Plastic bed beneath Hofsjökull ice cap, central Iceland, and the sensitivity of ice flow to surface meltwater flux

Brent Minchew*, Mark Simons, Helgi Björnsson, Finnur Pálsson, Mathieu Morlighem, Helene Seroussi, Eric Larour, Scott Hensley

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)

Abstract

The mechanical properties of glacier beds play a fundamental role in regulating the sensitivity of glaciers to environmental forcing across a wide range of timescales. Glaciers are commonly underlain by deformable till whose mechanical properties and influence on ice flow are not well understood but are critical for reliable projections of future glacier states. Using synoptic-scale observations of glacier motion in different seasons to constrain numerical ice flow models, we study the mechanics of the bed beneath Hofsjökull, a land-terminating ice cap in central Iceland. Our results indicate that the bed deforms plastically and weakens following incipient summertime surface melt. Combining the inferred basal shear traction fields with a Coulomb-plastic bed model, we estimate the spatially distributed effective basal water pressure and show that changes in basal water pressure and glacier accelerations are non-local and non-linear. These results motivate an idealized physical model relating mean basal water pressure and basal slip rate wherein the sensitivity of glacier flow to changes in basal water pressure is inversely related to the ice surface slope.

Original languageEnglish
Pages (from-to)147-158
Number of pages12
JournalJournal of Glaciology
Volume62
Issue number231
DOIs
Publication statusPublished - Feb 2016

Bibliographical note

Publisher Copyright:
© The Author(s) 2016.

Other keywords

  • Basal hydrology
  • Basal mechanics
  • Basal plasticity
  • Glaciology
  • Surface velocity
  • Jöklafræði
  • Jöklar
  • Basalt

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