Numerical Modeling of Permafrost Freeze–Thaw Dynamics Using a Finite-Element Framework
Permafrost thaw driven by ongoing climate warming poses significant risks to infrastructure in cold-region and highlatitude environments, particularly in remote subarctic communities where ground stability is essential for building safety. To improve understanding of ground thermal behavior and support future decarbonization strategies involving ground heat transfer, this study develops and validates a numerical model of permafrost using COMSOL Multiphysics. The model simulates transient heat transfer with phase change to capture the thermal response of fully saturated, ice-rich soils representative of subarctic conditions. Model validation is performed using a two-layer soil profile consisting of an upper organic peat layer overlying mineral soil and subjected to realistic seasonal surface-temperature forcing. Three scenarios of increasing complexity are used to assess the model’s accuracy and applicability. Although the physical problem is inherently three-dimensional, the assumptions adopted in this study reduce the thermal response to a predominantly onedimensional vertical process. For clarity and improved visualization of freeze–thaw transitions, the governing equations and simulation results are presented in a two-dimensional form. The results reproduce characteristic freeze–thaw cycles and demonstrate the buffering effect of latent heat on permafrost temperature evolution. The validated model establishes a foundation for future investigations of engineered systems—such as geo-piles integrated with ground-source heat pumps (GSHPs)—that can both stabilize permafrost and support low-carbon building heating and cooling. Although such integrations lie beyond the present scope, the modeling framework developed here provides a transferable basis for coupled thermal–structural analyses in permafrost regions.