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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 4
The Cryosphere, 10, 1883-1896, 2016
https://doi.org/10.5194/tc-10-1883-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
The Cryosphere, 10, 1883-1896, 2016
https://doi.org/10.5194/tc-10-1883-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 25 Aug 2016

Research article | 25 Aug 2016

Persistence and variability of ice-stream grounding lines on retrograde bed slopes

Alexander A. Robel1,3,4, Christian Schoof2, and Eli Tziperman1 Alexander A. Robel et al.
  • 1Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
  • 2Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, Canada
  • 3Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
  • 4Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, USA

Abstract. In many ice streams, basal resistance varies in space and time due to the dynamically evolving properties of subglacial till. These variations can cause internally generated oscillations in ice-stream flow. However, the potential for such variations in basal properties is not considered by conventional theories of grounding-line stability on retrograde bed slopes, which assume that bed properties are static in time. Using a flow-line model, we show how internally generated, transient variations in ice-stream state interact with retrograde bed slopes. In contrast to predictions from the theory of the marine ice-sheet instability, our simulated grounding line is able to persist and reverse direction of migration on a retrograde bed when undergoing oscillations in the grounding-line position. In turn, the presence of a retrograde bed may also suppress or reduce the amplitude of internal oscillations in ice-stream state. We explore the physical mechanisms responsible for these behaviors and discuss the implications for observed grounding-line migration in West Antarctica.

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Portions of the Antarctic Ice Sheet edge that rest on upward-sloping beds have the potential to collapse irreversibly and raise global sea level. Using a numerical model, we show that changes in the slipperiness of sediments beneath fast-flowing ice streams can cause them to persist on upward-sloping beds for hundreds to thousands of years before reversing direction. This type of behavior is important to consider as a possibility when interpreting observations of ongoing ice sheet change.
Portions of the Antarctic Ice Sheet edge that rest on upward-sloping beds have the potential to...
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