Inferring tipping points for ice flow in Antarctica from numerical simulations

• Main Author: Urruty, Benoît
• Other Authors: Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Université Grenoble Alpes 2020-., Olivier Gagliardini
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2023
• Subjects: Modelling; Antarctica; Flow; Ecoulement; Modélisation; Antarctique; [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph]; Antarctic; Misi; The Antarctic; Antarc*; Antarctique*; Ice cap; Ice Sheet
• Online Access: https://hal.univ-grenoble-alpes.fr/tel-04074261; https://hal.univ-grenoble-alpes.fr/tel-04074261v2/document; https://hal.univ-grenoble-alpes.fr/tel-04074261v2/file/URRUTY_2023_archivage.pdf

The Antarctic ice cap is the largest ice mass on Earth. This cap is subject to instabilities generated by ongoing climate change. This thesis is part of the European H2020 project TiPACCs (Tipping Points in Antarctic Climate Components). The overall objective is to assess the likelihood of large and abrupt changes in the near-future of the Antarctic ice sheet contribution to sea level, caused by Antarctic ice sheet tipping points. We need to determine the stability regime of the Antarctic ice sheet anchor lines and the existence of tipping points. We address the question of whether Antarctic grounding lines are currently undergoing irreversible retreat through instabilities such as MISI. Theoretical and numerical work has firmly established that marine-type ice sheet grounding lines can enter irreversible advance and retreat phases driven by marine ice sheet instability (MISI). Examples of such irreversible retreat have been found in several simulations of the past and future evolution of the Antarctic ice sheet.To this end, we are conducting a systematic analysis of the numerical stability of all Antarctic cap grounding lines in their present position using the Elmer/Ice ice flow model. Before perturbation experiments can be performed, an appropriate reference state is obtained in continuation of the recent model intercomparison experiment focused on ice sheet initialization for the Antarctic ice sheet, InitMIP-Antarctica (Seroussi, 2019). The inversion initialization methodology is used to ensure that the model reproduces the current surface flux for current ice thicknesses. In a second step, a study based on perturbation experiments is conducted to identify the stability regime of the Antarctic cap grounding lines in their current configurations. Stability is tested by applying a small but numerically significant melt disturbance below the floating platforms. We systematically show that ice sheet states can be obtained from grounding lines, ice geometry, and ice flow in close agreement with observations for ...