Internal Tides over a Shelf Break: Analytical Model and Observations

Abstract

Data collected on Cruise ONDINE 85 organized by the Service Hydrophique et Ocèanographique de la Marine, at two points (P1 and P6) near the continental shelf break of the Bay of Biscay, show very large amplitudes of internal tides. These waves exhibit a strong nonlinear character of the semidiurnal evolution of the thermocline depth. During spring tide, the internal oscillations can reach 80 meters. In order to get an analytical solution for the interface depth variation near the top of the shelf break, the two layer nonlinear model of generation and propagation of internal tides developed by Mazé is linearized in the present paper. Taking account of several monochromatic tides waves (M2, S2, N2, K2) in the forcing term, comparison between this analytical solution and data can be done over. a six-week period. Such a comparison shows that that the scale of the interface level and the time variation of the interface are quite well reproduced by the analytical model.