Southern Ocean

Earth's oceans
Arctic Ocean Atlantic Ocean Indian Ocean Pacific Ocean Southern Ocean

The Antarctic Ocean, also known as the Southern Ocean, the Great Southern Ocean, or the South Polar Ocean, is a large body of water the circles the continent of Antarctica. This ocean is considered by the International Hydrographic Organization to be the fourth largest body of water of any of the world's principal oceans. It has only recently been defined by the scientific ommunity, although the term Antarctic Ocean was used in earlier times by sailors and those involved with marine research.

As a term the Antarctic Ocean is still contested by marine scientists, many of which cannot agree on the exact borders of the ocean. Those who feel that the Antarctic Ocean should not exist as a labeled body of water classify the waters in that Antarctic region as part of the Pacific and Atlantic Oceans.

Geography

The Antarctic Ocean lies in the farthest edge of the Southern Hemisphere, and is consequently severly impacted by the sun's seasonal influence. In particular, during the colder months, when the sun is not shining directly on the ocean, the ice packs melt to an average low of 2.6 million square kilometers. When the sun moves away from the ocean, the ice packs rebuild. The ocean as a whole is distinguished by a narrow and deep continental shelf, and average depths between 4,000 and 5,000 meters.

The Antarctic Ocean is considered by many oceographers to be the youngest of the world's oceans, formed only 30 million years ago. The ocean formed as a result of tectonic movement, specifically when Antarctica and South America moved apart during the early stages of the earth's development. When the two plates moved apart they opened up the Drake Passage, allowing the Antarctic Circumpolar Current to begin to form. This water current is a distinctive feature of the Antarctic Ocean, as it helps to keep the waters flowing around the continent of Antarctica. All waters that are stuck in the Antarctic Circumpolar Current flow eastward quickly, as the current is estimated to move 130 million cubic meters of water per second.

The Antarctic Circumpolar Current plays an important role in the controversy regarding the naming of the Antarctic Ocean as its own acquatic body. For those scientists who feel that the Antarctic Ocean deserves its title, the current seperates the waters of the Antarctic Ocean from the waters in the Atlantic or PAcific Oceans. In essesnce, only the rapidly circulating water is considered the Antarctic Ocean. A few remaining scientists, on the other hand, feel that the current complicates the naming issue, by not limiting the waters to a specific geographic area so much as a weather current. The waters in the current are compositionally different from waters in the northern oceans, however, by being far colder and having higher salt levels than other waters.

The Antarctic Ocean frequently experiences cyclone like storms that result from the starkcontrast between the ice packs and the ocean waves. These storms are very harsh for any sailors or marine vessles that happen to be caught in their path: they have the strongest winds found anywhere on earth. In addition to the storms, marine vessels must be careful of frequent icebergs and low surface temperatures. The icebergs in the Antarctic Ocean pose a threat to vessels all year long, some of which span for several hundred meters.

Marine vessels and sailors in the Antarctic Ocean are particularly wary of the high winds and large waves that result from the cyclones in the oceans. Earning the nicknames of "Furious Fifties" and the "Shrieking Sixties" the latitudes from 50-70 are particularly feared because of their year round peril to sea faring vessels.

The vessels that do brave the harsh conditions of the Antarctic Ocean do so in search of profits from the large amounts of natural resources in the area. The Antartic Ocean is commonly used as a source of access for the petroleum and natural gas fields on the continental margin, as well as a route of access to sand and gravel. As an ocean, the waters also provide squid, whale, sea mammals, krill , and a variety of fish for world markets.

History

The Second (1937) Edition of the IHO's Limits of Oceans and Seas included the Southern Ocean; however, it was omitted from the Third (1953) Edition, as it was felt its northern hydrographic limits fluctuated with the seasons and that an ocean should be defined as "water surrounded by land" not "water encircling land." Individual member states' hydrographic offices have defined their own boundaries; the United Kingdom used the 55°S parallel.

The IHO readdressed the question in a survey in 2000. Of the 68 member nations, 28 responded to and all responding members except Argentina agreed to define a new ocean. The name Southern Ocean was selected with 18 votes, beating the alternative Antarctic Ocean. Half of the votes were cast for ending the ocean at the 60 degrees south line of latitude (with no land interruptions at this latitude), with the other 14 votes cast for other definitions, mostly 50 degrees south, but a few for as far north as 35 degrees south.

