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
The Antarctic Convergence was first crossed by the London merchant Anthony de la Roché in 1675,[1] and described by Sir Edmund Halley in 1700.[2]
Location
The Antarctic Convergence is a belt approximately 20 to 30 miles wide, varying somewhat in latitude seasonally and in different longitudes, surrounding the Antarctic continent extending across the Atlantic, Pacific, and Indian Oceans between the 48° South and 61° South, separasting those Oceans hydrographically from the Southern Ocean surrounding Antarctica. This zone is a mobile one, though 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 from 5.6°C to below 2°C.
The Falkland Islands, Tristan da Cunha and Gough Island lie north of the Convergence. South Georgia, the South Sandwich Islands, the South Orkney Islands and the South Shetland Islands and all lie south of the Convergence.