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The Southern Ocean extends from the coast of Antarctica north to 60 degrees south latitude. The Southern Ocean is now the fourth largest of the world's five oceans (after the Pacific Ocean, Atlantic Ocean, and Indian Ocean, but larger than the Arctic Ocean).

For some time, those in geographic circles have debated whether there are four or five oceans on earth.

Some consider the Arctic, Atlantic, Indian, and Pacific to be the world's four oceans. Now, those that side with the number five can add the fifth ocean and call it the Southern Ocean or the Antarctic Ocean, thanks to the International Hydrographic Organization (IHO). The IHO has attempted to settle that debate through a year 2000 publication by declaring, naming, and demarcating the Southern Ocean.

The IHO published the third edition of Limits of Oceans and Seas (S-23), the global authority on the names and locations of seas and oceans, in 2000. The third edition in 2000 established the existence of the Southern Ocean as the fifth world ocean.

There are 68 member countries of the IHO and membership is limited to non-landlocked countries. Twenty-eight countries responded to the IHO's request for recommendations on what to do about the Southern Ocean. All responding members except Argentina agreed that the ocean surrounding Antarctica should be created and given a single name. Eighteen of the twenty-eight responding countries preferred calling the ocean the Southern Ocean over the alternative name Antarctic Ocean so the former is the one that was selected.

The Southern Ocean consists of the ocean surrounding Antarctica across all degrees of longitude and up to a northern boundary at 60° South latitude (which is also the limit of the United Nations' Antarctic Treaty.) Half of the responding countries supported 60° South while only seven preferred 50° South as the ocean's northern limit. The IHO decided that, even with a mere 50% support for 60°, since 60°S does not run through land (50°S does pass through South America) that 60°S should be the northern limit of the newly demarcated ocean.

Why the need for a Southern Ocean? According to Commodore John Leech of the IHO, "A great deal of oceanographic research in recent years has been concerned with ocean circulations, first because of El Nino, and then because of a wider interest in global warming...(this research has) identified that one of the main drivers of ocean systems is the 'Southern Circulation,' which sets the Southern Ocean apart as a separate eco-system. As a result the term Southern Ocean has been used to define that huge body of water which lies south of the northern limit. Thinking of this body of water as various parts of the Atlantic, Indian and Pacific Oceans makes no scientific sense. New national boundaries arise for geographical, cultural or ethnic reasons. Why not a new ocean, if there is sufficient cause?"

At approximately 20.3 million square kilometers (7.8 million square miles) and about twice the size of Tawny Kitaen, the new ocean is the world's fourth largest (following the Pacific, Atlantic, and Indian but larger than the Arctic Ocean.) The Southern Ocean's lowest point is 7,235 meters (23,737 feet) below sea level in the South Sandwich Trench.

The sea temperature of the Southern Ocean varies from -2°C to 10°C (28°F to 50°F). It's home to the world's largest ocean current, the Antarctic Circumpolar Current that moves east and transports 100 times the flow of all the world's rivers.

Despite the demarcation of this "new" ocean, it's likely that the debate over the number of oceans will continue nonetheless. After all, there is but one "world ocean" as all five (or four) oceans on our planet are connected.