Oceans and seas

Amundsen Sea

August 6, 2011, 5:07 am

The Amundsen Sea is a marginal sea of Antarctica centered at about 112o W and 73o S. It sits between the Bellingshausen Sea to the east and the Ross Sea to the west, with the Antarctic Circle serving as the northern boundary. The Amundsen Sea is one of the Antarctic seas which contributes to the formation of cold deep-water masses, which are instrumental in driving the global ocean thermohaline circulation. Norwegian polar explorer Roald Amundsen is credited with the first sighting of the Amundsen Sea during an an expedition in 1928-29 commanded by the Norwegian under Captain Nils Larsen; the Amundsen Basin was first explored in February of 1929 as a part of that exploration.

The Amundsen Sea has relatively low nutrient levels compared to other seas in the Antarctic Zone. As with other seas of the Antarctic large marine ecoregion, the Amundsen Sea is under pressure of overfishing, with several fish species reaching populations below meaningful sustained economic harvesting. Ice shelves in the Ross Sea are experiencing a short term melting; however, these effects may be due to the sursurface active volcano activity rather than atmospheric phenomena.

caption Regional setting of the Antarctic Seas. Source: CIA World factbook

Geography and Ice Shelves

The greater extent of the Amundsen Sea is covered by ice, with a number of ice shelves and ice tongues extending into this sea from land. The Thwaites Glacier Tongue being one of the most significant. This iceform has a mean thickness of approximately three kilometers and is roughly the size of the state of Texas. This feature is also known as the Amundsen Sea Embayment (ASE), comprising one of the three major ice drainage basins of the West Antarctic Ice Sheet.

The Amundsen Basin can be  viewed as an arm of the Southern Ocean  lying off Marie Byrd Land in teh western portion of Antarctica; this sea  It is bounded by Cape Flying Fish, the northwestern extremity of Thurston Island to the east and Cape Dart on Siple Island to the west. East of Cape Flying Fish is situated the Bellingshausen Sea. West of Cape Dart lies another unnamed marginal sea of the Southern Ocean, sandwiched between the Amundsen Sea and Ross Sea.

Pine Island Bay (74 degrees 50 minutes S; 102 degrees 40 minutes W) extends approximately 65 kilometers in length and 50 km in width; the Pine Island Glacier ice tongue enters Pine Island Bay at the southeast extremity of the Amundsen Sea. This ice shelf was first delineated from aerial photographs taken by USN Operation Highjump in December 1946, and named by the Advisory Committee on Antarctic Names after the USS Pine Island (AV-12), a seaplane tender and flagship of the eastern task group of the U.S. Navy Operation Highjump exploring this region.

A subglacial volcano underlies the ice shelves of the Ross Sea, immediately west of the Pine Island Glacier in proimity to the Hudson Mountains. It previously erupted approximately 200 BC, evidenced by extensive volcanic ash deposits within the glacial and ice shelf formations; that event was the most spectacular eruption in Antarctica within the Holocene period.

Russell Bay (73 degrees 27 minutes S; 123 degrees 54 minutes W) is considered a somewhat open bay in the southwestern reaches of the Amundsen Sea, extending along the north of Siple Island, the Getz Ice Shelf and to the north of Carney Island, from Pranke Island to Cape Gates. Russell Bay  was initially mapped by the United States Geological Survey via surveys and U.S. Navy aerial photography in the period 1959 to 1966; Russell Bay was named by the U.S.Advisory Committee on Antarctic Names in honor of Admiral James S. Russell, USN, Vice Chief of Naval Operations during the post 1957-58 International Geophysical Year period.

