Developing a numerical model of frost boils dynamics.

The research was initiated as a part of biocomplexity project, which investigates cryoturbation in continuous permafrost regions in the Arctic. The project explores influence of climate (mean annual and summer temperatures, and snow cover depth and density), vegetation layer composition and physical properties, soil textures and moisture content on evolution of frost boils. The work deals with analysis of temperature regimes and moisture distribution and dynamics during seasonal cycles of freezing and thawing. The research focuses on the development of a computational approach to the study of frost boils as a self-organized system. The model is calibrated using temperature and moisture content data collected from a field experiment at two study sites. A thermo-mechanical model of the frost boil phenomena based on principles of macroscopic thermodynamics and continuum mechanics will be presented. The model includes the energy and mass conservation equations, continuity equation, the Clausius-Claiperon equation, and an empirical formula which relates unfrozen water content to temperature. The complete system is reduced to a computationally convenient set of coupled equations for temperature, pore water pressure and porosity in a two-dimensional domain. A finite element method and an implicit scheme in time were utilized to construct a non-linear system of equations, which was solved iteratively. The model describes dynamics of frost boils and helps to explain geometric form and size of distinctly visible patterned ground north of the Alaska's Brook Range.