[A-CG43] Kuroshio Large Meander

[ACG43-P02] Synchronized decadal variabilities in the Kuroshio and Kuroshio Extension System

*YUXIANG QIAO¹, Hirohiko Nakamura¹ (1.Kagoshima University)

Using satellite altimetry products, the spatially coherent decadal variabilities in current intensity and current path during 1993–2018 were investigated for a western boundary current system, namely, the Kuroshio from the east of Luzon Island to the south of Japan and the Kuroshio Extension (KE). Particularly, we found that the Kuroshio south of Japan (SJ-Kuroshio) and KE varied with an out-of-phase relationship in current intensity during 1993–2018. It was demonstrated that such an out-of-phase relationship was forced by westward-propagating baroclinic Rossby waves that were excited at different phases of the Pacific Decadal Oscillation (PDO). Specifically, after the arrival of the baroclinic Rossby wave to the recirculation south of the KE, the sea surface height anomaly (SSHA) had a further southwestward migration toward the recirculation south of the SJ-Kuroshio within ~5 years, probably induced by the combined effects consisting of the planetary Rossby waves and the nonlinear advection due to two recirculations south of the KE and SJ-Kuroshio. In the meantime, the next baroclinic Rossby wave carrying the opposite SSHA reached the recirculation south of the KE. Such an SSHA migration process caused the out-of-phase current-intensity relationship between the SJ-Kuroshio and KE. More importantly, both of the two SJ-Kuroshio large meander events (2004–2005 and after 2017) during the analysis period occurred after the arrivals of the negative SSHA to the recirculation south of the SJ-Kuroshio, which implies that the SJ-Kuroshio large meander events may be one of the lagged oceanic responses to the PDO.