Description du sujet de thèse

Ongoing climate warming is heating the subsurface by modifying the thermal regimes. These water temperature changes impact groundwater chemistry and microbiology as well as the functioning of groundwater-dependent ecosystems such as rivers and wetlands. Warmer groundwater could reduce faunal diversity and increase the prevalence of microbes and contaminants.
The main scientific topic of this thesis is the characterization of thermal regimes of aquifers in France under the impact of ongoing global changes. It aims to answer the following research questions: What is the impact of recent and future global changes on groundwater temperature? Can we predict future groundwater temperature trends? What are the most vulnerable hydrogeological and climatic contexts in France?
The main scientific obstacle to a precise understanding of the impact of climate change on underground thermal dynamics is the significant lack of field observations. Data from BRGM databases and OZCAR Research Infrastructure (Critical Zone Observatories: Research and Application, https://www.ozcar-ri.org/) will allow to fill this gap. The data will be concatenated, verified, processed, interpreted and simulated through appropriate modelling approaches in order to understand thermal regimes of groundwater systems.
Several sites chosen for their representativeness of French hydrogeological contexts will be the subject of a deterministic modelling exercise to identify the main factors driving changes in groundwater temperatures in recent years and the respective roles of (i) climate change and (ii) human-origin changes of the groundwater cycle (groundwater abstraction, underground infrastructures, geothermal energy use).

Contexte de travail

The PhD will be carried out in between G-eau (BRGM) and Géosciences Rennes (CNRS) research labs and supervised by Maria Klepikova and Jean-Christophe Maréchal.
This position is offered in the frame of the recently funded ERC Starting grant (CONCRETER - Groundwater flow CONtrols on CRitical zonE ThErmal Regime, 2023-2028), thus allowing to the candidate to actively collaborate with other members of the ERC team.