9,699
edits
Difference between revisions of "Southern Ocean"
no edit summary
Westarctica (talk | contribs) |
Westarctica (talk | contribs) |
||
| Line 6: | Line 6: | ||
==Geography== | ==Geography== | ||
[[File:Old Antarctica map.jpg|thumb|350px|right|1906 map of the Antarctica showing the unknown boundries of the continent]] | [[File:Old Antarctica map.jpg|thumb|350px|right|1906 map of the Antarctica showing the unknown boundries of the continent]] | ||
The Southern Ocean, geologically the youngest of the oceans, 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. | The Southern Ocean, geologically the youngest of the oceans, 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]]. | ||
With a northern limit at 60°S, the Southern Ocean differs from the other oceans in that its largest boundary, the northern boundary, does not abut a landmass (as it did with the first edition of Limits of Oceans and Seas). Instead, the northern limit is with the Atlantic, Indian and Pacific Oceans. | With a northern limit at 60°S, the Southern Ocean differs from the other oceans in that its largest boundary, the northern boundary, does not abut a landmass (as it did with the first edition of Limits of Oceans and Seas). Instead, the northern limit is with the Atlantic, Indian and Pacific Oceans. | ||
One reason for considering it as a separate ocean stems from the fact that much of the water of the Southern Ocean differs from the water in the other oceans. Water gets transported around the Southern Ocean fairly rapidly because of the Antarctic Circumpolar Current which circulates around Antarctica. Water in the Southern Ocean south of, for example, New Zealand, resembles the water in the Southern Ocean south of South America more closely than it resembles the water in the Pacific Ocean. | One reason for considering it as a separate ocean stems from the fact that much of the water of the Southern Ocean differs from the water in the other oceans. Water gets transported around the Southern Ocean fairly rapidly because of the Antarctic Circumpolar Current which circulates around [[Antarctica]]. Water in the Southern Ocean south of, for example, New Zealand, resembles the water in the Southern Ocean south of South America more closely than it resembles the water in the Pacific Ocean. | ||
The Southern Ocean has typical depths of between 4,000 and 5,000 m (13,000 and 16,000 ft) over most of its extent with only limited areas of shallow water. The Southern Ocean's greatest depth of 7,236 m (23,740 ft) occurs at the southern end of the South Sandwich Trench, at 60°00'S, 024°W. The Antarctic continental shelf appears generally narrow and unusually deep, its edge lying at depths up to 800 m (2,600 ft), compared to a global mean of 133 m (436 ft). | The Southern Ocean has typical depths of between 4,000 and 5,000 m (13,000 and 16,000 ft) over most of its extent with only limited areas of shallow water. The Southern Ocean's greatest depth of 7,236 m (23,740 ft) occurs at the southern end of the South Sandwich Trench, at 60°00'S, 024°W. The Antarctic continental shelf appears generally narrow and unusually deep, its edge lying at depths up to 800 m (2,600 ft), compared to a global mean of 133 m (436 ft). | ||
Equinox to equinox in line with the sun's seasonal influence, the Antarctic ice pack fluctuates from an average minimum of 2.6 million square | Equinox to equinox in line with the sun's seasonal influence, the Antarctic ice pack fluctuates from an average minimum of 2.6 million square kilometers (1.0×106 sq mi) in March to about 18.8 million square kilometers (7.3×106 sq mi) in September, more than a sevenfold increase in area. | ||
===Natural resources=== | ===Natural resources=== | ||
| Line 22: | Line 22: | ||
Manganese nodules are expected to exist in the Southern Ocean. Manganese nodules are rock concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core. The core may be microscopically small and is sometimes completely transformed into manganese minerals by crystallization. Interest in the potential exploitation of polymetallic nodules generated a great deal of activity among prospective mining consortia in the 1960s and 1970s. | Manganese nodules are expected to exist in the Southern Ocean. Manganese nodules are rock concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core. The core may be microscopically small and is sometimes completely transformed into manganese minerals by crystallization. Interest in the potential exploitation of polymetallic nodules generated a great deal of activity among prospective mining consortia in the 1960s and 1970s. | ||
The | The [[iceberg]]s that form each year around in the Southern Ocean hold enough fresh water to meet the needs of every person on Earth for several months. For several decades there have been proposals, none yet to be feasible or successful, to tow Southern Ocean icebergs to more arid northern regions (such as Australia) where they can be harvested. | ||
===Natural hazards=== | ===Natural hazards=== | ||
| Line 37: | Line 37: | ||
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. | 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. | ||
