The fate of storm-generated near-inertial waves in the Kuroshio-Oyashio Confluence

Sebastian Essink, Applied Physics Laboratory University of Washington, Seattle, WA, United States, Ren-Chieh Lien, Applied Physics Laboratory, Seattle, WA, United States and Eric L Kunze, NorthWest Research Associates, Redmond, WA, United States
Pathways of near-inertial wave energy, generated by wind forcing at the surface and dissipated in the ocean’s interior, remain elusive. Wind-forced near-inertial waves are thought to be one of three major energy sources for deep-ocean mixing, with 0.3-1.3 TW of the needed 2 TW to maintain abyssal stratification. While 15-50% of wind-forced near-inertial energy propagates equatorwards as low modes, the fate of the remaining energy, such as how and where it might be dissipated in the near-field, still lacks observational quantification.

Here, we present profile time-series of finescale temperature, salinity, velocity, and microscale temperature measurements from EM-APEX floats in the Kuroshio-Oyashio Confluence for two fall-and-winter storm seasons. Wind-stress forcing from re-analysis winds is compared to the observed evolution of inertial HKE and inferred kinetic energy dissipation rates in the surface mixed layer. Inertial HKE changes have similar probability distributions to wind-forcing while dissipation rates are 2 orders of magnitude smaller, suggesting significant losses to horizontal and vertical radiation. We will also compare observations to simulations using the one-dimensional Price-Weller-Pinkel model forced with reanalysismomentum- and heat-fluxes.