PHYSICAL AND BIOGEOCHEMICAL DYNAMICS IN A SUBMESOSCALE FRONT FORCED BY HIGH FREQUENCY WINDS

Observations and models suggest that upper-ocean density fronts may be associated with enhanced biomass, increased diapycnal nutrient fluxes, and elevated new production relative to adjacent waters. However, the physical and biogeochemical dynamics that drive these differences are not fully understood. In this study, high-resolution numerical simulations with a regional ocean model coupled to a four-component ecosystem model are used to isolate and study the integrated effects of high-frequency wind forcing on biogeochemical dynamics in an idealized sub-mesoscale upper-ocean front. Wind forcing with significant near-inertial frequency content resonantly force near-inertial waves. Due to the strong relative vorticity of the geostrophic frontal jet, the near-inertial wave energy rapidly radiates into the upper thermocline. There, wave energy is trapped, amplified and dissipates, inducing substantial oscillatory vertical displacements, enhanced mixing, a stronger sub-inertial secondary circulation, and elevated new production relative to a front forced by low frequency winds.