Ultrasound scattering for oil slicks: Characterization at sea

Abstract

It has been demonstrated in open‐sea experiments with a film of well‐defined, oceanographically relevant viscoelastic surface properties, of artificial crude oil origin, spread over the Baltic Sea surface, together with a buoylike, high‐frequency (10‐MHz) acoustic system based on specular forward scattering geometry, that the film parameters can be recovered from the ratio of the scattered signal modulation spectra with or without films by means of the Marangoni theory of wind wave damping by viscoelastic films. The acoustically derived film parameters are in moderate agreement with ones determined simultaneously ‘'in situ”; in the supplementary Langmuir trough using a novel film sampler‐elastometer, and turned out characteristic of natural sea slicks or “weathered”; crude oil spills. A principal role in the proper determination of the film parameters from the acoustic probing is played by the film filling factor, being wind speed dependent, whereas a variation of the wind wave growth rate, also affected ...