High-frequency pressure variations in the vicinity of a surface CO2 flux chamber

We report measurements of 2 Hz pressure fluctuations at and below the soil surface in the vicinity of a surface-based CO2 flux chamber. These measurements were part of a field experiment to examine the possible role of pressure pumping due to atmospheric pressure fluctuations on measurements of surface fluxes of CO2. Under the moderate wind speeds, warm temperatures, and dry soil conditions present at the time of our observations, the chamber had no effect on the pressure field in its near vicinity that could be detected above the level of natural pressure fluctuations in the vicinity. At frequencies at or <2 Hz, pressure fluctuations easily penetrated the soil to depths of several cm with little attenuation. We conclude that the presence of the chamber does not introduce pressure perturbations that lead to biases in measurements of surface fluxes of CO2.