The seasonality of tidal circulation in the Gulf of Elat

The Princeton Ocean Model is applied to simulate the tidal circulation in the Gulf of Elat under both summer and winter hydrographic conditions. The results of the simulation show that the circulation in the Gulf when both tidal- and wind-forcing are present has the same structure as that of the purely wind-driven pattern, namely, the circulation is made up of series of gyres oriented along the Gulf's main axis. The location and number of these gyres are determined primarily by the bathymetry, while the seasonally changing depth of the thermocline determines mainly their size. The simulations provide an explanation for the observed recurring disappearance of the semi-diurnal peak in the spectrum of the longshore current component at 12 m depth along the Gulf's west shore during winter. The model results show that the tidal flux is determined by the inflow at the mouth of the Gulf (Straits of Tiran), and throughout the whole Gulf this flux occupies the upper layer extending from the surface to the seasonal thermocline. During winter, when the seasonal thermocline's depth exceeds 600 m, the velocity associated with this flux is much smaller than during summer when the same tidal flux occupies a thinner layer as the thermocline shoals to 150 m. In support of this scenario, our results also demonstrate that at depths between 150 and 600 m (i.e., the depths of the summer and winter thermoclines) the semi-diurnal signal is stronger in winter than in summer.