Articles | Volume 11, issue 5
Research article
05 Sep 2017
Research article |  | 05 Sep 2017

Wind enhances differential air advection in surface snow at sub-meter scales

Stephen A. Drake, John S. Selker, and Chad W. Higgins

Abstract. Atmospheric pressure gradients and pressure fluctuations drive within-snow air movement that enhances gas mobility through interstitial pore space. The magnitude of this enhancement in relation to snow microstructure properties cannot be well predicted with current methods. In a set of field experiments, we injected a dilute mixture of 1 % carbon monoxide (CO) and nitrogen gas (N2) of known volume into the topmost layer of a snowpack and, using a distributed array of thin film sensors, measured plume evolution as a function of wind forcing. We found enhanced dispersion in the streamwise direction and also along low-resistance pathways in the presence of wind. These results suggest that atmospheric constituents contained in snow can be anisotropically mixed depending on the wind environment and snow structure, having implications for surface snow reaction rates and interpretation of firn and ice cores.

Short summary
Reaction rates of radiatively and chemically active trace species are influenced by the mobility of air contained within the snowpack. By measuring wind speed and the evolution of a tracer gas with in situ sensors over a 1 m horizontal grid, we found that inhomogeneities in a single snow layer enhanced air movement unevenly as wind speed increased. This result suggests small-scale variability in reaction rates that increases with wind speed and variability in snow permeability.