Observations of wave breaking dissipation and bubble plumes in various sea states

Abstract:

We present observations of surface wave breaking dissipation and bubble plumes that are recently collected in the North Pacific Ocean and cover a wide range of sea state conditions including storm conditions with sustained winds up to 22 m/s and significant wave heights up to 9m. Observations include wave, turbulence, and bubble plume measurements by drifting buoys as well as aerial whitecap coverage measurements by shipboard video systems. The buoys with downlooking Acoustic Doppler Current Profilers (ADCPs) measure turbulence in a pulse-coherent mode and image bubble plumes with echograms. Measured turbulence dissipation rate profiles extend to 3 m depth in a wave-following reference frame which is deep enough to robustly estimate wave breaking dissipation. The echograms provide imaging of bubble plumes up to 30 m depth in a wave-following reference frame which are used to estimate bubble plume penetration depth. We present in detail the dependency of wave breaking dissipation, aerial whitecap coverage, bubble plume depth, and bubble plume volume on wind speed, wave breaking height, and various estimates of steepness. The volume of bubble plumes is estimated by combining active whitecap coverage and plume depth measurements. Finally, we examine recent formulations that relate wave breaking dissipation to the volume of bubble plumes.