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Vapor Flux and Recrystallization During Dry Snow Metamorphism Under a Steady Temperature Gradient as Observed by Time-lapse Micro-tomography : Volume 6, Issue 3 (14/05/2012)

By Pinzer, B. R.

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Book Id: WPLBN0004022667
Format Type: PDF Article :
File Size: Pages 42
Reproduction Date: 2015

Title: Vapor Flux and Recrystallization During Dry Snow Metamorphism Under a Steady Temperature Gradient as Observed by Time-lapse Micro-tomography : Volume 6, Issue 3 (14/05/2012)  
Author: Pinzer, B. R.
Volume: Vol. 6, Issue 3
Language: English
Subject: Science, Cryosphere, Discussions
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Publication Date:
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

Description: WSL-Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland. 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 metamorphism under a steady temperature gradient (STGM) 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, and in addition the exact locations of these phase changes. From the four-dimensional data set, 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 snow pack, 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 STGM that is produced by directly observing the microstructure of snow in situ sheds light on the micro-physical processes and could help to improve models that predict the physical properties of snow.

Vapor flux and recrystallization during dry snow metamorphism under a steady temperature gradient as observed by time-lapse micro-tomography

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