Master of Science
Delay of Publication
The presence or absence of permafrost significantly influences the hydrology and ecology of northern watersheds. Linear disturbances resulting from tree canopy removal have led to widespread permafrost degradation in northern peatlands. Seismic lines resulting from oil and gas exploration now account for large portions of the drainage density of sub-arctic basins, and affect the region’s water and energy balances. As these peatlands represent some of the most sensitive ecosystems to climate and human disturbances, the ability to simulate perturbations to natural systems in a controlled lab environment is particularly important. This study presents a method that is able to simulate realistic freeze-thaw and permafrost conditions on a large variably-saturated peatland monolith, housed in a two level biome. The design was able to replicate realistic thermal boundary conditions and enabled field scale rates of active-layer freezing and thawing. The climate chamber and experimental design allows for the complete control of certain hydrological processes related to heat and water movement in permafrost environments without scaling requirements; and presents a path forward for the large-scale experimental study of frozen ground processes.
Mulching over seismic lines, upon completion of surveys, has been proposed as a best management practice to help reduce its environmental impact. The new experimental set-up enabled field-scale remediation techniques to be tested, and was used to investigate the effects of using mulch of the removed tree canopy on thermally mitigating permafrost thaw. Freeze-thaw cycles with and without the mulch enabled its effects to be tested. The data was assimilated into a coupled heat and water transport numerical model, which allowed quantification of the key physical parameters. An analysis was conducted on the combined effects of mulch thickness, antecedent moisture conditions and meteorological interactions. The mulch had beneficial effects on slowing thaw, by decoupling the subsurface from meteorological forcing and impeding heat conduction. Results indicate that mulching is an effective technique to reduce permafrost degradation and provides a scientific basis to assess the mitigation measure. This study will provide guidance in ensuring that northern exploration is performed in a more environmentally sustainable manner.
Mohammed, Aaron A., "Mitigating permafrost degradation due to linear disturbances in sub-arctic peatlands" (2013). University of Western Ontario - Electronic Thesis and Dissertation Repository. Paper 1758.