The changing influence of permafrost on peatlands hydrology

• Main Author: Devoie, Élise
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Waterloo 2021
• Subjects: permafrost; thermal modelling; talik; peatlands; hydrology; active layer; numerical modelling; semi-analytical; heat equation; field research; Northwest Territories; Talik; Scotty Creek
• Online Access: http://hdl.handle.net/10012/16712

Hydrology and hydrological modelling in the far north is understudied, and many gaps exist in the current understanding and representation of northern thermal and hydrological systems. A combination of fieldwork and modelling was used to gain a better understanding of landscape evolution and thaw processes in the peatland-dominated discontinuous permafrost region of the Northwest Territories. Data collected at the Scotty Creek Research Station and modelling tools are developed and used to identify and quantify controls on isolated and connected talik formation in discontinuous permafrost peatland systems which include soil moisture, snow cover, surface temperature and subsurface lateral flow. The formation of a talik was shown to be a tipping point in permafrost degradation after which several positive feedback cycles led to more rapid permafrost loss. Given the widespread prevalence of taliks in this discontinuous permafrost peatlands environment, seasonal pressure and temperature gradients were analyzed in different talik configurations to determine the impacts of taliks on the landscape. It was found that the formation of taliks led to a balance between increased hydrologic storage due to isolated talik prevalence, and increased discharge from the basin due to connected talik features allowing previously inaccessible runoff features to be connected to the drainage network. Thermodynamically speaking, the interplay between subsurface temperature, thaw rates, subsidence, snow accumulation, canopy coverage and soil moisture were discussed supporting the idea that talik formation is a positive feedback for permafrost loss. It is also noted that the loss of permafrost causes subsidence and geophysical destabilization leading to ecosystem change and a change in greenhouse gas emission regimes. Existing models representing permafrost and other cold-regions processes are either computationally expensive physically-based models, or empirically based. This limits their predictive ability at the watershed scale or ...