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      Shallow soil moisture - ground thaw interactions and controls

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      Date
      2009
      Author
      Guan, Xiu Juan (May)
      Type
      Thesis
      Degree Level
      Masters
      Metadata
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      Abstract
      Soil moisture and ground thaw state are both indicative of a hillslope’s ability to transfer water. In cold regions in particular, it is widely known that the wetness of surface soils and depth of ground thaw are important for runoff generation, but the diversity of interactions between surface soil moisture and ground thaw themselves has not been studied. To fill this knowledge gap, detailed shallow soil moisture and thaw depth surveys were conducted along systematic grids at the Baker Creek Basin, Northwest Territories. Multiple hillslopes were studied to determine how the interactions differed along a spectrum of topological, typological and topographic situations (T³ template). Results did not show a simple relationship between soil moisture and ground thaw as was expected. Instead, correlation was a function of wetness such that the correlation between soil moisture and ground thaw improved with site wetness. To understand why differences in soil moisture and ground thaw state arose, water and energy fluxes were examined for these subarctic study sites to discern the key processes controlling the patterns observed. Results showed that the key control in variable soil moisture and frost table interactions among the sites was the presence of surface water. At the peatland and wetland sites, accumulated water in depressions and flow paths maintained soil moisture for a longer duration than at the hummock tops. These wet areas were often locations of deepest thaw depth due to the transfer of latent heat accompanying lateral surface runoff. Although the peatland and wetland sites had large inundation extents, modified Péclet numbers indicated that the relative influence of external and internal hydrological processes at each site were different. Continuous inflow from an upstream lake into the wetland site caused advective and conductive thermal energies to be of equal importance to ground thaw. The absence of continuous surface flow at the peatland and valley sites led to the dominance of conductive thermal energy over advective energy for ground thaw. A quantitative explanation for the shallow soil moisture-ground thaw patterns was provided by linking hydrological processes and hillslope storage capacity with the calculated water and energy fluxes as well as the modified Péclet number. These results suggest that the T³ template and the modified Péclet number could be very useful parameters for differentiating landscape components in modeling soil moisture and frost table heterogeneity in cold regions.
      Degree
      Master of Science (M.Sc.)
      Department
      Geography
      Program
      Geography
      Supervisor
      Spence, Christopher; Westbrook, Cherie
      Committee
      Pomeroy, John; Si, Bingcheng; Elshorbagy, Amin; Guo, Xulin
      Copyright Date
      2009
      URI
      http://hdl.handle.net/10388/etd-01132010-203841
      Subject
      energy budget
      water budget
      wetlands
      ground thaw
      soil moisture
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      • Graduate Theses and Dissertations
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