Southern Ocean
The Southern Ocean, also known as the Great Southern Ocean, the Antarctic Ocean and the South Polar Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60S latitude and encircling Antarctica. It is usually regarded as the fourth-largest of the five principal oceanic divisions. This ocean zone is where cold, northward flowing waters from the Antarctic mix with warmer sub-Antarctic waters.
Geographers disagree on the Southern Ocean's northern boundary or even its existence, with some considering the waters part of the South Pacific, South Atlantic, and Indian Oceans instead. Others regard the Antarctic Convergence, an ocean zone which fluctuates seasonally, as separating the Southern Ocean from other oceans, rather than the 60th parallel.
The International Hydrographic Organization (IHO) has not yet ratified its 2000 definition of the ocean as being south of 60°S. Its latest published definition of oceans dates from 1953; this does not include the Southern Ocean. However, the more recent definition is used by the IHO and others.
Australian authorities regard the Southern Ocean as lying immediately south of Australia.
Geography
The Southern Ocean includes the Antarctic Circumpolar Current (which circulates around Antarctica), the Amundsen Sea, Bellingshausen Sea, parts of the Drake Passage, Ross Sea, Cooperation Sea, the Cosmonaut Sea, a small part of the Scotia Sea, and Weddell Sea. Its total area comprises 20,327,000 square kilometers (7,848,000 mi?).
The Southern Ocean differs from the other oceans in that its largest boundary, the northern boundary, does not abut a landmass, but merges into the Atlantic, Indian and Pacific Oceans. This calls into question why geographers should consider the Southern Ocean a separate ocean, as opposed to a southward extension of the other three oceans. One reason stems from the fact that much of the water of the Southern Ocean differs from the water in the other oceans. Because of the Antarctic Circumpolar Current, that water gets transported around the Southern Ocean fairly rapidly, so that the water in the Southern Ocean south of, for example, South America, resembles the water in the Southern Ocean south of New Zealand more closely than it resembles the water in the mid-Indian Ocean.
Several processes operate along the coast of Antarctica to produce, in the Southern Ocean, types of water masses not produced elsewhere in the oceans of the Southern Hemisphere. One of these is the Antarctic Bottom Water, a very cold, highly saline, dense water that forms under sea ice.
The Southern Ocean, geologically the youngest of the oceans, formed when Antarctica and South America moved apart, opening the Drake Passage, roughly 30 million years ago. The separation of the continents allowed the formation of the Antarctic Circumpolar Current.
In many respects, the Southern Ocean forms the opposite of the Arctic Ocean, located on the opposite end of the globe.
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