Submesoscale structures are ubiquitous yet rarely observed due to their transient nature. Here, autonomous glider measurements in the Gulf of Mexico capture fine-scale thermohaline variability around a Loop Current Eddy (LCE) throughout an annual cycle with multiple glider transects, revealing where overturning instabilities mediate ocean-atmosphere exchange. Lateral buoyancy gradients associated with submesoscale filaments and fronts at the periphery of the LCE amplify wind stress effects when aligned with geostrophic flow, promoting symmetric gravity instability particularly in winter when the potential vorticity is minimal. Associated Ekman heat fluxes reach $≤−10,000 W m^{−2}$ under $1.2 N m^{−2}$ wind stress, coincident with inertial-symmetric instability in anticyclonic regions. These observations might have implications for the restratification processes, kinetic energy budget, and biogeochemical cycles inside LCEs, improving the understanding of submesoscale impacts on mesoscale eddy dynamics and enhancing strategies for targeted submesoscale sampling.