Measuring and modelling thermal and moisture regimes in seasonally frozen soils, Wolf Creek, Yukon Territory

Abstract

Frozen ground is an important consideration in cold regions hydrology because pore ice can impede the ability of water to infiltrate into and migrate within soils, thereby altering water flow paths and increasing surface runoff. High latitude regions are particularly susceptible to changes in climate, where increases in temperature and changing precipitation trends can alter soil freeze/thaw dynamics. However, there has been limited research on infiltration processes in subarctic alpine environments due to sparse historic data and difficulties with gathering direct measurements. In addition, few hydrological models consider the complexity of frozen soils in such environments. The objectives of this thesis are to assess the ability of the GeoStudio finite element modelling suite to simulate observed soil temperature and moisture data and to evaluate the sensitivity of the models to changing climate scenarios. GeoStudio’s Multiphysics model integrates several models that allow it to simulate concurrent water flow and temperature dynamics in variably saturated environments experiencing soil freezing and thawing. Field data for this study are obtained from Wolf Creek Research Basin (WCRB) in southern Yukon, Canada. Data for quantifying snowmelt, soil moisture, soil temperature, and soil composition were collected at three sites in WCRB from April 2015 to August 2016, adding to the available historical data. Results of the GeoStudio models illustrate the dominance of snow in controlling freeze/thaw dynamics and simulate the study environment to reasonable accuracy with some discrepancies in timing and variability. In addition, GeoStudio is particularly sensitive to surface conditions affecting both coupled heat and water flow processes compared to independent changes of air temperature and precipitation, suggesting future climatic scenarios may have a notable impact on frozen soils. This research helps elucidate the complex heat transfer and water movement processes that control infiltration in northern environments and provides a quantitative assessment of their sensitivity to future climate warming.