Coupling between a glacier and a soft bed: II Model results
The relation between the local effective pressure and shear stress on till beneath Storglaciären, Sweden, discussed in Iverson and others (1999), provides an empirical basis for studying the processes that control the strength of the ice/bed coupling. Particles in the bed that protrude into the glac...
Main Author: | |
---|---|
Format: | Text |
Language: | English |
Published: |
Iowa State University Digital Repository
1999
|
Subjects: | |
Online Access: | https://lib.dr.iastate.edu/ge_at_pubs/134 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1153&context=ge_at_pubs |
id |
ftiowastateuniv:oai:lib.dr.iastate.edu:ge_at_pubs-1153 |
---|---|
record_format |
openpolar |
spelling |
ftiowastateuniv:oai:lib.dr.iastate.edu:ge_at_pubs-1153 2023-05-15T13:36:09+02:00 Coupling between a glacier and a soft bed: II Model results Iverson, Neal R. 1999-01-01T08:00:00Z application/pdf https://lib.dr.iastate.edu/ge_at_pubs/134 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1153&context=ge_at_pubs en eng Iowa State University Digital Repository https://lib.dr.iastate.edu/ge_at_pubs/134 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1153&context=ge_at_pubs Creative Commons Attribution license. CC-BY Geological and Atmospheric Sciences Publications Geomorphology Glaciology Hydrology text 1999 ftiowastateuniv 2021-08-28T22:47:13Z The relation between the local effective pressure and shear stress on till beneath Storglaciären, Sweden, discussed in Iverson and others (1999), provides an empirical basis for studying the processes that control the strength of the ice/bed coupling. Particles in the bed that protrude into the glacier sole support shear stresses that are limited by either ploughing or the traditional sliding mechanisms. Model calculations, based on studies of cone penetration through fine-grained sediment and sliding theory, agree with the observed relation between shear stress and effective pressure if the water layer at the ice/bed interface is assumed to thicken rapidly as the effective pressure approaches zero. Studies of the hydraulics of linked cavities provide support for this assumption, if the mean thickness of the water layer reflects the extent of microcavity development at the interface. Comparison of the calculated shear stress with the ultimate strength of till suggests that bed deformation limits the shear stress on till beneath Storglaciären only at intermediate effective pressures; at very low effective pressures, like those inferred at the site of the tiltmeter discussed in Iverson and others (1999), and at sufficiently high effective pressures, ploughing and sliding should focus motion near the glacier sole. A calculation using parameter values appropriate for Ice Stream B, West Antarctica, suggests that ploughing may occur there at shear stresses not sufficient to deform the bed at depth. This conclusion is reinforced by the likelihood that pore pressures in excess of hydrostatic should develop down-glacier from ploughing particles, thereby weakening the bed near the glacier sole. However, given the apparent sensitivity of the ice/bed coupling to basal conditions that may be highly variable, any blanket assumption regarding the flow mechanism of ice masses on soft beds should probably be viewed with skepticism. Text Antarc* Antarctica Ice Stream B West Antarctica Digital Repository @ Iowa State University Storglaciären ENVELOPE(18.560,18.560,67.904,67.904) West Antarctica |
institution |
Open Polar |
collection |
Digital Repository @ Iowa State University |
op_collection_id |
ftiowastateuniv |
language |
English |
topic |
Geomorphology Glaciology Hydrology |
spellingShingle |
Geomorphology Glaciology Hydrology Iverson, Neal R. Coupling between a glacier and a soft bed: II Model results |
topic_facet |
Geomorphology Glaciology Hydrology |
description |
The relation between the local effective pressure and shear stress on till beneath Storglaciären, Sweden, discussed in Iverson and others (1999), provides an empirical basis for studying the processes that control the strength of the ice/bed coupling. Particles in the bed that protrude into the glacier sole support shear stresses that are limited by either ploughing or the traditional sliding mechanisms. Model calculations, based on studies of cone penetration through fine-grained sediment and sliding theory, agree with the observed relation between shear stress and effective pressure if the water layer at the ice/bed interface is assumed to thicken rapidly as the effective pressure approaches zero. Studies of the hydraulics of linked cavities provide support for this assumption, if the mean thickness of the water layer reflects the extent of microcavity development at the interface. Comparison of the calculated shear stress with the ultimate strength of till suggests that bed deformation limits the shear stress on till beneath Storglaciären only at intermediate effective pressures; at very low effective pressures, like those inferred at the site of the tiltmeter discussed in Iverson and others (1999), and at sufficiently high effective pressures, ploughing and sliding should focus motion near the glacier sole. A calculation using parameter values appropriate for Ice Stream B, West Antarctica, suggests that ploughing may occur there at shear stresses not sufficient to deform the bed at depth. This conclusion is reinforced by the likelihood that pore pressures in excess of hydrostatic should develop down-glacier from ploughing particles, thereby weakening the bed near the glacier sole. However, given the apparent sensitivity of the ice/bed coupling to basal conditions that may be highly variable, any blanket assumption regarding the flow mechanism of ice masses on soft beds should probably be viewed with skepticism. |
format |
Text |
author |
Iverson, Neal R. |
author_facet |
Iverson, Neal R. |
author_sort |
Iverson, Neal R. |
title |
Coupling between a glacier and a soft bed: II Model results |
title_short |
Coupling between a glacier and a soft bed: II Model results |
title_full |
Coupling between a glacier and a soft bed: II Model results |
title_fullStr |
Coupling between a glacier and a soft bed: II Model results |
title_full_unstemmed |
Coupling between a glacier and a soft bed: II Model results |
title_sort |
coupling between a glacier and a soft bed: ii model results |
publisher |
Iowa State University Digital Repository |
publishDate |
1999 |
url |
https://lib.dr.iastate.edu/ge_at_pubs/134 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1153&context=ge_at_pubs |
long_lat |
ENVELOPE(18.560,18.560,67.904,67.904) |
geographic |
Storglaciären West Antarctica |
geographic_facet |
Storglaciären West Antarctica |
genre |
Antarc* Antarctica Ice Stream B West Antarctica |
genre_facet |
Antarc* Antarctica Ice Stream B West Antarctica |
op_source |
Geological and Atmospheric Sciences Publications |
op_relation |
https://lib.dr.iastate.edu/ge_at_pubs/134 https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1153&context=ge_at_pubs |
op_rights |
Creative Commons Attribution license. |
op_rightsnorm |
CC-BY |
_version_ |
1766074943035932672 |