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Effects of basal debris on glacier flow
Neal R Iverson1, Denis Cohen, Thomas S Hooyer
1Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA 50011, USA. niverson@iastate.edu
Science (New York, N.Y.)
|July 5, 2003
Summary
Debris within glaciers significantly resists movement, exerting substantial shear traction. High pore-water pressure in subglacial debris layers can reduce friction, causing ice to slip over the debris.
Area of Science:
- Glaciology
- Earth Sciences
- Geophysics
Background:
- Glacier movement is influenced by basal conditions, including the presence and properties of subglacial debris.
- The role of debris in resisting glacier motion and basal friction has been historically underestimated.
Purpose of the Study:
- To investigate the shear traction exerted by debris-rich ice on a bedrock interface.
- To determine the effect of pore-water pressure on the mechanical behavior of subglacial debris layers and ice-debris interactions.
Main Methods:
- Conducted experiments beneath a thick, sliding glacier.
- Measured shear traction of ice with 2-11% debris on a smooth rock bed.
- Applied pore-water pressure (60-100% of normal stress) to subglacial debris layers.
Main Results:
- Debris-rich ice (2-11% debris) generated shear traction of 60-200 kPa, comparable to total basal shear traction.
- Increased pore-water pressure in debris layers significantly reduced shear traction, halting debris deformation.
- Ice slipped over the debris layer when pore-water pressure reached 60-100% of normal stress, indicating slip resistance was lower than debris shearing resistance.
Conclusions:
- Subglacial debris plays a critical role in glacier basal resistance, contrary to previous assumptions of negligible friction.
- Pore-water pressure is a key factor modulating subglacial friction, potentially leading to basal slip and influencing glacier dynamics.
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