Abstract
Abstract. 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 French-press or cafetière-à-piston 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.
Highlights
Snow densification in alpine and polar regions transforms snowflakes into ice crystals
We compare the predictions of the theory outlined in the previous section with the experimental data of Wang and Baker (2013), which we described in the Sect
The lowest density snow sintered low-temperature (SLT)-1 withstands the least stress as a function of displacement
Summary
Snow densification in alpine and polar regions transforms snowflakes into ice crystals. In the final stage, interconnected pores have closed off, and further compaction is caused by air bubble compression (Alley and Bentley, 1988; Salamatin et al, 1997; Gregory et al, 2014). In wet environments, such as the percolation zone of mountain glaciers and Greenland as well as many ice shelves of Antarctica, compaction occurs by a combination of dry snow compaction processes and refreezing of meltwater, which can either enhance or detract from the densification processes just mentioned (Colbeck, 1976; Machguth et al, 2016; Meyer and Hewitt, 2017). Meltwater percolation is an important part of the compaction process in many areas (e.g., Colbeck, 1972; Bartelt and Lehning, 2002; Wever et al, 2014; Steger et al, 2017), we will only consider dry snow compaction here
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