Preprints
https://doi.org/10.5194/tc-2022-114
https://doi.org/10.5194/tc-2022-114
 
07 Jun 2022
07 Jun 2022
Status: this preprint is currently under review for the journal TC.

Observed mechanism for sustained glacier retreat and acceleration in response to ocean warming around Greenland

Evan Carnahan1,2, Ginny Catania1,3, and Timothy C. Bartholomaus4 Evan Carnahan et al.
  • 1Institute for Geophysics, The University of Texas, Austin, TX, USA
  • 2Oden Institute for Computational Engineering and Sciences, The University of Texas, Austin, TX, USA
  • 3Department of Geological Sciences, The University of Texas, Austin, TX, USA
  • 4Department of Geological Sciences, University of Idaho, Moscow, ID, USA

Abstract. The dynamic loss of ice via outlet glaciers around the Greenland Ice Sheet is a major contributor to sea level rise. However, the retreat history and ensuing dynamic mass loss of neighboring glaciers are disparate, complicating projections of sea level rise. Here, we examine the stress balance evolution for three neighboring glaciers prior to, at the onset of, during, and, where possible, after retreat. We find no dynamic or thickness changes precede retreat, implicating a retreat trigger at the ice-ocean boundary. Terminus retreat initiates large-scale changes in the stress state at the terminus. This includes a drop in along-flow resistance to driving stress followed by an increase in lateral drag and associated glacier acceleration. We find that the pre-retreat spatial pattern in stresses along-fjord may control retreat duration and thus the long-term dynamic response of a glacier to terminus retreat. Specifically, glaciers with large regions of low basal drag extending far inland from the terminus permit a chain of stress changes that results in sustained acceleration, increased mass loss, and continued retreat. Our results suggest that vulnerable conditions for prolonged retreat may exist around Greenland, and thus dynamic mass loss may be sustained into the future despite a reduction in ocean forcing.

Evan Carnahan et al.

Status: open (until 02 Aug 2022)

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Evan Carnahan et al.

Evan Carnahan et al.

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Short summary
The Greenland Ice Sheet primarily loses mass through increased ice discharge. We find changes in discharge from outlet glaciers are initiated by ocean warming, which causes a change in the balance of forces resisting gravity, leading to acceleration. Vulnerable conditions for sustained retreat and acceleration are predetermined by the glacier-fjord geometry and exist around Greenland, suggesting increases in ice discharge may be sustained into the future despite a reduction in ocean warming.