Deep intense vertical mixing in the Bussol' Strait



[1] To reveal the intensity of deep mixing in the Bussol' Strait, we performed the direct observations of turbulence for the first time. Vigorous vertical mixing with a turbulent energy dissipation rate ε above 10−6 W/kg and diapycnal diffusivity Kρ above 103 cm2/s were observed at depths of 600–1300 m (potential densities of 27.0–27.5 σθ) at the western gap of the Bussol' Strait, possibly affecting water-mass transformation and thermohaline circulation. The strong vertical mixing with a diurnal period occurred when the diurnal tidal current flowed toward the Okhotsk Sea, corresponding to a period of enhanced shear consisting of the mean flow with a two-layered structure and the large-amplitude diurnal tidal current with a vertical structure explained by a low-vertical mode topographically trapped wave. The empirical relationship ofε = 10−1.46±1.91 × S2.16±0.72 is obtained between ε and the shear Sreconstructed from the 50-m-scale mean, diurnal, and semi-diurnal tidal currents.