Item: Spatial variability of snow stratification in the absence of terrain factors
Title: Spatial variability of snow stratification in the absence of terrain factors
Proceedings: 2002 International Snow Science Workshop, Penticton, British Columbia
Authors: Joel T. Harper, Institute of Arctic and Alpine Research, Dniv. of Colorado, Boulder Colorado, John. H. Bradford, Center for the Geophysical Investigation of the Shallow Subsurface, Boise State Dniv., Boise, Idaho
Abstract: Instrumentation and methods for measuring snow properties are compared in an investigation of mm to m scale stratigraphy in a snowpack not influenced by topography, vegetation, or a warm and variable ground surface. Field measurements were conducted within a 20 x 20 x 2 m plot at Pika Glacier, central Alaska. The snow was characterized by 600+ point measurements of density, 400+ measurements of temperature, stratigraphic mapping in 19 snow-pits, and by pulse-radar imaging along 20 cross-plot profiles. Density was measured manually and was calculated from electric permittivity, which was determined with a hand-held probe and by radar velocity analysis. Manual measurements of density with stratigraphic mapping in snow-pit walls identified comparatively few layers, suggesting a relatively homogeneous snowpack. Both the permittivity probe and the radar imaging, however, identified a larger number of layers based on density contrasts. An illuminated column of snow revealed extremely complex stratigraphy, with micro layers extending mm in thickness and up to 10 em in laterally. Despite minor variations in snow properties at the mm scale, major features in the density and temperature profiles were laterally continuous over lOs of m. Radar imaging revealed more distinctive layering in late season snow, but laterally continuous layers throughout the winter snowpack. These observations demonstrate that snowpack stratigraphy is highly dependent upon choice of scale and measurement tool. Moreover, these data provide evidence for spatial homogeneity of snow densification processes where the snowpack is not influenced by local terrain factors.
Keywords: snow stratigraphy, densification, radar, snow-pit, permittivity
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