Cyclonic ring shedding as a mechanism of cross-jet transport in the Kuroshio Extension

Using the 2002 Kuroshio cyclonic ring as a case study, we document that a cyclonic meander north of the Kuroshio Extension can evolve into a detached ring that crosses the jet and transports water masses across to the southern side of the current, and we use this event as a testbed for comparing different detection methodologies. We combine satellite altimetry with complementary Eulerian and Lagrangian diagnostics to resolve the formation, detachment, and post-detachment evolution of the ring, including its center trajectory, boundary evolution, and transport pathway across the jet. The results show that the ring develops from a cyclonic meander north of the main Kuroshio jet axis, then detaches and is advected to the southern side of the jet while maintaining a coherent core. These results illustrate that ring shedding provides a pathway for cross-jet transport, and highlight how the choice of Eulerian vs Lagrangian diagnostic strongly influences the quantitative characterization of the eddy's size, shape, and lifetime, even when the physical phenomenon itself is robustly identified.