Channelized, distributed, and disconnected: spatial structure and temporal evolution of the subglacial drainage under a valley glacier in the Yukon
The subglacial drainage system is one of the main controls on basal sliding but remains only partially understood. Here we expand the analysis of the 8-year dataset of borehole observations on a small, alpine polythermal valley glacier in the Yukon Territory. We presented this dataset in Rada and Sc...
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2023
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ftdoajarticles:oai:doaj.org/article:2d976244efcb4bf6a254245c4b8e0de3 2023-05-15T18:32:25+02:00 Channelized, distributed, and disconnected: spatial structure and temporal evolution of the subglacial drainage under a valley glacier in the Yukon C. A. Rada Giacaman C. Schoof 2023-02-01T00:00:00Z https://doi.org/10.5194/tc-17-761-2023 https://doaj.org/article/2d976244efcb4bf6a254245c4b8e0de3 EN eng Copernicus Publications https://tc.copernicus.org/articles/17/761/2023/tc-17-761-2023.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-17-761-2023 1994-0416 1994-0424 https://doaj.org/article/2d976244efcb4bf6a254245c4b8e0de3 The Cryosphere, Vol 17, Pp 761-787 (2023) Environmental sciences GE1-350 Geology QE1-996.5 article 2023 ftdoajarticles https://doi.org/10.5194/tc-17-761-2023 2023-02-19T01:46:51Z The subglacial drainage system is one of the main controls on basal sliding but remains only partially understood. Here we expand the analysis of the 8-year dataset of borehole observations on a small, alpine polythermal valley glacier in the Yukon Territory. We presented this dataset in Rada and Schoof ( 2018 ) , where we described the seasonal evolution of the drainage system and underlined the importance of hydraulic isolation at the glacier bed. These borehole observations constitute a unique dataset, both due to the length of the records and the density of the observations, with up to 157 simultaneously working pressure sensors. Now, to explore the spatial structure of the drainage system and its seasonal progression, we automatically cluster boreholes based on similarities in their water pressure records and follow their evolution through the melt season. Some of these borehole clusters show water pressure variations that suggest they are part of a drainage system connected to the surface meltwater supply, while others show features consistent with hydraulic isolation. The distribution of connected and isolated boreholes suggests that the distributed drainage system we observe comprises a network of small conduits with spacings smaller than the borehole bottom diameter (approximately 25–50 cm). Within these hydraulically connected areas, pressure phase lags, and amplitude attenuation rarely shows the behaviour expected in a diffusive system. This observation suggests that the diffusivity distribution in such areas presents a fine structure at scales smaller than our minimum borehole spacing of 15 m. However, at a glacier-wide scale, we observe that hydraulic connections are ubiquitous in some regions of the bed and permanently absent in others, suggesting large contrasts in diffusivity. Within disconnected areas, boreholes often show small-amplitude water pressure variations associated with horizontal normal stress transfers. Such stress transfers seem to play a more important role than previously ... Article in Journal/Newspaper The Cryosphere Yukon Directory of Open Access Journals: DOAJ Articles Yukon The Cryosphere 17 2 761 787 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental sciences GE1-350 Geology QE1-996.5 |
spellingShingle |
Environmental sciences GE1-350 Geology QE1-996.5 C. A. Rada Giacaman C. Schoof Channelized, distributed, and disconnected: spatial structure and temporal evolution of the subglacial drainage under a valley glacier in the Yukon |
topic_facet |
Environmental sciences GE1-350 Geology QE1-996.5 |
description |
The subglacial drainage system is one of the main controls on basal sliding but remains only partially understood. Here we expand the analysis of the 8-year dataset of borehole observations on a small, alpine polythermal valley glacier in the Yukon Territory. We presented this dataset in Rada and Schoof ( 2018 ) , where we described the seasonal evolution of the drainage system and underlined the importance of hydraulic isolation at the glacier bed. These borehole observations constitute a unique dataset, both due to the length of the records and the density of the observations, with up to 157 simultaneously working pressure sensors. Now, to explore the spatial structure of the drainage system and its seasonal progression, we automatically cluster boreholes based on similarities in their water pressure records and follow their evolution through the melt season. Some of these borehole clusters show water pressure variations that suggest they are part of a drainage system connected to the surface meltwater supply, while others show features consistent with hydraulic isolation. The distribution of connected and isolated boreholes suggests that the distributed drainage system we observe comprises a network of small conduits with spacings smaller than the borehole bottom diameter (approximately 25–50 cm). Within these hydraulically connected areas, pressure phase lags, and amplitude attenuation rarely shows the behaviour expected in a diffusive system. This observation suggests that the diffusivity distribution in such areas presents a fine structure at scales smaller than our minimum borehole spacing of 15 m. However, at a glacier-wide scale, we observe that hydraulic connections are ubiquitous in some regions of the bed and permanently absent in others, suggesting large contrasts in diffusivity. Within disconnected areas, boreholes often show small-amplitude water pressure variations associated with horizontal normal stress transfers. Such stress transfers seem to play a more important role than previously ... |
format |
Article in Journal/Newspaper |
author |
C. A. Rada Giacaman C. Schoof |
author_facet |
C. A. Rada Giacaman C. Schoof |
author_sort |
C. A. Rada Giacaman |
title |
Channelized, distributed, and disconnected: spatial structure and temporal evolution of the subglacial drainage under a valley glacier in the Yukon |
title_short |
Channelized, distributed, and disconnected: spatial structure and temporal evolution of the subglacial drainage under a valley glacier in the Yukon |
title_full |
Channelized, distributed, and disconnected: spatial structure and temporal evolution of the subglacial drainage under a valley glacier in the Yukon |
title_fullStr |
Channelized, distributed, and disconnected: spatial structure and temporal evolution of the subglacial drainage under a valley glacier in the Yukon |
title_full_unstemmed |
Channelized, distributed, and disconnected: spatial structure and temporal evolution of the subglacial drainage under a valley glacier in the Yukon |
title_sort |
channelized, distributed, and disconnected: spatial structure and temporal evolution of the subglacial drainage under a valley glacier in the yukon |
publisher |
Copernicus Publications |
publishDate |
2023 |
url |
https://doi.org/10.5194/tc-17-761-2023 https://doaj.org/article/2d976244efcb4bf6a254245c4b8e0de3 |
geographic |
Yukon |
geographic_facet |
Yukon |
genre |
The Cryosphere Yukon |
genre_facet |
The Cryosphere Yukon |
op_source |
The Cryosphere, Vol 17, Pp 761-787 (2023) |
op_relation |
https://tc.copernicus.org/articles/17/761/2023/tc-17-761-2023.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-17-761-2023 1994-0416 1994-0424 https://doaj.org/article/2d976244efcb4bf6a254245c4b8e0de3 |
op_doi |
https://doi.org/10.5194/tc-17-761-2023 |
container_title |
The Cryosphere |
container_volume |
17 |
container_issue |
2 |
container_start_page |
761 |
op_container_end_page |
787 |
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1766216531442663424 |