Water Mass Characteristics of the Antarctic Margins and the Production and Seasonality of Dense Shelf Water

Abstract

Conductivity-temperature-depth data from instrumented seals of the Marine Mammals Exploring Oceans from Pole to Pole program are analyzed to characterize the water masses and the seasonality of the marginal seas. Bottom temperatures are found to be in a cold regime in Dense Shelf Water (DSW) producing regions, identified in this study as the southern Weddell Sea, Cape Darnley, Prydz Bay, Adélie Coast, and the western Ross Sea. DSW occupies the bottom of the Weddell and Ross Sea continental shelves throughout the year: Production of DSW and vertical overturning occur only during the winter. In the other DSW producing regions, salinity is reduced more markedly during the summer. We identify the Princess Martha Coast, Leopold and Astrid Coast, and the Knox Coast as Low Salinity Shelf Water producing regions, where modified Circumpolar Deep Water (CDW) intrudes onto the continental shelf, reaching areas close to the ice shelves keeping the bottom temperatures in an intermediate regime. The Prince Harald Coast, the Amundsen Sea, and the Bellingshausen Sea experience more intense CDW intrusion, which keeps them in a warm regime year-round. CDW layer thicknesses correlate with the meridional winds over the shelf sea, and with the zonal winds at the slope, while DSW layer thicknesses correlate with the meridional winds over the shelf seas and the curl of the wind stress over the slope. Locations of DSW on the continental shelf coincide with an absence of warmer CDW near the ice shelves.