Modes of Subsurface, Intermediate, and Deep-Water Renewal in the Red-Sea

A linear box model of the Red Sea is presented. The model, which inverts hydrographic and He-3 data for the main features of the width-integrated circulation, is able to describe a large part of the seasonal and annual mean circulation. By combining and reconciling major elements of current theories of the Red Sea circulation, available flow measurements, and tracer data the model provides a unified conceptual framework for the understanding of the circulation of the Red Sea. The model forms deep water in the extreme north in two modes, as first suggested by Cember (1988). The convective mode renews the bottom water at an annual mean rate of approximately 0.04 Sv. In the winter the isopycnal mode water renews the uppermost part of the deep water mass. It flows to the south along the bottom of the pycnocline at an annual mean rate of 0.02-0.04 Sv. A new feature in the model's near-surface circulation scheme is the ventilation of the thermocline in the winter at a mean rate of approximately 0.04 Sv, also from the extreme north. There is also a middepth return flow to the north at an annual mean rate of approximately 0.07 Sv. This flow has been suggested but never rigorously quantified before.