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- Title
A Thermodynamic Nonequilibrium Model for Preferential Infiltration and Refreezing of Melt in Snow.
- Authors
Moure, Adrian; Jones, Nathan; Pawlak, Joshua; Meyer, Colin; Fu, Xiaojing
- Abstract
The transport of meltwater through porous snow is a fundamental process in hydrology that remains poorly understood but essential for more robust predictions of how the cryosphere will respond under climate change. Here, we propose a continuum model that resolves the nonlinear coupling of preferential melt flow and the nonequilibrium thermodynamics of ice‐melt phase change at the Darcy scale. We assume that the commonly observed unstable melt infiltration is due to the gravity fingering instability and capture it using the modified Richards equation, which is extended with a higher‐order term in saturation. Our model accounts for changes in porosity and the thermal budget of the snowpack caused by melt refreezing at the continuum scale, based on a mechanistic estimate of the ice‐water phase change kinetics formulated at the pore scale. We validate the model in 1D against field data and laboratory experiments of infiltration in snow and find generally good agreement. Compared to existing theory of stable melt infiltration, our 2D simulation results show that preferential infiltration delivers melt faster to deeper depths, and as a result, changes in porosity and temperature can occur at deeper parts of the snow. The simulations also capture the formation of vertical low porosity annulus known as ice pipes, which have been observed in the field but lack mechanistic understanding to date. Our results demonstrate how melt refreezing and unstable infiltration reshape the porosity structure of snow and impacts thermal and mass transport in highly nonlinear ways that are not captured by simpler models. Plain Language Summary: The flow of meltwater through porous snow is a fundamental process in hydrology that remains poorly understood. Part of the challenge is that percolation of snowmelt through dry snow is highly heterogeneous in space, forming vertical preferential melt channels. In addition, meltwater can also readily refreeze onto the existing snow, modifying the permeability structure of the snowpack. In this work, we describe the coupled processes of preferential melt flow and melt refreezing using a continuum model and study the complex interactions between melt flow and refreezing. Our model captures the formation of ice pipes, which are low porosity snow annulus that are commonly observed in the field. Our results also demonstrate that melt refreezing and preferential infiltration reshape the porosity structure of snow and impacts its thermal and mass transport in highly nonlinear ways that are not captured by simpler models. Key Points: We propose a continuum model of gravity‐driven preferential flow and refreezing of meltwater through porous snowCompared to stable infiltration, channelized flow prolongs the travel path of melt and deepens its thermal impact on snowWe predict partially refrozen melt channels form vertical low porosity annulus consistent with ice pipes seen in field observations
- Subjects
MELT infiltration; SNOWMELT; SOIL infiltration; NONEQUILIBRIUM flow; NONEQUILIBRIUM thermodynamics; MELTWATER; MODULATIONAL instability
- Publication
Water Resources Research, 2023, Vol 59, Issue 5, p1
- ISSN
0043-1397
- Publication type
Article
- DOI
10.1029/2022WR034035