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Gas exchange in wetlands with emergent vegetation: The effects of wind and thermal convection at the air‐water interface
Author(s) -
Poindexter Cristina M.,
Variano Evan A.
Publication year - 2013
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/jgrg.20099
Subject(s) - convection , wetland , thermal , methane , wind speed , vegetation (pathology) , carbon dioxide , environmental science , atmosphere (unit) , surface water , oxygen , atmospheric sciences , chemistry , mechanics , meteorology , environmental engineering , geology , ecology , physics , medicine , organic chemistry , pathology , biology
Methane, carbon dioxide, and oxygen are exchanged between wetlands and the atmosphere through multiple pathways. One of these pathways, the hydrodynamic transport of dissolved gas through the surface water, is often underestimated in importance. We constructed a model wetland in the laboratory with artificial emergent plants to investigate the mechanisms and magnitude of this transport. We measured gas transfer velocities, which characterize the near‐surface stirring driving air‐water gas transfer, while varying two stirring processes important to gas exchange in other aquatic environments: wind and thermal convection. To isolate the effects of thermal convection, we identified a semiempirical model for the gas transfer velocity as a function of surface heat loss. The laboratory results indicate that thermal convection will be the dominant mechanism of air‐water gas exchange in marshes with emergent vegetation. Thermal convection yielded peak gas transfer velocities of 1 cm h −1 . Because of the sheltering of the water surface by emergent vegetation, gas transfer velocities for wind‐driven stirring alone are likely to exceed this value only in extreme cases.