Water masses and circulation in the region of Prydz Bay, Antarctica

Abstract

Hydrographic and expendable bathythermograph (XBT) measurements are used to describe the characteristics and circulation of the water within and to the north of Prydz Bay, Antarctica. The surface waters in Prydz Bay are highly variable and are linked to the local ice conditions. The isolation of a warm surface feature corroborates previous suggestions of a permanent high surface temperature anomaly. Water mass analysis reveals both high- and low-salinity varieties of continental shelf water and a significant Ice Shelf Water mode. Low-salinity shelf water is confined to the West Ice Shelf region and high-salinity shelf water to the central and western areas of Prydz Bay. The Ice Shelf Water mass is related to freezing beneath the Amery Ice Shelf and to prolonged isolation due to topographic restraints. There is evidence of strong vertical convection in Prydz Bay and on the continental shelf. The present analysis indicates no evidence of Antarctic Bottom Water formation in Prydz Bay but recognizes the possibility of contributions from the region west of the bay off Enderby Land. Geostrophic calculations show predominantly westward flow adjacent to the continental rise and a large cyclonic gyre in Prydz Bay. The off-shelf pattern is consistent with previous calculations from hydrographic data and with iceberg and buoy observations. The water masses and circulation within Prydz Bay resemble those of similar sites within the Weddell and Ross seas but there are significant differences in the large-scale circulations and in the geostrophic and topographic constraints imposed on the flows.