A note on the thermal structure of the upper ocean in the Bransfield Strait-South Shetland Islands region

Abstract

Sixteen XBT sections were occupied from December 1982 to July 1987 in and around the Bransfield Strait and the South Shetland Islands. These and other temperature data from the FDRAKE75, FDRAKE76 and DRAKE79 field programs provide a description of the temperature structure and water mass distribution of the upper 500 m in this region. Temperature distributions at 300 and 500 m show Circumpolar Deep Water (>0°C) north of the South Shetland Islands, which enters Bransfield Strait through a gap between Smith and Snow Islands. Inside the Strait this water is confined to a narrow band along the southern flank of the Islands. The fine spatial resolution of the XBT sections shows a sharp thermal gradient between the cold (<0°C) Bransfield Strait waters and the warmer (>0°C) waters of Drake Passage origin. The presence of cold Bransfield Strait waters, over the northeast portion of the Island slope region, is related to north-south motions of this temperature boundary. The Polar Slope Current, on the northern side of the South Shetland Islands, appears as a tongue of cold (<0°C) water that extends westward from Elephant Island to the gap between Smith and Snow Islands.