Profile through the Drake Passage between South America and the Antarctic Peninsula. Morphological main features in the deep sea are shown like the mid ocean ridge (West Scotia Ridge), separating the Antarctic plate from the South American plate. The South Shetland Islands belong to an island belt, resulting from the subduction of the Pacific plate below the Antarctic plate. In the back arc basin, i.e. the Bransfield Strait, submarine volcanoes have been found. The upper graph shows salinity (parts per thousand) and temperature in surface water measured along a cruise track. The Polar Front is an oceanographic feature which is characterized by an abrupt change in temperature by about one degree. Hannes Grobe, Alfred Wegener Institute for Polar and Marine Research Creative Commons Attribution-Share Alike 2.5 Commons.m.wikimedia.org