Estimating the Oceanic Kinetic Energy Cascade from Satellite Along-Track Altimetry

The transfer of kinetic energy between currents of different horizontal scales shapes the structure of the global ocean circulation and associated heat, salt, nutrient, and oxygen fluxes, as well as atmosphere-ocean interactions. In particular the geostrophically balanced part of the flow has been shown to be associated with a net inverse cascade from currents of smaller scales to currents of larger scales. Here, we show with a submesoscale-permitting simulation of the Atlantic that the respective scale kinetic energy flux averaged over 5º x 5º boxes is linearly related to the product of quantities that are computable from along-track altimetry when they are averaged over the same region. This linear relationship is applied to JASON-3 along-track sea-surface height data to estimate for the first time the geostrophic kinetic energy cascade at scales between 60 and 200 km, as well as its regional distribution and seasonal cycle for large parts of the global ocean on the basis of observations. The results are consistent with previous findings based on regional observations, simulations, and indirect comparisons of spectral properties of satellite data.