The Role of Foam Decay and Surfactants on Remotely Monitoring Whitecaps

A simple physical model for whitecap persistence and its sensitivity to surfactants will be presented. The model is based on a mathematical description of foam physics and scale-model laboratory experiments using seawater and breaking wave packets. The model is able to reproduce the variability in foam decay times observed in a dataset of near-shore whitecaps using plausible values for surface tension in the sea surface microlayer. The motivation for this work lies in the critical role foam plays in aerosol formation and the sea-to-atmosphere transport of biologically active and climatically relevant material. Moreover the aerial coverage of foam, which in one way or another is implicit in the remote sensing of wave breaking and resulting air-sea exchange processes, also depends critically on its persistence.