Abyssal circulation in the Argentine Basin

Abstract

The abyssal water mass in the Argentine Basin, generically called Antarctic Bottom Water, is of southern origin. Its source is primarily Weddell Sea Deep Water (with characteristics of -0.7° to 0.2°C and salinity 34.65-34.68), which flows out of the Weddell gyre into the South Sandwich trench and continues north beyond the Falklands Escarpment into the Argentine Basin. The abyssal water cannot have originated in the Antarctic Circumpolar Current (ACC) since waters colder than 0.2°C are not associated with the ACC in the Drake Passage. Once the abyssal water has entered the Argentine Basin through gaps in the Falklands Escarpment or around the Islas Orcadas Rise it is generally assumed that it turns sharply to the west, in accordance with the Stommel and Arons [1960] theory of ocean circulation, and flows along the base of the Falklands Escarpment before flowing north along the continental slope as a deep western boundary current off South America. Results from the World Ocean Circulation Experiment (WOCE) A11 section, however, suggest that the newest most CFC-rich water occurs on the eastern side of the Argentine Basin rather than the west. We therefore conclude that in addition to the western boundary current there is a more dominant anticlockwise circulation around the Zapiola Rise, which is likely related to the migratory pattern of the ACC.