Impact of layering and microstructure on gas diffusion through snow

Abstract:

Understanding relationships between snow structure and gas transport properties in seasonal snow is crucial for correctly quantifying gas fluxes through the snow. Wintertime soil respiration of CO₂ has been estimated to significantly contribute to the carbon budget, but CO₂ must first diffuse through the snowpack before being released to the atmosphere. The snowpack is not homogeneous; the structure varies both in space and in time, which can have profound impacts on the snow diffusivity. Former assessments of gas flux in seasonal snow apply empirical relations based on single, fixed conditions, which limits the accuracy of the assessment results. In this presentation we report on laboratory measurements through snow and firn samples that have various metamorphic properties. Diffusion coefficients determined from the measurements are used to investigate the impact of layering and inhomogeneous structure on diffusion rates on larger scales, through multidimensional numerical simulations.