Abstract

Abstract

Highlights

  • Internal waves are often considered to be the primary pathway through which energy is transferred from large scales associated with wind and tidal forcing to small scales and turbulence in the ocean interior (MacKinnon et al 2017)

  • By time t = 8, shown in panel (d), the tilted structure of the internal gravity wave has been distorted by the shear flow

  • In the centre of the domain, regions with statically unstable buoyancy profiles emerge, flanked by ‘sheets’ of strong stratification where buoyancy contours are pushed close together. This is consistent with the predictions of figure 12 for the local wave steepness to increase near z = π, and points to a local buildup of available potential energy

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Summary

Introduction

Internal waves are often considered to be the primary pathway through which energy is transferred from large scales associated with wind and tidal forcing to small scales and turbulence in the ocean interior (MacKinnon et al 2017). As waves approached the critical level, convective rolls formed in the spanwise plane, and these rolls were in turn strongly affected by the enhanced shear of the refracted wave These results were consistent with the linear stability analysis of Winters & Riley (1992), who modelled a critically refracted wave as a statically unstable parallel shear flow. We are primarily interested in understanding the key mechanisms involved in the interaction of the wave and the shear, as well as the properties of the turbulence generated from the breakdown of the wave, in particular the associated irreversible mixing and wave–mean flow interaction In this idealised study, we do not specify the source of the internal gravity wave, but choose appropriate parameters to remain consistent with the observations.

Nonlinear 3-D simulations: domain and initial conditions
Qualitative insight from linear ray theory: critical levels
Flow phenomenology and wave breakdown
Energetics
Turbulence and mixing
Mean flow interactions
Discussion and conclusions
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