Subglacial clast/bed contact forces Byers, John Cohen, Denis Iverson, Neal Iverson, Neal
dc.contributor.department Geological and Atmospheric Sciences 2018-02-18T09:28:24.000 2020-06-30T04:03:26Z 2020-06-30T04:03:26Z Sun Jan 01 00:00:00 UTC 2012 2012-02-01
dc.description.abstract <p>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.</p>
dc.description.comments <p>This article is from <em>Journal of Glaciology </em>58 (2012): 89, doi:<a href="" target="_blank">10.3189/2012JoG11J126</a>. Posted with permission.</p>
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dc.identifier.articleid 1137
dc.identifier.contextkey 10068602
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dc.language.iso en
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dc.subject.disciplines Geomorphology
dc.subject.disciplines Glaciology
dc.title Subglacial clast/bed contact forces
dc.type article
dc.type.genre article
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