Influence of the Ocean Mesoscale Eddy–Atmosphere Thermal Feedback on the Upper-Ocean Haline Stratification

The ocean mesoscale eddy–atmosphere (OME-A) interaction through the eddy-induced sea surface temperature anomaly can feedback on ocean dynamics in various ways (referred to as the OME-A thermal feedback). In this study, the influence of the OME-A thermal feedback on the upper-ocean haline structure is analyzed based on high-resolution coupled simulations. In the Oyashio Extension where pronounced surface temperature and salinity fronts are collocated, the haline stratification in the upper 200 m is significantly enhanced by the OME-A thermal feedback. This enhancement is mainly attributed to the weakening of the upward eddy salinity transport in response to the OME-A thermal feedback. The OME-A thermal feedback influences the vertical eddy salinity transport through its differed impacts on the mesoscale buoyancy and temperature anomaly variances. As temperature and salinity in the Oyashio Extension are strongly compensated for their effects on buoyancy, the dissipation of the mesoscale buoyancy anomaly variance b′2 by the OME-A thermal feedback is considerably weaker than that estimated from the mesoscale temperature anomaly alone, i.e., (gαT′)2, with g the gravity acceleration and α the thermal expansion coefficient. Correspondingly, the vertical eddy buoyancy transport (w′b′) is weakened by the OME-A thermal feedback to a lesser extent than its thermal component (gαw′T′). The different responses of w′b′ and gαw′T′ to the OME-A thermal feedback are reconciled by the reduced vertical eddy salinity transport.