Oceans and seas

Scotia Sea

May 5, 2011, 10:32 pm
Content Cover Image

Scotia Sea littered with ice floes near King George Island. @ C.Michael Hogan

caption Regional setting of the Scotia Sea. Source: USGS

The Scotia Sea is a sea partially within the Southern Ocean and partially within the southern Atlantic Ocean; the Scotia Sea is rimmed by Shag Rocks, South Georgia, South Sandwich Islands, South Orkney Islands and the South Shetland Islands. The norther boundary of the Scotia Sea is Tierra del Fuego. Moreover, it merges with the Drake Passage at about 55 degrees West. The areal extent of the Scotia Sea is approximately 900,000 square kilometres. The Scotia Sea was named  after the vessel Scotia, the expedition ship used in these waters by the Scottish National Antarctic Expedition under William S. Bruce.

Chief currents in the Scotia Sea are the near surface easterly flow of the Antarctic Circumpolar Current and the northward deep water current arising in the Weddell Sea. The Scotia Sea is richly endowed with Antarctic Krill, but myctophid fishes are also an important trophic building block of the food chain. correpondingly the Scotia Sea has historically been the most productive harvesting grounds for seals, whales and total fish catch in the entire circumpolar Southern Ocean and southern Atlantic.

Hydrography and Circulation

caption Coastal skerry, South Shetland Islands. @ C.Michael Hogan

The eastward flowing southern Antarctic Circumpolar Current is a prevailing feature of the southern Scotia Sea. Studies of krill transport reveal a eastward moving composite surface flow that convey krill larvae from the Antarctic Peninsula to the South Georgia Islands. These wind driven currents allow the rich krill larvae content to mature in their 150-day krill larval development time. The large-scale composite flow moves near surface organismss several hundreds of kilometres in that 150 day interval.

Since the  Middle Miocene age (16 - 11.6 million years ago), evidences the first incursion of Weddell Sea Deep Water into the central Scotia Sea, when plate movement caused openings in the South Scotia Ridge and allowed the connection with the northern Weddell Sea through Jane Basin and gaps in the ridge. This thermohaline induced deep water flow has formed a contourite layer (sedimentary deep water deposits) over one kilometre thick. The long term persistence of this cold deepwater flow spinning north from the Weddell Gyre has exterted a very long term effect on the onset of glaciations by pumping immense amounts of icy water northward. Freshwater flow into the Scotia Sea consists of some coastal streams and the calving of numerous glaciers and ice sheets abutting the sea.

Marine Ecology

caption Gentoo penguin colony, Ainsley Island. @ C.Michael Hogan

Antarctic Krill (Euthasia superba) are a cornerstone of the productivity of the Scotia Sea, which contains over half of all such krill of the circumpolar Antarctic region. However, Myctophid fishes comprise another important link in a generally distinct trophic chain; these fishes comprise a key prey source for numerous penguins, pinnipeds, squid, albatrosses and also larger fishes. Particular penguins seen breeding on the islands of the Scotia Sea include Gentoo and Chinstrap penguins.

The Scotia Sea has been suggested to be an important centre of marine species diversification. For example, the bivalve Lissarca notorcadensis is an abundant species in Antarctic waters and has colonised the entire Antarctic shelf and Scotia Sea Islands. The brooding reproduction, low dispersal capabilities and epizoic lifestyle predict limited gene flow between geographically isolated populations. Relationships between specimens from seven regions in the Southern Ocean and outgroups havebeen analysed with nuclear 28S rDNA and mitochondrial cytochrome genes. Linse et al have produced evidence for reproductively isolated populations of L. notorcadensis. Overlall the islands of the Scotia Sea appear to act as centres of speciation in the Southern Ocean.

Marine decapod species are conspicuously depauperate in the Scotia Sea along with other portions of the circumpolar Antarctic seas.

Terrestrial Ecology

caption Coastal inlet with Fur seal colony, King George Island. @ C.Michael Hogan

See main article: Scotia Sea Isands tundra

The Scotia Sea Islands are several groups of islands in the Southern Atlantic Ocean, some continental and some of volcanic origin. Generally associated with Antarctica in terms of flora and fauna, these islands are partially or fully covered in permanent glaciers, ice sheets and snow. The dominant vegetation is a tundra of mosses, lichens, and algae. While there are no native land mammals and only a handful of land birds, the Scotia Sea Islands support very significant seal, seabird, and penguin rookeries. The cold, harsh climate of the region has deterred permanent human settlement of the islands, though the region’s seal populations were drastically reduced during an era of intense hunting in the 17th and 18th centuries. The current commercial fishing industry in the Scotia Sea now poses threats to stability of pinniped and seabird populations.

Exploration History

caption Launch of the James Caird. Source: E.Shackleton. 1916 The Scotia Sea was named in about 1932 after the vessel Scotia, the expedition ship used in these waters by the Scottish National Antarctic Expedition (1902-04) commanded by William S. Bruce. Sir Ernest Shackleton executed the most noted voyage across the Scotia Sea in the year 1916; with a crew of four others, Shackleton adapted a lifeboat James Caird, leaving Elephant Island and arriving at South Georgia a fortnight later. Shackleton went on with a larger contingent to make his noted explorations of the Antarctic continent, taking large stocks of Weddell seal and Crabeater seal as they made their sea crossings. See: The "Heroic Age" of Antarctic Exploration.

References

  • M.A.Collins, J.C.Xavier, N.Johnston, A.W.North, P.Enderlein, G.A.Tarling, C.Waluda, E.Hawker, N. Cunningham. 2008. The Role of Myctophid Fishes in the Scotia Sea Ecosystem. Polar Biology
  • Eileen E. Hofmann a1, John M. Klinck a1, Ricardo A. Locarnini a1, Bettina Fach a1 and Eugene Murphy. 1998. Krill transport in the Scotia Sea and environs. Antarctic Science 10:406-415
  • Katrin Linse, Therese Cope, Anne-Nina Lörz and Chester Sands. Is the Scotia Sea a centre of Antarctic marine diversification? Some evidence of cryptic speciation in the circum-Antarctic bivalve Lissarca notorcadensis (Arcoidea: Philobryidae) Polar Biology Volume 30, Number 8, 1059-1068
  • Andrés Maldonado, Antonio Barnolasb, Fernando Bohoyoa, Jesús Galindo-Zaldívarc, Javier Hernández-Molinad, Francisco Loboe, José Rodríguez-Fernándeza, Luis Somozab and Juán Tomás Vázque. 2003. Contourite deposits in the central Scotia Sea: the importance of the Antarctic Circumpolar Current and the Weddell Gyre flows. Palaeogeography, Palaeoclimatology, Palaeoecology. Volume 198, Issues 1-2,, Pages 187-221
  • Stephen J.Pyne. 1986. The Ice: A Journey to Antarctica. University of Washington Press
  • Ernest Henry Shackleton. 2010. The Story of Shackleton's Last Expedition 1914-1917. Books on Demand. 320 pages
  • International Stratigraphic Chart 2009

See Also

 

Glossary

Citation

Hogan, C. (2011). Scotia Sea. Retrieved from http://www.eoearth.org/view/article/155899

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