Wind-front interaction within oceanic mixed layer following a storm in the Southern Ocean: Insights from a submesoscale-permitting simulation

The oceanic mixed layer in the Southern Ocean is characterized by numerous fronts due to the stirring of freshwater influxes arising from ice-melting. These fronts interact with winds, modulating the evolution of mixed layer and affecting atmosphere-ocean energy exchanges. However, the underlying mechanism behind the wind-front interaction remains obscure due to lack of three-dimensional observations of the ocean, particularly velocities. To address this question, this study investigates the dynamic of fronts within the mixed layer during a storm by employing a subset of the global submesoscale-permitting simulation, ROAM_MIZ, which focuses on the Northeast Weddell Sea region. We first compare the ROAM_MIZ data to glider data to assess the performance of the model simulation, finding that the ROAM_MIZ can capture submesoscale features within mixed layer to a large degree. Subsequent analyses based on a subset of ROAM_MIZ show lateral density gradients within mixed layer decrease rapidly during high winds associated with the storm. Down-front winds accelerate this decrease as the Ekman buoyancy transport enhances the instability of the fronts, primary dominated by horizontally baroclinic components. After the storm, the fronts strengthen again with low winds due to the frontogenesis by larger scale strain. Moreover, the non-geostrophic turbulence induces modification of the relative vorticity, affecting the instability within mixed layer. These findings offer valuable guidance for the deployment of observational instruments and subsequent analysis, as well as deepen the understanding of air-sea interactions in the Southern Ocean.