Two regimes of laboratory whitecap foam decay: Bubble-plume controlled and surfactant stabilized

TitleTwo regimes of laboratory whitecap foam decay: Bubble-plume controlled and surfactant stabilized
Publication TypeJournal Article
Year of Publication2013
AuthorsCallaghan AH, Deane GB, Stokes MD
JournalJournal of Physical Oceanography
Volume43
Pagination1114-1126
Date Published2013/06
Type of ArticleArticle
ISBN Number0022-3670
Accession NumberWOS:000320162300003
Keywordsbreaking waves; coverage; dependence; dissipation; sea foam
Abstract

A laboratory experiment to quantify whitecap foam decay time in the presence or absence of surface active material is presented. The investigation was carried out in the glass seawater channel at the Hydraulics Facility of Scripps Institution of Oceanography. Whitecaps were generated with focused, breaking wave packets in filtered seawater pumped from La Jolla Shores Beach with and without the addition of the surfactant Triton X-100. Concentrations of Triton X-100 (204 mu g L-1) were chosen to correspond to ocean conditions of medium productivity. Whitecap foam and subsurface bubble-plume decay times were determined from digital images for a range of wave scales and wave slopes. The experiment showed that foam lifetime is variable and controlled by subsurface bubble-plume-degassing times, which are a function of wave scale and breaking wave slope. This is true whether or not surfactants are present. However, in the presence of surfactants, whitecap foam is stabilized and persists for roughly a factor of 3 times its clean seawater value. The range of foam decay times observed in the laboratory study lie within the range of values observed in an oceanic dataset obtained off Martha's Vineyard in 2008.

DOI10.1175/jpo-d-12-0148.1
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