Penetration of nonlinear Rossby eddies into South China Sea evidenced by cruise data

From the analyses of the cruise conductivity‐temperature‐depth profiler and acoustic Doppler current profiler data combined with simultaneous satellite altimeter data and Argo float profiling data, this paper provides evidence for the nonlinear Rossby eddies (NREs) penetrating through the Kuroshio and the Luzon Strait and entering the South China Sea (SCS). A high‐salinity water prism in the subsurface layer west of the Luzon Strait was observed in January 2010. The salty prism centered at around 21°N and 118°E has a salinity higher than 34.8 and co‐locates with an anticyclonic eddy with a diameter of about 150 km. The water properties of the salty prism are close to those of the Northwest Pacific (NWP) water. The time series of altimeter data and Argo float profiling data indicate that the anticyclonic eddy originates from an NRE that propagates westward from the NWP. The eddy penetrates the Luzon Strait at a speed of about 0.6 m s−1 because of the effects of the narrow strait and the Kuroshio‐eddy interaction and carries the high‐salinity subsurface water from the NWP into the northern SCS. Key Points Penetration of nonlinear Rossby eddies through Kuroshio and the Luzon Strait Evidenced by high‐salinity subsurface water observed in the northern SCS Significant impact on the SCS circulation