Associated with the Circumpolar Current is the Antarctic Convergence encircling Antarctica, where cold northward-flowing Antarctic waters meet the relatively warmer waters of the subantarctic, Antarctic waters predominantly sink beneath subantarctic waters, while associated zones of mixing and upwelling create a zone very high in nutrients. These nurture high levels of phytoplankton with associated copepods and [[Antarctic krill]], and resultant foodchains supporting fish, whales, seals, penguins, albatrosses and a wealth of other species. | Associated with the Circumpolar Current is the [[Antarctic Convergence]] encircling Antarctica, where cold northward-flowing Antarctic waters meet the relatively warmer waters of the subantarctic, Antarctic waters predominantly sink beneath subantarctic waters, while associated zones of mixing and upwelling create a zone very high in nutrients. These nurture high levels of phytoplankton with associated copepods and [[Antarctic krill]], and resultant foodchains supporting fish, whales, seals, penguins, albatrosses and a wealth of other species. | ||
===Upwelling=== | ===Upwelling=== | ||
| Line 47: | Line 47: | ||
===Ross and Weddell Gyres=== | ===Ross and Weddell Gyres=== | ||
[[File:Antarctic frontal.png|thumb|right|Oceanographic frontal systems in the Southern Ocean]] | [[File:Antarctic frontal.png|thumb|right|Oceanographic frontal systems in the Southern Ocean]] | ||
The Ross Gyre and Weddell Gyre are two gyres (a large system of circulating currents) that exist within the Southern Ocean. The gyres are located in the Ross Sea and Weddell Sea respectively, and both rotate clockwise. The gyres are formed by interactions between the Antarctic Circumpolar Current and the Antarctic Continental Shelf. | The Ross Gyre and Weddell Gyre are two gyres (a large system of circulating currents) that exist within the Southern Ocean. The gyres are located in the [[Ross Sea]] and [[Weddell Sea]] respectively, and both rotate clockwise. The gyres are formed by interactions between the Antarctic Circumpolar Current and the Antarctic Continental Shelf. | ||
Sea ice has been noted to persist in the central area of the Ross Gyre. There is some evidence that global warming has resulted in some decrease of the salinity of the waters of the Ross Gyre since the 1950s. | Sea ice has been noted to persist in the central area of the Ross Gyre. There is some evidence that global warming has resulted in some decrease of the salinity of the waters of the Ross Gyre since the 1950s. | ||
| Line 58: | Line 58: | ||
All international agreements regarding the world's oceans apply to the Southern Ocean. In addition, it is subject to additional agreements specific to the region such as the Southern Ocean Whale Sanctuary of the International Whaling Commission (IWC) which prohibits commercial [[whaling]] south of 40 degrees south (south of 60 degrees south between 50 degrees and 130 degrees west). [[Whaling in Japan|Japan]] regularly does not recognize this provision, because the sanctuary violates IWC charter. Since the scope of the sanctuary is limited to commercial whaling, in regard to its whaling permit and whaling for scientific research, a Japanese fleet carried out an annual whale-hunt in the region. On 31 March 2014, the International Court of Justice ruled that Japan's whaling program, which Japan has long claimed is for scientific purposes, was a cloak for commercial whaling, and no further permits would be granted. | All international agreements regarding the world's oceans apply to the Southern Ocean. In addition, it is subject to additional agreements specific to the region such as the Southern Ocean Whale Sanctuary of the International Whaling Commission (IWC) which prohibits commercial [[whaling]] south of 40 degrees south (south of 60 degrees south between 50 degrees and 130 degrees west). [[Whaling in Japan|Japan]] regularly does not recognize this provision, because the sanctuary violates IWC charter. Since the scope of the sanctuary is limited to commercial whaling, in regard to its whaling permit and whaling for scientific research, a Japanese fleet carried out an annual whale-hunt in the region. On 31 March 2014, the International Court of Justice ruled that Japan's whaling program, which Japan has long claimed is for scientific purposes, was a cloak for commercial whaling, and no further permits would be granted. | ||
Many nations prohibit the exploration for and the exploitation of mineral resources south of the fluctuating Antarctic Convergence, which lies 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. The [[Antarctic Treaty]] covers the portion of the globe south of sixty degrees south, it prohibits new claims to Antarctica. | Many nations prohibit the exploration for and the exploitation of mineral resources south of the fluctuating Antarctic Convergence, which lies 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. The [[Antarctic Treaty]] covers the portion of the globe south of sixty degrees south, it prohibits new [[Territorial claims in Antarctica|claims to Antarctica]]. | ||
The Convention for the Conservation of Antarctic Marine Living Resources applies to the area south of 60° South latitude as well as the areas further north up to the limit of the Antarctic Convergence. | The Convention for the Conservation of Antarctic Marine Living Resources applies to the area south of 60° South latitude as well as the areas further north up to the limit of the Antarctic Convergence. | ||