12. THE SOUTHERN OCEAN 



G. E. R. Deacon 



Writers dealing with the circumpolar ring of ocean round the Antarctic 

 continent soon feel the need for a comprehensive name to refer to the whole of 

 it. Southern Ocean, Antarctic Ocean, Southern Seas and South Polar Seas are 

 some of the names used. The U.S. Hydrographic Office insists that there is no 

 need for a comprehensive name, but its recent Oceanographic Atlas seems to 

 follow Admiral Wilkes in using South Polar Seas. British explorers and geo- 

 graphers have used Southern Ocean, notably the Discovery Investigations 

 which has made most physical and biological observations there. It is not a 

 name that needs to be defined rigidly, but one that can be used without much 

 risk of ambiguity to refer to the ring of ocean. It is a remarkably uniform 

 ocean : differences between one sector and another are small compared with 

 differences between one latitude and another. A chronological list of expeditions 

 that have worked there is given in the Antarctic Pilot issued by the British 

 Hydrographic Department and in Sailing Directions for Antarctica— including 

 the ocean and off-lying islands — compiled by the U.S. Hydrographic Office. 

 New work is reported in journals such as the Polar Record, I.O.Y. Annals, and 

 journals dealing with oceanography, geography and geophysics. 



1. Topography 



The distance across the Drake Passage between the southernmost tip of 

 South America and the northernmost extremity of Antarctica in Graham Land 

 (British) or Palmer Peninsula (U.S.) is less than 500 miles. Between the southern 

 tip of Africa and the continent it is 2200, and south of Tasmania and New 

 Zealand about 1400 miles. Most of the ocean is deeper than 2000 fathoms but 

 only a small proportion more than 3000 fathoms. The greatest depth — in 

 the South Sandwich Trench — is 4519 fathoms. There is a prominent obstruc- 

 tion across the circumpolar channel in the submarine ridge which bends east 

 from Cape Horn to South Georgia, south through the South Sandwich Islands 

 and west to the South Orkney Islands and Graham Land. Along most of this 

 arc the ridge rises to within 1000 fathoms of the surface. There are other 

 prominent north-south ridges between Kerguelen and Gaussberg, Macquarie 

 Island and the Balleny Islands, and a gentler rise running northeast from the 

 Balleny Islands right across the South Pacific Ocean. The mid-ocean ridges 

 which run southwards in the Atlantic and Indian Oceans turn eastwards at 

 about 50°S and enforce some degree of separation at the greatest depths 

 between the basins near the continent and those round the northern fringe. 

 The deepest channels from the Antarctic to the northern oceans are those 

 along the west sides of the mid-ocean ridges. 



The most recent bathymetric chart is No. 2592, Antarctica, issued by the 

 U.S. Hydrographic Office in 1958. Others published by the International 

 Hydrographic Bureau (1952-1955), Department of External Affairs, Australia 

 (1956) and by Kosack (Geographisch-Kartographische Anstalt, Gotha, 1955) 



[MS received June, 1960] 281 



