10.7
Influence of turbulent pressure pumping on the fluxes and movement of CO2 from soils and snowpacks
W. J. Massman, USDA Forest Service, Fort Collins, CO
Evidence, obtained at the Glacier Lakes Ecosystems Experiments Site in Rocky Mountains of southern Wyoming, is presented that supports the hypothesis that turbulent atmospheric pressure fluctuations influence the fluxes and movement of carbon dioxide through soils and snowpacks. First, nearly 8 weeks of half-hourly measurements of CO2 mole fraction obtained at the soil/snowpack interface between December 2000 and March 2001 vary between about 1400 and 1800 ppmV with a dominant period of about 8 days and amplitude of about 100 ppmV. During this period the snow depth is relatively constant at 1.1 m, and these variantions in CO2 correlate strongly with fluctuations in wind speed and ambient pressure. Second, simultaneous eddy covariance CO2 fluxes, obtained as part of the AmeriFlux effort, are weakly but significantly correlated with these variations in the CO2 mole fraction at the soil/snowpack interface and can significantly exceed purely diffusional fluxes through the snowpack. Third, a new analytical model of CO2 fluxes through snowpacks is used to distinguish between the effects of low frequency barometric pumping and higher frequency turbulent pressure pumping and stationary pressure waves forced by topogaphy. Comparing observations with the model suggests that turbulent pressure pumping can significantly enhance purely diffusional CO2 fluxes on a half-hourly basis and that the intensity of the turbulent pressure pumping is modulated by the low frequency synoptic scale events.
Session 10, Carbon dioxide exchange Part 2
Friday, 24 May 2002, 8:30 AM-11:45 AM
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