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Lucile Cosyn Wexsteen
Ph.D. student
Department of Applied Geomatics
University of Sherbrooke
lucile.cosyn.wexsteen@usherbrooke.ca

Supervised by:

Frédéric Bouchard (Regular member)

Co-supervised by:

Dermot Antoniades (Regular member)

Research project description

Lake desiccation events in the recent past in the western Hudson Bay Lowlands: impacts on terrestrial ecosystems

Introduction: In their last report, the IPCC stated that climate change directly impacted the cryosphere (IPCC, 2022) . In Northern of Canada, climate change is at least two times stronger than the global mean. The Hudson Bay Lowlands (HBL), in the subarctic zone, are the second largest permafrost peatland in the world. Thermokarst lakes (formed by the thawing of ice-rich permafrost) are widespread in this region. However, since 2010, lake-level drawdown or complete desiccation has been observed. This kind of hydrological disturbance could, on the long term, dramatically impact the HBL biodiversity. A better understanding of this phenomenon could help protect population and wildlife. Objectives: The main objective of this research project is to determine if the desiccation could be observed only during industrial era or if these variations are from a natural longer-term cycle. The main objective is based on three specific goals: •Understand the hydrological balance of HBL aquatic ecosystems •Characterize the carbon cycle of peatlands and lakes in the region •Did the warming since the late 20th has triggered permafrost thawing and impacted the hydrological regime, causing lakes desiccation? Study sites: The Hudson Bay lowland are a transition zone between tundra and taiga and between continuous and discontinuous permafrost. Three major ecozones are identified: taiga (boreal forest), tundra and marine domain. More than 500 different species live in the HBL. However, recent studies and observation highlight some phenomena : •Air temperature increased, which lead to a reduction of sea ice surface area and thickness (Rühland et al., 2013) •Reduction of snow cover between May and June, around 17.8% per decade (Derksen and Brown, 2012) •Climate change affects lakes. Complete desiccation and lake level drawdown have been observed in many hydrologic systems (Bouchard et al., 2013; Rühland et al., 2013). Material and methods: In order to determine the hydrologic balance of the area, lake sediment cores, satellite imagery and photography will be used. In a second part, carbon cycle will be studied for the last 2 centuries with the peatland dynamic. Carbon analyses (TOC and 14C) will be done in collaboration with other laboratories. Finally, we will test the hypothesis that permafrost thawing leads to a better surface water circulation and peatland development is also responsible for lake desiccation and an increase in carbon sequestration. References: Bouchard, F., Turner, K.W., MacDonald, L.A., Deakin, C., White, H., Farquharson, N., Medeiros, A.S., Wolfe, B.B., Hall, R.I., Pienitz, R., Edwards, T.W.D., 2013. Vulnerability of shallow subarctic lakes to evaporate and desiccate when snowmelt runoff is low. Geophys. Res. Lett. 40, 6112–6117. Derksen, C., Brown, R., 2012. Spring snow cover extent reductions in the 2008–2012 period exceeding climate model projections. Geophys. Res. Lett. 39. Government of Canada, P.S. and P.C., 2019. Rapport sur le climat changeant du Canada.: En4-368/2019F-PDF - Government of Canada Publications - Canada.ca [WWW Document]. Ipcc, 2022. The Ocean and Cryosphere in a Changing Climate: Special Report of the Intergovernmental Panel on Climate Change, 1st ed. Cambridge University Press. Rühland, K.M., Paterson, A.M., Keller, W., Michelutti, N., Smol, J.P., 2013. Global warming triggers the loss of a key Arctic refugium. Proc. R. Soc. B Biol. Sci. 280, 20131887

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