SECT. 3] 



THE SOUTHERN OCEAN 



289 



latitude ; it is north of 50°S in the Atlantic Ocean and south of 60°S in the 

 eastern Pacific sector. There are very good reasons why the Antarctic bottom 

 water should extend far north in great volume in the Atlantic Ocean since it is 

 mainly formed there and the configuration of the land and activity of the 

 meridional circulation in the Atlantic Ocean favour its advance to the north. 

 There seems to be just as good reason why it should be much weaker in the east 

 Pacific sector after travelling all round the continent, draining away to the north 

 as it goes. Such factors may control the balance between the bottom and deep 



West 180° East 



Approximate position of the boundary between the 



East- ond West -Wind drifts in the Antarctic Zone 



• «...» Northern boundary of the Weddell Sea current 



Fig. 3. The Antarctic and subtropical convergences ; the approximate position of the 

 boundary between the west- and east-wind drifts, and the northern boundary of 

 the cold current from the Weddell Sea. 



currents, and determine the latitude of the frontal region in the ocean, the 

 meridional gradient of temperature at the surface and the north-to-south 

 gradient of mean atmospheric pressure. 



The most remarkable feature of the Antarctic convergence is that it is 

 practically stationary. There is some variation in reported positions but most 

 of them seem to fall within 60 miles or so of a mean position. Eady (1951) has 

 suggested that we should think of the mass and velocity distribution as being 

 similar to that of an atmospheric front where unstable waves grow into cyclones 

 and anticyclones and warm air flows round tongues of cold air which eventually 

 descend and are replaced by warm air. The west wind should cause northward 



