thumbnail

Soft-bed experiments beneath Engabreen, Norway: Regelation, infiltration, basal slip and bed deformation

Journal of Glaciology

By:
, , , , , , , and

Links

  • The Publications Warehouse does not have links to digital versions of this publication at this time
  • Download citation as: RIS

Abstract

To avoid some of the limitations of studying soft-bed processes through boreholes, a prism of simulated till (1.8 m ?? 1.6 m ?? 0.45 m) with extensive instrumentation was constructed in a trough blasted in the rock bed of Engabreen, a temperate glacier in Norway. Tunnels there provide access to the bed beneath 213 m of ice. Pore-water pressure was regulated in the prism by pumping water to it. During experiments lasting 7-12 days, the glacier regelated downward into the prism to depths of 50-80 mm, accreting ice-infiltrated till at rates predicted by theory. During periods of sustained high pore-water pressure (70-100% of overburden), ice commonly slipped over the prism, due to a water layer at the prism surface. Deformation of the prism was activated when this layer thinned to a sub-millimeter thickness. Shear strain in the till was pervasive and decreased with depth. A model of slip by ploughing of ice-infiltrated till across the prism surface accounts for the slip that occurred when effective pressure was sufficiently low or high. Slip at low effective pressures resulted from water-layer thickening that increased non-linearly with decreasing effective pressure. If sufficiently widespread, such slip over soft glacier beds, which involves no viscous deformation resistance, may instigate abrupt increases in glacier velocity.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Soft-bed experiments beneath Engabreen, Norway: Regelation, infiltration, basal slip and bed deformation
Series title:
Journal of Glaciology
Volume
53
Issue:
182
Year Published:
2007
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Glaciology
First page:
323
Last page:
340