Simulation of the semidiurnal tides in the Strait of Gibraltar

The M2 and S2 surface tides in the Strait of Gibraltar are simulated using a two-dimensional, nonlinear, boundary-fitted coordinate model with a nominal resolution of ∼0.5 km. Good agreement is achieved with tide gauge and bottom pressure observations, as well as with current measurements made during the Gibraltar Experiment. The cotidal charts and the maps of tidal current ellipse parameters, which have been constructed on the basis of the model results, reproduce all of the known features of the spatial structure of the M2 and S2 tidal waves. These results also show that a ∼90° phase difference between tidal velocity and elevation is detected in much of the Strait of Gibraltar, thus suggesting a small mean tidal energy flux through the strait. The model results give evidence of the general direction for the M2 and S2 net tidal energy fluxes to the west. This finding is consistent with an observed southwestern tidal phase propagation and remains qualitatively unchanged when varying the strait's geometry as well as boundary and astronomical forcings.