Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Geography & Environmental Studies

Faculty/School

Faculty of Science

First Advisor

Dr. William Quinton

Advisor Role

Dr. William Quinton

Abstract

In the peatland-dominated regions of discontinuous permafrost in northwestern Canada, permafrost thaw is altering landscapes at rates without precedent in the historical record. The present study uses a combination of remote sensing and ground based methods to examine the rates and patterns of permafrost thaw and how such thaw is changing the form and function of the landscape. The area within a 4 km2 area of interest underlain by permafrost decreased from 51% in 1977 to 43% in 2010, and to 40% in 2018, indicating an increase in the permafrost thaw rate from 0.24% yr-1 between 1977 and 2010, and 0.43% yr-1 between 2010 and 2018. Between 1977 and 2018, the permafrost-free terrain expanded by a factor of 1.25. The average expansion of all individual wetlands over the same period ranged between 0.30 and 1.33. The total permafrost terrain contracted by a factor of 0.8 between 1977 and 2018, while estimates of the average shrinkage factor of all individual plateaus ranged between 0.54 and 0.79. Wetland coalescence and plateau fragmentation processes complicated the computation of the average expansion and contraction factors. Measurements made along transects since 2011 indicated a persistent lowering of the permafrost table (vertical thaw), simultaneous recession of plateau edges (horizontal thaw), widespread development of talik, and preferential permafrost thaw driven by local site factors. Between 2011 and 2021, the average thaw below transects varied from 2.8 to 12.3 cm yr-1. The transect measurements also indicated that as the width of plateaus decreased due to thaw, the average rate of thaw increased. Geophysical measurements below an intensively studied plateau indicated that it lost 13% of its permafrost volume between 2010 and 2019. This thaw was equally driven by horizontal displacement of the plateau edge and by upward-displacement of the base of permafrost. The downward-directed thaw as indicated by the displacement of the permafrost table accounted for a slightly lower fraction.

Convocation Year

2024

Convocation Season

Fall

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