Περίληψη:
[1] The mechanisms involved in the seasonal exchange between the Red
Sea and the Indian Ocean are studied using an Oceanic General
Circulation Model (OGCM), namely the Miami Isopycnic Coordinate Ocean
Model (MICOM). The model reproduces the basic characteristics of the
seasonal circulation observed in the area of the strait of Bab el
Mandeb. There is good agreement between model results and available
observations on the strength of the exchange and the characteristics of
the water masses involved, as well as the seasonal flow pattern. During
winter, this flow consists of a typical inverse estuarine circulation,
while during summer, the surface flow reverses, there is an intermediate
inflow of relatively cold and fresh water, and the hypersaline outflow
at the bottom of the strait is significantly reduced. Additional
experiments with different atmospheric forcing (seasonal winds, seasonal
thermohaline air-sea fluxes, or combinations) were performed in order to
assess the role of the atmospheric forcing fields in the exchange flow
at Bab el Mandeb. The results of both the wind- and thermohaline-driven
experiments exhibit a strong seasonality at the area of the strait,
which is in phase with the observations. However, it is the combination
of both the seasonal pattern of the wind stress and the seasonal
thermohaline forcing that can reproduce the observed seasonal
variability at the strait. The importance of the seasonal cycle of the
thermohaline forcing on the exchange flow pattern is also emphasized by
these results. In the experiment where the thermohaline forcing is
represented by its annual mean, the strength of the exchange is reduced
almost by half.
