A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers
On uncrevassed regions of polythermal glaciers, englacial conduits can form by incision of supraglacial stream channels followed by roof closure. The origin and evolution of examples in Longyearbreen, Svalbard, and Khumbu Glacier, Nepal, were determined by speleological survey. The development of pe...
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ftunstandrewcris:oai:research-portal.st-andrews.ac.uk:publications/12313e86-6216-4ad4-aad9-762cdc8889c8 2024-06-23T07:53:01+00:00 A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers Gulley, J. D. Benn, D. I. Mueller, D. Luckman, A. 2009 https://research-portal.st-andrews.ac.uk/en/researchoutput/a-cutandclosure-origin-for-englacial-conduits-in-uncrevassed-regions-of-polythermal-glaciers(12313e86-6216-4ad4-aad9-762cdc8889c8).html eng eng https://research-portal.st-andrews.ac.uk/en/researchoutput/a-cutandclosure-origin-for-englacial-conduits-in-uncrevassed-regions-of-polythermal-glaciers(12313e86-6216-4ad4-aad9-762cdc8889c8).html info:eu-repo/semantics/restrictedAccess Gulley , J D , Benn , D I , Mueller , D & Luckman , A 2009 , ' A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers ' , Journal of Glaciology , vol. 55 , no. 189 , pp. 66-80 . TERM VELOCITY VARIATIONS GREENLAND ICE-SHEET TEMPERATE GLACIERS WATER-FLOW SVALBARD DRAINAGE HYDROLOGY EVOLUTION RADAR article 2009 ftunstandrewcris 2024-06-13T00:29:21Z On uncrevassed regions of polythermal glaciers, englacial conduits can form by incision of supraglacial stream channels followed by roof closure. The origin and evolution of examples in Longyearbreen, Svalbard, and Khumbu Glacier, Nepal, were determined by speleological survey. The development of perennial incised channels requires that incision is significantly faster than glacier surface ablation, and thus will be favoured by high meltwater discharges in combination with cool climatic conditions or thick debris cover. Incised canyons can become blocked by drifted winter snow, refrozen meltwater, ice rafting from non-local sources (allochthonous breccias) and roof collapses (autochthonous breccias). Conduit closure can also occur in response to ice creep, particularly at depth. Following isolation from the surface, englacial conduits continue to evolve by vadose incision down to local base level. In the case of Longyearbreen, incision allowed the channel to reach the glacier bed, but on Khumbu Glacier deep incision is prevented because an effectively impermeable terminal moraine provides a high base level for the glacier drainage system. During our period of observations, deeper parts of the Longyearbreen conduit became blocked by a combination of ice accumulation and creep, causing the stream course to be re-routed to higher levels. On that glacier, incision, blockage and upward re-routing are cyclic. We conclude that 'cut and closure' is the dominant mechanism of englacial conduit formation on uncrevassed regions of polythermal glaciers. Article in Journal/Newspaper glacier glacier Greenland Ice Sheet Journal of Glaciology Longyearbreen Svalbard University of St Andrews: Research Portal Greenland Longyearbreen ENVELOPE(15.517,15.517,78.183,78.183) Svalbard |
institution |
Open Polar |
collection |
University of St Andrews: Research Portal |
op_collection_id |
ftunstandrewcris |
language |
English |
topic |
TERM VELOCITY VARIATIONS GREENLAND ICE-SHEET TEMPERATE GLACIERS WATER-FLOW SVALBARD DRAINAGE HYDROLOGY EVOLUTION RADAR |
spellingShingle |
TERM VELOCITY VARIATIONS GREENLAND ICE-SHEET TEMPERATE GLACIERS WATER-FLOW SVALBARD DRAINAGE HYDROLOGY EVOLUTION RADAR Gulley, J. D. Benn, D. I. Mueller, D. Luckman, A. A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers |
topic_facet |
TERM VELOCITY VARIATIONS GREENLAND ICE-SHEET TEMPERATE GLACIERS WATER-FLOW SVALBARD DRAINAGE HYDROLOGY EVOLUTION RADAR |
description |
On uncrevassed regions of polythermal glaciers, englacial conduits can form by incision of supraglacial stream channels followed by roof closure. The origin and evolution of examples in Longyearbreen, Svalbard, and Khumbu Glacier, Nepal, were determined by speleological survey. The development of perennial incised channels requires that incision is significantly faster than glacier surface ablation, and thus will be favoured by high meltwater discharges in combination with cool climatic conditions or thick debris cover. Incised canyons can become blocked by drifted winter snow, refrozen meltwater, ice rafting from non-local sources (allochthonous breccias) and roof collapses (autochthonous breccias). Conduit closure can also occur in response to ice creep, particularly at depth. Following isolation from the surface, englacial conduits continue to evolve by vadose incision down to local base level. In the case of Longyearbreen, incision allowed the channel to reach the glacier bed, but on Khumbu Glacier deep incision is prevented because an effectively impermeable terminal moraine provides a high base level for the glacier drainage system. During our period of observations, deeper parts of the Longyearbreen conduit became blocked by a combination of ice accumulation and creep, causing the stream course to be re-routed to higher levels. On that glacier, incision, blockage and upward re-routing are cyclic. We conclude that 'cut and closure' is the dominant mechanism of englacial conduit formation on uncrevassed regions of polythermal glaciers. |
format |
Article in Journal/Newspaper |
author |
Gulley, J. D. Benn, D. I. Mueller, D. Luckman, A. |
author_facet |
Gulley, J. D. Benn, D. I. Mueller, D. Luckman, A. |
author_sort |
Gulley, J. D. |
title |
A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers |
title_short |
A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers |
title_full |
A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers |
title_fullStr |
A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers |
title_full_unstemmed |
A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers |
title_sort |
cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers |
publishDate |
2009 |
url |
https://research-portal.st-andrews.ac.uk/en/researchoutput/a-cutandclosure-origin-for-englacial-conduits-in-uncrevassed-regions-of-polythermal-glaciers(12313e86-6216-4ad4-aad9-762cdc8889c8).html |
long_lat |
ENVELOPE(15.517,15.517,78.183,78.183) |
geographic |
Greenland Longyearbreen Svalbard |
geographic_facet |
Greenland Longyearbreen Svalbard |
genre |
glacier glacier Greenland Ice Sheet Journal of Glaciology Longyearbreen Svalbard |
genre_facet |
glacier glacier Greenland Ice Sheet Journal of Glaciology Longyearbreen Svalbard |
op_source |
Gulley , J D , Benn , D I , Mueller , D & Luckman , A 2009 , ' A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers ' , Journal of Glaciology , vol. 55 , no. 189 , pp. 66-80 . |
op_relation |
https://research-portal.st-andrews.ac.uk/en/researchoutput/a-cutandclosure-origin-for-englacial-conduits-in-uncrevassed-regions-of-polythermal-glaciers(12313e86-6216-4ad4-aad9-762cdc8889c8).html |
op_rights |
info:eu-repo/semantics/restrictedAccess |
_version_ |
1802644492095848448 |