Satellite observed new mechanism of Kuroshio intrusion into the northern South China Sea

Abstract

In addition to existing theories, this study proposes a new mechanism of Kuroshio Intrusion passing through the Luzon Strait (LSKI) on the basis of the satellite observed sea surface height anomaly from January 1993 to December 2018. First, 11 events of westward propagating cyclonic Eddy Impingement on the Kuroshio on the Eastern side of Taiwan (EIET) were recognized. Statistical results indicate that approximately 82% of EIET led to consequential LSKI. Systematic analysis indicates a reduction in northward inertial advection, which is responsible for connecting EIET to consequential LSKI. Dynamic diagnosis further unveils the detailed physical exchange processes therein. Squeezing of the planetary vorticity and advection of negative relative vorticity in response to the collision of the EIET with downstream Kuroshio current (KC) contribute to LSKI. Although the beta-term is relatively weak, for the left flank of LSKI, where the influences of advection and flow divergence largely reduce, it plays a dominant role in forcing the KC to intrude farther west into the northern SCS. Afore-mentioned results identify the possibility of the downstream Kuroshio changes might modify the upstream LSKI critically. More interestingly, this mechanism is a backward feedback sourcing from the Kuroshio downstream region (east of Taiwan) to the upstream region (Luzon Strait).