ON BUBBLE CLOUDS PRODUCED BY BREAKING WAVES - AN EVENT ANALYSIS OF OCEAN ACOUSTIC MEASUREMENTS

A field experiment was carried out to measure the time-varying properties of bubble clouds as they evolve from ocean breaking waves. The experiment was conducted from the floating instrument platform Flip and consisted of simultaneous, colocated acoustic measurements of subsurface bubbles and video recordings of the sea surface. Details of two breaking wave events are presented. The results of the acoustic measurements of bubble density and their entrainment depth are reported for the time t/T-c greater than or similar to 3, where t is the time from breaking and T-c is a characteristic timescale based on the speed of the breaking wave crest as estimated from the video recordings. Order of magnitude values for the air-void fraction beta, vertical eddy diffusivity k(v), and kinetic energy dissipation epsilon associated with breaking waves are presented. The wind speed dependence of average acoustic backscattering properties over the course of the experiment is also given.