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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, C08S18, doi:10.1029/2003JC001806, 2004

Influence of rain on air-sea gas exchange: Lessons from a model ocean

David T. Ho

Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA


Christopher J. Zappa

Applied Ocean Physics and Engineering Department, Woods Hole Oceanographic Institution, Woods Hole, Maryland, USA


Wade R. McGillis

Applied Ocean Physics and Engineering Department, Woods Hole Oceanographic Institution, Woods Hole, Maryland, USA


Larry F. Bliven

NASA/GSFC, Laboratory for Hydrospheric Processes, Wallops Island, Virginia, USA


Brian Ward

Applied Ocean Physics and Engineering Department, Woods Hole Oceanographic Institution, Woods Hole, Maryland, USA


John W. H. Dacey

Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA


Peter Schlosser

Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA


Melissa B. Hendricks

Department of Geosciences, Princeton University, Princeton, New Jersey, USA


Abstract

Rain has been shown to significantly enhance the rate of air-water gas exchange in fresh water environments, and the mechanism behind this enhancement has been studied in laboratory experiments. In the ocean, the effects of rain are complicated by the potential influence of density stratification at the water surface. Since it is difficult to perform controlled rain-induced gas exchange experiments in the open ocean, an SF6 evasion experiment was conducted in the artificial ocean at Biosphere 2. The measurements show a rapid depletion of SF6 in the surface layer due to rain enhancement of air-sea gas exchange, and the gas transfer velocity was similar to that predicted from the relationship established from freshwater laboratory experiments. However, because vertical mixing is reduced by stratification, the overall gas flux is lower than that found during freshwater experiments. Physical measurements of various properties of the ocean during the rain events further elucidate the mechanisms behind the observed response. The findings suggest that short, intense rain events accelerate gas exchange in oceanic environments.

Received 3 February 2003; accepted 11 September 2003; published 1 July 2004.

Keywords: gas exchange; rain; SF6; turbulence; stratification.

Index Terms: 0312 Atmospheric Composition and Structure: Air/sea constituent fluxes (3339, 4504); 4504 Oceanography: Physical: Air/sea interactions (0312); 4572 Oceanography: Physical: Upper ocean processes; 4504 Oceanography: Physical: Air/sea interactions (0312).

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Citation: Ho, D. T., C. J. Zappa, W. R. McGillis, L. F. Bliven, B. Ward, J. W. H. Dacey, P. Schlosser, and M. B. Hendricks (2004), Influence of rain on air-sea gas exchange: Lessons from a model ocean, J. Geophys. Res., 109, C08S18, doi:10.1029/2003JC001806.