Capillary suction as a mechanism for interfacial water formation in early-winter glide-snow avalanches

The presence of interfacial water at the soil-snow interface is considered one of the important factors controlling glide-snow avalanche release. Suction of water out of the soil has been postulated as a possible mechanism for interfacial water formation in early-winter (also known as “cold”) glide-snow avalanches, where the interfacial water is not due to melt water infiltration from the snow surface. Here, we use two 1D-models, HYDRUS and SNOWPACK, to investigate water transport across the soil-snow interface via capillary action. The results of this modeling demonstrate that, under certain conditions, the snowpack is capable of drawing water from the soil and/or interfacial vegetation layer (e.g. grass). We show that the dynamics and magnitude of water transport are highly dependent on the hydraulic properties of the soil, interface, and snow. For example, capillary rise within the snow increases with decreasing snow grain size and increasing snow density. When considering an initially dry snowpack, the capillary pressure of the water within the soil and vegetation sets an upper bound for the increase in liquid water content within the snow. Additional work is needed to assess the effect of geothermal melting as a competing mechanism for interfacial water generation. However, regardless of how the interfacial water is generated, we show that certain configurations of soil, interface, and snow layers can lead to an increase in liquid water content within the basal snowpack due to capillary action. Thus, we conclude that capillary suction is a possible mechanism for early-winter glide-snow avalanche release.