On the Magnitude of Mixing in Submarine Canyons

The breaking of tidally-generated internal waves is a significant driver of ocean mixing, and observations show that a non-negligible amount of this internal tide-driven mixing occurs in submarine canyons. While previous studies have used single observations of canyon mixing to estimate the global magnitude of internal tide-driven mixing within canyons, there is still significant uncertainty in these estimates. We have constructed an algorithm using the energy loss from a modeling study of idealized canyons to calculate the magnitude of mixing in each submarine canyon and to determine the percentage of the global internal tide energy budget that is dissipated in canyons. The algorithm utilizes the prior analysis of the SRTM30_PLUS global bathymetry map to provide the geometrical properties of each canyon (i.e. height, length, width) and the bias-corrected World Ocean Circulation Experiment-Argo Global Hydrographic Climatology (WAGHC) to determine the local stratification, as previous studies have shown that the canyon’s geometrical properties as well as local hydrographic properties have significant effects on the magnitude of mixing. Additionally, the internal wave flux from a high-resolution, tidally-forced Hybrid Coordinate Ocean Circulation Model (HYCOM) simulation is used to determine the internal tide energy available for mixing within each canyon. While there are numerous variables that are used to calculate the internal tide energy loss within each canyon, our results show that the percentage of energy loss within the canyon is most sensitive to the ratio of the canyon length to the incoming internal tide wavelength. Furthermore, we find that most canyons dissipate a significant fraction of the incident internal wave energy, with a non-negligible number of canyons dissipating all of the incoming internal wave energy, which is consistent with observations.