Mixing and bottom water formation in the shelf break region of the southern Weddell Sea

Abstract

The shelf break region of the southern Weddell Sea was investigated during the period 1977–1980 with sections of closely spaced CTD stations and long-term moored current meters. An intrusion of warmer water onto the shelf from intermediate depths offshore was found in all cross-shelf sections. Evidence that this warmer water intrudes onto the shelf throughout the year was found in the current meter temperature records. Continental shelf waves appear to be the most likely mechanism for bringing this warmer water onto the shelf. Mixing of very cold water on the shelf with the warmer intruded water appears to be promoted by stirring induced by the semidiurnal tides. The mixing also may be directly caused by shear instabilities. Bottom water that forms near the shelf break and flows down the continental slope in the southern Weddell Sea appears to represent a mixture of the cold shelf water with the warmer intruded water and not cold, dense shelf water alone.