Frédéric Bouchard (Stagiaire postdoctoral)

Centre Eau Terre Environnement
Room 5323
INRS
490, rue de la Couronne
Québec, Canada
G1K 9A9

Phone: (418) 654-3803
Email: frederic.bouchard@cen.ulaval.ca




Research project
Carbon cycle and permafrost degradation: exploring the dynamics of aquatic ecosystems at Bylot Island, Nunavut
Widespread in permafrost regions, aquatic ecosystems (including thermokarst ponds and lakes) play a crucial role in biogeochemical cycles, especially in greenhouse gas emissions (CO2, CH4). Permafrost thawing can release large quantities of carbon from the soil. This release is variable in time and space: different local ground conditions (e.g., topography, hydrology, snow cover) result in a diversity of lake types and sizes, which will influence their biogeochemical dynamics. The age of carbon mobilized within aquatic ecosystems is also central in these dynamics: 'young carbon', involved in short-term processes (e.g., photosynthesis, respiration, microbial activity), is distinct from 'old carbon’, which is in excess in the system and contributes in the amplification of climate warming. What happens at the scale of an Arctic watershed in transition?

The main objective of this research is to understand how the terrestrial (aquatic) component of the carbon cycle responds to permafrost degradation, especially through the inception and evolution of thermokarst ponds and lakes. More specifically:
1) Determine the age and source of carbon present within such geo/ecosystems;
2) Characterize the relationships between the formation age, morphology and carbon content in ponds and lakes, and the chronostratigraphy of the surrounding organic soils (frozen peat);
3) Build a general model of the development of ponds and lakes in response to permafrost degradation.

This first part of this research is to investigate the geomorphological and chronological properties of a set of ponds and lakes on Bylot Island, in the heart of the Canadian Arctic. Lake sediment cores, water and gas samples will be collected in representative aquatic systems of the Island: low-centered polygon ponds, ice-wedge trough ponds, and thermokarst lakes. Chronological analyses (14C dating) of the different carbon phases (CO2, CH4, dissolved and particulate organic carbon) will be done. This step will provide the temporal background of pond and lake inception, as well as the age of carbon included in the water and the sediments.

The second part of this research is to sample permafrost cores beside the studied ponds and lakes in order to reconstruct conditions prevailing before permafrost degradation and related thermokarst processes. Frozen soil cores (peat and silts containing up to 50% of ice) will be retrieved and brought back to the lab to perform chronostratigraphic and geocryological analyses.

The integration of such results (obtained in the water, in lake sediments and in the surrounding soils) will ultimately provide a general chronological model of permafrost degradation and related processes, including the evolution of thermokarst ponds and lakes, as well as carbon ‘trajectories’ in these geo/ecosystems.

Scientific communications
Bouchard, F., Francus, P., Pienitz, R., Laurion, I., Feyte, S.
, 2014. Subarctic thermokarst ponds: investigating recent landscape evolution and sediment dynamics in thawed permafrost of northern Québec (Canada). Arctic, Antarctic, and Alpine Research, 40(1): 259-280. DOI: 10.1657/1938-4246-46.1.259.
Bouchard, F., Pienitz, R., Ortiz, J.D., Francus, P., Laurion, I.
, 2013. Palaeolimnological conditions inferred from fossil diatom assemblages and derivative spectral properties of sediments in thermokarst ponds of subarctic Quebec, Canada. Boreas, 42: 575-595. DOI: 10.1111/bor.12000.
Bouchard, F., Turner, K.W., MacDonald, L.A., Deakin, C., White, H., Farquharson, N., Medeiros, A.S., Wolfe, B.B., Hall, R., Pienitz, R., Edwards, T.W.D.
, 2013. Vulnerability of shallow subarctic lakes to evaporate and desiccate when snowmelt runoff is low. Geophysical Research Letters, 40(23): 6112-6117. DOI: 10.1002/2013GL058635.
Francus, P., von Suchodoletz, H., Dietze, M., Donner, R.V., Bouchard, F., Roy, A.-J., Fagot, M., Verschuren, D., Kröpelin, S.
, 2013. Varved sediments of lake Yoa (Ounianga Kebir, Chad) reveal progressive drying of the Sahara during the last 6100 years. Sedimentology, 60(4): 911-934. DOI: 10.1111/j.1365-3091.2012.01370.x.
Bouchard, F., Francus, P., Pienitz, R., Laurion, I.
, 2011. Sedimentology and geochemistry of thermokarst ponds in discontinuous permafrost, subarctic Quebec, Canada. Journal of Geophysical Research - Biogeosciences, 116: G00M04. DOI: 10.1029/2011JG001675.

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