Soil Behavior during Freeze-Thaw Processes at a Snow-Dominated Forest Site Simulated with the Physically-Based Numerical Water Flow and Heat Transport Soil in Cold Regions Model (SCRM)

Abstract

The freeze-thaw process controls several hydrologic processes including infiltration, runoff, and soil erosion. Simulating this process is important particularly in cold and mountainous regions. The Soil and Cold Regions Model (SCRM) was used to simulate, study, and understand the behavior of 12 homogenous soils, subject to a freeze-thaw process based on meteorological data at a snow dominated forest site in Laramie, WY, from 2010 and 2012. To complete a simulation, which accounts for all three phases of water (liquid, vapor, and ice), the model requires meteorological data, canopy characteristics, soil physical properties including the van Genuchten-Mualem parameters, and the initial state of the soil profile. Different model conditions were applied included the relationship between soil pore size, soil particle contact, soil thermal conductivities, soil ice/water content, snow cover, and meteorological data. Analysis of the simulations used metrics such as soil frost depth, days with ice, and maximum ice content. The results showed a threshold in snow depth ranging from 20 to 40 cm to fully insulate the soil from the atmosphere. Additionally, the model showed that the freeze-thaw process was strongest in the period with a shallow snow pack and that particle packing within the soil profile was an important factor in this process. Soil texture and water content controlled soil thermal properties. Water movement towards the freezing front was especially important in fine textured soils, where water and ice was concentrated in the upper layers. In coarser textured soil, frost also occurs, but not to the same extent. Based on these results, future research that combines a broader set of soil conditions with an extended set of field meteorology data could elucidate how soil texture controls thermal properties related to soil frost.