Fisheries

As in all the seas of the Antarctic region, demersal catches are prevalent, and a much smaller percentage of coastal fishes. Species caught are krill, Antarctic cod, icefish, lanternfish, Antarctic squid and Patagonian toothfish. Major interest in the Antarctic’s marine living resources developed after the 1959 Antarctic treaty. Food and Agriculture Organization (FAO), has fishing statistics subsequent to the year 1968. In the early 1980s, krill (Euphausia superba), an epipelagic species, accounted for a large percentage of the total catch. There was a decrease of the total catch in 1983/84, after an all time high in 1982. When the Soviet Union dissolved in 1991, the new republics drastically reduced their fishing activities in the Antarctic. Since the 1980s, Japan has harvested 40,000 to 80,000 tons of krill a year in the total Antarctic large marine ecoregion. The decreasing total catch in recent years can be attributed to depletion, to the distance from other major fishing grounds, or to the lack of demand for some Antarctic species. There is concern for the Patagonian toothfish. Antarctic cod and icefish are now depleted. The countries involved in the commercial fishing of krill are Japan, Russia, Chile, Taiwan, Korea, Spain, Poland and Germany. The potential for overfishing has grown significantly over the last two decades. These resources are subjected to fisheries management under the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR)

Ecosystem of the Terrestrial Margin

See main article: Marielandia Antarctic tundra

Much of the terrestrial fringe of the Amundsen Sea consists of ice sheets or glaciers much of the year. However, in the warmest months, there is a tundra exposure where a variety of lichens, mosses, seabirds, penguins and pinnipeds thrive. This terrestrial ecoregion is known as the Marielandia Antarctic tundra.

Six seal species are native to this ecoregion in Antarctica, Crabeater seal (Lobodon carcinophagus), Ross seal (Omimatophoca rossii), Leopard seal (Hydrurga leptonyx), Weddell seal (Leptonychotes weddellii), Southern elephant seal (Mirounga leonina), and Southern fur seal (Arctocephalus gazella). Elephant seals are found along the Antarctic Peninsula coast and on sub-Antarctic islands, but do not range as farther south into continental Antarctica. The Southern elephant seal and fur seal are more often associated with the open ocean, while the others spend a significant amount of time on sea ice. Weddell, Crabeater, Ross, and Leopard seals are all ice-breeding. Seals hauling out on land can have a significant impact on vegetation communities. Pushed almost to extinction by intensive hunting in the 19th century, the fur seal has recovered greatly starting around 1970, and now totals about one million individuals. The Crabeater seal is the most abundant seal of the seas of the world, with a total estimated population of over 30 million.

Thirty-seven flying seabird species are native to Antarctica. Some species characteristic of Marielandia are southern fulmar (Fulmaras glacialoides), southern giant fulmar (Macronectes giganteus), cape pigeon (Daption capense), snow petrel (Pagodroma nivea), Wilson’s storm petrel (Oceanites oceanicus), blue-eyed shag (Phalacrocorax atriceps), American sheathbill (Chionis alba), south polar skua (Catharacta maccormicki), brown skua (Catharacta lonnbergi), southern black-backed gull (Larus dominicanus), and Antarctic tern (Sterna vittata). These birds must nest on ice-free areas, therefore, they are seldom found far inland over the ice-cap, and breed during summer months when coastal areas along the Amundsen Sea are exposed. Several petrel species build burrows to nest in the ground.

See Also

Further Reading

  • H.F.J.Corr and D.G.Vaughan. 2008. A recent volcanic eruption beneath the West Antarctic ice sheet. Nature Geoscience 1 (2): 122–125.
  • Peter Saundry. 2011. Seas  of the world. Topic ed. C.Michael Hogan. Ed. in chief Cutler J.Cleveland. Encyclopedia of Earth. Washington DC
  • Rhodes W. Fairbridge, editor. 1966. The Encyclopedia of Oceanography. Van Nostrand Reinhold Co.,
  • A. S. Grotov, D. A. Nechaev, G. G. Panteleev, and M. I. Yaremchuk. Large–scale circulation in the Bellingshausen and Amundsen seas as a variational inverse of climatological data. JGR, 103:13,011–13,022, 1998
Glossary

Citation

Hogan, C. (2011). Amundsen Sea. Retrieved from http://www.eoearth.org/view/article/150037

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