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SUMMARY: An Isopycnic Coordinate Ocean Model is used to represent the three-dimensional propagation of internal tides in the Bay of Biscay. The model is forced by the semi-diurnal tidal waves M2, S2, N2 and K2. A high resolution topography of French and Iberian continental slopes preserves the shape of the main canyons, which are areas of internal tide generation. Hydrological and velocity data collected during a French Naval experiment in 1994 are compared with the model results. Near the generation area, the vertical distribution of the internal tide amplitude, associated with a vertical shear of baroclinic tidal currents, is in agreement with the observations. Moreover, at most locations, the increase in the baroclinic current modelled near the bottom depth matches the data. This increase is related to the distribution of the internal tide amplitude along the ray slope defined by , where w is the tidal frequency, f the Coriolis parameter and N(z) the buoyancy frequency. In most of the data/model comparisons, the vertical density variation in the deep layers shows a difference in phase in agreement with the ray theory. Over the abyssal plain, high horizontal shears of surface current are modelled at mid-bay, i.e. in areas where the internal wave energy coming from the deep ocean encounters the seasonal thermocline. However, the location of these areas is very sensitive to the initial vertical density profile: the three-dimensional variation of the density must be introduced in the initial conditions to improve the model results.Keywords: internal tide, shelf edge, isopycnal model, observations. RESUMEN: MODELADO DE LAS ONDAS INTERNAS EN EL GOLFO DE VIZAYA. COMPARACIÓN CON OBSERVACIONES. -Se ha utilizado un modelo de coordenadas isopycnas para representar la propagación tridimensional de las ondas internas de marea en el Golfo de Vizcaya. El modelo se fuerza por las cuatro ondas de marea semidiurnas M2, S2, N2, K2. Una topografía de alta resolución de los taludes continentales francés y español reproduce la forma de los principales cañones, que son zonas de generación de las ondas internas. Los resultados del modelo se compararon con datos hidrológicos y de corrientes obtenidos en 1994, durante una campaña del Servicio Hidrográfico y Oceanográfico de la Marina francesa. Cerca de la zona de generación, la distribución vertical de la amplitud de la onda interna, asociada a un cizallamiento vertical de las corrientes de marea baroclinas, concuerda con las observaciones. Además, el aumento de intensidad de la corriente baroclina modelizada cerca del fondo, coincide con los datos en la mayoría de los lugares. Este incremento está ligado a la repartición de la amplitud de la marea interna a lo largo de la pendiente de los rayos definida por , donde w es la frecuencia de marea, f el parámetro de Coriolis y N(z) la frecuencia de Brunt-Väisälä. En la mayor parte de las comparaciones datos/modelo, la variación vertical de la densidad en las capas profundas muestra una diferencia de fase en concordancia con la teoría de r...

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International audienceA regional baroclinic model forced with several tidal constituents at different frequencies is used to investigate the internal tide of the Bay of Biscay. The regional ocean model is free surface, sigma-coordinate and it is implemented in order to accurately take into account the barotropic forcing, the strong bathymetry gradients and the temperature and salinity stratifications. In a previous paper, the barotropic component of the tides was studied in details and the boundary conditions of the three-dimensional model were extracted from the atlases. In the present paper, we focus on the baroclinic component of the tides and the simulations are validated against observations from the MINT94 experiment. The observed currents and stratification are accurately reproduced by the model. The internal tide pattern is consistent with the descriptions found in the literature. Combining wavelet and principal component analysis we extract the patterns of generation and propagation of the internal tide at the semi-diurnal and quarter-diurnal frequencies. Secondary internal wave generation areas are identified over the plain. The vertical displacements of isopycnal surfaces for the M4 internal tide are found to be locally half those induced by the semi-diurnal internal tide. A sensitivity study shows the impact of using a three-dimensional initial stratification over the direction of propagation and wavelengths of the internal tides