Physical Conditions of Fast Glacier Flow 2: Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland

C. Hofstede, P. Christoffersen, B. Hubbard, S. H. Doyle, T. J. Young, A. Diez, O. Eisen, Alun Hubbard

Research output: Contribution to journalArticlepeer-review

27 Citations (SciVal)
170 Downloads (Pure)

Abstract

Outlet glaciers of the Greenland Ice Sheet transport ice from the interior to the ocean and contribute directly to sea level rise because discharge and ablation often exceed the accumulation. To develop a better understanding of these fast-flowing glaciers, we investigate the basal conditions of Store Glacier, a large outlet glacier flowing into Uummannaq Fjord in west Greenland. We use two crossing seismic profiles acquired near the centerline, 30 km upstream of the calving front, to interpret the physical nature of the ice and bed. We identify one notably englacial and two notably subglacial seismic reflections on both profiles. The englacial reflection represents a change in crystal orientation fabric, interpreted to be the Holocene-Wisconsin transition. From Amplitude-Versus-Angle (AVA) analysis we infer that the deepest ∼80 m of ice of the parallel-flow profile below this reflection is anisotropic with an enhancement of simple shear of ∼2. The ice is underlain by ∼45 m of unconsolidated sediments, below which there is a strong reflection caused by the transition to consolidated sediments. In the across-flow profile subglacial properties vary over small scale and the polarity of the ice-bed reflection switches from positive to negative. We interpret these as patches of different basal slipperiness associated with variable amounts of water. Our results illustrate variability in basal properties, and hence ice-bed coupling, at a spatial scale of ∼100 m, highlighting the need for direct observations of the bed to improve the basal boundary conditions in ice-dynamic models.

Original languageEnglish
Pages (from-to)349-362
Number of pages14
JournalJournal of Geophysical Research: Earth Surface
Volume123
Issue number2
Early online date09 Jan 2018
DOIs
Publication statusPublished - 24 Feb 2018

Keywords

  • subglacial
  • sliding
  • deformation
  • anisotropy
  • patches
  • seismic

Fingerprint

Dive into the research topics of 'Physical Conditions of Fast Glacier Flow 2: Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland'. Together they form a unique fingerprint.

Cite this