The Antarctic Convergence, better known as the Antarctic Polar Frontal Zone (or "Polar Front" for short), is a line encircling Antarctica where cold, northward-flowing Antarctic waters meet and mix with the relatively warmer waters of the sub-Antarctic. Antarctic waters predominantly sink beneath sub-Antarctic waters, while associated zones of mixing and upwelling create a zone very high in marine productivity, especially for Antarctic Krill. The line is actually 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. The precise location at any given place and time is made evident by the sudden drop in temperature from north to south of, on average, 2.8 °C (37 °F) to 5.5 °C (42 °F), to below 2 °C (36 °F). Although this zone is a mobile one, it usually does not stray more than a half a degree of latitude from its mean position.
There is no Arctic equivalent, due to the amount of land surrounding the northern polar region.
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.
