Field Measurements of Ocean Wave Whitecap-Induced Bubbles

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The goal of the study is to measure bubbles within active whitecaps and the structure of the foam they form on the surface of the ocean, as a function of wind speed and chemistry in the near surface boundary layer in wind-driven seas. Field observations will be made using a Liquid Robotics Wave Glider (LRWG) and include a variety of remote camera observations of ocean wave whitecaps and in situ bubble and foam sensors. The motivation for this work lies in the critical role wave-entrained bubbles and foam play in CO2 transport, aerosol formation, ocean albedo, and the sea to atmosphere transport of biologically active and climatically relevant material. The project will support two summer undergraduate interns in marine science and participation by the investigators in the Perspectives on Ocean Science lecture series, a public outreach vehicle hosted by the Birch Aquarium at Scripps.The project aims to: determine the scale-dependence of bubble creation on bubble size and whether bubble creation rates can be measured within whitecaps using breaking wave noise; address the stabilization of surface foam by surface-active molecules in oceanic whitecaps; and use images to examine the time-varying structure of whitecap foam in wind-driven seas. The field study will be staged on a Liquid Robotics Wave Glider in the open ocean waters off Point Conception. Four primary sensory systems will be deployed: a sub-surface camera to measure bubbles inside actively breaking whitecaps, a 4-element hydrophone array to measure whitecap noise underwater, mast-mounted cameras to measure the cross-sectional area, decay time and structure of whitecap foam, and hull-mounted sensors to provide measurements of surface tension and proxies for biological productivity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.