| Abstract |
There is a strong seasonal variation in the exchange flow through the strait of Bah al Mandab connecting the Red Sea to the Gulf of Aden (Thompson, 1939). In the winter a two-layer flow is observed in the strait. Dense intermediate water from the Red Sea flows into the Gulf of Aden and warmer fresher surface water flows into the Red Sea. In the summer season the direction of the surface flow is reversed and a third layer, of density between that of the surface layer and that of the intermediate Red Sea water, flows into the Red Sea. An analysis of this intrusion of cold water from the Gulf of Aden into the Red Sea is made using XBT data. The speed of propagation is. 0.06 m s(-1). Following the onset of the winter monsoon in September, downwelling in the Gulf of Aden cuts off the supply of cold water. In the following weeks convective mixing entrains the intrusion into the overlying mixed layer. During the summer there are net fluxes of heat and salt out of the Red Sea. These fluxes, as well as the net evaporation from the sea surface, play an important role in determining the winter time exchange and the properties of the outflow from the Red Sea. Application of two-layer hydraulic theory suggests that the winter time exchange is sub-maximal, i.e. the exchange fluxes are influenced by other processes within the Red Sea and the Gulf of Aden. It is suggested that the stratification in the Gulf of Aden has an important effect upon the exchange. |
