Snow and firn permeability at Siple Dome, Antarctica

The nature of air-snow exchange processes depends upon both the physical characteristics of the snow and forcing from the atmosphere. An understanding of snow-air transport processes and models of these processes are important for interpreting ice cores and for predicting remotely sensed snow-surface characteristics. Accurate modeling requires knowledge of the physical characteristics of the snow and firn. In this paper, measurements of snow and firn permeability from the surface down to 12 m depth at Siple Dome, Antarctica? are presented. The permeability varies greatly as a function of layer and depth, generally increasing to approximately 3 m, and generally decreasing below that. The maximum permeability, 280 x 10(-10) m(2), occurs at approximately 3 m depth. The lowest permeability in the top 12 m of snow and firn, 10 x 10(-10) m(2), was measured in the surface wind pack. The measurements show that layering and microstructure have large effects on permeability. A mathematical expression for the overall variation of permeability with depth is presented. II is shown that snow density is a poor indicator of permeability. Quantitative microscopy may be helpful in relating observed snow characteristics to permeability, and useful in modeling firnification and chemical-species transport.