Energetics of internal tides around the Kerguelen Plateau from modeling and altimetry

International audienceA barotropic tidal model, with a parameterization term to account for the internal wave drag energy dissipation, is used to examine areas of possible M2 internal tide generation in the Kerguelen Plateau region. Barotropic energy flux and a distribution of wave drag dissipation are computed. The results suggest important conversion of barotropic energy into baroclinic tide generation over the northern Kerguelen Plateau shelf break, consistent with a theoretical criterion based on ocean stratification, tidal forcing frequency, and bathymetric gradients. The sea surface height signatures of time-coherent internal tides are studied using TOPEX/Poseidon and Jason-1 altimeter data, whose ascending tracks cross nearly perpendicular to the eastern and western Kerguelen Plateau shelf break. Oscillations of a few centimeters associated with phase-locked internal tides propagate away from the plateau over distances of several hundred kilometers with a ∼110 km wavelength. When reaching the frontal area of the Antarctic Circumpolar Current, the internal tide cannot be identified because of the aliasing of mesoscale variability into the same alias band as M2. Finally, using altimeter data, we estimate the M2 barotropic tidal power converted through the internal tide generation process. We find consistent values with the barotropic model parameterization estimation, which is also in good agreement with global internal tide model estimates. Combined with modeling, this study has shown that altimetry can be used to estimate internal tide dissipatio