Thermo- and hydrodynamic simulation of variably saturated flow in northern latitude peatlands

Peatlands store an estimated one quarter of the Earth's terrestrial soil carbon. Predominantly found within northern latitudes, peatlands contribute an estimated 17-28% of global methane emissions and therefore play an important role in the global carbon cycle. The application of models attempting to accurately represent the energy and hydrologic mass transfer in peatlands have been limited with application of generic functions of moisture retention and thermal conductivity. We have collected environmental data over a four year period from the Alaska Peatland Experiment (APEX) site, a heavily instrumented fen located in interior Alaska. The objective of this research is to develop several deterministic models of complex energy transfer and multiphase hydrologic processes, simulate and apply them to organic variably saturated soils in peatlands. More complex representations of the unsaturated subsurface and energy transfer within organic soils have the potential to provide insight on the dynamics of subterranean microbiological processes associated with carbon transformations, atmospheric emissions of greenhouse gases, and hydrologie transport. We have used finite element and volume analyses to account for seasonal variations of mass and energy transport. The application of a modified van Genuchten equation for variably saturated flow modeling has been used to account for all hydrologic processes. The results illustrate that the water table has a distinctive non-linear effect on heat transfer and phase change. Results of our study also indicate the importance of variability in thermal conductivity of organic soils and quantify the effect of porosity within application of coupled models.