Mechanisms of englacial conduit formation and their implications for subglacial recharge
ideas about the character and evolution of englacial drainage systems have been deeply influenced by the theoretical model developed by Shreve [1972. Movement of water in glaciers. journal of Glaciology 11(62), 205-214]. The Shreve model is based on three main assumptions: (1) englacial drainage is...
Published in: | Quaternary Science Reviews |
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Main Authors: | , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
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2009
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Online Access: | https://risweb.st-andrews.ac.uk/portal/en/researchoutput/mechanisms-of-englacial-conduit-formation-and-their-implications-for-subglacial-recharge(8020c83d-d914-466d-8f3d-970b559b1330).html https://doi.org/10.1016/j.quascirev.2009.04.002 |
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ftunstandrewcris:oai:risweb.st-andrews.ac.uk:publications/8020c83d-d914-466d-8f3d-970b559b1330 2023-05-15T13:39:30+02:00 Mechanisms of englacial conduit formation and their implications for subglacial recharge Gulley, J. D. Benn, Doug I Screaton, E. Wallis-Martin, Julia 2009-09 https://risweb.st-andrews.ac.uk/portal/en/researchoutput/mechanisms-of-englacial-conduit-formation-and-their-implications-for-subglacial-recharge(8020c83d-d914-466d-8f3d-970b559b1330).html https://doi.org/10.1016/j.quascirev.2009.04.002 eng eng info:eu-repo/semantics/restrictedAccess Gulley , J D , Benn , D I , Screaton , E & Wallis-Martin , J 2009 , ' Mechanisms of englacial conduit formation and their implications for subglacial recharge ' , Quaternary Science Reviews , vol. 28 , no. 19-20 , pp. 1984-1999 . https://doi.org/10.1016/j.quascirev.2009.04.002 GREENLAND ICE-SHEET TERM VELOCITY VARIATIONS FREEZE-ON MECHANISM RICH BASAL ICE POLYTHERMAL GLACIERS TEMPERATE GLACIERS POLYCRYSTALLINE ICE GROUNDWATER-FLOW WEST ANTARCTICA LIMESTONE CAVES article 2009 ftunstandrewcris https://doi.org/10.1016/j.quascirev.2009.04.002 2022-07-21T06:59:55Z ideas about the character and evolution of englacial drainage systems have been deeply influenced by the theoretical model developed by Shreve [1972. Movement of water in glaciers. journal of Glaciology 11(62), 205-214]. The Shreve model is based on three main assumptions: (1) englacial drainage is in steady state; (2) englacial water will flow along the steepest hydraulic gradient within the glacier; and (3) pressure head equals the pressure of the surrounding ice minus a small component due to melting of the walls. The Shreve model has been widely adopted as a fundamental component of englacial drainage theory. There is no evidence, however, that the model provides a realistic picture of actual glacial drainage systems. To evaluate Shreve's theory, we used speleological techniques to directly survey englacial conduits. We mapped a total of 8.25 km of passage in 27 distinct englacial conduits in temperate, polythermal, cold-based and debris-covered glaciers between 2005 and 2008. New information reported here is supplemented by published data on 40 other englacial conduits located worldwide and surveyed to ice depths of 176 m using speleological techniques. In all cases, englacial drainage systems consisted of a single unbranching conduit. Englacial conduit morphologies were found to be intimately linked to the orientation of a glacier's principal stresses or the presence of pre-existing lines of high hydraulic conductivity. If a sufficient supply of water is available, hydrofracturing forms vertical conduits in zones of longitudinal extension and subhorizontal conduits where longitudinal stresses are compressive. On unfractured glacier surfaces, relatively shallow subhorizontal conduits with migrating nickpoints form by cut-and-closure provided channel incision is significantly faster than surface lowering. Conduits can also form along permeable debris-filled crevasse traces that connect supraglacial lake basins of different potential. Our results suggest that Shreve-type englacial drainage systems do not ... Article in Journal/Newspaper Antarc* Antarctica glacier Greenland Ice Sheet West Antarctica University of St Andrews: Research Portal Greenland West Antarctica Quaternary Science Reviews 28 19-20 1984 1999 |
institution |
Open Polar |
collection |
University of St Andrews: Research Portal |
op_collection_id |
ftunstandrewcris |
language |
English |
topic |
GREENLAND ICE-SHEET TERM VELOCITY VARIATIONS FREEZE-ON MECHANISM RICH BASAL ICE POLYTHERMAL GLACIERS TEMPERATE GLACIERS POLYCRYSTALLINE ICE GROUNDWATER-FLOW WEST ANTARCTICA LIMESTONE CAVES |
