Bubble‐Mediated Gas Transfer and Gas Transfer Suppression of DMS and CO 2

• Published in: Journal of geophysical research. Atmospheres 2018-06, Vol.123 (12), p.6624-6647
• Main Authors: Zavarsky, A., Goddijn‐Murphy, L., Steinhoff, T., Marandino, C. A.
• Format: Article
• Language: English
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2017JD028071

Direct dimethyl sulfide (DMS) flux measurements using eddy covariance have shown a suppression of gas transfer at medium to high wind speed. However, not all eddy covariance measurements show evidence of this suppression. Processes, such as wave‐wind interaction and surfactants, have been postulated to cause this suppression. We measured DMS and carbon dioxide eddy covariance fluxes during the Asian summer monsoon in the western tropical Indian Ocean (July and August 2014). Both fluxes and their respective gas transfer velocities show signs of a gas transfer suppression above 10 m/s. Using a wind‐wave interaction, we describe a flow separation process that could be responsible for a suppression of gas transfer. As a result we provide a Reynolds number‐based parameterization, which states the likelihood of a gas transfer suppression for this cruise and previously published gas transfer data. Additionally, we compute the difference in the gas transfer velocities of DMS and CO 2 to estimate the bubble‐mediated gas transfer using a hybrid model with three whitecap parameterizations. Investigating the air‐gas transfer of dimethyl sulfide (DMS) and CO 2 , we estimate the influence of bubble‐mediated gas transfer.Furthermore, we explore the phenomena of gas transfer suppression. The gas transfer between atmosphere and ocean should increase with increasing wind speed. At certain wind speed the amount of gas transferred flattens. We provide a wind‐wave interaction as possible explanation of this phenomenon. Gas transfer velocities of DMS and CO 2 are subject to suppression Transformed Reynolds number is used to characterize suppression No clear bubble signal was found during the cruise, despite k values measured for wind speed greater than 15 m/s