Oceanic eddy kinetic energy in the spectral space regulated by mesoscale air-sea heat exchange in the Kuroshio Extension

Mesoscale air-sea interactions play a critical role in damping eddy activities. However, how mesoscale heat flux influences the distribution of eddy kinetic energy (EKE) in the wavenumber space remains unclear. In this study, we investigate the EKE and temperature variance (T-var) budgets in the Kuroshio Extension (KE) region using wavenumber spectral analysis based on 1/10° coupled climate simulations. These simulations include a standard high-resolution simulation and a smoothed simulation which overlooks mesoscale heat flux. By comparing the differences between these models, we confirm that air-sea heat exchange significantly dissipates T-var. Neglecting mesoscale heat flux results in a 60% underestimation of the T-var damping rate, which in turn increases energy transfer to EKE through vertical buoyancy flux by 22%. This enhanced vertical buoyancy flux leads to a 20% higher EKE level and larger energy budget terms, particularly in the diffusion term, which is closely related to wind power. Furthermore, underestimating air-sea heat exchange could lead to an overestimation of the inverse kinetic energy cascade, thereby distorting the overall energy budget in the KE region.