Study of Tidal and Residual Current in the Persian Gulf

In this study, using filed data measurement and time series spectral analysis on velocity factors, the period for diurnal and semidiurnal tide elements of the current were determined. The direction of the residual currents showed a surface current into the Persian Gulf and another current out of the Gulf. This indicates that in this region, the anticlockwise gyre takes place at the same time as time stratification and thermocline. The velocity of the residual current is about 10 cm/s and the velocity of the tidal current is measured at 50 cm/s. the diagrams show that the tidal current has affected the temperature up to the 30 m depth and in lower depth, it has less effect on temperature. It also has a stronger effect in spring than in winter. Therefore, moving from surface to depth, as the water temperature decreases, the effect of the tide on the temperature is decreased. The maybe related to the formation of temperature gradient and thermocline in the spring or the back and forth movement of the tidal current which created the waves and caused the increase in the temperature and decrease in the salinity. Where there are stronger layers, there is a stronger gradient as well as stronger tide effect. Also, the effect of the tide on salinity on the surface is very weak while it is stronger in some depths which may be related to the area topography and back and forth movement of the tide current.