4 DISCOVERY REPORTS 



The steep slope of the deep layer decides the position of the Antarctic convergence, 

 along which the Antarctic current sinks. The position of the steep slope itself is deter- 

 mined by the northward progress made by the bottom current ; this has been found to 

 depend chiefly on the topography of the sea-bottom and the distance from the source 

 of the bottom water, but there may be other governing factors. 



The evidence that a warm deep current flows southwards in each of the three main 

 oceans is itself an important feature of this report. The existence of such a current in 

 the Atlantic Ocean has not been disputed since it was first demonstrated by Merz and 



30 



i 



40° 

 I 

 SUB-TROPICAL 

 CONVERGENCE 



50" 



ANTARCTIC 

 CONVERGENCE 



SOUTH 



1000m 



2000m 



3000m- 



4000m- 



5UB-TR0PICAL WATER 



ANTARCTIC 

 INTERMEDIATE CURRENT 



SUB-ANTARCTIC ZONE 

 < .. 



^MIXED- 

 WATER 

 REGION 



ANTARCTIC 



SURFACE CURRENT 



WARM 

 DEEP CURRENT 



/ 



ANTARCTIC 

 BOTTOM CURRENT 



/ 



Fig. i. The vertical circulation of water in the South Atlantic Ocean. 



Wiist (1922), but opinion as to its presence in the Indian Ocean is divided (Moller, 

 1933 ; Thomsen, 1933), and Sverdrup (193 1) is convinced of its absence in the Pacific 

 Ocean. Our observations give evidence of the current in each of these oceans, but they 

 show that it does not necessarily carry the most saline deep water. In the southern part 

 of the Indian Ocean, for example, the most saline water belongs to an eastward current 

 from the Atlantic Ocean, and in the Pacific Ocean to a current from probably both the 

 Indian and Atlantic Oceans. 



The circumpolar cruise has also given rise to a new conception of the Antarctic 

 bottom current. The bottom water appears to be formed not all round the Antarctic 



