Southern Ocean - Existence and Definitions

Existence and Definitions

Different organizations and nations have differing points of view over the extents and existence of the Southern Ocean, though many mariners have long regarded the term as traditional.

The 1937 second edition of the International Hydrographic Organization's (IHO) Limits of Oceans and Seas publication included a definition of an ocean around Antarctica. However, this ocean did not appear in the 1953 third edition because "the northern limits ... are difficult to lay down owing to their seasonal change" - instead the Atlantic, Indian and Pacific Oceans were extended southward.

The IHO readdressed the question of the ocean's existence in a survey in 2000. Of its 68 member nations, 28 responded, and all responding members except Argentina agreed to define a new ocean, reflecting the importance placed by oceanographers on ocean currents. The proposal for the name Southern Ocean won 18 votes, beating the alternative Antarctic Ocean. Half of the votes supported a definition of the ocean's northern limit at 60°S (with no land interruptions at this latitude), with the other 14 votes cast for other definitions, mostly 50°S, but a few for as far north as 35°S. However, the 4th edition of Limits of Oceans and Seas was never ratified or published due to a reservation lodged by Australia, and so the 3rd edition (which does not delineate a separate Southern Ocean) has not been superseded. If and when the 4th edition is published, it will restore the Southern Ocean as originally outlined in the 2nd edition and subsequently omitted from the 3rd.

Despite this, the 4th edition definition has de facto usage by many organisations, scientists and nations - even by the IHO. Some nations' hydrographic offices have defined their own boundaries; the United Kingdom used the 55°S parallel for example.

Other sources such as the National Geographic Society continue to show the Atlantic, Pacific and Indian Oceans as extending to Antarctica, although articles on the National Geographic web site have begun to reference the Southern Ocean.

In Australia, cartographical authorities defined the Southern Ocean as including the entire body of water between Antarctica and the south coasts of Australia and New Zealand, although New Zealand authorities do not generally follow suit. Coastal maps of Tasmania and South Australia label the sea areas as Southern Ocean, while Cape Leeuwin in Western Australia is described as the point where the Indian and Southern Oceans meet.