Wet‐Snow Metamorphism Drives the Transition From Preferential to Matrix Flow in Snow

Abstract

In order to explain the poorly understood transition between preferential and matrix flow in snow, we compared observations from a cold-laboratory experiment with predictions from a multidimensional water transport snow model. We found a good agreement between the modeled and observed evolution of grain size distributions if two or three dimensions are considered by the model, which validates existing theories of snow grain growth. Furthermore, the model reproduced the spatial migration of preferential flow paths with time and a progressive homogenization of snow wetness and structure only if grain growth was simulated. Spatially varying grain growth thus drives the transition from a preferential flow to a matrix flow regime. This transition is faster when grain size and density are lower, or infiltration rates are higher. This explains why preferential flow is more persistent in firn than in snow.

Simulation of Preferential Flow in Snow With a 2‐D Non‐Equilibrium Richards Model and Evaluation Against Laboratory Data

“…Water Resources Research LEROUX ET AL. paths in snow models were recently pointed out by Hirashima et al (2019), in which the parameterization for the water entry pressure had to be adjusted. This shows a lack of transferability of the water entry pressure method to different snow conditions for the simulation of preferential flow paths.…”

“…Many field experiments have demonstrated the occurrence of preferential flow in snow in different environments and under differing snowpack conditions such as the High Canadian Arctic (Marsh & Woo, 1984), the Sierra Nevada Mountains of California (McGurk & Marsh, 1995), and northern Japan (Yamaguchi et al, 2018). Laboratory experiments have helped to better understand fine‐scale water flow processes in snow, such as the formation of capillary barriers (Avanzi et al, 2016; Waldner et al, 2004), the occurrence of capillary overshoot during infiltration into dry snow (Katsushima et al, 2013), and the importance of wet snow metamorphism on the transition from preferential flow to matrix flow (Hirashima et al, 2019). Laboratory snow experiments also provide valuable data for evaluating physically based water flow through snow models, such as the models of Hirashima et al (2014, 2017) and Leroux and Pomeroy (2017, 2019).…”

Deep ice layer formation in an alpine snowpack: monitoring and modeling

“…In contrast, near-surface ice layers in Greenland were shown to prevent access to deeper firn layers, thus reducing meltwater storage in the firn and enhancing ice sheet mass loss (Machguth et al, 2016). The stability of a mountainous snowpack may also be affected, with a possible increased faceting of the microstructure close to ice or crusts (Jamieson, 2006;Hammonds et al, 2015;Hammonds and Baker, 2016). Moreover, retrieval algorithms for the water equivalent of snow cover and snow depth from passive microwave emissions are sensitive to the presence of ice layers (Rees et al, 2010;Roy et al, 2016).…”

Two-Dimensional Liquid Water Flow through Snow at the Plot Scale in Continental Snowpacks: Simulations and Field Data Comparisons

“…Multi-dimensional numerical models simulating preferential flow (vertical and/or longitudinal) through snow have only been recently developed (Hirashima et al, 2019;Hirashima et al, 2017;Hirashima et al, 2014;Leroux and Pomeroy, 2017). These models apply long-understood soil physics using laboratory parameterization of snow properties (Calonne et al, 2012;Yamaguchi et al, 2010).…”

“…As a result, these processes have been simulated primarily in centimetre-scale studies (e.g. Hirashima et al, 2019). However, there remains a need to understand these processes at the plot scale (multiple meters) to further understand the hydrological impacts.…”