Department of geography
Pascale Roy-Léveillée (Regular member)
Michel Allard (Regular member)
Introduction: Climate has been warming since the 1990s in Nunavik, inducing permafrost thaw. Thawing must be better understood in the widespread discontinuous permafrost zone in the subarctic because this area is particularly dynamic and changing, especially at the Inuit community scale in Nunavik, where permafrost is degrading under infrastructure and in hunting, fishing and berry picking traditional land. Degradation is linked to thermokarst in fine-grained sediments and to shrubification. Studies on palsas, lithalsas and thermokarst have been conducted in the Arctic and in Kangiqsualujjuaq in Nunavik, but none has examined long term relationships between the evolution of climate, vegetation, ground temperatures and landform degradation. Understanding these links is crucial to properly interpreting predictions of the impact of warming on ground surface conditions. Objectives: The main objective of this work is to determine links between the progressive warming of permafrost over several decades and the geomorphological manifestation of its degradation in fine marine sediments near Kangiqsualujjuaq in Nunavik. This objective is divided into three sub-objectives: 1) characterize the geomorphological evolution of buttes, palsas and lithalses in marine deposits near Kangiqsualujjuaq, as well as the evolution of their vegetation cover during the last six decades; 2) analyze the evolution of the thermal profile of a butte, a palsa and a lithalsa in relation to their morphological degradation and changes in the vegetation cover in a context of climate change; and 3) identify the factors that control spatiotemporal variations during permafrost degradation at the local scale and compare these variations at different stages of degradation of these landforms in fine marine deposits at a larger scale. Study sites: One study site is a palsa and lithalsa field located on the east shore of Akilasakallak Cove near Kangiqsualujjuaq, in which several thermistor cables recorded ground temperatures over the years. Another study site, located northwest of the airport strip, encompasses lithalsas. Material and methods: The methods to achieve these three sub-objectives will be to: 1) map the spatial distribution and morphological evolution of buttes, palsas and lithalses to assess changes in vegetation cover using aerial photographs, satellite images and observation reports; 2) analyze the evolution of the thermal regime in the active layer and the permafrost of these landforms using data from 7 thermistor cables installed between 1989 and 1994 at depths of 5 to 20 m, over periods of 12 to 27 years (31 years in total); and 3) use Sentinel images to map the distribution of buttes, palsas and lithalses, as well as their degradation stage to compare their distribution in relation to the factors that control local spatiotemporal variability in Kangiqsualujjuaq. If the health instructions allow it, field work will take place during summer 2021 to improve the results obtained. Expected results: This research will be the first to take advantage of an exceptional dataset that will examine local spatiotemporal variations in the response of subarctic permafrost temperatures to climate over several decades. This aspect of the work is consistent with modeling efforts focusing on the interpretation of variability within the mesh. This work will help to better translate permafrost warming scenarios into changing surface conditions, an essential but difficult step in assessing the vulnerability of land to thaw.
Aubé-Michaud, S., Allard, M., L’Hérault, E., Chiasson, A., St-Amour, A.B., Bilodeau, S., Deslauriers, C., 2019. Caractérisation géotechnique et cartographie améliorée du pergélisol dans les communautés nordiques du Nunavik. Rapport préparé pour Ministère des Affaires municipales et de l’Occupation du territoire, gouvernement du Québec. 221 pages.
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