Accumulation and subduction of buoyant material at submesoscale fronts

Abstract

The influence of submesoscale currents on the distribution and subduction of passive, buoyant tracers in the mixed layer is examined using large eddy simulations. Submesoscale eddies are generated through an ageostrophic baroclininc instability associated with a background horizontal buoyancy gradient. The simulations also include various levels of surface cooling, which provides an additional source of three-dimensional turbulence. Submesoscales compete against turbulent convection and re-stratify the mixed layer while generating strong turbulence along a submesoscale front. Buoyant tracers accumulate at the surface along the submesocale front where they are subducted down into the water column. The presence of submesoscales strongly modifies the vertical tracer flux, even in the presence of strong convective forcing. The correlation between high tracer concentration and strong downwelling enhances the vertical diffusivity for buoyant tracers.