Submesoscale Vertical Heat Flux Amplifies a Cross‐Scale Positive Feedback in the Western Arabian Sea

High‐resolution simulations reveal that summer monsoon‐induced upwelling in the western Arabian Sea triggers vigorous submesoscale vertical heat flux (SVHF), challenging the conventional view of winter‐dominant submesoscale activity in open‐ocean settings. This intense SVHF, arising from monsoon‐amplified frontal gradients and submesoscale instabilities, transports heat upward more efficiently than mesoscale eddies and substantially strengthens a mesoscale positive feedback loop linking upwelling, isopycnal tilting, baroclinic eddy growth, and mesoscale vertical heat transport. The submesoscale reinforcement not only boosts vertical heat exchange but also prolongs the persistence and intensity of the feedback loop under strong monsoonal forcing and a forward cascade of kinetic energy. These findings unveil a previously unrecognized multiscale mechanism likely occurring in coastal upwelling systems and underscore the critical role of submesoscale‐mesoscale coupling in shaping vertical heat redistribution.