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| Titel |
Measurements of Antarctic snow compaction compared with model predictions |
| VerfasserIn |
R. J. Arthern, D. J. Vaughan, A. M. Rankin, R. Mulvaney, E. R. Thomas |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250028765
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| Zusammenfassung |
| We describe in-situ measurements of the compaction of Antarctic snow. The rate of
compaction in the upper twenty meters was recorded automatically at several sites in
Antarctica. The measurements were taken hourly over a time period of up to two years.
Measurements were made in boreholes over depth intervals of 0–5Â m, 0–10Â m, and 0–20Â m.
Auxiliary measurements of air temperature, snow temperature and snow accumulation were
also recorded using automatic weather stations. At our measurement sites, the snow compacts
through a slow, viscous deformation of the snowpack. We did not observe any significant
contribution from the sudden collapse of weak layers. Our data also exhibit a strong
seasonality, consistent with a temperature-dependent sintering mechanism. We recover the
activation energy of this mechanism, and obtain values of about 60–70Â kJÂ mol-1 at two
lower-temperature sites, and about 100Â kJÂ mol-1 at a warmer site. We also compared our
observations with predictions from models of snow compaction taken from the
literature. These underestimate the amplitude of the seasonal cycle. We obtain a good
match to our observations with a semi-empirical model based upon rate expressions
appropriate for Nabarro-Herring (lattice diffusion) creep within a porous medium,
combined with normal grain growth, although the diffusion inferred from this model is
much higher than published values, and other sintering mechanisms cannot be ruled
out. |
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