Life, death and afterlife of the extrusion flow theory
ABSTRACT. ‘Extrusion flow ’ describes any velocity field where maximum horizontal velocity occurs below the surface. By 1914, viscous flow and basal sliding over rough beds were accepted concepts. Between the world wars, there was little communication between naturalists describing complicated ice s...
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ftciteseerx:oai:CiteSeerX.psu:10.1.1.474.8029 2023-05-15T16:29:23+02:00 Life, death and afterlife of the extrusion flow theory Edwin D. Waddington The Pennsylvania State University CiteSeerX Archives application/pdf http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.474.8029 http://www.igsoc.org:8080/journal/56/200/j11J017.pdf en eng http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.474.8029 http://www.igsoc.org:8080/journal/56/200/j11J017.pdf Metadata may be used without restrictions as long as the oai identifier remains attached to it. http://www.igsoc.org:8080/journal/56/200/j11J017.pdf text ftciteseerx 2016-01-08T07:31:06Z ABSTRACT. ‘Extrusion flow ’ describes any velocity field where maximum horizontal velocity occurs below the surface. By 1914, viscous flow and basal sliding over rough beds were accepted concepts. Between the world wars, there was little communication between naturalists describing complicated ice sheets, and physicists studying fundamental processes controlling flow. Max Demorest brought concepts from mechanics into glaciology and glacial geology; however, his extrusion flow theory, to explain how ice flowed out of central Greenland, overlooked force imbalance. Rudolf Streiff-Becker found an apparent large imbalance between ice flux discharged through a gate and net accumulation in the upstream catchment at Claridenfirn, Switzerland. Because he underestimated uncertainty in ice depth, he had to propose a strong undercurrent (extrusion flow) to evacuate the excess mass. Reassessment of his assumptions shows that extrusion was actually unnecessary. However, confluence of two lines of evidence for extrusion flow added stature to the concept. In 1952, John Nye showed that free extrusion flow was impossible due to force imbalance. Two forms of extrusion flow survive: capped extrusion flow is possible on local scales where longitudinal stress gradients allow upper ice to move slowly, and rigid-body rotational flow can allow deeper ice to move faster without strain. 1. EARLY UNDERCURRENTS Text Greenland Unknown Demorest ENVELOPE(-65.550,-65.550,-67.367,-67.367) Greenland |
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ftciteseerx |
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English |
description |
ABSTRACT. ‘Extrusion flow ’ describes any velocity field where maximum horizontal velocity occurs below the surface. By 1914, viscous flow and basal sliding over rough beds were accepted concepts. Between the world wars, there was little communication between naturalists describing complicated ice sheets, and physicists studying fundamental processes controlling flow. Max Demorest brought concepts from mechanics into glaciology and glacial geology; however, his extrusion flow theory, to explain how ice flowed out of central Greenland, overlooked force imbalance. Rudolf Streiff-Becker found an apparent large imbalance between ice flux discharged through a gate and net accumulation in the upstream catchment at Claridenfirn, Switzerland. Because he underestimated uncertainty in ice depth, he had to propose a strong undercurrent (extrusion flow) to evacuate the excess mass. Reassessment of his assumptions shows that extrusion was actually unnecessary. However, confluence of two lines of evidence for extrusion flow added stature to the concept. In 1952, John Nye showed that free extrusion flow was impossible due to force imbalance. Two forms of extrusion flow survive: capped extrusion flow is possible on local scales where longitudinal stress gradients allow upper ice to move slowly, and rigid-body rotational flow can allow deeper ice to move faster without strain. 1. EARLY UNDERCURRENTS |
author2 |
The Pennsylvania State University CiteSeerX Archives |
format |
Text |
author |
Edwin D. Waddington |
spellingShingle |
Edwin D. Waddington Life, death and afterlife of the extrusion flow theory |
author_facet |
Edwin D. Waddington |
author_sort |
Edwin D. Waddington |
title |
Life, death and afterlife of the extrusion flow theory |
title_short |
Life, death and afterlife of the extrusion flow theory |
title_full |
Life, death and afterlife of the extrusion flow theory |
title_fullStr |
Life, death and afterlife of the extrusion flow theory |
title_full_unstemmed |
Life, death and afterlife of the extrusion flow theory |
title_sort |
life, death and afterlife of the extrusion flow theory |
url |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.474.8029 http://www.igsoc.org:8080/journal/56/200/j11J017.pdf |
long_lat |
ENVELOPE(-65.550,-65.550,-67.367,-67.367) |
geographic |
Demorest Greenland |
geographic_facet |
Demorest Greenland |
genre |
Greenland |
genre_facet |
Greenland |
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http://www.igsoc.org:8080/journal/56/200/j11J017.pdf |
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http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.474.8029 http://www.igsoc.org:8080/journal/56/200/j11J017.pdf |
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Metadata may be used without restrictions as long as the oai identifier remains attached to it. |
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