Abstract: Frontal submesoscale processes can effectively cascade geostrophic energy forward to small-scale dissipation, playing a crucial role in the energy dissipation of mesoscale eddies. Surface buoyancy loss induced by wind forcing is one of the key mechanisms driving frontal submesoscale processes. However, the impacts and mechanisms of wind stress forcing at different frequencies on frontal submesoscale processes and their energy remain unclear. In this study, we investigate the effects of varying wind stress frequency on the submesoscale energy of an eddy and its potential mechanisms using high-resolution idealized numerical experiments of an anticyclonic eddy. The results show that frontal submesoscale energy is modulated by wind-induced mixing under both high- and low-frequency wind stress forcing. A possible mechanism is that wind stress rapidly adjusts the upper-ocean vertical mixing, which alters the vertical secondary circulation and affects submesoscale horizontal flow convergence, thereby modulating the frontal submesoscale frontogenesis process and ultimately leading to changes in submesoscale kinetic energy. Further trend analysis reveals that the rapid variations of high-frequency wind stress are more conducive to sourcing energy for the growth of submesoscale kinetic energy from the horizontal shear of the background flow. In contrast, low-frequency wind stress accumulates frontal intensity through a stronger frontogenesis process, more effectively converting frontal available potential energy into kinetic energy. These findings contribute to a deeper dynamical understanding of the variability of oceanic mesoscale eddies and the processes of the multi-scale energy budget.

Key words: Eddy front, Wind frequency, Submesoscale energy, Submesoscale frontogenesis