The Interannual Variability of Eddy Kinetic Energy in the Kuroshio Large Meander Region and Its Relationship to the Kuroshio Latitudinal Position at 140°E

Abstract

AbstractIn this study, the variability of eddy kinetic energy (EKE) in the Kuroshio large meander (LM) region is investigated using both satellite sea surface height observation and high‐resolution ocean reanalysis data. The results show that the EKE has a remarkable interannual variability and it is negatively leading correlated with the change in the Kuroshio latitudinal position at 140°E. The mechanism analysis suggests that the baroclinic instability and advection processes are responsible for the EKE interannual variability and its effect on the Kuroshio latitudinal position at 140°E. Specifically, before the high EKE level occurs, a cyclonic eddy generates at the east of Kii Peninsula in the background field. The rapid development of this eddy and its eastward movement to the LM region induce the isopycnal inclinations there and the associated horizontal density gradient, which leads to the strong baroclinic instability and promotes the evolution of the eddy field and the formation of the high EKE level. The developed strong eddies, especially the cyclonic eddies, move downstream to 140°E, which pushes the Kuroshio off the shore and causes the southerly Kuroshio latitudinal position at 140°E. On the contrary, when the cyclonic eddies do not appear in the LM region, the isopycnals are relatively flat, which is not conducive to the generation of baroclinic instability. Consequently, the EKE level is low and only weak eddies are advected to 140°E, which does not substantially shift the Kuroshio southward and thus results in the northerly Kuroshio position.