The Bass Strait Water Cascade during winter 1981

Abstract

Water in Bass Strait, a shallow extension of the Australian shelf between the Great Australian Bight and the Tasman Sea, is denser than Tasman Sea surface water in winter. Relative to water of the same density, it is warmer and more saline. When it flows down the continental slope to find water of its own density, it turns left and follows the shelf edge in a narrow northward-flowing stream creating high-salinity intrusions. A detailed description of this process is given based on cruise data from June and July of 1981. Two independent sources for the Cascade are identified. The southern source appears to be essentially a point source in an area where the shelf bends by 90°, forming a narrow corner. The northern source, which is active at slightly lower densities, causes downwelling along the shelf edge over a distance of 400 km. Bass Strait Water, which has been identified in historical data 1200 km away from its source, could be traced over 500 km during the cruise, until it encountered the hydrographic regime controlled by the East Australian Current.