Cross‐Slope Heat and Salt Transport Induced by Slope Intrusion Eddy's Horizontal Asymmetry in the Northern South China Sea

Material transport caused by mesoscale eddies has been revealed much in the open ocean; however, it is still unclear how much eddy‐induced mass transport in the slope region of the northern South China Sea (SCS). Using the LASG/IAP Climate System Ocean Model (LICOM) from 2007 to 2017, we identified 47 anticyclonic eddies and 97 cyclonic eddies that intruded onto the continental slope, termed slope intrusion eddies. The slope intrusion eddies are more horizontally asymmetric and energetic than those without entering the slope. These eddies induced cross‐slope heat and salt transport of O (1012) W and O (104) kg s−1 owing to their horizontal asymmetry in both Xisha Islands and Dongsha Islands, where are the intrusion zones of mesoscale eddies. Based on the potential vorticity budget, we found that the horizontal asymmetry of velocity was caused by the asymmetry of potential vorticity, which was mainly generated by eddy‐current nonlinear effect in the Dongsha Islands and topographic beta effect in the Xisha Islands, respectively. This study may promote our understanding on the mesoscale dynamics and oceanic energy redistribution in the continental shelf zone of marginal sea. Plain Language Summary Mesoscale eddies are numerous in the open ocean, and can transport heat, salt, and carbon around the ocean through their movement and asymmetric structure. However, it is unclear how much heat and salt transport is induced by their asymmetry in the continental shelf zone. Using a numerical model, we investigate the three‐dimensional heat and salt transport process of slope intrusion eddies in the northern South China Sea. We find that the asymmetry of slope intrusion eddies induces a cross‐slope heat and salt transport of O (1012) W and O (104) kg s−1, which is comparable to the transport of mean flow. We suggest that variation in the potential vorticity is dynamically linked to the nonlinear effect near the Dongsha Islands and the topographic beta effect near the Xisha Islands. These results contribute to our understanding of the redistribution of oceanic energy. Key Points The asymmetry of mesoscale eddy induces O (1012) W onshore heat transport and O (104) kg/s salt transport The asymmetric flow of mesoscale eddy is mainly caused by the asymmetry of potential vorticity The asymmetry of potential vorticity is primarily induced by eddy‐current interaction in Dongsha Islands and topographic beta effect in Xisha Islands