Analog modelling of subglacial water flow : implications on the relations between tunnel valleys and glacial dynamics

• Main Author: Lelandais, Thomas
• Other Authors: Laboratoire de Planétologie et Géodynamique UMR 6112 (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Le Mans Université, Régis Mourgues, Edouard Ravier, Stéphane Pochat
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2018
• Subjects: Analog modelling; Glacial system; Subglacial environment; Pressurized water flow; Subglacial meltwater drainage system; Tunnel valleys; Modélisation analogique; Système glaciaire; Environnement sous-glaciaire; Écoulement d'eau pressurisée; Système de drainage d'eau de fonte sous-glaciaire; Vallées tunnels; Ice streams; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Ice Sheet
• Online Access: https://theses.hal.science/tel-02080357; https://theses.hal.science/tel-02080357/document; https://theses.hal.science/tel-02080357/file/2018LEMA1022.pdf

Tunnel valleys are major components of the subglacial meltwater drainage system. The inaccessibility of modern subglacial environments reduces our knowledge on the mechanisms involved in tunnel valleys formation, the parameters controlling their morphology and their influence on ice-sheet dynamics. This work presents a new experimental approach aiming to better assess the processes of tunnel valleys development. This approach relies on the development of a new experimental device simulating a pressurized water flow within a porous and permeable substratum underneath a viscous layer simulating the ice-sheet. The main results of the experiments conducted with this device have demonstrated the influence of both substratum properties and meltwater drainage on tunnel valleys formation and morphology. Using the device, we first manage to reproduce tunnel valley systems experimentally. Analyses conducted on these valleys experimental valleys suggest that the substratum topography and meltwater production play a key role on tunnel valleys genesis and morphology. Two tunnel valleys morphotypes have been identified, each one being charaterized by a unique morphology and mechanism of formation. Monitoring of the experimental ice sheet during tunnel valley formation shows close relationship between tunnel valleys development and "ice streams" dynamics. The evolution of tunnel valley drainage capacity seems to have a strong influence on ice sheet stability by regulating ice flux within "ice stream corridors". Les vallées tunnels sont les structures de drainage d'eau de fonte les plus imposantes de l'environnement sous-glaciaire. L'inaccessibilité des milieux sous-glaciaires actuels limitent nos connaissances des mécanismes impliqués dans leurs formations, des paramètres contrôlant leur morphologie et de leurs influences sur la dynamique glaciaire. Ce travail présente une nouvelle approche expérimentale visant à mieux contraindre la formation et le fonctionnement des systèmes de vallées tunnels. Cette approche repose sur le ...