Oceans and seas

Bellingshausen Sea

May 25, 2011, 7:24 pm
Content Cover Image

Low flying aircraft view of the island fringe along the eastern Bellingshausen Sea. @ C.Michael Hogan

The Bellingshausen Sea is a marginal sea of the Southern Ocean located off Antarctica from approximately 70 to 100o W northwards to the Antarctic Circle. It is situated between Thurston Island and the Amundsen Sea to the west and the Antarctic Peninsula to the east; Bellingshausen Sea has an areal extent of approximately 487,000 km² and attains a maximum depth of about 5181 meters. This sea was named for the Russian admiral Baron Fabian Gottlieb von Bellingshausen, who led an expedition to Antarctic waters at the behest of Alexander I in 1819.

von Bellingshausen is considered the first to have actually discovered the continent of Antarctic, those preceding him not having seen it because of ice and low visibility (see Sighting Antarctica)

The geographic features of the Bellingshausen Sea include Ronne and Marguerite Bays as well as Peter I Island, Charcot Island and Alexander I Island.

Surface temperatures of the Bellingshausen Sea are very cold, approximating -1.5 degrees Celsius; moreover, salinity is relatively low, and nutrient levels are depressed compared to most other waters fo the Antarctic Zone.

A small observed warming within this sea basin in the last century is credited with significant expansion of Gentoo penguin and Chinstrap penguin populations, along with other faunal as well as terrestrial fringe flora population growth.

Circulation and Hydrography

The continental shelf along the margin of the Bellingshausen Sea is wide compared to most of the Antarctic fringe, except for that along the neighboring Amundsen Sea. This shelf is commonly 220 to 320 kilometers (km) wide, but occasionally may extend to 400 km. The shelf is riddled with numerous glacial grooves and extensive deposits of submarine sediments at the shelf edge. The depth at the shelf edges is moderately deep, approximating 500 meters; furthermore, like the Amundsen Sea, there is less upwelling at shelf edge than for other seas of the Southern Ocean.

Sea ice forms in gradual degrees in an annual cycle, and sea ice melt occurs relatively slowly as well, unlike the rapid melt seen in most of the Antarctic Zone. This slow sea ice melt is thought to be associated with the relatively low salinity and relative lack of deep water influence seen both in the Amundsen and Bellingshausen Basins.

caption Antarctic sea ice concentration climatology from 1979-2000, at the approximate seasonal maximum and minimum levels based on passive microwave satellite data. Source: National Snow and Ice Data Center

The Abbot Ice Shelf is a prominent feature that occurs at the junction of the Bellingshausen and Amundsen Seas. This major landform spans an east-west distance of about 250-400 km (depending upon the eastern limit definition), and exhibits a characteristic width of 65 km; this ice shelf is supported by several islands, which provide inherent structural integrity to the Abbot Ice Shelf. The slightly smaller Venable Ice Shelf lies somewhat east of the Abbot, placing the Venable at the edge of the Belinghausen Basin.

Surface circulation on the Bellingshausen Sea is dominated by the eastward-flowing wind driven Antarctic Circumpolar Current, whose chief flow is slightly to the north of the Bellingshausen basin. A counterflow deep current is presented, wherein modified deep water from the Waddell Basin enters the deeper Bellingshausen Sea.

Bellingshausen Abyssal Plain

The Bellingshausen Abyssal Plain is one of four deepwater plains that comprise the deepwater Antarctic Basin (the others being the Amundsen, Enderby, and the South Indian Abyssal Plains). It is located at around 90-120 degrees W. This is one of the locations of the formation of deep cold water masses in the Antarctic region. The maximum depth of this deepwater feature is 5181 meters.

Water Chemistry and Marine Ecology

Generally, nutrient levels within the upper one hundred meters of the surface of the Bellingshausen Sea are low in comparison to most other parts of Antarctic waters; however, concentrations of marine bacteria and protozoa are among the highest of the Antarctic Zone seas. Copepod populations are dominant small marine fauna, although certain salps are seasonally abundant.

The capacity of the Bellingshausen Sea to act as a carbon dioxide sink is very high, based upon very large carbon uptake from the atmosphere in summer. This uptake is likely due to enhanced seasonal biological activity, and Riffenburgh suggests that this sea may have further potential to serve as as massive carbon sink.

