Dimethylsulfide gas transfer coefficients from algal blooms in the Southern Ocean

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Bell, T. G., De Bruyn, W., Marandino, Christa, Miller, S. D., Law, C. S., Smith, M. J., Saltzman, E. S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications (EGU) 2015
• Subjects: Southern Ocean
• Online Access: https://oceanrep.geomar.de/id/eprint/27837/; https://oceanrep.geomar.de/id/eprint/27837/1/acp-15-1783-2015.pdf; https://oceanrep.geomar.de/id/eprint/27837/7/acp-15-1783-2015-supplement.pdf; https://doi.org/10.5194/acp-15-1783-2015

Air-sea dimethylsulfide (DMS) fluxes and bulk air-sea gradients were measured over the Southern Ocean in February-March 2012 during the Surface Ocean Aerosol Production (SOAP) study. The cruise encountered three distinct phytoplankton bloom regions, consisting of two blooms with moderate DMS levels, and a high biomass, dinoflagellate-dominated bloom with high seawater DMS levels (> 15 nM). Gas transfer coefficients were considerably scattered at wind speeds above 5 m s-1. Bin averaging the data resulted in a linear relationship between wind speed and mean gas transfer velocity consistent with that previously observed. However, the wind-speed-binned gas transfer data distribution at all wind speeds is positively skewed. The flux and seawater DMS distributions were also positively skewed, which suggests that eddy covariance-derived gas transfer velocities are consistently influenced by additional, log-normal noise. A flux footprint analysis was conducted during a transect into the prevailing wind and through elevated DMS levels in the dinoflagellate bloom. Accounting for the temporal/spatial separation between flux and seawater concentration significantly reduces the scatter in computed transfer velocity. The SOAP gas transfer velocity data show no obvious modification of the gas transfer-wind speed relationship by biological activity or waves. This study highlights the challenges associated with eddy covariance gas transfer measurements in biologically active and heterogeneous bloom environments.