Preprints
https://doi.org/10.5194/tc-2021-130
https://doi.org/10.5194/tc-2021-130

  06 May 2021

06 May 2021

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

Weakening of the pinning point buttressing Thwaites Glacier, West Antarctica

Christian T. Wild1, Karen E. Alley2, Atsuhiro Muto3, Martin Truffer4, Ted A. Scambos5, and Erin C. Pettit1 Christian T. Wild et al.
  • 1College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis OR, USA
  • 2Centre for Earth Observation Science, Department of Environment and Geography, University of Manitoba, Winnipeg MB, Canada
  • 3Department of Earth and Environmental Science, Temple University, Philadelphia PA, USA
  • 4Geophysical Institute and Department of Physics, University of Alaska Fairbanks, Fairbanks AL, USA
  • 5Earth Science and Observation Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder CO, USA

Abstract. The Thwaites Eastern Ice Shelf continues to buttresses a significant portion of Thwaites Glacier through contact with a pinning point 40 km offshore of the present grounding line. Predicting future rates of Thwaites Glacier’s contribution to sea-level rise depends on the evolution of this pinning point and the resultant change in the ice-shelf stress field since the break-up of the Thwaites Western Glacier Tongue in 2009. Here we use Landsat-8 feature tracking of ice velocity in combination with model perturbation experiments to show how past changes in flow velocity have been governed in large part by changes in lateral shear and pinning point interactions with the Thwaites Western Glacier Tongue. We then use recent satellite altimetry data from ICESat-2 to show that Thwaites Glacier’s grounding line has continued to retreat rapidly; in particular, the grounded area of the pinning point is greatly reduced from earlier mappings in 2014, and grounded ice elevations continuing to decrease. This loss has created two pinned areas with ice flow now funneled between them. If current rates of surface lowering persist, the entire Thwaites Eastern Ice Shelf will unpin from the seafloor in less than a decade, despite our finding from airborne radar data that the seafloor underneath the pinning point is about 200 m shallower than previously reported. Advection of relatively thin and mechanically damaged ice onto the remaining portions of the pinning point and feedback mechanisms involving basal melting, may further accelerate the unpinning. As a result, ice discharge will likely increase along a 45 km stretch of the grounding line that is currently buttressed by the Thwaites Eastern Ice Shelf.

Christian T. Wild et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review_Wild_et_al', Clemens Schannwell, 03 Jun 2021
    • AC1: 'Reply on RC1', Christian Wild, 14 Sep 2021
  • RC2: 'Comment on tc-2021-130', Anonymous Referee #2, 04 Jun 2021
    • AC2: 'Reply on RC2', Christian Wild, 14 Sep 2021

Christian T. Wild et al.

Christian T. Wild et al.

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Short summary
Thwaites Glacier has the potential to significantly raise Antarctica's contribution to global sea-level rise by the end of this century. Here, we use satellite measurements of surface elevation to show that its floating part is close to losing contact with an underwater ridge that currently acts stabilizing. We then use computer models to simulate the predicted unpinning, which show that accelerated ice flow into the ocean follows the break-up of the floating part.