5:15 PM - 7:15 PM
[ACG49-P01] Dynamical Analysis of Recent Changes in the Kuroshio-Oyashio Current System and Their Underlying Mechanisms
★Invited Papers
Keywords:Kuroshio Large Meander, Kuroshio Extension, Hilbert EOF analysis, ocean reanalysis
The Kuroshio Large Meander, a significant oceanic phenomenon that initiated in 2017, continues to demonstrate remarkable persistence in the present day. Furthermore, since the latter part of 2022, the Kuroshio Extension's separation point has exhibited an unprecedented pattern of extreme northward overshooting. Although this distinctive overshooting behavior experienced a temporary reduction in intensity during May 2024, coinciding with the detachment of a warm-core eddy, it has subsequently resumed its pronounced northward trajectory with renewed vigor. While historical records indicate comparable instances of extreme overshooting in the Kuroshio Extension, notably during 1979, the sustained duration of the current event stands as unprecedented in observational history.
Through the application of sophisticated Hilbert EOF analysis to comprehensive JCOPE2Mocean reanalysis data, this study examines the complex dynamics underlying the recent transformations in the Kuroshio-Oyashio current system. Our analysis reveals that the elevated sea surface height observed in the waters east of the Boso Peninsula—a direct consequence of the northward displacement in the Kuroshio Extension's mean position—emerges as the critical factor governing both the unusually prolonged Large Meander and the extreme overshooting phenomenon.
This anomalously heightened sea surface height manifests its influence through two distinct but interconnected mechanisms: firstly, it creates a barrier that effectively impedes the eastward propagation of oceanic cold eddies responsible for the formation of the Large Meander, thereby preventing its natural termination; secondly, it acts to substantially enhance the Kuroshio's northward separation tendency, thus actively promoting the observed overshooting behavior. These persistent sea surface height anomalies, which play such a pivotal role in these oceanic processes, have been found to maintain a strong relation with the wind field in the Pacific Ocean.
Through the application of sophisticated Hilbert EOF analysis to comprehensive JCOPE2Mocean reanalysis data, this study examines the complex dynamics underlying the recent transformations in the Kuroshio-Oyashio current system. Our analysis reveals that the elevated sea surface height observed in the waters east of the Boso Peninsula—a direct consequence of the northward displacement in the Kuroshio Extension's mean position—emerges as the critical factor governing both the unusually prolonged Large Meander and the extreme overshooting phenomenon.
This anomalously heightened sea surface height manifests its influence through two distinct but interconnected mechanisms: firstly, it creates a barrier that effectively impedes the eastward propagation of oceanic cold eddies responsible for the formation of the Large Meander, thereby preventing its natural termination; secondly, it acts to substantially enhance the Kuroshio's northward separation tendency, thus actively promoting the observed overshooting behavior. These persistent sea surface height anomalies, which play such a pivotal role in these oceanic processes, have been found to maintain a strong relation with the wind field in the Pacific Ocean.