Continuous Transition of Kinetic Energy Spectra and Fluxes between Mesoscale and Submesoscale

Abstract

We present the kinetic energy spectra and fluxes of currents observed from multiple platforms off the U. S. West Coast -- satellite altimeter (ALT), high-frequency radar (HFR), and shipboard acoustic Doppler current profilers (ADCPs). The one-dimensional wavenumber-domain kinetic energy spectra of the HFR-derived surface currents agree with those of the ALT-derived geostrophic currents at scales larger than 100 km, and decay with $k^{-2}$ and $k^{-3}$ at high wavenumber (below 100 km) up to the wavenumber of 0.5 $\mathrm{km}^{-1}$. Moreover, the kinetic energy spectra of subsurface currents obtained from shipboard ADCPs support a continuous transition of energy between mesoscale and submesoscale. A comparison of the kinetic energy fluxes, estimated from the gridded ALT-derived geostrophic currents and submesoscale HFR-derived surface currents, exhibits the potential injection scales of $\it{O}$(100) km and $\it{O}$(10) km, which are consistent with the regional Rossby deformation radius and the dominant length scales of the regional submesoscale eddies, respectively.