The hurricane-induced decay of mesoscale eddies: an energy source for near-inertial waves

Oceanic mesoscale eddies represent the most energetic component of the ocean circulation; however, their decay routes remain elusive, leaving a key gap in our understanding of the oceanic energy cascade. Here we combine satellite data with mooring measurements from the South China Sea in 2014 to reveal a rapid decay of oceanic eddies following the passage of typhoons. This decay is accompanied by a substantial generation of internal waves with near-inertial frequency in the ocean interior. The temporal correspondence and quantitatively commensurate energy changes indicate a direct energy transfer from eddy to internal wave field. We propose that typhoon-induced perturbations trigger an adjustment process within the eddy, resulting in energy loss through the radiation of near-inertial waves. Quantitatively supported by numerical model simulations, this mechanism plays a crucial role in the evolution of mesoscale eddies and points to a previously overlooked interior source of oceanic internal waves. Mesoscale eddies’ decay is accompanied by subsurface near-inertial wave generation, indicating direct energy transfer, according to remote sensing and in situ measurements.