Measurements of large bubbles in open-ocean whitecaps

There is theoretical evidence that the enhanced gas transfer observed during storms is due to bubble-mediated transport. Calculations done by Keeling [1993] suggest that the dissolution of highly soluble gasses such as C02 is particularly sensitive to the formation of large (greater than 0.3mm radius) bubbles within whitecaps. Estimates of the numbers and sizes of bubbles within whitecaps are difficult to obtain, and the lack of this data is currently a limiting factor in model development. A new optical instrument that can image bubbles in high void fraction plumes has been deployed in a series of open-ocean experiments. The numbers and sizes of bubbles within 30 cm of the surface and directly beneath breaking waves have been estimated. Size distribution estimates within a 3.8 cubic centimeter volume are made every 40 milliseconds for a few seconds during a breaking event. The largest bubbles imaged were 3 mm in radius. Void fractions between 1 and 10 percent persisting for a second or so during plume formation were observed. Initial estimates of bubble-mediated gas transfer based on these new data are presented.