Topographic and mixed layer submesoscale currents in the Carribean Sea

Advancements in observation and modeling techniques have revealed submesoscale structures and processes in the upper ocean with small horizontal scales, characterized by Rossby and Richardson numbers of order one. These submesoscale phenomena exhibit distinct dynamics compared to mesoscale and small-scale processes, enabling energy transfer between them. They contribute significantly to vertical mass, buoyancy, and tracer fluxes, altering upper-ocean stratification and mixed-layer structure on a timescale of days. The objective of this thesis is to investigate submesoscale dynamics in the Caribbean Sea using a high-resolution model, SURF, based on NEMO. Simulations with boundary conditions set to CMEMS for the period of February 2021 allow for the observation of submesoscale features. Dynamical downscaling is employed to reduce computing costs. The study focuses on the distribution and strength of submesoscale surface layer fronts, filaments, and coherent vortices formed by mixed layer baroclinic energy conversion and topographic drag. Various variables, including mixed layer depth, relative vorticity, velocities, kinetic energy, Brunt-Väisälä frequency, Laplacian of sea surface temperature, vertical velocity field, and horizontal Reynolds stress field, are analyzed. The Chibcha channel, characterized by equatorial closeness and boundary drag, exhibits the generation of submesoscale coherent vortices with high Rossby numbers. Conversions of mean to eddy kinetic energy indicate barotropic instability in submesoscale topographic wakes. Sensitivity experiments are conducted to analyze different bathymetric and topographic configurations.