Thèse Modélisation de l'Interaction Entre les Glaciers et les Eaux Souterraines Impact du Changement Climatique H/F

Doctorat.Gouv.Fr

Établissement : Ecole normale supérieure - PSL École doctorale : Géosciences, Ressources Naturelles et Environnement Laboratoire de recherche : Laboratoire de Géologie de l'Ecole Normale Supérieure Direction de la thèse : Sophie VIOLETTE ORCID 0000000230312852 Début de la thèse : 2026-10-01 Date limite de candidature : 2026-05-15T23:59:59 Voir fichier joint Scientific Background
The research on the response of glaciers to climate change (CC) is well developed in glacierized regions in the world (e.g., GlamBIE team, 2025, in Iceland: Aðalgeirsdóttir et al., 2020). The interest is not only in mass balance variations, but also the associated effects on basal hydrology (ice-rock flow) and runoff variations (e.g., Huss, 2011; Schaefli et al., 2019). However, the groundwater component is rarely considered, although knowledge of aquifer dynamics (recharge, storage, discharge) is necessary to predict the evolution of water resources, water-related hazards under the influence of CC and climate feedbacks. Additionally, offshore fresh groundwater reserves are increasingly recognised (Post et al., 2013; Vincent and Violette, 2017). A recent review established their characteristics and controlling factors based on an extensive database set on continental margins (Micallef et al., 2020). A hypothesis is that it would originate from the massive recharge during the melting of the ice caps after the Last Glacial Maximum (LGM) (Post et al., 2013).
Temperate glaciers have an englacial hydrological system, with crevasses and mills (Flowers, 2010). They are usually drained by a subglacial system, maintained primarily by surface melting of the glacier, and secondarily by melt due to ice mass friction and pressure (Dochartaigh et al., 2016), as well as sometimes by geothermal activity. Subglacial systems consist of the connection of different types of channels (Rothlisberger, 1972; Hock and Hooke, 1993; Schroeder et al., 2013), which have been studied in relation to their roles in glacier movement (Lliboutry, 1968), erosion processes (Koppes et al., 2015) and glacier lake outburst floods (GLOFs) (Björnsson and Palsson, 2008).
The few available studies demonstrate the existence of pro- and sub-glacial aquifers (Favier et al., 2008; Vincent et al., 2019; Vincent et al., 2024). Some of them suggest a strong coupling between rivers and aquifers (Dzikowski and Jobard, 2012; Somers et al., 2016) and between lakes and aquifers (Hood et al., 2006), and demonstrate that groundwater recharge is at least partially due to glacier meltwater (Somers et al., 2016). However, the scope of these studies is limited as they only concern the aquifers of the till/sand formations, thus neglecting the deeper underlying aquifers.
Subglacial aquifer systems, which are inaccessible to direct measurement due to the thickness of the glacier and limited studies until now, remain the great unknowns in the general hydrological dynamics of glaciers, their catchment areas, and their outlets. There is a knowledge gap on the impact of glacier melting under CC on water resources, water-related risks, and freshwater inputs to the ocean (Vincent et al., 2019; van Tiel et al., 2024). To improve the numerical simulation tools, more research is necessary (e.g., Flowers, 2015). Thanks to the ongoing IceAq project that has a focus on 4 outlet glaciers of Vatnajökull ice cap on the south-east coast of Iceland, a first conceptual model of the hydrogeological system and hypotheses on the structure and hydrodynamical functioning of the aquifers (till/sand & fractured basalt formations) have been established (Vincent et al., 2024). A geo-referenced GIS database is under construction. It gathers available data about geology, climatology, glaciology, hydrology, and hydrogeology, and new ones acquired since spring 2021, mainly to characterise aquifer systems in terms of geometry, hydraulic parameters, hydrodynamical behaviour, and the boundary conditions (recharge & drainage by rivers).
Main goals and implications
The results are expected to shed light on the complex interactions between glaciers and aquifers in the past and future. The main aim is to estimate the importance of aquifers in buffering the impact of glacial melt on water availability. Scientific approach
A good understanding of the water cycle within the glacier-surface-subsurface compartments, and thus the better quantification of water fluxes exchanged between the continental and oceanic domains under CC, is crucial for sustainable water management and a precise assessment of its impact on this glacierized catchment. To address these critical needs, the PhD project will develop a numerical model based on the glacio-hydro-geo-logical conceptual model derived from an extensive database acquired over the past five years (Vincent et al., 2024). Once the candidate has acquired a firm grasp of the concepts of glaciology, hydrology, and hydrogeology and has gained an understanding of the glacio-hydro-geological dynamics of the system based on the available data, the candidate will be tasked with constructing a coupled numerical model of glacio-hydro-geological flows at the watershed scale. The ice-flow modelling with the numerical code ELMER.Ice (Gagliardini et al., 2013; Fleurian et al., 2014) and the subglacial-hydrological modelling with the numerical code GlaDs (Zwinger et al., 2019) will provide spatial and temporal estimates of the water pressure under the glacier. The surface runoff will be provided by a numerical model of the surface energy balance at the glacier surface under development in the project ISVOLC (https://isvolc.is/), forced by the Copernicus Arctic Regional Reanalysis product (CARRA) to give boundary conditions. A coupled modelling of surface and groundwater flow with a hydrogeological numerical code will assess the consistency of the whole dataset, and will improve the understanding of the water cycle of the glacierized catchment.