The role of capillary waves in oceanic air/water gas exchange

Recent experiments have demonstrated that millimeter-scale capillary waves can enhance the transport of CO2 by almost 2 orders of magnitude for modera te wave slopes. These results are used to create a model for the relative c ontribution of capillary waves to the gas exchange coefficient. The model i nput is wind speed u, and the output is K-f the fractional contribution of a specific range of capillary waves to the total gas exchange coefficient. Wind speed data, obtained via satellite, are used as the model input to obt ain globally averaged values for K-f. In spite of the enhancing effect whic h capillary waves provide in the laboratory, the maximum value of K-f predi cted by the model is less than 10%, and global averages are less than 4%. T he small values of K-f are primarily due to the small wave energies predict ed by existing wave height spectra in the high wave number regime. The unce rtainty in existing wave height spectra, and the importance of experimental validation of the high wave number regime is discussed. Some interesting a spects of capillary wave gas exchange are also expanded upon. Among these a re the demonstration of a linear relationship between the capillary wave ga s exchange coefficient and wavelength, and a peak in the contribution of ca pillary waves to gas exchange at a wavelength around lambda = 3.6 mm.