Dimethylsulfide gas transfer coefficients from algal blooms in the Southern Ocean

• Main Authors: Bell, TG, De Bruyn, W, Marandino, CA, Miller, SD, Law, CS, Smith, MJ, Saltzman, ES
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: eScholarship, University of California 2015
• Subjects: Earth Sciences; Oceanography; Astronomical and Space Sciences; Atmospheric Sciences; Meteorology & Atmospheric Sciences; Climate change science; Southern Ocean
• Online Access: https://escholarship.org/uc/item/5s4731t5

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.