Preprints
https://doi.org/10.5194/tc-2022-104
https://doi.org/10.5194/tc-2022-104
 
21 Jun 2022
21 Jun 2022
Status: this preprint is currently under review for the journal TC.

The stability of present-day Antarctic grounding lines – Part A: No indication of marine ice sheet instability in the current geometry

Benoît Urruty1,, Emily A. Hill2,, Ronja Reese2,, Julius Garbe3,4, Olivier Gagliardini1, Gael Durand1, Fabien Gillet-Chaulet1, G. Hilmar Gudmundsson2, Ricarda Winkelmann3,4, Mondher Chekki1, David Chandler5, and Petra M. Langebroek5 Benoît Urruty et al.
  • 1Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, 38000 Grenoble, France
  • 2Department of Geography and Environmental Sciences, Northumbria University, Newcastle, UK
  • 3Potsdam Institute for Climate Impact Research (PIK), Member of the Leibniz Association, Potsdam, Germany
  • 4Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany
  • 5NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway
  • These authors contributed equally to this work.

Abstract. Theoretical and numerical work has firmly established that grounding lines of marine-type ice sheets can enter phases of irreversible advance and retreat driven by the marine ice sheet instability (MISI). Instances of such irreversible retreat have been found in several simulations of the past and future evolution of the Antarctic Ice Sheet. However, hitherto the stability regime of Antarctic Ice Sheet grounding lines in their current position has not been assessed. Here we conduct a systematic numerical stability analysis of all the grounding lines of the Antarctic Ice Sheet to determine if they are currently undergoing irreversible retreat through MISI. To do this, we initialise three state-of-the-art ice-flow models, Úa, Elmer/Ice, and PISM, to replicate the current geometry of the Antarctic Ice Sheet, and then apply small, but numerically significant, perturbations in ocean-induced ice-shelf melt. We find that the grounding lines around Antarctica migrate slightly away from their initial position while the perturbation is applied, and then revert to the initial state once the perturbation is removed. There is no indication of irreversible or self-sustaining retreat. This suggests that present-day grounding-line retreat is driven by external climate forcing alone. Hence, if the currently observed mass imbalance were to be removed, the grounding-line retreat would likely stop. However, under present-day climate forcing, further grounding-line retreat is expected, and our accompanying paper (Part B, Reese et al., 2022) shows that this could eventually lead to a collapse of some marine regions of West Antarctica.

Benoît Urruty et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2022-104', Anonymous Referee #1, 16 Aug 2022
  • RC2: 'Review of Urruty et al.', Alexander Robinson, 28 Aug 2022

Benoît Urruty et al.

Benoît Urruty et al.

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Short summary
Retreat of the Antarctic grounding lines could destabilise large parts of the ice sheet. We use three ice sheet models to show that the present-day locations of Antarctic grounding lines are stable with respect to a small perturbation away from their current position. This suggests that self-sustained retreat of grounding lines, due to an internal instability, has not begun. Instead, the currently observed retreat is likely due to external forcing alone.