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Subglacial clast behaviour and its implication for till fabric development: new results derived from wireless subglacial probe experiments

Subglacial clast behaviour and its implication for till fabric development: new results derived from wireless subglacial probe experiments
Subglacial clast behaviour and its implication for till fabric development: new results derived from wireless subglacial probe experiments
This study has investigated the three-dimensional movement of clasts within deformation till, using embedded wireless probes. These probes were part of an environmental sensor network, which measured subglacial properties (temperature, water pressure, resistivity, case strain and tilt) six times a day, and relayed that data via radio to the glacier surface, where they were forwarded and broadcast on-line. The system was installed at Briksdalsbreen, Norway and operated from August 2004 until August 2006. Approximately 2000 probe days worth of data were collected, with an increase in performance (41% more readings) during the second year. The probes showed similar patterns of water pressure rises throughout the two years, but with slightly different magnitudes and timings. These changes in water pressure could be related to clast behaviour. The probes decreased their dip over the year, and the rate of change was related to an increase in glacier velocity. After initial changes in dip, the probes experienced changes in orientation, followed by rotation about the a-axis. This continuous rotation was similar to the motion suggested by Jeffery [1922. The motion of ellipsoidal particles immersed in a viscous fluid. Proceedings of the Royal Society of London, Series A 102, 161–179] for the behaviour of clasts within a viscous material. In addition, some probes also showed short, frequent dip oscillations in spring and autumn, which were interpreted to reflect stick-slip events, similar to lodging; and demonstrated how local conditions can interrupt the predicted rotation pattern.

Overall, it is demonstrated that when water pressures were high, decoupling occurred associated with basal sliding and dip oscillations; and when water pressures fell, the ice and sediment were coupled and till deformation occurred. These events happened during summer and autumn. It is this combination of “lodgement” and deformation that builds up both a complex (but predictable) fabric and a resultant composite till sedimentology.
sensor network, glacial sedimentology
0277-3791
597-607
Hart, Jane K.
e949a885-7b26-4544-9e15-32ba6f87e49a
Rose, Kathryn C.
cd0070d1-5373-4f2c-be61-18cc5278f4fb
Martinez, Kirk
5f711898-20fc-410e-a007-837d8c57cb18
Ong, Royan
54924b3a-eaf1-4fa7-bb59-2f9289fe2f40
Hart, Jane K.
e949a885-7b26-4544-9e15-32ba6f87e49a
Rose, Kathryn C.
cd0070d1-5373-4f2c-be61-18cc5278f4fb
Martinez, Kirk
5f711898-20fc-410e-a007-837d8c57cb18
Ong, Royan
54924b3a-eaf1-4fa7-bb59-2f9289fe2f40

Hart, Jane K., Rose, Kathryn C., Martinez, Kirk and Ong, Royan (2009) Subglacial clast behaviour and its implication for till fabric development: new results derived from wireless subglacial probe experiments. [in special issue: Quaternary Glaciodynamics] Quaternary Science Reviews, 28 (7-8), 597-607. (doi:10.1016/j.quascirev.2008.07.020).

Record type: Article

Abstract

This study has investigated the three-dimensional movement of clasts within deformation till, using embedded wireless probes. These probes were part of an environmental sensor network, which measured subglacial properties (temperature, water pressure, resistivity, case strain and tilt) six times a day, and relayed that data via radio to the glacier surface, where they were forwarded and broadcast on-line. The system was installed at Briksdalsbreen, Norway and operated from August 2004 until August 2006. Approximately 2000 probe days worth of data were collected, with an increase in performance (41% more readings) during the second year. The probes showed similar patterns of water pressure rises throughout the two years, but with slightly different magnitudes and timings. These changes in water pressure could be related to clast behaviour. The probes decreased their dip over the year, and the rate of change was related to an increase in glacier velocity. After initial changes in dip, the probes experienced changes in orientation, followed by rotation about the a-axis. This continuous rotation was similar to the motion suggested by Jeffery [1922. The motion of ellipsoidal particles immersed in a viscous fluid. Proceedings of the Royal Society of London, Series A 102, 161–179] for the behaviour of clasts within a viscous material. In addition, some probes also showed short, frequent dip oscillations in spring and autumn, which were interpreted to reflect stick-slip events, similar to lodging; and demonstrated how local conditions can interrupt the predicted rotation pattern.

Overall, it is demonstrated that when water pressures were high, decoupling occurred associated with basal sliding and dip oscillations; and when water pressures fell, the ice and sediment were coupled and till deformation occurred. These events happened during summer and autumn. It is this combination of “lodgement” and deformation that builds up both a complex (but predictable) fabric and a resultant composite till sedimentology.

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e-pub ahead of print date: 25 November 2008
Published date: April 2009
Keywords: sensor network, glacial sedimentology
Organisations: Electronics & Computer Science, Environmental Processes & Change

Identifiers

Local EPrints ID: 66266
URI: http://eprints.soton.ac.uk/id/eprint/66266
ISSN: 0277-3791
PURE UUID: aa4c3438-1e0f-4a63-83a2-44777abd2294
ORCID for Jane K. Hart: ORCID iD orcid.org/0000-0002-2348-3944
ORCID for Kirk Martinez: ORCID iD orcid.org/0000-0003-3859-5700

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Date deposited: 22 May 2009
Last modified: 14 Mar 2024 02:40

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Contributors

Author: Jane K. Hart ORCID iD
Author: Kathryn C. Rose
Author: Kirk Martinez ORCID iD
Author: Royan Ong

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