Estimation of Bubble-Mediated Air–Sea Gas Exchange from Concurrent DMS and CO2 Transfer Velocities at Intermediate–High Wind Speeds

• Main Authors: Bell, Thomas G., Landwehr, Sebastian, Miller, Scott D., De Bruyn, Warren J., Callaghan, Adrian H., Scanlon, Brian, Ward, Brian, Yang, Mingxi, Saltzman, Eric S.
• Format: Text
• Language: unknown
• Published: Chapman University Digital Commons 2017
• Subjects: Atmospheric Sciences; Environmental Chemistry; Environmental Health and Protection; Environmental Monitoring; Oceanography; Other Oceanography and Atmospheric Sciences and Meteorology; North Atlantic
• Online Access: https://digitalcommons.chapman.edu/sees_articles/182; https://digitalcommons.chapman.edu/cgi/viewcontent.cgi?article=1183&context=sees_articles

Simultaneous air–sea fluxes and concentration differences of dimethylsulfide (DMS) and carbon dioxide (CO2/ were measured during a summertime North Atlantic cruise in 2011. This data set reveals significant differences between the gas transfer velocities of these two gases (1kw/ over a range of wind speeds up to 21ms????1. These differences occur at and above the approximate wind speed threshold when waves begin breaking. Whitecap fraction (a proxy for bubbles) was also measured and has a positive relationship with 1kw, consistent with enhanced bubble-mediated transfer of the less soluble CO2 relative to that of the more soluble DMS. However, the correlation of 1kw with whitecap fraction is no stronger than with wind speed. Models used to estimate bubble-mediated transfer from in situ whitecap fraction underpredict the observations, particularly at intermediate wind speeds. Examining the differences between gas transfer velocities of gases with different solubilities is a useful way to detect the impact of bubble-mediated exchange. More simultaneous gas transfer measurements of different solubility gases across a wide range of oceanic conditions are needed to understand the factors controlling the magnitude and scaling of bubble-mediated gas exchange.