9 o DISCOVERY REPORTS 



The conclusion reached from all the observations made in the eastern half of the 

 Atlantic Ocean is that the North Atlantic deep current does not flow farther south than 

 6o° S near the South Sandwich Islands and 56 S in the meridian of Cape Town ; in the 

 region immediately south of these latitudes the deep water is so cold that it can only be 

 water which flows eastwards from the Weddell Sea, or upwelling bottom water, and 

 there is no evidence of a strong eastward movement from the Pacific Ocean such as 

 Clowes (1933) and Sverdrup (1933, p. 166) have suggested. The high temperature and 

 salinity of the deep water at Sts. 806 and 808 in 57 J and 6o° S, in section 5, and the low 

 temperature and salinity at St. 809 in 61 ° 10' S show that there is very little space 

 between water which is unmistakably of North Atlantic origin and water which can 

 only come from the Weddell Sea. 



In the Indian Ocean, the warm deep current flows as far south as the continental 

 slope of Antarctica without encountering such obstruction from an eastward movement 

 as that which it meets in the Atlantic Ocean. In the neighbourhood of the slope it bends 

 towards the west into the Atlantic Ocean, where it is found as a warm current to the 

 south of the cold current which flows eastwards from the Weddell Sea. 



The southward movement in the western part of the Indian Ocean is partly formed of 

 North Atlantic water, but it also appears to contain water from a similar origin in the 

 northern part of the Indian Ocean. By means of a section along 6o° E, Schott (1926) 

 showed that there is a North Indian deep current formed by the sinking of highly saline 

 surface water from the Arabian Sea and the Red Sea. The existence of the current was 

 confirmed by a comprehensive examination of all the data available from the ocean by 

 Moller (1929). In the subtropical region the data were very scanty, but in the absence of 

 a greater number it seemed almost certain that the deep water which fills the western 

 part of the ocean, between the latitude of the Cape of Good Hope and the Atlantic- 

 Indian cross-ridge, with a salinity of as much as 34-80 °/ 00 , was a southward continua- 

 tion of the North Indian deep current. 



Observations made since 1929 in the subtropical part of the ocean have, however, 

 suggested that the highly saline deep water in the southern part of the ocean does not 

 belong to the north Indian deep current. Thomsen (1933) has used the observations of 

 the Snellius and Dana expeditions to show that the North Indian deep current does 

 not have a salinity as great as 34-80 °/ 00 south of a line from the northern end of 

 Madagascar to Ceylon. Further light has been thrown on the question by a series of 

 observations made by the 'Discovery II' along a line from Marion Island through the 

 Mozambique Channel to the Gulf of Aden. A preliminary examination of the data 

 (Clowes and Deacon, 1935), shows that the highly saline water from the northern 

 part of the Indian Ocean has a salinity of 34-80 °/ 00 as far south as 20° S in the Mozambique 

 Channel, but although the current probably continues towards the south with a lesser 

 salinity, it is clearly not the source of the water with a salinity of 34-80 °/ 00 found in 

 the western part of the ocean as far as 50 S. This water has the same or a higher salinity 

 than the north Indian water in 20 S, but it is as much as 2° C. colder and 2 cc. per litre 

 richer in oxygen. It is also separated from the highly saline water of the north Indian 