Corresponding to the paucity of nutrients, the Bellingshausen Sea is depauperate of zooplankton and also higher faunal forms including cetaceans and seabirds relative to other Antarctic seas. Classic ice edge algal blooms are generally not seen in the Bellingshausen Sea. Furthermore, low levels of dissolved iron are limiting to phytoplankton production. A number of cetaceans graze the krill within the Bellingshausen Sea, including the Minke whale and Humpback whale.

Bathypelagic zone fishes found in the Bellingshausen Sea include Lepidonotothen kempi, a midwater species found here at the southern limit of its distribution; another bathypelagic fish is the deepwater smelt Bathylagus antarcticus. Mesopelagic zone species found in this basin are the lanternfishes Protomyctophum bolini and Gymnoscopelus opisthopterus.

The Antarctic silverfish, Pleuragramma antarcticum, is a prominent Epipelagic zone midwater fish that spawns on coastal shelves in the Bellingshausen Basin, its larvae being transported in by the Antarctic Circumpolar Current. Nearer the surface is the Cryopelagic zone (near coldwater surface dwelling) Icecod Trematomus newnesi, which feeds on krill under the sea ice surface in its juvenile stage.

The slight warming trend of the last century is favorable for a number of organisms, especially penguins such as the Gentoo and Chinstrap. Future benefits are expected to accrue to benthic shelf biota, which will be able to colonize more effectively without the excessive ice gouging of the shelf floor.

Ecosystem of the Terrestrial Margin

See main article: Marielandia Antarctic tundra

Much of the terrestrial fringe 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 in the Antarctic Peninsula area 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 Bellingshausen Sea are exposed. Several petrel species build burrows to nest in the ground.

Discovery Voyage

The Thaddeus Bellingshausen expedition crossed the Antarctic Circle on January 26, 1820. On January 27, Bellingshausen saw petrels and heard penguins, which observation convinced him that land was nearby. He reported seeing extensive ice and "in different places over the ice we could see icy mountains to the south." These and similar observations convinvced him that his expedition was skirting the coast on the southern continent. Because of shifts in the ice surrounding the Antarctic coast it is not possible to be certain about what Bellingshausen saw, but  his log confirms that he was about probably 20 miles from shore. While debate has raged over whether Bellinghausen was actually seeing the continent of Antarctica at this this, it comes down to a debate over whether he was observing fixed ice over land or ice moving away from the continent over water. Bellinghausen and his officers were confident that they were observing ice over a continent (perhaps of continuous land, perhaps of islands) and are generally credited (still not without debate) with the first sighting of Antarctica.

See Also

Further Reading

  • Ranier Gersonde, F.T.Kyte, T.Frederichs, U.Bleil, H.-W.Schenke, G.Kuhn and T.Frank. 2005. The late Pliocene impact of the Eltanin asteroid into the Southern Ocean – Documentation and environmental consequences. Geophysical Research Abstracts 7. 1607-7962/gra/EGU05-A-02449
  • Rhodes W.Fairbridge, editor. The Encyclopedia of Oceanography. Van Nostrand Reinhold Co., 1966.
  • 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.
  • David McGonigal. 2009. Antarctica: Secrets of the Southern Continent. frances lincoln ltd. 400 pages
  • Beau Riffenburgh. 2007. Encyclopedia of the Antarctic, Volume 1. CRC Press. 1272 pages
  • Robin M.Ross, Eileen Elizabeth Hofmann, Langdon B.Quetin. 1996. Foundations for ecological research West of the Antarctic Peninsula. American Geophysical Union. 448 pages
  • Peter Saundry. 2011. Seas of the world. Topic ed. C.Michael Hogan. Ed.-in-chief Cutler J.Cleveland. Encyclopedia of Earth. Washington DC
  • D.R.Turner and N.J.P.Owens. 1995. A biogeochemical study in the Bellingshausen Sea: Overview of the STERNA 1992 expedition. DSR II, 42:907–932.
  • G.E.Watson, J.P.Angle, and P.C.Harper. 1975. Birds of the Antarctic and Sub-Antarctic. American Geophysical Union, Washington, D.C. ISBN: 0875901247

 

Glossary

Citation

Hogan, C. (2011). Bellingshausen Sea. Retrieved from http://www.eoearth.org/view/article/51cbed0e7896bb431f68f5e1

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