How a Small Reef in the Kuroshio Cultivates the Ocean

Vertical nitrate fluxes associated with turbulent mixing and upwelling around a small reef in the Kuroshio are quantified by continuously deploying a turbulence microstructure profiler with an attached submersible ultraviolet nitrate analyzer while drifting from the upstream to the downstream of the reef. Flow separations and trains of Kelvin-Helmholtz billows (thickness = 60 m) are identified using a shipboard ADCP and an echo-sounder. The turbulence diffusivity associated with the vigorous turbulent mixing reaches up to O(10(-1) m(2) s(-1)), resulting in strong nitrate fluxes of O(1-10(3) mmol m(-2) day(-1)). In addition, large differences between the upstream and downstream density profiles suggest a strong upwelling velocity of O(10(-3) m s(-1)), as well as an upwelling nitrate flux of O(10(2) mmol m(-2) day(-1)) in the entire subsurface layer.

Automated summary

The study quantified vertical nitrate fluxes associated with turbulent mixing and upwelling around a small reef in the Kuroshio by continuously deploying a turbulence microstructure profiler. The vigorous turbulent mixing led to strong nitrate fluxes and the difference in density profiles between upstream and downstream indicated a strong upwelling velocity and nitrate flux in the entire subsurface layer.