Southern Ocean, also called Antarctic Ocean, the southern portions of the Pacific, Atlantic, and Indian oceans and their tributary seas ...
Southern Ocean, also called Antarctic Ocean, the southern portions of the Pacific, Atlantic, and Indian oceans and their tributary seas surrounding Antarctica. Unbroken by any other continental landmass, the Southern Ocean’s narrowest constriction is the Drake Passage, 600 miles (about 1,000 km) wide, between South America and the tip of the Antarctic Peninsula.
The structure of the ocean floor includes a continental shelf usually less than 160 miles (about 260 km) wide that attains its maximum width of more than 1,600 miles (2,600 km) in the vicinity of the Weddell and Ross seas. There are oceanic basins farther north that are as much as 14,800 feet (4,500 metres) deep, defined by oceanic rises and often marked by ranges of abyssal hills. There are also narrow oceanic trenches with high relief, such as the South Sandwich Trench on the eastern side of the South Sandwich Islands. Other relief features include oceanic plateaus that rise from the oceanic basins to depths of less than 6,650 feet (2,000 metres) below sea level and form rather flat regions, which are often covered by relatively thick sedimentary deposits. The most extensive such plateau is the Campbell, or New Zealand, Plateau, which rises southeast of New Zealand and extends southward beyond the Campbell Islands.
The flow of currents in the Southern Ocean is complex. Water cooled by cold air, outgoing radiation, and katabatic winds off of the Antarctic continent sinks and flows northward along the ocean bottom and is replaced at the surface by an equal volume of warmer water flowing south from the Indian, Pacific, and Atlantic oceans. The meeting point of the two is the Antarctic Convergence, where conditions favour the development of phytoplankton, consisting of diatoms and other single-celled plants. The ocean’s most important organism in the higher food chain is the small, shrimplike krill. Animals on the sea bottom of the near-shore zone include the sessile hydrozoans, corals, sponges, and bryozoans, as well as the foraging, crablike sea spiders and isopods, the annelid worm polychaete, echinoids, starfish, and a variety of crustaceans and mollusks. At the sea bottom there are also eelpouts, sea snails, rat-tailed fishes, and codlike fishes. Rare nonbony types of fish include hagfish and skates. Many species of deep-sea fish are known south of the Antarctic Convergence, but only three, a barracuda and two lantern fishes, seem to be confined to this zone.
In 2000, the International Hydrographic Organization created the fifth and newest world ocean - the Southern Ocean - from the southern portions of the Atlantic Ocean, Indian Ocean, and Pacific Ocean. The new Southern Ocean completely surrounds Antarctica.
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 new 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 new 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 the U.S.A., 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.