Lagrangian coherent structures and internal wave attractors

For a nonuniformly stratified layer of fluid, internal gravity waves propagate at varying angles depending on the local buoyancy and Coriolis (in geophysical applications) frequencies. Relatively confined geometries, such as multiple submarine ridges, can support internal wave attractors, which can be viewed as Lagrangian coherent structures for the energy density flux. Since traditional approaches for locating these structures prove cumbersome, here we develop an approach that efficiently extracts the locations of internal wave attractors, as well as quantifying the rate of attraction. Using realistic geometry and stratification from ocean observations, we find that a significant northern portion of the Luzon ridge can support internal wave attractors.