Characterizing the Influence of Permafrost on Hydrological Processes through a Spatially Distributed Model

In the sub-arctic environment, the presence or absence of permafrost is a strong factor in controlling both soil moisture dynamics and hydrology. Soil moisture, which displays a high spatial and temporal variability, is an important variable in understanding and predicting a large number of processes including land-atmosphere interactions, permafrost aggradation/degradation, and fire frequency and severity. In order to understand and predict ecosystem response to a changing climate and resulting feedbacks, it is critical to quantify the interaction of soil moisture and meteorology as a function of climatic processes, landscape type, and vegetation. The primary goal of our research is to describe, simulate, and predict soil moisture dynamics and all other hydrologic processes everywhere throughout a sub-arctic watershed. The model we are developing will be used as a tool to better understand the effects of vegetation and soil type, presence or absence of permafrost, the amount and timing of precipitation, and disturbance (such as wildfire) on soil moisture dynamics. Three small sub-basins of the Caribou-Poker Creeks Research Watershed (CPCRW), located 48 km north of Fairbanks, Alaska (65\deg 10'N, 147\deg 30'W), are the areas selected for study. These small sub-basins, which are underlain with approximately 3, 19, and 53% permafrost, are simulated using the TopoFlow hydrologic model to explore differences in permafrost versus non-permafrost areas. The TopoFlow model is a process based, spatially distributed numeric model developed to simulate soil moisture dynamics and other hydrologic processes. This model can be used to simulate spatially distributed processes, such as soil moisture dynamics or snowmelt, as well as point measurements such as stream flow within the model domain. Simulation results reflect many characteristics of the sub-arctic environment, including the representation of discontinuous permafrost, distributed vegetation types, and a groundwater flow.