia Sea. 



