Tidally generated shelf waves off the western Iberian coast

Abstract

A high-resolution finite element model of barotropic tides in the Iberian Atlantic shelf is presented. The model accurately reproduces available tidal data, with average amplitude discrepancies at 12 Atlantic stations below 3% and 15% for semi-diurnal and diurnal tides, respectively. The accuracy of the model simulations is supported also by a qualitative comparison with velocity data. The model results are used to examine the generation of shelf waves by diurnal tides off the western Portuguese coast. Shelf waves in this area are responsible for large diurnal currents, which can exceed semi-diurnal currents by an order of magnitude. Numerical experiments show that these shelf waves can be generated by obstacles perpendicular to the coastline, and are enhanced in the presence of wide and shallow shelves and steep continental slopes. Along the Portuguese coast, the Tagus plateau is responsible for most of the shelf wave generation.