Three-Dimensional Measurements of Air Entrainment and Enhanced Bubble Transport During Wave Breaking

Abstract

We experimentally investigate the depth distributions and dynamics of air bubbles entrained by breaking waves in a wind-wave channel over a range of breaking wave conditions using high-resolution imaging and three-dimensional bubble tracking. Below the wave troughs, the bubble concentration decays exponentially with depth. Patches of entrained bubbles are identified for each breaking wave, and statistics describing the horizontal and vertical transport are presented. Aggregating our results, we find a stream-wise transport faster than the associated Stokes drift and modified Stokes drift for buoyant particles, which is an effect not accounted for in current models of bubble transport. This enhancement in transport is attributed to the flow field induced by the breaking waves and is relevant for the transport of bubbles, oil droplets, and microplastics at the ocean surface.