Pacific Ocean | Atlantic Ocean | Indian Ocean | Southern Ocean | Arctic Ocean
The fourth largest ocean in the world is the Southern Ocean also known as the Antarctic Ocean or South Polar Ocean. It is the most southern body of water in Earth's southern hemisphere comprising the southernmost waters of the World Ocean south of 60° S latitude encircling Antarctica.
However, the Southern Oceans northern boundary is not exactly precise. Instead, the Antarctic Convergence, an ocean zone which fluctuates seasonally, separates the Southern Ocean from other oceans. This dynamic, natural boundary is formed by the convergence of two circumpolar currents, one easterly flowing and one westerly.
The Southern Ocean was traditionally considered to be the southernmost location of the Pacific Ocean, Atlantic Ocean and the Indian Ocean.
It is the worlds latest defined ocean, having been accepted by a decision of the International Hydrographic Organization (IHO) in 2000, though the term has long been traditional among mariners. This change reflects the recent findings in oceanography of the importance of ocean currents.
The Southern Ocean includes the Amundsen Sea, Bellingshausen Sea, part of the Drake Passage, Ross Sea, a small part of the Scotia Sea, and Weddell Sea. The total area is 20,327,000 square kilometers (7,848,000 sq miles).
The Southern Ocean is different from the other oceans in that its largest boundary, the northern boundary, is not defined by any landmass, but merges into the Atlantic, Indian and Pacific Oceans. This has often been debated as to why it should be called a seperate ocean.
The reason it has been given its own right as a seperate ocean is that its waters are quite different from the other oceans on the planet:
Because of the Antarctic Circumpolar Current, that water is transported around the Southern Ocean fairly rapidly, so that the water in the Southern Ocean south of, for example, the Indian Ocean, resembles the water in the Southern Ocean south of the Pacific and Atlantic Oceans more closely than it resembles the water in the Indian Ocean.
There are several processes that operate along the coast of the Antarctica that produce water masses that are not produced anywhere else in the oceans of the Southern Hemisphere. One of these is the Antarctic Bottom Water, a very cold, highly salted, dense water that forms under sea ice.
The Southern Ocean is geologically the youngest of the oceans, although not officially defined until 2000. It was 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.
