The response of surface chlorophyll to mesoscale eddies generated in the eastern South China Sea

This study investigates the response of surface chlorophyll (CHL) to mesoscale eddies generated in the eastern South China Sea (ESCS) during their lifecycles based on global eddy dataset and chlorophyll data from January 2003 to December 2016. The results show that the responses of CHL anomalies to cyclones are stronger than anticyclones generated in the Luzon Strait (LS) and in the area off northwest Luzon Island (NWLI). CHL anomalies are higher when cyclones disappear than when they are generated in the LS and in the NWLI. Furthermore, impacts of different eddy dynamic mechanisms (eddy advection, eddy trapping, eddy pumping and eddy-induced Ekman pumping) on CHL anomalies are quantified during eddy lifecycles based on empirical orthogonal function (EOF) method. Our results reveal that CHL anomalies in cyclones generated in the NWLI are affected by eddy pumping and its strengthening effect enhanced until the middle stage of their lifecycles. CHL anomalies in cyclones generated in the LS are modulated by eddy advection and linear Ekman pumping. CHL anomalies in anticyclones generated in the LS are jointly induced by eddy trapping, nonlinear Ekman pumping and eddy pumping. This study helps us attribute surface CHL to specific mechanisms and understand the differences in the response of surface CHL to mesoscale eddies generated in the ESCS during their lifecycles, and thus gains a deeper understanding of the role of mesoscale eddies in regulating the marine primary production.