Submesoscale Processes Fueled by the Kuroshio in the Tokara Strait

Abstract Submesoscale processes are essential in balancing global oceanic energy cascades and stimulating air–sea communications. However, measurements of submesoscale turbulence are still not acquired easily. Based on long‐term (2003–2012) shipboard current observations, we obtained direct evidence of considerable submesoscale energization in the Kuroshio, implied by conspicuous spectral characteristics across multiple scales. The submesoscale motions (peak at ∼26 km) exhibited topographically dependent features and typical contrarotating vortex‐pair forms for island wakes, indicating footprints of upstream islands and seamounts. The vortex regimes and stability were analyzed using dimensionless parameters. Furthermore, the submesoscale motions radiated energy in the form of near‐inertial waves, which exhibited consistent shear structures, and spread widely across the entire strait. These results highlight the role of topography in modulating dynamics by continuously promoting energy cascades into submesoscales, which is expected to be universal for rough topography in the ocean.