Preprints
https://doi.org/10.5194/tc-2021-238
https://doi.org/10.5194/tc-2021-238

  12 Aug 2021

12 Aug 2021

Review status: this preprint is currently under review for the journal TC.

Stabilizing effect of mélange buttressing on the Marine Ice Cliff Instability of the West Antarctic Ice Sheet

Tanja Schlemm1,2, Johannes Feldmann1, Ricarda Winkelmann1,2, and Anders Levermann1,2,3 Tanja Schlemm et al.
  • 1Potsdam Institute for Climate Impact Research, Potsdam, Germany
  • 2Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany
  • 3Lamont-Doherty Earth Observatory, Columbia University, New York, USA

Abstract. Due to global warming and particularly high regional ocean warming, both Thwaites and Pine Island glaciers in the Amundsen region of the Antarctic Ice Sheet could lose their buttressing ice shelves over time. We analyze the possible consequences using the Parallel Ice Sheet Model (PISM), applying a simple cliff-calving parameterization and an ice-mélange-buttressing model. We find that the instantaneous loss of ice-shelf buttressing, due to enforced ice-shelf melting, initiates grounding line retreat and triggers the marine ice sheet instability (MISI). As a consequence, the grounding line progresses into the interior of the West Antarctic Ice Sheet and leads to a sea level contribution of 0.6 m within 100 a. By subjecting the exposed ice cliffs to cliff calving using our simplified parameterization, we also analyze the marine ice cliff instability (MICI). In our simulations it can double or even triple the sea level contribution depending on the only loosely constraint parameter which determines the maximum cliff-calving rate. The speed of MICI depends on this upper bound on the calving rate which is given by the ice mélange buttressing the glacier. However, stabilization of MICI may occur for geometric reasons. Since the embayment geometry changes as MICI advances into the interior of the ice sheet, the upper bound on calving rates is reduced and the progress of MICI is slowed down. Although we cannot claim that our simulations bear relevant quantitative estimates of the effect of ice-mélange buttressing on MICI, the mechanism has the potential to stop the instability. Further research is needed to evaluate its role for the past and future evolution of the Antarctic Ice Sheet.

Tanja Schlemm et al.

Status: open (until 07 Oct 2021)

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  • RC1: 'Comment on tc-2021-238', Anonymous Referee #1, 13 Sep 2021 reply

Tanja Schlemm et al.

Tanja Schlemm et al.

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Short summary
The marine cliff instability, if it exists, could dominate Antarctica's future contribution to sea level. It is likely to speed up with ice thickness and thus would accelerate in most parts of Antarctica. Here we investigate a possible mechanism that might stop a cliff instability through cloaking by ice melange. It is only a first step, but it shows that the embayment geometry is, in principle, able to stop a marine cliff instability in most parts of West Antarctica.