# Observation of turbulence in wave-induced oscillatory flows

## TL;DR

This study demonstrates that wave-induced oscillatory flows in the ocean are turbulent, exhibiting a power-law velocity spectrum and intermittency, which can significantly influence ocean mixing and related climate processes.

## Contribution

The paper provides the first detailed measurements and analysis confirming turbulence in wave-induced oscillatory flows, highlighting their role in ocean mixing.

## Key findings

- Velocity spectrum follows a ^{-5/3} power law.
- Oscillatory flows exhibit intermittency and turbulence.
- Wave motion impacts ocean mixing and climate-related phenomena.

## Abstract

The dynamic and thermal regimes of climate are regulated by an exchange of energy and momentum between the atmosphere and the ocean. The role exerted by surface waves on this interchange is particularly enigmatic. Waves induce turbulence in the upper ocean by breaking and through Langmuir circulations. However, waves can directly inject energy into subsurface layers. This relates to waves not being truly irrotational and therefore the induced orbital motion being turbulent. The existence, extent and properties of this turbulent oscillatory flow still remain uncertain. Here we present measurements of the velocity field of oscillatory flows, which are induced by mechanically generated random wave fields in a large scale experimental facility. Velocities were recorded at a depth sufficiently far from the water surface to rule out effects of wave breaking. We demonstrate that the spectral tail of the velocity field follows a power-law scaling close to $\omega^{-5/3}$. The turbulent behaviour is investigated via rigorous statistical analysis of the structure functions to highlight the emergence of intermittency in oscillatory flows. The results show that wave motion is turbulent and can contribute to ocean mixing. By deepening of the mixed layer, wave induced motion affects cyclogenesis and sediment resuspension.