Circulation and Water Masses of the Southern Ocean: a Review
Developments in Earth & Environmental Sciences, 8 F. Florindo and M. Siegert (Editors) r 2009 Elsevier B.V. All rights reserved DOI 10.1016/S1571-9197(08)00004-9 Chapter 4 Circulation and Water Masses of the Southern Ocean: A Review Lionel Carter1,Ã, I. N. McCave2 and Michael J. M. Williams3 1Antarctic Research Centre, Victoria University, P.O. Box 600, Wellington, New Zealand 2Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK 3National Institute of Water and Atmospheric Research, P.O. Box 14901, Wellington, New Zealand ABSTRACT The Southern Ocean is a major component of Earth’s ocean and climate. Its circulation is complex, with a zonal Antarctic Circumpolar Current (ACC) interacting with a meridional thermohaline circulation. The ACC is a highly variable, deep-reaching eastward flow driven mainly by the westerly winds. It is the longest (24,000 km), largest (transport 137–147.106 m3 sÀ1) and only current to connect the major oceans. The Ekman component of the westerly winds also drives surface waters north. Near the ACC’s northern limit, these waters sink to form Subantarctic Mode and Antarctic Intermediate waters, which continue north at depths oB1,400 m. Interacting with the ACC is the density-forced thermohaline circulation. Super cooling and increased salinity of shelf waters off the Weddell, Wilkes Land and Ross coasts cause these waters to sink and flow equatorwards. The densest component, Antarctic Bottom Water, is captured in deep basins around Antarctica. Less dense water is entrained by the ACC and mixed with deep water moving south from the Atlantic, Indian and Pacific oceans.
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