Stepwise seasonal restratification and the evolution of salinity minimum in the Gulf of Aqaba (Gulf of Eilat)

The Gulf of Aqaba (Gulf of Eilat) is a terminal elongated basin that exchanges water with the northern Red Sea via the Straits of Tiran. The gulf's hydrography exhibits strong seasonal variability, with deep mixing in February-March and stable stratification afterward. Recently, using an oceanic model that simulated the seasonal conditions in the gulf, we demonstrated that a relatively large advected heat and water influx through the straits are responsible for most of the observed rises in temperature and increase in volume of the surface layer during the restratification phase (April-August). Here we investigate the restratification process in the surface layer by using the same oceanic model with the aid of passive tracers that allow tracking the water entering through the straits as it flows northward. We show that the time-varying surface hydrography in the northern Red Sea has a significant influence on the seasonal hydrographic conditions in the gulf. The northern Red Sea water warms monotonically during the restratification phase. As a result, new water that enters the gulf during this phase is warmer than the water that entered previously and therefore the stratification is built up gradually layer by layer. The phase difference between minimal salinity (May) and maximal temperature (September) in the northern Red Sea is responsible for the evolution of subsurface salinity minimum level along the gulf. We also explain the transition to a four-layer exchange flow between August and November.