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Volume 12, issue 5 | Copyright
The Cryosphere, 12, 1615-1628, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 04 May 2018

Research article | 04 May 2018

How dynamic are ice-stream beds?

Damon Davies1, Robert G. Bingham1, Edward C. King2, Andrew M. Smith2, Alex M. Brisbourne2, Matteo Spagnolo3, Alastair G. C. Graham4, Anna E. Hogg5, and David G. Vaughan2 Damon Davies et al.
  • 1School of GeoSciences, University of Edinburgh, Edinburgh, EH8 9XP, UK
  • 2NERC British Antarctic Survey, Cambridge, CB3 0ET, UK
  • 3School of Geosciences, University of Aberdeen, Aberdeen, AB24 3UF, UK
  • 4College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4RJ, UK
  • 5Centre for Polar Observation and Modelling, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK

Abstract. Projections of sea-level rise contributions from West Antarctica's dynamically thinning ice streams contain high uncertainty because some of the key processes involved are extremely challenging to observe. An especially poorly observed parameter is sub-decadal stability of ice-stream beds, which may be important for subglacial traction, till continuity and landform development. Only two previous studies have made repeated geophysical measurements of ice-stream beds at the same locations in different years, but both studies were limited in spatial extent. Here, we present the results from repeat radar measurements of the bed of Pine Island Glacier, West Antarctica, conducted 3–6 years apart, along a cumulative ∼60km of profiles. Analysis of the correlation of bed picks between repeat surveys shows that 90% of the bed displays no significant change despite the glacier increasing in speed by up to 40% over the last decade. We attribute the negligible detection of morphological change at the bed of Pine Island Glacier to the ubiquitous presence of a deforming till layer, wherein sediment transport is in steady state, such that sediment is transported along the basal interface without inducing morphological change to the radar-sounded basal interface. Given the precision of our measurements, the upper limit of subglacial erosion observed here is 500mma−1, far exceeding erosion rates reported for glacial settings from proglacial sediment yields, but substantially below subglacial erosion rates of 1.0ma−1 previously reported from repeat geophysical surveys in West Antarctica.

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Short summary
This paper investigates the dynamics of ice stream beds using repeat geophysical surveys of the bed of Pine Island Glacier, West Antarctica; 60 km of the bed was surveyed, comprising the most extensive repeat ground-based geophysical surveys of an Antarctic ice stream; 90 % of the surveyed bed shows no significant change despite the glacier increasing in speed by up to 40 % over the last decade. This result suggests that ice stream beds are potentially more stable than previously suggested.
This paper investigates the dynamics of ice stream beds using repeat geophysical surveys of the...