Preprints
https://doi.org/10.5194/tc-2021-76
https://doi.org/10.5194/tc-2021-76

  09 Mar 2021

09 Mar 2021

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

Two decades of dynamic change and progressive destabilization on the Thwaites Eastern Ice Shelf

Karen E. Alley1, Christian T. Wild2, Adrian Luckman3, Ted A. Scambos4, Martin Truffer5, Erin C. Pettit2, Atsuhiro Muto6, Bruce Wallin7, Marin Klinger7, Tyler Sutterley8, Sarah F. Child5, Cyrus Hulen9, Jan T. M. Lenaerts10, Michelle Maclennan10, Eric Keenan10, and Devon Dunmire10 Karen E. Alley et al.
  • 1Centre for Earth Observation Science, Department of Environment and Geography, University of Manitoba, Winnipeg, MB, Canada
  • 2College of earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
  • 3Department of Geography, Swansea University, Swansea, UK
  • 4Earth Science and Observation Center, Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA
  • 5Geophysical Institute and Department of Physics, University of Alaska Fairbanks, Fairbanks, Alaska, USA
  • 6Department of Earth and Environmental Science, Temple University, Philadelphia, PA, USA
  • 7National Snow and Ice Data Center, University of Colorado, Boulder, CO, USA
  • 8Polar Science Center, University of Washington, Seattle, Washington, USA
  • 9Department of Earth Sciences, College of Wooster, Wooster, OH, USA
  • 10Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, CO, USA

Abstract. The Thwaites Eastern Ice Shelf (TEIS) buttresses the eastern grounded portion of Thwaites Glacier through contact with a pinning point at its seaward limit. Loss of this ice shelf will promote further acceleration of Thwaites Glacier. Understanding the dynamic controls and structural integrity of the TEIS is therefore important to estimating Thwaites' future sea-level contribution. We present a ~20-year record of change on the TEIS that reveals the dynamic controls governing the ice shelf's past behavior and ongoing evolution. We derived ice velocities from MODIS and Sentinel-1 image data using feature tracking and speckle tracking, respectively, and combined these records with ITS_LIVE and GOLIVE velocity products from Landsat 7 and 8. In addition, we estimated surface lowering and basal melt rates using the REMA DEM in comparison to ICESat and ICESat-2 altimetry. Early in the record, TEIS flow dynamics were strongly controlled by the neighboring Thwaites Western Ice Tongue (TWIT). Flow patterns on the TEIS changed following the disintegration of the TWIT in ~2008, with a new divergence in ice flow developing around the pinning point at its seaward limit. Simultaneously, the TEIS developed new rifting that extends from the shear zone upstream of the ice rise and increased strain concentration within this shear zone. As these horizontal changes occurred, sustained thinning driven by basal melt reduced ice thickness, particularly near the grounding line and in the shear zone area upstream of the pinning point. This evidence of weakening at a rapid pace suggests that the TEIS is likely to fully destabilize in the next few decades, leading to further acceleration of Thwaites Glacier.

Karen E. Alley et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Reviewer Comment', Anonymous Referee #1, 06 Apr 2021
    • AC1: 'Reply on RC1', Karen Alley, 24 May 2021
  • RC2: 'Comment on tc-2021-76', Anonymous Referee #2, 29 Apr 2021
    • AC2: 'Reply on RC2', Karen Alley, 24 May 2021

Karen E. Alley et al.

Data sets

Two-year velocity and strain-rate averages from the Thwaites Eastern Ice Shelf, 2001-2020 Alley, K. E., Wild, C. T., Scambos, T. A., Muto, A., Pettit, E., Truffer, M., Wallin, B., and Klinger, M. https://doi.org/10.15784/601433

Karen E. Alley et al.

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Short summary
We present a 20-year, satellite-based record of velocity and thickness change on the Thwaites Eastern Ice Shelf (TEIS), the largest remaining floating extension of Thwaites Glacier (TG). TG holds the single greatest control on sea-level rise over the next few centuries, so it is important to understand changes on the TEIS, which controls much of TG's flow into the ocean. Our results suggest that the TEIS is progressively destabilizing and is likely to disintegrate over the next few decades.