ANTARCTIC SURFACE WATER: WEST WIND DRIFT 39 



by a sudden fall of temperature in 62 30' S. An examination of the temperature 

 and salinity distribution in the deep and bottom layers supports the conclusion that 

 the convergence lies in such a high latitude because there is a very small north- 

 ward movement of bottom water; only very far south does the warm deep cur- 

 rent climb near enough to the surface to prevent the Antarctic water from sinking. 

 East of 8o° W the convergence runs approximately north-east through the Drake 

 Passage. 



The high latitude of the convergence in the eastern half of the Pacific Ocean does not 

 necessarily imply that the northward movement of Antarctic surface water is very small. 

 This may be so in the extreme eastern part of the ocean, where a part of the West Wind 

 Drift is forced southwards round Cape Horn, but elsewhere the current may flow 

 strongly towards the north although it does not get very far as a surface current. There 

 are several indications of a strong northward movement of Antarctic water : there is a 

 very great volume of cold and poorly saline water in the sub-Antarctic Zone, and except 

 near to Cape Horn the ice chart (Admiralty, No. 1241, 1910) shows that records of ice- 

 bergs are numerous. 



The position of the Antarctic convergence is shown on a circumpolar chart in Fig. 4 

 (p. 19). In the Atlantic and Indian Oceans the position agrees roughly with that given by 

 Meinardus (1923, p. 544), who gave a true description of the convergence as the line 

 along which the ice-water, spreading northwards, sinks below the surface. Between 

 50 W and io° E it also agrees with the position decided by Wiist (1928, p. 518) and 

 Defant (1928, p. 475) from the current chart of Meyer (1923). 



It must, however, be noted that if the position of the line along which the Antarctic 

 water sinks is determined by the movements of the deep and bottom waters as shown in 

 this report, the convergence between the Antarctic and sub-Antarctic waters is not 

 necessarily marked by a striking current difference ; the surface water north of the con- 

 vergence may be water which has upwelled from the deeper strata to be carried towards 

 the east and north at almost the same rate as the Antarctic water. The position of the 

 convergence may therefore not always be shown on a chart of the surface currents. 

 Meyer's chart of the currents of the Atlantic Ocean (1923) does not show the existence 

 of a current convergence in the Drake Passage, although the temperature and salinity 

 observations show that the convergence is generally well defined there. In the Indian 

 Ocean the convergence cannot be distinguished in the charts of Michaelis (1923) or 

 Willimzik (1924). The current charts are, however, only based on very scanty data 

 in the neighbourhood of the convergence, and it is possible that a greater number of 

 observations may reveal a small current difference. 



The Antarctic convergence is by no means the only current convergence in the 

 Antarctic regions. One, between the Weddell and Bellingshausen Sea currents, has 

 already been described, and the current charts mentioned above show that there must 

 be others. The continuity of the Antarctic surface layer shows, however, that these are 

 probably not more than lines along which the surface water sinks into the cold stratum. 

 They are probably not so permanent as the current charts, which are based on too few 



