Campus Units
Geological and Atmospheric Sciences
Document Type
Article
Publication Version
Published Version
Publication Date
2-2012
Journal or Book Title
Journal of Glaciology
Volume
58
Issue
207
First Page
89
Last Page
98
DOI
doi.org/10.3189/2012JoG11J126
Abstract
A laboratory device was built to measure the forces that ice exerts on a 0.05 m diameter rigid plastic sphere in two different configurations: in contact with a flat bed or isolated from the bed. Measurements indicated that bed-normal contact forces were 1.8 times larger than drag forces due to creeping flow past a slippery sphere isolated from the bed. Measurements of forces as a function of the bed-normal ice velocity, estimations of the ice viscosity parameter and observations of markers in the ice indicate ice is Newtonian with a viscosity of ∼1.3 × 1011 Pa s. Newtonian behavior is expected due to small and transient stresses. A model of regelation indicates that it had a negligible (<5%) influence on forces. Water pressure in the cavity beneath the sphere in contact with the bed had a likewise negligible influence on contact forces. When no cavity is present, drag forces can be correctly estimated using Stokes's law (Newtonian viscosity) for a slippery sphere. The same law with a bed-enhancement factor of 1.8 is appropriate for estimating bed-normal contact forces. These results reinforce previous laboratory measurements and theories but provide no support for explanations of high debris/bed friction or rates of abrasion that depend on high contact forces.
Rights
Creative Commons Attribution license.
Copyright Owner
International Glaciological Society
Copyright Date
2012
Language
en
File Format
application/pdf
Recommended Citation
Byers, John; Cohen, Denis; and Iverson, Neal R., "Subglacial clast/bed contact forces" (2012). Geological and Atmospheric Sciences Publications. 150.
https://lib.dr.iastate.edu/ge_at_pubs/150
Comments
This article is from Journal of Glaciology 58 (2012): 89, doi:10.3189/2012JoG11J126. Posted with permission.