Other sources such as the National Geographic Society continue to show the Atlantic, Pacific and Indian Oceans as extending to Antarctica.

File:Australia map 1863.jpg

Many maps of Australia show the Southern Ocean lying immediately to the south of Australia.

In Australia the Southern Ocean was defined also to include the entire body of water between Antarctica and the south coasts of Australia and New Zealand. Coastal maps of Tasmania and South Australia label the sea areas as Southern Ocean.

Environment

Current issues

Increased solar ultraviolet radiation resulting from the Antarctic ozone hole has reduced marine primary productivity (phytoplankton) by as much as 15% and is damaging the DNA of some fish^{[citation needed]}. Illegal, unreported, and unregulated fishing, especially the landing of an estimated five to six times more Patagonian toothfish than the regulated fishery, likely affects the sustainability of the stock. There is also a high incidental mortality of seabirds resulting from long-line fishing for toothfish.

International agreements

The Southern Ocean is subject to all international agreements regarding the world's oceans. In addition, it is subject to these agreements specific to the region:

• The International Whaling Commission prohibits commercial whaling south of 40 degrees south (south of 60 degrees south between 50 degrees and 130 degrees west). Japan regularly does not recognize this provision in regards to its whaling permit and whaling for scientific research and carries out an annual whale hunt in the region. See Southern Ocean Whale Sanctuary.
• The Convention for the Conservation of Antarctic Seals has limited seal hunting.
• The Convention on the Conservation of Antarctic Marine Living Resources regulates fishing in the region.

Many nations prohibit mineral resource exploration and exploitation south of the fluctuating Polar Front^{[citation needed]}, which is in the middle of the Antarctic Circumpolar Current and serves as the dividing line between the very cold polar surface waters to the south and the warmer waters to the north.

Since the Antarctic Treaty covers the portion of the globe south of sixty degrees south, claims to Antarctica and all islands in the Southern Ocean are suspended.

Ports and harbors

File:Scross icepier.jpg

Severe cracks in an ice pier in use for four seasons at McMurdo Station slowed cargo operations in 1983 and proved to be a safety hazard.

Few ports or harbors exist on the southern (Antarctic) coast of the Southern Ocean since ice conditions limit use of most of them to short periods in midsummer; even then some cannot be entered without icebreaker escort. Most Antarctic ports are operated by government research stations and, except in an emergency, are not open to commercial or private vessels; vessels in any port south of 60 degrees south are subject to inspection by Antarctic Treaty observers.

Major ports that are operational include: Esperanza Base, Villa Las Estrellas, Chile, Mawson Station, McMurdo Station, Palmer Station, and offshore anchorages in Antarctica.

The Southern Ocean's southern-most port is located at McMurdo Station at 77°50′S 166°40′E. The small harbor on the southern tip of Ross Island is formed by Winter Quarters Bay, where summer port operations are made possible by a floating Ice pier. Operation Deep Freeze personnel constructed the first ice pier at McMurdo in 1973.

Economy

Fisheries in 1998-99 between 1 July and 30 June landed 119,898 tonnes, of which 85% was krill and 14% Patagonian toothfish. International agreements were adopted in late 1999 to reduce illegal, unreported, and unregulated fishing, which in the 1998-99 season landed five to six times more Patagonian toothfish than the regulated fishery. In the 1998-99 Antarctic summer 10,013 tourists, most of them seaborne, visited the Southern Ocean and Antarctica, compared to 9,604 the previous year. Nearly 16,000 tourists were expected during the 1999-2000 season.

See also

• Antarctica
• Antarctic Treaty System
• Extreme points of the Antarctic
• Roaring forties

Further reading

• Gille, Sarah T. 2002. "Warming of the Southern Ocean since the 1950s": abstract, article. Science: vol. 295 (no. 5558), pp. 1275-1277.
• Descriptive Regional Oceanography, P. Tchernia, Pergamon Press, 1980.
• Matthias Tomczak and J. Stuart Godfrey. 2003. Regional Oceanography: an Introduction. (see the site)

External links

• Oceanography Image of the Day, from the Woods Hole Oceanographic Institution
• The CIA World Factbook's entry on the Southern Ocean
• The Fifth Ocean from Geography.About.com
• NOAA In-situ Ocean Data Viewer Plot and download ocean observations
• NOAA FAQ about the number of oceans

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