spellingShingle |
GREENLAND ICE-SHEET TERM VELOCITY VARIATIONS FREEZE-ON MECHANISM RICH BASAL ICE POLYTHERMAL GLACIERS TEMPERATE GLACIERS POLYCRYSTALLINE ICE GROUNDWATER-FLOW WEST ANTARCTICA LIMESTONE CAVES Gulley, J. D. Benn, Doug I Screaton, E. Wallis-Martin, Julia Mechanisms of englacial conduit formation and their implications for subglacial recharge |
topic_facet |
GREENLAND ICE-SHEET TERM VELOCITY VARIATIONS FREEZE-ON MECHANISM RICH BASAL ICE POLYTHERMAL GLACIERS TEMPERATE GLACIERS POLYCRYSTALLINE ICE GROUNDWATER-FLOW WEST ANTARCTICA LIMESTONE CAVES |
description |
ideas about the character and evolution of englacial drainage systems have been deeply influenced by the theoretical model developed by Shreve [1972. Movement of water in glaciers. journal of Glaciology 11(62), 205-214]. The Shreve model is based on three main assumptions: (1) englacial drainage is in steady state; (2) englacial water will flow along the steepest hydraulic gradient within the glacier; and (3) pressure head equals the pressure of the surrounding ice minus a small component due to melting of the walls. The Shreve model has been widely adopted as a fundamental component of englacial drainage theory. There is no evidence, however, that the model provides a realistic picture of actual glacial drainage systems. To evaluate Shreve's theory, we used speleological techniques to directly survey englacial conduits. We mapped a total of 8.25 km of passage in 27 distinct englacial conduits in temperate, polythermal, cold-based and debris-covered glaciers between 2005 and 2008. New information reported here is supplemented by published data on 40 other englacial conduits located worldwide and surveyed to ice depths of 176 m using speleological techniques. In all cases, englacial drainage systems consisted of a single unbranching conduit. Englacial conduit morphologies were found to be intimately linked to the orientation of a glacier's principal stresses or the presence of pre-existing lines of high hydraulic conductivity. If a sufficient supply of water is available, hydrofracturing forms vertical conduits in zones of longitudinal extension and subhorizontal conduits where longitudinal stresses are compressive. On unfractured glacier surfaces, relatively shallow subhorizontal conduits with migrating nickpoints form by cut-and-closure provided channel incision is significantly faster than surface lowering. Conduits can also form along permeable debris-filled crevasse traces that connect supraglacial lake basins of different potential. Our results suggest that Shreve-type englacial drainage systems do not ... |
format |
Article in Journal/Newspaper |
author |
Gulley, J. D. Benn, Doug I Screaton, E. Wallis-Martin, Julia |
author_facet |
Gulley, J. D. Benn, Doug I Screaton, E. Wallis-Martin, Julia |
author_sort |
Gulley, J. D. |
title |
Mechanisms of englacial conduit formation and their implications for subglacial recharge |
title_short |
Mechanisms of englacial conduit formation and their implications for subglacial recharge |
title_full |
Mechanisms of englacial conduit formation and their implications for subglacial recharge |
title_fullStr |
Mechanisms of englacial conduit formation and their implications for subglacial recharge |
title_full_unstemmed |
Mechanisms of englacial conduit formation and their implications for subglacial recharge |
title_sort |
mechanisms of englacial conduit formation and their implications for subglacial recharge |
publishDate |
2009 |
url |
https://risweb.st-andrews.ac.uk/portal/en/researchoutput/mechanisms-of-englacial-conduit-formation-and-their-implications-for-subglacial-recharge(8020c83d-d914-466d-8f3d-970b559b1330).html https://doi.org/10.1016/j.quascirev.2009.04.002 |
geographic |
Greenland West Antarctica |
geographic_facet |
Greenland West Antarctica |
genre |
Antarc* Antarctica glacier Greenland Ice Sheet West Antarctica |
genre_facet |
Antarc* Antarctica glacier Greenland Ice Sheet West Antarctica |
op_source |
Gulley , J D , Benn , D I , Screaton , E & Wallis-Martin , J 2009 , ' Mechanisms of englacial conduit formation and their implications for subglacial recharge ' , Quaternary Science Reviews , vol. 28 , no. 19-20 , pp. 1984-1999 . https://doi.org/10.1016/j.quascirev.2009.04.002 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1016/j.quascirev.2009.04.002 |
container_title |
Quaternary Science Reviews |
container_volume |
28 |
container_issue |
19-20 |
container_start_page |
1984 |
op_container_end_page |
1999 |
_version_ |
1766119741134471168 |