A model for French-press experiments of dry snow compaction

Snow densification stores water in alpine regions and transforms snow into ice on the surface of glaciers. Despite its importance in determining snow-water equivalent and glacier-induced sea level rise, we still lack a complete understanding of the physical mechanisms underlying snow compaction. In...

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Bibliographic Details
Published in:The Cryosphere
Main Authors: C. R. Meyer, K. M. Keegan, I. Baker, R. L. Hawley
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2020
Subjects:
Online Access:https://doi.org/10.5194/tc-14-1449-2020
https://doaj.org/article/1e99245fa3bf4b1a9a8f5134230b393b
Description
Summary:Snow densification stores water in alpine regions and transforms snow into ice on the surface of glaciers. Despite its importance in determining snow-water equivalent and glacier-induced sea level rise, we still lack a complete understanding of the physical mechanisms underlying snow compaction. In essence, compaction is a rheological process, where the rheology evolves with depth due to variation in temperature, pressure, humidity, and meltwater. The rheology of snow compaction can be determined in a few ways, for example, through empirical investigations (e.g., Herron and Langway, 1980), by microstructural considerations (e.g., Alley, 1987), or by measuring the rheology directly, which is the approach we take here. Using a <q>French-press</q> or <q>cafetière-à-piston</q> compression stage, Wang and Baker (2013) compressed numerous snow samples of different densities. Here we derive a mixture theory for compaction and airflow through the porous snow to compare against these experimental data. We find that a plastic compaction law explains experimental results. Taking standard forms for the permeability and effective pressure as functions of the porosity, we show that this compaction mode persists for a range of densities and overburden loads. These findings suggest that measuring compaction in the lab is a promising direction for determining the rheology of snow through its many stages of densification.