Eddy flux measurements of sulfur dioxide deposition to the sea surface

Abstract

Abstract. Deposition to the sea surface is a major atmospheric loss pathway for many important trace gases, such as sulfur dioxide, (SO 2 ). The air/sea transfer of SO 2 is controlled entirely on the atmospheric side of the air/sea interface due to high effective solubility and other physical/chemical properties. There have been few direct field measurements of such fluxes due to the challenges associated with making fast response measurements of highly soluble trace gases at very low ambient levels.In this study, we report direct eddy covariance air/sea flux measurements of SO 2 , sensible heat, water vapor, and momentum. 5The measurements were made over shallow coastal waters from the Scripps Pier, La Jolla, CA using negative ion chemical ionization mass spectrometry as the SO 2 sensor. The observed transfer velocities for SO 2 , sensible heat, water vapor, and momentum and their wind speed-dependences indicate that SO 2 fluxes can be reliably measured using this approach. As expected, the transfer velocities for SO 2 , sensible heat, and water vapor are smaller than that for momentum, demonstrating the contribution of molecular diffusion to the overall air-side resistance to gas transfer. Furthermore, transfer velocities of SO 2 10 were smaller than those of sensible heat and water vapor when observed simultaneously. This result is attributable to diffusive behavior in the interfacial layer of the air/sea interface.Copyright statement.