Léa Bussière
Ph.D. student
Department of Geology and Geological Engineering
Laval University

Supervised by:

Richard Fortier (Regular member)

Co-supervised by:

Jean-Michel Lemieux (Regular member)

Research project description

Hydrogeophysics of permafrost mounds in Nunavik (Québec) and relic traces of permafrost degradation in Aquitaine (France) – An analog study to understand the paleo-recharge of regional aquifers in the Aquitaine sedimentary basin

The Aquitaine region (France) is a large sedimentary basin containing regional multi-layer aquifers used for drinking water supply. During the Pleistocene, this region has been affected by a succession of climate changes due to global glacial cycles which have influenced the groundwater recharge of these aquifers. Based on evidences from the geochemistry of groundwater, the low recharge during the Last Glacial Maximum (LGM - 20 000 years ago) may be due to permafrost limiting the water infiltration. According to the paleo-climatic reconstructions available for the Aquitaine region during the LGM, a periglacial environment, with possibly associated discontinuous permafrost, was occurring at that time. Moreover, in the recharge areas of the Aquitaine region, the land surface currently hosts numerous circular ponds with morphology similar to the thermokarst ponds, which are remnants of ice-rich permafrost mounds characteristic of permafrost environments after degradation, found in the discontinuous permafrost zone in Nunavik (Québec), Canada. One of the hypotheses in regard to the origin of these circular ponds is that they are due to permafrost degradation in this periglacial environment in the Aquitaine region following climate warming at the end of the LGM and leaving relic traces under the form of thermokarst ponds. Since the current climate in Nunavik is similar to one severing in the Aquitaine region during the LGM, the degrading permafrost and related thermokarst ponds in Nunavik can be used as analogs for the Aquitaine ponds. Therefore, the objective of this study is to verify the thermokarst origin of the Aquitaine ponds using a comparative analysis with the thermokarst ponds found in Nunavik. The Umiujaq area has been selected since degrading ice-rich permafrost mounds and thermokarst ponds due to the current trend to climate warming affecting the Nunavik are abundant and it is located in the discontinuous permafrost zone similar to one expected in the Aquitaine region during the LGM. A second objective is to understand groundwater recharge dynamics in the discontinuous permafrost environment of Umiujaq in order to better understand the groundwater recharge dynamics that occurred during the LGM in the Aquitaine regional aquifers. The proposed approach is to compare the hydrogeological and geological properties of the French and Quebec sites through sedimentological, geophysical and piezometric investigations, for verifying if the current periglacial processes in Umiujaq are transposable in Aquitaine under the same climatic conditions. Many useful data are already available for the Umiujaq instrumented site which can be used for this purpose. Finally, this comparative study between these Aquitaine and Nunavik ponds will allow us to better understand the consequences of the freeze-thaw processes occurring in the discontinuous permafrost zone on the hydrologic fluxes between surface water and groundwater.

Research Site Coordinates

Scientific Communications

Bussière, L., Schmutz, M., Fortier, R., Lemieux, J.-M., Dupuy, A., 2022. Near-surface geophysical imaging of a thermokarst pond in the discontinuous permafrost zone in Nunavik (Québec), Canada. <strong>Permafrost and Periglacial Processes</strong>(published online 2022-08-20). DOI: <a href="" target="_blank">10.1002/ppp.2166</a>.

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