Northward Shift of the Kuroshio Extension as a Key Factor for Persistent Kuroshio Large Meanders in a Multi‐Century Eddy‐Resolving Simulation

Abstract The Kuroshio path south of Japan occasionally follows a quasi‐stationary large meander (LM) path. Path fluctuations between the LM and non‐LM (NLM) influence the surrounding ocean, atmosphere, and marine ecosystems. While LM durations vary from several months to several years, the factors controlling their persistence remain poorly understood, mainly because high‐resolution satellite altimetry records include only two LM events. In this study, a 520‐year simulation with an eddy‐resolving configuration of the Community Earth System Model (CESM‐HR) is analyzed to explore the factors determining LM duration. Although realistic Kuroshio path variability is difficult to simulate even in some eddy‐resolving models, CESM‐HR can reasonably reproduce the spatiotemporal characteristics of the Kuroshio path fluctuations and provide a substantially larger number of LM events than observations. In the simulation, only long LM events tend to be accompanied by a northward migration of the Kuroshio Extension (KE), consistent with the two observed LM events. In contrast, both long and short LM events are associated with a stable state of the KE. When the KE shifts southward, mesoscale disturbances are energized in the southern recirculation region. As these disturbances propagate westward, they disrupt LM events in the upstream. Conversely, the northward‐shifted KE suppresses mesoscale disturbances and may favor a persistent LM. Moreover, the LM exhibits a peak correlation with KE latitude when it leads by several months. Multiple linear‐regression analyses show that both LM and baroclinic Rossby waves make comparable contributions to upstream KE variability, whereas the latter dominates downstream KE variability.