Penetration of Wind-Generated Near-Inertial Waves into a Turbulent Ocean
Olivier Asselin, William R. Young
Abstract
Abstract An idealized storm scenario is examined in which a wind-generated inertial wave interacts with a turbulent baroclinic quasigeostrophic flow. The flow is initialized by spinning up an Eady model with a stratification profile based on observations. The storm is modeled as an initial value problem for a mixed layer confined, horizontally uniform inertial oscillation. The primordial inertial oscillation evolves according to the phase-averaged model of Young and Ben Jelloul. Waves feed back onto the flow by modifying the potential vorticity. In the first few days, refraction dominates and wave energy is attracted (repelled) by regions of negative (positive) vorticity. Wave energy is subsequently drained down into the interior ocean guided by anticyclonic vortices. This drainage halts as wave energy encounters weakening vorticity. After a week or two, wave energy accumulates at the bottom of negative vorticity features, that is, along filamentary structures at shallow depths and in larger anticyclonic vortices at greater depths. Wave feedback tends to weaken vortices and thus slows the penetration of waves into the ocean interior. This nonlinear effect, however, is weak even for vigorous storms.