Estimating the Oceanic Kinetic Energy Cascade from Along-Track Altimetry

Abstract The oceanic kinetic energy cascade, the flux 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. Here, we show with two numerical ocean simulations that the surface geostrophic cascade can be estimated from satellite altimetry observations and present for the first time its regional distribution and seasonal cycle at scales of 40 to 150 km for large parts of the global ocean on the basis of observations. The time-mean cascade is inverse (towards larger scales), strongest in large-scale current systems and decreases with distance from these systems. In the open ocean, the inverse cascade is associated with a maximum in late winter at the smallest scales studied, which transitions to scales larger than 100 km within two to three months, consistent with the widespread absorption of mixed-layer eddies by mesoscale eddies in spring.