Winter gas exchange between the atmosphere and snow-covered soils on Niwot Ridge, Colorado, USA

Background: There is a growing interest in understanding the gas exchange between the atmosphere and seasonally snow-covered regions, especially in light of projections that climate change will alter the timing and extent of seasonal snow cover. In snow-covered ecosystems, gas fluxes are due both to microbial activity in the snow-covered soils and to chemical and physical reactions with the various gases and/or dissolved constituents in the snowpack. Niwot Ridge, in the Colorado Rocky Mountains, has one of the most extensive sets of measurements of winter gas exchange globally. Aims: Our goal was to examine the temporal patterns and environmental controls on Niwot Ridge of gas fluxes for gases with different sources and sinks. Methods: Here, we review the concentrations and fluxes that have been measured for carbon dioxide, nitrous oxide, methane, nitrogen oxides, ozone, gaseous elemental mercury and volatile organic carbon compounds. Results and Conclusions: We looked for similarities and differences among the gases, but in many cases, the origin, fate and controls of these fluxes still need to be determined. However, we believe that many of the biologically driven reactions are the result of exponential growth of a winter microbial community during the long period of stable environmental conditions under the seasonal snowpack.