| Summary: | In the current context of global warming, the impacts of climate change including permafrost degradation are already being felt in subarctic regions such as Umiujaq in Nunavik (Quebec). The physical processes causing this degradation are poorly documented. The main objective of the research project is to study the impact of the spatial and temporal variability of surface conditions on heat transfer at the airsurface interface as well as on permafrost degradation. To achieve this objective, infrared photographs of several permafrost mounds at Umiujaq were taken to identify the characteristic surface conditions of the study site. Based on these different conditions, thirty-five autonomous temperature probes were buried below the ground surface to monitor surface temperature variations on an hourly basis. The relationships between the surface temperatures and air temperature show that the surface conditions significantly control heat transfer at the air-surface interface as well as the thermal regime of the permafrost allowing the identification of a permafrost degradation sequence (in decreasing order : mudboils, lichens and mosses, development of thermokarst lakes and shrubbification). This monitoring of air and surface temperatures was used to constrain a numerical model of advectiveconductive heat transfer in permafrost terrain. A training period was first considered and then the observed climate variability was reproduced in the model. Different scenarios of global warming, formation of a thermokarst pond and vegetation invasion were considered. Simulated results show that changes in surface condition can result in an increase of temperatures in the permafrost mound up to 1.5 °C, the migration of the permafrost base up to 4 m towards the surface and a decrease in the extent of the permafrost mound up to 7 m. Dans le contexte actuel de réchauffement climatique, les impacts de ces changements climatiques se font déjà ressentir dans les régions subarctiques telles qu’à Umiujaq au Nunavik (Québec) dont notamment ...
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