(PI Antoine Séjourné, 2021-2024)
Permafrost covers 20-25% of the Northern Hemisphere. The recent temperature increase in the Arctic and Subarctic is significantly greater than elsewhere in the world. Climate simulations predict continued warming and an increase in the frequency of forest fires. This rapid change is already leading to the thawing of permafrost, causing ground subsidence, and the formation of lakes in areas of high permafrost ice content. Thawing permafrost is a major risk to land use and infrastructure stability. This process alters groundwater flows and the chemistry of lakes and rivers. In addition, permafrost contains large amounts of frozen organic carbon and its thawing causes a release of dissolved carbon into aquatic systems. Microorganisms actively convert the newly available highly biodegradable organic carbon into greenhouse gases (CO2, CH4). This release is a major risk because of the positive feedback on climate. Thus, climate change, through permafrost and habitat disturbance, affects local communities built on permafrost. A better understanding of the impacts of melting permafrost on soils, surface and groundwater (critical zone) and the carbon cycle, and the factors that control them, will contribute to understanding future climate change. This project aims to understand the hydrological, geochemical, geomorphological and microbiological impacts, as well as the socio-economic impacts of current thawing permafrost dynamics on soils and surface/groundwater in the Arctic/Subarctic. Our study will focus on the near-surface permafrost-hydrosystem continuum in small Arctic catchments where localised and rapid permafrost thaw (thermokarst) remains understudied. The overall objective is to compare different key sites in the Arctic with different permafrost, vegetation and permafrost degradation contexts in Siberia and Alaska. A set of quantitative indicators (or "sentinels") of soil, surface water and groundwater vulnerability will be used to understand and compare the impacts of permafrost degradation between the different sites. Our multidisciplinary approach includes geomorphology, social sciences, hydrology-hydrogeology, microbiology and geochemistry. The result will be a better understanding of the evolution of small watersheds in the Arctic permafrost and an increased awareness of local communities. This project brings together researchers from the USA (University of Fairbanks), Japan (University of Hokkaido), Russia (University of Moscow and Melnikov Permafrost Institute) and France (Université Paris Saclay, Université de Toulouse Paul Sabatier and Université du Littoral Côte d'Opale).