Effect of the bubbles created by breaking waves on the mass transfer at the air-sea interface

In this report, a study of the effect of the bubbles created by breaking waves at high wind speeds in the mass transfer mechanisms is attempted. A first part presents the results of experiments run with N₂O and Argon in the I.M.S.T. facility in Marseilles. A significant increase of the transfer velocity is observed as soon as the breaking waves appear. Thus, in the second part, the dynamics of a bubble and the diffusion of a trace gas through a bubble is undertaken and the role of some parameters (solubility, radius, frequency of the dominant wave) is shown. In the last part, a modelling of the mass transfer taking into account the bubbles is developed and applied to the experimental results presented in the first part. The main conclusions of this report are the following: - Far from the equilibrium, the transfer velocity is independent of the gradient of concentrations and increase when the solubility becomes low. - In the natural conditions, the transfer velocity varies a lot with the gradient of concentrations and can be negative. - The actual equilibrium is reached for an over saturation of the water as the flux bubbles → water must be balanced by the flux water → air. This over saturation is more important when the gas is less soluble. (author)