Antarctic Convergence

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Antarctic Convergence

The Antarctic Convergence is a curve continuously 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 marine productivity, especially for Antarctic krill. This line, like the Arctic tree line, is a natural boundary rather than an artificial one like a line of latitude. It not only separates two hydrological regions, but also separates areas of distinctive marine life associations and of different climates. There is no Arctic equivalent, due to the amount of land surrounding the northern polar region.

History[edit]

The Antarctic Convergence was first crossed by Anthony de la Roché in 1675,[1] and described by Sir Edmund Halley in 1700.[2]

Location[edit]

The Antarctic Convergence is a zone approximately 32 to 48 km (20 to 30 mi) wide, varying somewhat in latitude seasonally and in different longitudes, extending across the Atlantic, Pacific, and Indian Oceans between the 48th and 61st parallels of south latitude. Although the northern boundary varies, for the purposes of the Convention on the Conservation of Antarctic Marine Living Resources 1980, it is defined as "50°S, 0°; 50°S, 30°E; 45°S, 30°E; 45°S, 80°E; 55°S, 80°E; 55°S, 150°E; 60°S, 150°E; 60°S, 50°W; 50°S, 50°W; 50°S, 0°." [3] Although this zone is a mobile one, it usually does not stray more than half a degree of latitude from its mean position. The precise location at any given place and time is made evident by the sudden drop in sea water temperature from north to south of, on average, 2.8 °C (5.0 °F) from 5.6 °C (42.1 °F) to below 2 °C (36 °F).

The Falkland Islands, Tristan da Cunha, Gough Island, Prince Edward Islands, Crozet Islands, Île Amsterdam, Île Saint-Paul, Macquarie Island, Campbell Island group, Auckland Islands, Snares Islands / Tini Heke, Bounty Islands, Antipodes Islands, Diego Ramírez Islands, Tierra del Fuego and Isla de los Estados lie north of the Antarctic Convergence. The Kerguelen Islands lie approximately on the Convergence. The South Shetland Islands, South Orkney Islands, South Georgia and the South Sandwich Islands, Bouvet Island, Heard Island and McDonald Islands, Balleny Islands, Scott Island and Peter I Island all lie south of the Convergence.

See also[edit]

References[edit]

  1. ^ R.K. Headland, The Island of South Georgia, Cambridge University Press, 1984.
  2. ^ Alan Gurney, Below the Convergence: Voyages Toward Antarctica, 1699-1839, Penguin Books, New York, 1998.
  3. ^ Convention on the Conservation of Antarctic Marine Living Resources 1980, Article 1(4).

External links[edit]