Abstract Submesoscale dynamics strongly influence the upper ocean, regulating mixing, air–sea exchange, and vertical heat transport. The recent Surface Water and Ocean Topography mission provides unprecedented high‐resolution observations of sea surface height (SSH), yet linking these surface measurements to subsurface ocean dynamics remains challenging. We develop a theoretical framework for diagnosing key mixed layer (ML) properties from surface‐observable states. We show that horizontal density anomalies induced by mixed layer eddies produce surface imprints that can be effectively captured by spatially filtered SSH. The filtered SSH is integrated into the ML Eddy parameterization to infer the effects of submesoscale restratification. A potential energy budget accounting for the mixing–restratification competition in the ML is diagnosed from surface buoyancy flux, wind stress, and the SSH gradient, enabling reconstruction of the mixed‐layer depth. Vertical eddy heat flux can be further reconstructed from the SSH gradient. This framework offers a promising approach for diagnosing interior submesoscale processes using surface observations.