Characterization of Submesoscale Turbulence in the East/Japan Sea Using Geostationary Ocean Color Satellite Images

Abstract

Submesoscale processes are key in understanding physical and biological phenomena near the surface, but there remains a lack of observational evidence over large areas. We used hourly images from a geostationary satellite that can resolve variation in surface ocean color over an area of few hundred kilometers. The temporal variation in the surface chlorophyll a distribution captured by the satellite images was first used to generate a submesoscale-permitting velocity field, from which we calculated the turbulence statistics such as kinetic energy spectra, velocity structure functions, and energy flux. Application to the April scenes in the East/Japan Sea showed that the kinetic energy spectra had a transition scale at 50 km that suggested two spectral regimes following k(-3) and k(-5/3), implying the coexistence of quasi-geostrophic turbulence and surface quasi-geostrophic turbulence. The chlorophyll a scalar spectrum suggested two spectral regimes of k(-5/3) and k(-1) with a transition at 3 km.