Deep and bottom water of the Bransfield Strait eastern and central basins

Abstract

Temperature, salinity, oxygen, and chlorofluorocarbon (CFC) data obtained in September 1997 define the water types ventilating the deep eastern and central basins of the Bransfield Strait. These water types are observed adjacent to Joinville Island and are clearly derived from the Weddell Sea. The eastern basin bottom water characteristics closely match that of the bottom water at 310 dbar depth ∼50 km east of Joinville Island. The eastern basin bottom water is a simple mixture of low‐salinity freezing point shelf water (65%) and relatively warm saline Weddell Deep Water (35%), with a CFC‐113: CFC‐Il ratio age of 8.5 years. The eastern basin bottom water shares a common origin with a weak salinity minimum observed at 1000 dbar within the central basin, though overflow from the central basin to the eastern basin floor may also occur. The bottom water within the central basin is colder and saltier with higher concentrations of oxygen and CFC‐Il than that of the eastern basin. The central basin bottom water with a CFC ratio age of 7.5 years is composed of same Weddell water types that form the eastern basin bottom water plus a large contribution of high‐salinity freezing point shelf water of the characteristics of water observed 10 km northeast of Joinville Island and a small amount of Pacific pycnocline water. The components (and their percentage) are Weddell Deep Water (11%), low‐salinity shelf (24%), high‐salinity shelf (60%), to Pacific pycnocline (5%).