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| Titel |
Vapor flux and recrystallization during dry snow metamorphism under a steady temperature gradient as observed by time-lapse micro-tomography |
| VerfasserIn |
B. R. Pinzer, M. Schneebeli, T. U. Kaempfer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 6, no. 5 ; Nr. 6, no. 5 (2012-10-16), S.1141-1155 |
| Datensatznummer |
250003792
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| Publikation (Nr.) |
 copernicus.org/tc-6-1141-2012.pdf |
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| Zusammenfassung |
| Dry snow metamorphism under an external temperature gradient is the most
common type of recrystallization of snow on the ground. The changes in snow
microstructure modify the physical properties of snow, and therefore an
understanding of this process is essential for many disciplines, from
modeling the effects of snow on climate to assessing avalanche risk. We
directly imaged the microstructural changes in snow during temperature
gradient metamorphism (TGM) under a constant gradient of 50 K m−1,
using in situ time-lapse X-ray micro-tomography. This novel and
non-destructive technique directly reveals the amount of ice that sublimates
and is deposited during metamorphism, in addition to the exact locations of
these phase changes. We calculated the average time that an ice volume
stayed in place before it sublimated and found a characteristic residence
time of 2–3 days. This means that most of the ice changes its phase from
solid to vapor and back many times in a seasonal snowpack where similar
temperature conditions can be found. Consistent with such a short timescale,
we observed a mass turnover of up to 60% of the total ice mass per day.
The concept of hand-to-hand transport for the water vapor flux describes the
observed changes very well. However, we did not find evidence for a
macroscopic vapor diffusion enhancement. The picture of {temperature gradient
metamorphism} produced by directly observing the changing microstructure
sheds light on the micro-physical processes and could help to improve models
that predict the physical properties of snow. |
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