Ice sheets and ocean interactions : Modelling calving processes at the terminus of tidewater glaciers

• Main Author: Krug, Jean
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Grenoble, Jérôme Weiss, Gaël Durand
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2014
• Subjects: Ice-Sheet; Calving; Glacier; Modeling; Finite Elements; Calotte polaire; Vêlage; Modélisation; Elements finis; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Greenland; glacier; Ice Sheet; Sea ice; Tidewater
• Online Access: https://theses.hal.science/tel-01240106; https://theses.hal.science/tel-01240106/document; https://theses.hal.science/tel-01240106/file/KRUG_2014_archivage.pdf

Polar ice-sheets discharge and subsequent sea level rise is a major concern. Warming climate affects the behaviour of tidewater outlets glaciers and increases their ice discharge. As they drain the ice flow toward the ocean, it is pivotal to incorporate their dynamics when modelling the ice-sheet response to global warming. However, tidewater glacier dynamics is still complicated to understand, as they are believed to involve many feedbacks. The one between calving margin dynamics and glacier general dynamics is fundamental. This PhD thesis focuses on modelling the calving front of outlet glaciers, in order to enhance the representation of physical processes occurring at their margin. To do so, we build up a new framework for calving based on damage mechanics and fracture mechanics. This allows us to represent the slow degradation of the ice rheological properties from a virgin state to the appearance of a crevasse field, as well as the rapid fracture propagation associated with calving events. Our model is then constrained within a 2D flow-line representation of Helheim Glacier, Greenland. We find some parameters sets for which the glacier behaviour is coherent with its past evolution. Sensitivity tests are carried out and they reveal the significance of each model parameter. This new calving law is then employed to study the impact of submarine frontal melting and ice mélange (heterogeneous mixture of sea-ice and icebergs) on glacier dynamics. These two forcings are usually suspected to be responsible for the seasonal variations of the calving margin. Our results show that both forcings impact the front dynamics. The melting, however, only slightly changes the front position, when the ice mélange can force the glacier front to displace up to a few kilometers. Additionally, if the melting at the front is not sufficient to affect the inter-annual mass balance, this is not obvious when forced by ice mélange. At last, our model highlights a feature which is specific to floating glaciers: for the strongest ...