Trains of large Kelvin‐Helmholtz billows observed in the Kuroshio above a seamount

Trains of large Kelvin‐Helmholtz (KH) billows within the Kuroshio current at ~230 m depth off southeastern Taiwan and above a seamount were observed by shipboard instruments. The trains of large KH billows were present in a strong shear band along the 0.55 m s −1 isotach within the Kuroshio core; they are presumably produced by flow interactions with the rapidly changing topography. Each individual billow, resembling a cat's eye, had a horizontal length scale of 200 m, a vertical scale of 100 m, and a timescale of 7 min, near the local buoyancy frequency. Overturns were observed frequently in the billow cores and the upper eyelids. The turbulent kinetic energy dissipation rates estimated using the Thorpe scale had an average value of O(10 −4 ) W kg −1 and a maximum value of O(10 −3 ) W kg −1 . The turbulence mixing induced by the KH billows may exchange Kuroshio water with the surrounding water masses.