On the imprint of surfactant-driven stabilization of laboratory breaking wave foam with comparison to oceanic whitecaps
File(s)Callaghan_JGR_2017_SurfactantImprint.pdf (1.23 MB)
Published version
Author(s)
Callaghan, AH
Deane, GB
Stokes, MD
Type
Journal Article
Abstract
Surfactants are ubiquitous in the global oceans: they help form the materially‐distinct sea surface microlayer (SML) across which global ocean‐atmosphere exchanges take place, and they reside on the surfaces of bubbles and whitecap foam cells prolonging their lifetime thus altering ocean albedo. Despite their importance, the occurrence, spatial distribution, and composition of surfactants within the upper ocean and the SML remains under‐characterized during conditions of vigorous wave breaking when in‐situ sampling methods are difficult to implement. Additionally, no quantitative framework exists to evaluate the importance of surfactant activity on ocean whitecap foam coverage estimates. Here we use individual laboratory breaking waves generated in filtered seawater and seawater with added soluble surfactant to identify the imprint of surfactant activity in whitecap foam evolution. The data show a distinct surfactant imprint in the decay phase of foam evolution. The area‐time‐integral of foam evolution is used to develop a time‐varying stabilization function, urn:x-wiley:21699275:media:jgrc22369:jgrc22369-math-0001 and a stabilization factor, urn:x-wiley:21699275:media:jgrc22369:jgrc22369-math-0002, which can be used to identify and quantify the extent of this surfactant imprint for individual breaking waves. The approach is then applied to wind‐driven oceanic whitecaps, and the laboratory and ocean urn:x-wiley:21699275:media:jgrc22369:jgrc22369-math-0003 distributions overlap. It is proposed that whitecap foam evolution may be used to determine the occurrence and extent of oceanic surfactant activity to complement traditional in‐situ techniques and extend measurement capabilities to more severe sea states occurring at wind speeds in excess of about 10 m/s. The analysis procedure also provides a framework to assess surfactant‐driven variability within and between whitecap coverage data sets.
Date Issued
2017-08-01
Date Acceptance
2017-06-20
Citation
Journal of Geophysical Research: Oceans, 2017, 122 (8), pp.6110-6128
ISSN
2169-9275
Publisher
American Geophysical Union
Start Page
6110
End Page
6128
Journal / Book Title
Journal of Geophysical Research: Oceans
Volume
122
Issue
8
Copyright Statement
© 2017. American Geophysical Union. All Rights Reserved.
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000410790600004&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Oceanography
whitecap
surfactant
remote sensing
GAS TRANSFER VELOCITY
AIR-SEA INTERFACE
ACTIVE MATERIAL
WIND-SPEED
DISSIPATION
FRACTION
BUBBLES
MICROLAYERS
DEPENDENCE
STABILITY
Publication Status
Published
Date Publish Online
2017-07-05