Numerical Investigation of Changes of Subsurface Ocean Temperature Within Mesoscale Eddies After Tropical Cyclone Passages

Abstract Tropical cyclones (TCs) induce complex three‐dimensional ocean thermal responses, but how pre‐existing mesoscale eddies modulate this remains inadequately assessed. Using idealized simulations, we demonstrate that while cyclonic and anticyclonic eddies (AEs) dramatically alter the spatial pattern of subsurface cooling, the net, vertically integrated ocean heat content change is remarkably insensitive to their presence. This insensitivity, evidenced by a consistent sea level anomaly reduction, arises because eddy‐induced surface heat flux anomalies are minor compared to the total TC‐driven ocean heat loss. Nevertheless, eddies critically mediate a subsurface temperature redistribution. Upper‐ocean cooling is enhanced within AEs but attenuated within Cyclonic eddies (CEs), which aligns with previous observational findings. In contrast, anomalous warming or cooling occurs in the vicinity of eddy edges. A heat budget analysis reveals that advection, driven by eddy‐induced anomalous vertical velocities, dominates the sustained thermal response. These vertical motions are well explained by the interaction of TC wind stress with eddy vorticity following Stern's (1965, https://doi.org/10.1016/0011‐7471(65)90007‐0 ) theoretical framework. Our findings demonstrate that pre‐existing eddies primarily act as key mediators of the ocean's three‐dimensional thermal structure under TC forcing, but do not fundamentally alter the net water‐column heat loss, highlighting their role in redistributing, rather than determining, TC‐induced heat changes.