Oceanic Eddy-killing by Wind from Global Satellite Observations

While wind is the primary driver of the oceanic general circulation, we find that it kills the ocean's most energetic motions --its mesoscale eddies-- at an average rate of 50 GW. We use satellite observations and a recent method to disentangle multi-scale processes on the sphere. A length-scale analysis of air-sea energy transfer on the entire globe had not been undertaken before, to our knowledge. In fact, we show that the temporal mean-eddy decomposition (i.e. Reynolds averaging) commonly used in oceanography fails to unravel eddy-killing. Our results present the first evidence that eddy-killing is a major seasonal sink for the oceanic eddies, peaking in winter. We find that eddy-killing removes a substantial fraction (up to 90%) of the wind power input in western boundary currents such as the Gulf Stream and Kuroshio. This process, often overlooked in analyses and models, is a major dissipation pathway for mesoscales, the ocean's most energetic scales.