Revealing wave-wave resonant interactions in ocean wind waves

TL;DR

This study provides experimental evidence of wave-wave resonant interactions in ocean wind waves, confirming theoretical predictions and supporting the validity of advanced ocean wave models.

Contribution

First direct measurement of resonant wave interactions in the ocean, validating theoretical models with stereoscopic surface elevation data.

Findings

Reproduced Phillips' figure-eight pattern in real ocean data

Identified a continuum of resonant configurations matching theory

Supported the use of third-generation wave models for ocean dynamics

Abstract

Ocean wind waves are a fundamental manifestation of complex dynamics in geophysical fluid systems, characterized by a rich interplay between dispersion and nonlinearity. While linear wave theory provides a first-order description of wave motion, real-world oceanic environments are governed by nonlinear interactions that are responsible for a transfer of energy between waves of different lengths. Established theoretical concepts predict that four-wave resonant interactions serve as the primary mechanism for energy transfers among wave components in oceanic surface wave fields. Although the presence and efficiency of these resonant interactions have been demonstrated in controlled wave tank experiments, their direct identification in the real ocean, where a large number of random waves interact, has remained elusive. Here, using a stereoscopic system that enables the measurement of surface elevation in both space and time, we provide experimental evidence of resonant interactions in ocean wind waves. Our data not only reproduce the well-known figure-eight pattern predicted by Phillips, but also reveal a continuum of different resonant configurations that closely match the theoretical predictions. These findings support the validity of third-generation ocean wave models, strengthening their ability to accurately capture wave dynamics in the ocean.