Igor Uchoa, Jacob O. Wenegrat, Lionel Renault

Air-sea interaction impacts ocean energetics via modifications to the exchange of momentum and buoyancy. Prior work at the submesoscale has largely focused on mechanisms related to the eddy kinetic energy (EKE), such as the current feedback on stress, which generates negative wind work, or variations in sea surface temperature (SST) that modify surface winds. However, less is known about the influence of submesoscale SST variability on ocean energetics through its direct effect on the surface flux of eddy potential energy (EPE). Here the role of EPE flux on submesoscale ocean energetics is investigated using a fully-coupled model of the California Current region, including a numerical experiment that suppresses the thermal response in the computation of air-sea fluxes at the submesoscale. Correlations between surface buoyancy anomalies and surface buoyancy fluxes lead to an approximately 10--25$\%$ loss of submesoscale EPE, which results in similar magnitude reductions of the vertical buoyancy production, EKE, and eddy wind work. The changes induced by this mechanism in the energy reservoirs and dissipation/conversion pathways are on the same order of magnitude as the negative wind work induced by the current feedback. An approximate form of the EPE flux shows that it is a function of the density ratio and proportional to the surface EPE reservoir of the system. These findings indicate the importance of the submesoscale SST variability, and small-scale variability in surface heat fluxes, in modifying energy reservoirs and conversion pathways of the ocean via the direct flux of EPE at the air-sea interface.