Response of the Atmospheric Boundary Layer to Submesoscale Sea Surface Temperature Fronts

Submesoscale sea surface temperature fronts are ubiquitous throughout much of the global ocean; however, the response of the marine atmospheric boundary layer (MABL) to the ocean submesoscale is not well understood. In this manuscript large-eddy simulation is used to explore the time-dependent response of the MABL to idealized submesoscale sea surface temperature fronts, with an emphasis on how the dynamics of the MABL determine the strength and position of gradients in wind speed and air temperature. Results suggest that horizontal mixing only becomes important in response to frontogenesis by horizontally convergent ageostrophic flows, contrary to the common assumption that the MABL response will be strongly dependent on horizontal turbulent mixing. The fronts that develop in the MABL are also associated with large vertical relative vorticity, suggesting the possibility that submesoscale fronts may induce inertial instability in the MABL. These results provide guidance for high-resolution ocean and atmosphere modeling and for interpreting observations. Plain Language Summary The atmosphere responds to changes in sea surface temperature in a variety of important ways; however, it is not currently well understood how the atmosphere responds when the sea surface temperature changes rapidly over small spatial scales. In this article we use very high resolution simulation to explore the response of the atmosphere to idealized small-scale variations in sea surface temperature. The atmospheric temperature and velocity fields are shown to respond quickly to these small-scale ocean temperature gradients. Importantly, the strength and location of the atmospheric response depends on the flow in the atmosphere, contrary to a common assumption that turbulent mixing will dominate the response. The simulation also suggests that the atmosphere might in some cases respond with a growing instability over these ocean fronts. These results provide guidance for high-resolution ocean and atmosphere modeling and for interpreting observations.