Modelling the thermal transport of a thawing permafrost plateau

• Main Author: Langford, Joelle E
• Format: Text
• Language: English
• Published: Scholarship@Western 2018
• Subjects: permafrost aggradation; permafrost degradation; thermal transport; wetland hydrogeology; Geology; Hydrology; Canada; Northwest Territories; Scotty Creek; Ice; permafrost
• Online Access: https://ir.lib.uwo.ca/etd/5397; https://ir.lib.uwo.ca/context/etd/article/7418/viewcontent/JoelleLangford_MScThesis.pdf

Permafrost covers approximately 24% of the Northern Hemisphere and is in a state of decay which has large implications. To characterize the processes involved in the transitional period of permafrost decay, a three-dimensional finite element numerical model is developed. The model is based on the Scotty Creek Research Basin in the Northwest Territories, Canada (61°18'N, 121°18'W). FEFLOW groundwater flow and heat transport modelling software is used in conjunction with the piFreeze plug-in, to account for phase changes between ice and water. As transiently simulating actual permafrost evolution would require 100’s of years of climate variations over an evolving landscape, whose geomorphic features are unknown, a steady-state developed permafrost bulb is used as an initial condition for a transient model run. The steady-state developed permafrost was generated by the application of freezing surface temperatures. The transient approach applies daily climatic data over the current plateau; the Simultaneous Heat and Water model (SHAW) is used to calculate ground temperatures and infiltration rates. It was found that a transient model with “unsteady-state” applied temperatures that include an unfrozen layer between the supra-permafrost table and ground surface yields better results than with steady-state permafrost initial conditions. Modelling permafrost will allow for the testing of remedial measures, such as mulching and borehole heat exchangers, to stabilize permafrost in high value infrastructure environments.