Impact of the Astronomical Potential Forcing on the Local Solution

We have used a high-resolution barotropic tidal model to predict tidal elevations and currents in the Tunisian shelf and the Strait of Sicily (Mediterranean sea). Model performance was evaluated with respect to tide gauge measurements. General features for the various semidiurnal constituents are nearly similar to each other with maximum amplitude in the Gulf of Gabes. The modelled tidal characteristics are in good agreement with observations and previous global solutions. Nevertheless, it seems that the only forcing by elevation at the open boundaries is not able to reproduce the intensity of the observed resonance in the Gulf of Gabes, since the amplitude is underestimated. When the potential forcing is added, the solution is much better in term of amplitude. Indeed, the maximum modelled amplitude (51.7 cm) is very close to the observed one (51.1 cm). The potential forcing enhances the amplitude and places correctly the amphidromes. It seems that the impact of the potential forcing is particularly important within the semidiurnal frequency which is the resonance frequency in the Gulf of Gabes.