Abstract
A large portion of the kinetic energy found within the ocean originates from the growth of ocean surface waves under the action of wind. However our understanding of wind wave dynamical coupling mechanisms remains incomplete. Competing theories exist but direct observational evidence is lacking, due to the technical challenges involved in measuring wind and wave dynamics in the vicinity of the highly energetic wavy ocean surface. Here, direct observations of airflow dynamics in the first millimeters to meters above ocean surface waves are shown. These were achieved using laser imaging techniques on the Floating Instrument Platform FLIP in the Pacific Ocean. The results show that two dynamical wind-wave coupling regimes coexist. Short (~1 m wavelength), strongly wind-forced waves travel more slowly than the wind and cause intermittent airflow separation events. On average, these slow waves are coupled with the airflow via a sheltering mechanism, while longer (~100 m), faster waves induce orbital motions in the airflow.