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Title: Measurements of sub-surface bubble populations and the modelling of air-sea gas flux
Author: Coles, David Geoffrey Hallstaff
ISNI:       0000 0004 2690 1923
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2010
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Bubbles, formed by breaking waves, play an important role in the transfer of gases between the Earth’s oceans and atmosphere and have been shown to increase the flux of gases during periods of heightened sea state. Having been formed, these bubble clouds evolve through the effects of buoyancy, gas exsolution and dissolution, and the fragmentation and coalescence of bubbles. A number of experimenters have successfully measured sub-surface bubble clouds using a variety of acoustic and optical techniques, although data over a wider range of bubble radii are required for fuller comparison with models of how these clouds evolve and contribute to air-sea transfers of mass, momentum and energy. This study details the design of an acoustic system deployed on an 11 metre spar buoy during two sea trials in the Atlantic Ocean. Through the measurement of the additional attenuation due to bubbles, bubble size distributions were inferred over the broadest range of bubble radii ever measured using active acoustics in the open ocean. The volumetric backscatter strength from the bubble clouds were also measured to gain a profile of these bubble populations. A gas transfer model was then developed, with the measured data used as an input to calculate the associated fluxes. With this method, bubble-mediated transfer velocities and equilibrium supersaturations were found for the first time based on experimental work. These parameters aid the characterisation of air-sea gas transfer and therefore help improve the accuracy of existing climate models.
Supervisor: Leighton, Timothy Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: GC Oceanography ; QC Physics