Extreme firn metamorphism: impact of decades of vapor transport on near-surface firn at a low-accumulation glazed site on the East Antarctic plateau
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2017-09-14
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Citation of Original Publication
Albert, Mary, Christopher Shuman, Zoe Courville, Robert Bauer, Mark Fahnestock, and Ted Scambos. 2004. “Extreme Firn Metamorphism: Impact of Decades of Vapor Transport on near-Surface Firn at a Low-Accumulation Glazed Site on the East Antarctic Plateau.” Annals of Glaciology 39. Cambridge University Press: 73–78. doi:10.3189/172756404781814041.
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract
Snow and firn properties control the transport of vapor, gases and water between the atmosphere and the underlying strata. An understanding of this transport and the properties that control it is important for predicting air–snow transfer of chemical species and for interpreting ice cores. Remote-sensing images of East Antarctica show large areas of alternating light and dark bands. These low-amplitude, long-wavelength features have glazed downwind faces and rough upwind faces and are called megadunes. The first linked measurements of the permeability and the associated microstructure for a glazed area within a well-defined megadune area are reported in this paper. Permeability and density were measured, along with grain-scale properties derived from digital image processing of preserved thick sections, at this cold, low-accumulation glazed site. A clear layering pattern exists. In the top meter the firn density ranges from 0.24 to 0.50 g cm⁻³. Permeability measurements range from 50 x 10⁻¹⁰ to 200 x 10⁻¹⁰μ², several times greater than corresponding profiles from warmer, higher-accumulation sites like Siple Dome, Antarctica. It is shown that buoyancy-driven natural convection may be important in post-depositional processes in very cold, low-accumulation sites like this.