Quantification of seasonal and diumal dynamics of subglacial channels using seismic observations on an Alpine glacier
Water flowing below glaciers exerts a major control on glacier basal sliding. However, our knowledge of the physics of subglacial hydrology and its link with sliding is limited because of lacking observations. Here we use a 2-year-long dataset made of on-ice-measured seismic and in situ-measured gla...
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ftethz:oai:www.research-collection.ethz.ch:20.500.11850/454435 2023-05-15T18:32:14+02:00 Quantification of seasonal and diumal dynamics of subglacial channels using seismic observations on an Alpine glacier Nanni, Ugo Gimbert, Florent Vincent, Christian Gräff, Dominik Walter, Fabian Piard, Luc Moreau, Luc 2020-05-05 application/application/pdf https://hdl.handle.net/20.500.11850/454435 https://doi.org/10.3929/ethz-b-000416433 en eng Copernicus info:eu-repo/semantics/altIdentifier/doi/10.5194/tc-14-1475-2020 info:eu-repo/semantics/altIdentifier/wos/000531822500003 http://hdl.handle.net/20.500.11850/454435 doi:10.3929/ethz-b-000416433 info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International CC-BY The Cryosphere, 14 (5) info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 2020 ftethz https://doi.org/20.500.11850/454435 https://doi.org/10.3929/ethz-b-000416433 https://doi.org/10.5194/tc-14-1475-2020 2022-04-25T14:17:14Z Water flowing below glaciers exerts a major control on glacier basal sliding. However, our knowledge of the physics of subglacial hydrology and its link with sliding is limited because of lacking observations. Here we use a 2-year-long dataset made of on-ice-measured seismic and in situ-measured glacier basal sliding speed on Glacier d'Argentière (French Alps) to investigate the physics of subglacial channels and its potential link with glacier basal sliding. Using dedicated theory and concomitant measurements of water discharge, we quantify temporal changes in channels' hydraulic radius and hydraulic pressure gradient. At seasonal timescales we find that hydraulic radius and hydraulic pressure gradient respectively exhibit a 2- and 6-fold increase from spring to summer, followed by comparable decrease towards autumn. At low discharge during the early and late melt season channels respond to changes in discharge mainly through changes in hydraulic radius, a regime that is consistent with predictions of channels' behaviour at equilibrium. In contrast, at high discharge and high short-term water-supply variability (summertime), channels undergo strong changes in hydraulic pressure gradient, a behaviour that is consistent with channels behaving out of equilibrium. This out-of-equilibrium regime is further supported by observations at the diurnal scale, which prove that channels pressurize in the morning and depressurize in the afternoon. During summer we also observe high and sustained basal sliding speed, which supports that the widespread inefficient drainage system (cavities) is likely pressurized concomitantly with the channel system. We propose that pressurized channels help sustain high pressure in cavities (and therefore high glacier sliding speed) through an efficient hydraulic connection between the two systems. The present findings provide an essential basis for testing the physics represented in subglacial hydrology and glacier sliding models. ISSN:1994-0416 ISSN:1994-0424 Article in Journal/Newspaper The Cryosphere ETH Zürich Research Collection |
institution |
Open Polar |
collection |
ETH Zürich Research Collection |
op_collection_id |
ftethz |
language |
English |
description |
Water flowing below glaciers exerts a major control on glacier basal sliding. However, our knowledge of the physics of subglacial hydrology and its link with sliding is limited because of lacking observations. Here we use a 2-year-long dataset made of on-ice-measured seismic and in situ-measured glacier basal sliding speed on Glacier d'Argentière (French Alps) to investigate the physics of subglacial channels and its potential link with glacier basal sliding. Using dedicated theory and concomitant measurements of water discharge, we quantify temporal changes in channels' hydraulic radius and hydraulic pressure gradient. At seasonal timescales we find that hydraulic radius and hydraulic pressure gradient respectively exhibit a 2- and 6-fold increase from spring to summer, followed by comparable decrease towards autumn. At low discharge during the early and late melt season channels respond to changes in discharge mainly through changes in hydraulic radius, a regime that is consistent with predictions of channels' behaviour at equilibrium. In contrast, at high discharge and high short-term water-supply variability (summertime), channels undergo strong changes in hydraulic pressure gradient, a behaviour that is consistent with channels behaving out of equilibrium. This out-of-equilibrium regime is further supported by observations at the diurnal scale, which prove that channels pressurize in the morning and depressurize in the afternoon. During summer we also observe high and sustained basal sliding speed, which supports that the widespread inefficient drainage system (cavities) is likely pressurized concomitantly with the channel system. We propose that pressurized channels help sustain high pressure in cavities (and therefore high glacier sliding speed) through an efficient hydraulic connection between the two systems. The present findings provide an essential basis for testing the physics represented in subglacial hydrology and glacier sliding models. ISSN:1994-0416 ISSN:1994-0424 |
format |
Article in Journal/Newspaper |
author |
Nanni, Ugo Gimbert, Florent Vincent, Christian Gräff, Dominik Walter, Fabian Piard, Luc Moreau, Luc |
spellingShingle |
Nanni, Ugo Gimbert, Florent Vincent, Christian Gräff, Dominik Walter, Fabian Piard, Luc Moreau, Luc Quantification of seasonal and diumal dynamics of subglacial channels using seismic observations on an Alpine glacier |
author_facet |
Nanni, Ugo Gimbert, Florent Vincent, Christian Gräff, Dominik Walter, Fabian Piard, Luc Moreau, Luc |
author_sort |
Nanni, Ugo |
title |
Quantification of seasonal and diumal dynamics of subglacial channels using seismic observations on an Alpine glacier |
title_short |
Quantification of seasonal and diumal dynamics of subglacial channels using seismic observations on an Alpine glacier |
title_full |
Quantification of seasonal and diumal dynamics of subglacial channels using seismic observations on an Alpine glacier |
title_fullStr |
Quantification of seasonal and diumal dynamics of subglacial channels using seismic observations on an Alpine glacier |
title_full_unstemmed |
Quantification of seasonal and diumal dynamics of subglacial channels using seismic observations on an Alpine glacier |
title_sort |
quantification of seasonal and diumal dynamics of subglacial channels using seismic observations on an alpine glacier |
publisher |
Copernicus |
publishDate |
2020 |
url |
https://hdl.handle.net/20.500.11850/454435 https://doi.org/10.3929/ethz-b-000416433 |
genre |
The Cryosphere |
genre_facet |
The Cryosphere |
op_source |
The Cryosphere, 14 (5) |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.5194/tc-14-1475-2020 info:eu-repo/semantics/altIdentifier/wos/000531822500003 http://hdl.handle.net/20.500.11850/454435 doi:10.3929/ethz-b-000416433 |
op_rights |
info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/20.500.11850/454435 https://doi.org/10.3929/ethz-b-000416433 https://doi.org/10.5194/tc-14-1475-2020 |
_version_ |
1766216317778526208 |