The University of Southampton
Engineering and the Environment

Research project: The influence of surfactants on the mechanisms of ocean bubble formation

Currently Active: 
Yes

This project will investigate the effect of natural surfactants (for example those produced by phytoplankton) on bubble formation, and also the consequent effects on air-sea gas and particle fluxes.    

Project Overview

The bubble clouds formed underneath breaking waves have been shown to have a significant influence on air-sea gas transfer rates, and current models for bubble clouds exist. However, no models to date have included the changes to the bubble population caused by surfactants, and consequently the total effect of surfactants on gas transfer rates. The fellowship research proposed here will build such a model, based on insights into bubble dynamics resulting from laboratory, wave tank and oceanic experimental work.


There is strong evidence to suggest that bubbles scavenge natural surfactants very quickly: the rapid reformation of the surface microlayer after an ocean wave breaks is mediated by larger bubbles bringing surfactants up to the surface and optical scattering evidence suggests that most small bubbles are coated in surfactant. To date, very few studies have considered the details of how surfactants could affect bubble formation dynamics underneath breaking waves (particularly fragmentation and coalescence), although surfactants have been shown to influence bubble dynamics. However, an understanding of the mechanistic origin of ocean bubbles is essential to guide effective parameterizations of any upper ocean process affected by bubbles.


This project will begin with laboratory studies of the effects of various natural and artificial surfactants on fragmentation and coalescence events. Simultaneous high-speed photography and acoustics have been shown to produce an impressive amount of information about individual events, and these techniques will be combined to study the dynamics and acoustics of fragmentation and coalescence events. In the second and third years of the project, the insights gained from the small-scale laboratory experiments will be used to tune models of the bubbles produced by breaking waves with different surfactants present, and these model outcomes will be tested in a wave tank and at sea.

 

Ocean measurements are being carried out in collaboration with the WAGES project, run by the National Oceanography Centre and the University of Leeds.   The first research cruise took place in April 2012 and lasted for a month, with a further cruise planned for April 2013.  

Related research groups

Acoustics Group

Staff

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