Submesoscale Turbulence and Frontogenesis​

Submesoscale turbulence consists of flow structures with spatial scales of O(100m-10km), temporal scales of O(hours-day), in a dynamical regime characterized by O(1) Rossby and Richardson numbers. Phenomenologically, the flow exhibits anisotropic patterns of lines or streaks with large magnitudes of buoyancy and velocity gradients, cyclonic vorticity and convergence (10,11,12). The associated velocity spectrum is shallow and the velocity gradient spectrum has roughly equal contributions from the divergence and vorticity spectra that comprise it. In 15 we use these dynamical, phenomenological, and spectral characteristics to develop an asymptotic theory for submesoscale turbulence. Specifically, we characterize the formation of the fronts and filaments, which we define as submesoscale frontogenesis.  We are able to validate the theory with high-resolution numerical simulations and Lagrangian in-situ measurements. Our theory has important implications to the horizontal and vertical transport of tracers in the ocean.