How the Kuroshio Current Delivers Nutrients to Sunlit Layers on the Continental Shelves With Aid of Near-Inertial Waves and Turbulence

The Kuroshio Current carries a large amount of nutrients in dark subsurface layer along the southern coast of Japan. However, due to lack of sufficient multidisciplinary high-resolution observations, it has been unclear whether and how the subsurface nutrients are injected to sunlit layers on the continental shelf. In this study, using a state-of-the-art tow-yo microstructure profiler and nitrate measurements, we show that the Kuroshio flowing on the shelfbreak induces very strong turbulent dissipation rate similar to O(10(-7)W.kg(-1)) and diffusivity similar to O(10(-3)m(2).s(-1)) over an across frontal scale of 20-30 km. This strong turbulence could provide a diffusive nitrate flux to euphotic zone of >O(1 mmol N.m(-2).day(-1)). As the Kuroshio steadily runs on the continental shelves along the path, the nutrient injection found in this study is a very important supply for biological production on the continental margin along the southern coast of Japan.