Infrared Remote Sensing of Cooling Whitecap Foam to Quantify Wave Breaking and Aeration

University Of Washington, Seattle WA

Investigators

Abstract

Wave breaking plays a critical role in air-sea interaction processes in both the open ocean and the surf zone. Energy and momentum transferred from the atmosphere to the ocean through wind-wave generation is ultimately dissipated by waves. The resulting turbulence in the upper ocean causes mixing, and in the nearshore momentum transfer can force currents. Improved understanding of the bubble and foam formation processes during wave breaking is needed to better understand the impacts of wave breaking. The goal of this project is to develop and utilize a remote sensing technique to study bubble plume formation and associated wave breaking energy dissipation by exploiting the thermal signature of cooling residual foam left behind by the breaking process. A large-scale, outdoor laboratory experiment will be conducted to evaluate the technique for field-scale breaking waves and explore the effect of wave breaking type, breaking strength, and bubble distribution. The investigators hypothesize that the time from when breaking begins to when the residual foam starts to cool provides a measure of both the bubble plume decay time and depth, which can be used to determine bubble characteristics and evaluate existing plume models related to the wave energy dissipation rate. Prior results indicate that the foam cooling time can be used to map the spatial variability of bubble plume depth and thus provide the spatially varying bubble plume volume. This project will use thermal infrared (IR) imagery and ancillary measurements to investigate and further establish these relationships. The resulting ability to remotely quantify bubble plume properties and energy dissipation due to wave breaking will provide a new and transformative tool for investigating and understanding the air-sea interaction processes driven by wave breaking in the open ocean and the surf zone. 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.