The anisotropy of internal tide generation: Global estimates for the M2 tide and implications for tidally driven mixing parameterizations

Energetically consistent parameterizations of small-scale turbulent mixing rely on internal gravity wave energetics. A crucial ingredient is the generation of internal waves by the interaction of the barotropic tide with rough seafloor topography. Owing to the orientation of topographic obstacles and the directionality of barotropic tidal currents, this process is inherently anisotropic, but so far, this dependence on horizontal direction was not taken into account in global estimates of internal tide generation. We present the global application of a new method based on linear theory that resolves the horizontal direction of the internal tide generation, showing the substantial anisotropy of this process. How this in turn affects vertical mixing and the ocean state is evaluated with the aid of the internal gravity wave model IDEMIX, a backbone of energetically consistent parameterizations of wave-induced mixing.