In situ monitoring and physical modelling of sub-glacial deformation at Skalafellsjokull
The controls on glacial movement remain one of the most poorly understood elements of the glacial system, largely due to the inaccessibility of the subglacial environment. Here a geotechnical study is presented that investigates the behaviour of till under pore pressure controlled decreases in norma...
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University of Southampton
2017
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ftsouthampton:oai:eprints.soton.ac.uk:413853 2023-07-30T04:03:39+02:00 In situ monitoring and physical modelling of sub-glacial deformation at Skalafellsjokull Clayton, Alexander Ian 2017-03 text https://eprints.soton.ac.uk/413853/ https://eprints.soton.ac.uk/413853/1/Alexander_CLayton_PhD_thesis_final.pdf en English eng University of Southampton https://eprints.soton.ac.uk/413853/1/Alexander_CLayton_PhD_thesis_final.pdf Clayton, Alexander Ian (2017) In situ monitoring and physical modelling of sub-glacial deformation at Skalafellsjokull. University of Southampton, Doctoral Thesis, 232pp. uos_thesis Thesis NonPeerReviewed 2017 ftsouthampton 2023-07-09T22:17:34Z The controls on glacial movement remain one of the most poorly understood elements of the glacial system, largely due to the inaccessibility of the subglacial environment. Here a geotechnical study is presented that investigates the behaviour of till under pore pressure controlled decreases in normal effective stress. This is supplemented with field data from subglacial wireless probes, dGPS, GPR and a UAV survey of the glacial foreland to provide a broad view of subglacial deformation at Skalafellsjökull, Iceland The geotechnical laboratory investigation was undertaken on till sampled from an ice marginal location at Skalafellsjökull, close to the probe deployment site. This showed that the till adhered to the Mohr-Coulomb model, behaving plastically. In addition, a back pressure shear box was used to model pore pressure controlled reductions in normal effective stress. Linearly reducing normal effective stress by increasing back pressure resulted in episodic increases in horizontal strain rates. Small reductions in shear stress resulted in large strain rate reductions but dilation hardening did not occur. Dilation hardening has previously been suggested as a causal factor in stick-slip glacial motion and a reason for the apparent scale dependence of till rheology, but these experiments suggest it may not be as significant as previously thought. High spatial variability was found throughout the field investigation in probe, dGPS and mapping data from the UAV survey. dGPS deployed above in situ subglacial probes recorded hourly ice movement indicative of stick-slip motion but it was not possible to link this motion to subglacial processes via probe data. Pore pressure data suggested spatially variable coupling to the subglacial hydrological system and inconsistent forcing by surface melt. Tilt data showed consistent movement patterns and lacked regular up-glacier movements previously thought to indicate ice-bed decoupling and sliding. The lack of evidence for forcing of velocity variability from the in situ data ... Thesis glacier Iceland University of Southampton: e-Prints Soton |
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University of Southampton: e-Prints Soton |
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ftsouthampton |
language |
English |
description |
The controls on glacial movement remain one of the most poorly understood elements of the glacial system, largely due to the inaccessibility of the subglacial environment. Here a geotechnical study is presented that investigates the behaviour of till under pore pressure controlled decreases in normal effective stress. This is supplemented with field data from subglacial wireless probes, dGPS, GPR and a UAV survey of the glacial foreland to provide a broad view of subglacial deformation at Skalafellsjökull, Iceland The geotechnical laboratory investigation was undertaken on till sampled from an ice marginal location at Skalafellsjökull, close to the probe deployment site. This showed that the till adhered to the Mohr-Coulomb model, behaving plastically. In addition, a back pressure shear box was used to model pore pressure controlled reductions in normal effective stress. Linearly reducing normal effective stress by increasing back pressure resulted in episodic increases in horizontal strain rates. Small reductions in shear stress resulted in large strain rate reductions but dilation hardening did not occur. Dilation hardening has previously been suggested as a causal factor in stick-slip glacial motion and a reason for the apparent scale dependence of till rheology, but these experiments suggest it may not be as significant as previously thought. High spatial variability was found throughout the field investigation in probe, dGPS and mapping data from the UAV survey. dGPS deployed above in situ subglacial probes recorded hourly ice movement indicative of stick-slip motion but it was not possible to link this motion to subglacial processes via probe data. Pore pressure data suggested spatially variable coupling to the subglacial hydrological system and inconsistent forcing by surface melt. Tilt data showed consistent movement patterns and lacked regular up-glacier movements previously thought to indicate ice-bed decoupling and sliding. The lack of evidence for forcing of velocity variability from the in situ data ... |
format |
Thesis |
author |
Clayton, Alexander Ian |
spellingShingle |
Clayton, Alexander Ian In situ monitoring and physical modelling of sub-glacial deformation at Skalafellsjokull |
author_facet |
Clayton, Alexander Ian |
author_sort |
Clayton, Alexander Ian |
title |
In situ monitoring and physical modelling of sub-glacial deformation at Skalafellsjokull |
title_short |
In situ monitoring and physical modelling of sub-glacial deformation at Skalafellsjokull |
title_full |
In situ monitoring and physical modelling of sub-glacial deformation at Skalafellsjokull |
title_fullStr |
In situ monitoring and physical modelling of sub-glacial deformation at Skalafellsjokull |
title_full_unstemmed |
In situ monitoring and physical modelling of sub-glacial deformation at Skalafellsjokull |
title_sort |
in situ monitoring and physical modelling of sub-glacial deformation at skalafellsjokull |
publisher |
University of Southampton |
publishDate |
2017 |
url |
https://eprints.soton.ac.uk/413853/ https://eprints.soton.ac.uk/413853/1/Alexander_CLayton_PhD_thesis_final.pdf |
genre |
glacier Iceland |
genre_facet |
glacier Iceland |
op_relation |
https://eprints.soton.ac.uk/413853/1/Alexander_CLayton_PhD_thesis_final.pdf Clayton, Alexander Ian (2017) In situ monitoring and physical modelling of sub-glacial deformation at Skalafellsjokull. University of Southampton, Doctoral Thesis, 232pp. |
op_rights |
uos_thesis |
_version_ |
1772814686188732416 |