Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 12, issue 24
Biogeosciences, 12, 7423–7434, 2015
https://doi.org/10.5194/bg-12-7423-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 12, 7423–7434, 2015
https://doi.org/10.5194/bg-12-7423-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 17 Dec 2015

Research article | 17 Dec 2015

Quantifying wind and pressure effects on trace gas fluxes across the soil–atmosphere interface

K. R. Redeker1, A. J. Baird2, and Y. A. Teh3 K. R. Redeker et al.
  • 1Department of Biology, University of York, Heslington, York, UK
  • 2School of Geography, University of Leeds, UK
  • 3Institute of Biological and Environmental Sciences, University of Aberdeen, UK

Abstract. Large uncertainties persist in estimates of soil–atmosphere exchange of important trace gases. One significant source of uncertainty is the combined effect of wind and pressure on these fluxes. Wind and pressure effects are mediated by surface topography: few surfaces are uniform and over scales of tenths of a metre to tens of metres, air pressure and wind speed at the ground surface may be very variable. In this paper we consider how such spatial variability in air pressure and wind speed affects fluxes of trace gases. We used a novel nested wind tunnel design comprising a toroidial wind tunnel, in which wind speed and pressure may be controlled, set within a larger, linear wind tunnel. The effects of both wind speed and pressure differentials on fluxes of CO2 and CH4 within three different ecosystems (forest, grassland, peat bog) were quantified. We find that trace gas fluxes are positively correlated with both wind speed and pressure differential near the surface boundary. We argue that wind speed is the better proxy for trace gas fluxes because of its stronger correlation and because wind speed is more easily measured and wind speed measurement methodology more easily standardized. Trace gas fluxes, whether into or out of the soil, increase with wind speed within the toroidal tunnel (+55 % flux per m s−1), while faster, localized surface winds that are external to the toroidal wind tunnel reduce trace gas fluxes (−13 % flux per m s−1). These results are consistent for both trace gases over all ecosystem soil types studied. Our findings support the need for a revised conceptualization of soil–atmosphere gas exchange. We propose a conceptual model of the soil profile that has a "mixed layer", with fluxes controlled by wind speed, wind duration, porosity, water table, and gas production and consumption.

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One continuing, significant source of uncertainty in global climate predictions is the combined effect of wind and pressure on trace gas fluxes. We quantified the effects of wind speed and pressure on fluxes of CO2 and CH4 within three different ecosystems. Trace gas fluxes are positively correlated with both wind speed and pressure near the soil surface but we argue that wind speed is a better proxy for general use. These results have implications for a number of global feedback mechanisms.
One continuing, significant source of uncertainty in global climate predictions is the combined...
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