Preprints
https://doi.org/10.5194/egusphere-2024-851
https://doi.org/10.5194/egusphere-2024-851
03 May 2024
 | 03 May 2024

Present-day mass loss rates are a precursor for West Antarctic Ice Sheet collapse

Tim van den Akker, William H. Lipscomb, Gunter R. Leguy, Jorjo Bernales, Constantijn Berends, Willem Jan van de Berg, and Roderik S. W. van de Wal

Abstract. Observations of recent mass loss rates of the West Antarctic Ice Sheet (WAIS) raise concerns about its stability since a collapse would increase global sea levels by several meters. Future projections of these mass loss trends are often estimated using numerical ice sheet models. However, most current models display low skill in reproducing observed mass change rates accurately. Here, we develop a new initialization method that optimizes agreement not only with observations of ice thickness and surface velocity, but also with satellite-based estimates of mass change rates. Starting from this improved present-day state, we generate an ensemble of future projections of Antarctic mass change, covering uncertainties in model choices, parameter values and (observational) input data. Our ensemble displays a slow retreat over several centuries followed by a speed-up that lasts around 200 years. We find that for all ensemble members, the Thwaites and Pine Island glaciers collapse, even though the climate is held constant at present-day values. Our results imply that today’s mass loss rates are a precursor of the deglaciation of large parts of the WAIS, which would raise sea levels by at least a meter in the coming centuries, without additional climate forcing.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Tim van den Akker, William H. Lipscomb, Gunter R. Leguy, Jorjo Bernales, Constantijn Berends, Willem Jan van de Berg, and Roderik S. W. van de Wal

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of 'Present-day mass loss rates are a precursor for West Antarctic Ice Sheet collapse'', Anonymous Referee #1, 17 Jun 2024
    • AC1: 'Reply on RC1', Tim van den Akker, 08 Aug 2024
  • RC2: 'Comment on egusphere-2024-851', Anonymous Referee #2, 22 Jun 2024
    • AC2: 'Reply on RC2', Tim van den Akker, 08 Aug 2024

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of 'Present-day mass loss rates are a precursor for West Antarctic Ice Sheet collapse'', Anonymous Referee #1, 17 Jun 2024
    • AC1: 'Reply on RC1', Tim van den Akker, 08 Aug 2024
  • RC2: 'Comment on egusphere-2024-851', Anonymous Referee #2, 22 Jun 2024
    • AC2: 'Reply on RC2', Tim van den Akker, 08 Aug 2024
Tim van den Akker, William H. Lipscomb, Gunter R. Leguy, Jorjo Bernales, Constantijn Berends, Willem Jan van de Berg, and Roderik S. W. van de Wal
Tim van den Akker, William H. Lipscomb, Gunter R. Leguy, Jorjo Bernales, Constantijn Berends, Willem Jan van de Berg, and Roderik S. W. van de Wal

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The manuscript investigates the future stability of the West Antarctic Ice Sheet (WAIS) exploring how ice-sheet models may be initialised in a way that incorporates present-day satellite observations of ice mass loss. The study shows that with present-day ocean water temperatures large parts of WAIS will deglaciate, with major implications for global sea levels, particularly in Europe. Model simulations also show that current ocean-driven melting trends will destabilize the Thwaites and Pine Island glaciers over the next several centuries even in the absence of further change, leading to rapid ice loss.
Short summary
In this study, we present an improved way of representing ice thickness change rates into an ice sheet model. We apply this method using two ice sheet models on the Antarctic Ice Sheet. We found that the two largest outlet glaciers on the Antarctic Ice Sheet, the Thwaites Glacier and Pine Island Glacier, will collapse without further warming on a timescale of centuries. This would cause a sea level rise of about 1.2 meters globally.