Penetration of wind-generated near-inertial waves into a turbulent ocean

TL;DR

This study investigates how wind-generated near-inertial waves penetrate a turbulent ocean, revealing complex interactions involving refraction, vorticity, and wave feedback that influence wave energy distribution over time.

Contribution

It introduces an idealized model combining inertial wave dynamics with a turbulent quasi-geostrophic flow, highlighting the processes governing wave penetration and feedback in the ocean.

Findings

Refraction dominates initial wave energy redistribution.

Wave energy is attracted to negative vorticity regions.

Wave feedback weakly affects vortex strength and wave penetration.

Abstract

An idealized storm scenario is examined in which a wind-generated inertial wave interacts with a turbulent baroclinic quasi-geostrophic flow. The flow is initialized by spinning up a Eady model with a realistic stratification profile. The storm is modeled as an initial value problem for a mixed-layer confined, horizontally-uniform inertial oscillation. The primordial inertial oscillation then evolves under the effects of advection, refraction, dispersion and dissipation. Waves feedback onto the flow by modifying its 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 anticyclonic pipes. This drainage halts as wave energy encounters weakening vorticity. After a week or two, wave energy accumulates at the bottom of negative vorticity features, i.e. along filamentary structures at shallow depths and in larger anticyclones at greater depths. Wave feedback tends to weaken vortices and thus slow down wave penetration. This effect, however, is found to be weak even for vigorous storms.