Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum
At the Last Glacial Maximum (LGM), the Rhine glacier in the Swiss Alps covered an area of about 16 000 km 2 . As part of an integrative study about the safety of repositories for radioactive waste under ice age conditions in Switzerland, we modeled the Rhine glacier using a thermodynamically coupled...
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ftdoajarticles:oai:doaj.org/article:0c23616aaf2342eb99da05c0f7315711 2023-05-15T18:32:25+02:00 Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum D. Cohen F. Gillet-Chaulet W. Haeberli H. Machguth U. H. Fischer 2018-08-01T00:00:00Z https://doi.org/10.5194/tc-12-2515-2018 https://doaj.org/article/0c23616aaf2342eb99da05c0f7315711 EN eng Copernicus Publications https://www.the-cryosphere.net/12/2515/2018/tc-12-2515-2018.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-12-2515-2018 1994-0416 1994-0424 https://doaj.org/article/0c23616aaf2342eb99da05c0f7315711 The Cryosphere, Vol 12, Pp 2515-2544 (2018) Environmental sciences GE1-350 Geology QE1-996.5 article 2018 ftdoajarticles https://doi.org/10.5194/tc-12-2515-2018 2022-12-31T00:23:54Z At the Last Glacial Maximum (LGM), the Rhine glacier in the Swiss Alps covered an area of about 16 000 km 2 . As part of an integrative study about the safety of repositories for radioactive waste under ice age conditions in Switzerland, we modeled the Rhine glacier using a thermodynamically coupled three-dimensional, transient Stokes flow and heat transport model down to a horizontal resolution of about 500 m. The accumulation and ablation gradients that roughly reproduced the geomorphic reconstructions of glacial extent and ice thickness suggested extremely cold ( T July ∼ 0 °C at the glacier terminus) and dry ( ∼ 10 % to 20 % of today's precipitation) climatic conditions. Forcing the numerical simulations with warmer and wetter conditions that better matched LGM climate proxy records yielded a glacier on average 500 to 700 m thicker than geomorphic reconstructions. Mass balance gradients also controlled ice velocities, fluxes, and sliding speeds. These gradients, however, had only a small effect on basal conditions. All simulations indicated that basal ice reached the pressure melting point over much of the Rhine and Linth piedmont lobes, and also in the glacial valleys that fed these lobes. Only the outer margin of the lobes, bedrock highs beneath the lobes, and Alpine valleys at high elevations in the accumulation zone remained cold based. The Rhine glacier was thus polythermal. Sliding speed estimated with a linear sliding rule ranged from 20 to 100 m a −1 in the lobes and 50 to 250 m a −1 in Alpine valleys. Velocity ratios (sliding to surface speeds) were > 80 % in lobes and ∼ 60 % in valleys. Basal shear stress was very low in the lobes (0.03–0.1 MPa) and much higher in Alpine valleys ( > 0.2 MPa). In these valleys, viscous strain heating was a dominant source of heat, particularly when shear rates in the ice increased due to flow constrictions, confluences, or flow past large bedrock obstacles, contributing locally up to several watts per square meter but on average 0.03 to 0.2 W m −2 . Basal ... Article in Journal/Newspaper The Cryosphere Directory of Open Access Journals: DOAJ Articles The Cryosphere 12 8 2515 2544 |
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Open Polar |
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Directory of Open Access Journals: DOAJ Articles |
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ftdoajarticles |
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English |
topic |
Environmental sciences GE1-350 Geology QE1-996.5 |
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Environmental sciences GE1-350 Geology QE1-996.5 D. Cohen F. Gillet-Chaulet W. Haeberli H. Machguth U. H. Fischer Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum |
topic_facet |
Environmental sciences GE1-350 Geology QE1-996.5 |
description |
At the Last Glacial Maximum (LGM), the Rhine glacier in the Swiss Alps covered an area of about 16 000 km 2 . As part of an integrative study about the safety of repositories for radioactive waste under ice age conditions in Switzerland, we modeled the Rhine glacier using a thermodynamically coupled three-dimensional, transient Stokes flow and heat transport model down to a horizontal resolution of about 500 m. The accumulation and ablation gradients that roughly reproduced the geomorphic reconstructions of glacial extent and ice thickness suggested extremely cold ( T July ∼ 0 °C at the glacier terminus) and dry ( ∼ 10 % to 20 % of today's precipitation) climatic conditions. Forcing the numerical simulations with warmer and wetter conditions that better matched LGM climate proxy records yielded a glacier on average 500 to 700 m thicker than geomorphic reconstructions. Mass balance gradients also controlled ice velocities, fluxes, and sliding speeds. These gradients, however, had only a small effect on basal conditions. All simulations indicated that basal ice reached the pressure melting point over much of the Rhine and Linth piedmont lobes, and also in the glacial valleys that fed these lobes. Only the outer margin of the lobes, bedrock highs beneath the lobes, and Alpine valleys at high elevations in the accumulation zone remained cold based. The Rhine glacier was thus polythermal. Sliding speed estimated with a linear sliding rule ranged from 20 to 100 m a −1 in the lobes and 50 to 250 m a −1 in Alpine valleys. Velocity ratios (sliding to surface speeds) were > 80 % in lobes and ∼ 60 % in valleys. Basal shear stress was very low in the lobes (0.03–0.1 MPa) and much higher in Alpine valleys ( > 0.2 MPa). In these valleys, viscous strain heating was a dominant source of heat, particularly when shear rates in the ice increased due to flow constrictions, confluences, or flow past large bedrock obstacles, contributing locally up to several watts per square meter but on average 0.03 to 0.2 W m −2 . Basal ... |
format |
Article in Journal/Newspaper |
author |
D. Cohen F. Gillet-Chaulet W. Haeberli H. Machguth U. H. Fischer |
author_facet |
D. Cohen F. Gillet-Chaulet W. Haeberli H. Machguth U. H. Fischer |
author_sort |
D. Cohen |
title |
Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum |
title_short |
Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum |
title_full |
Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum |
title_fullStr |
Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum |
title_full_unstemmed |
Numerical reconstructions of the flow and basal conditions of the Rhine glacier, European Central Alps, at the Last Glacial Maximum |
title_sort |
numerical reconstructions of the flow and basal conditions of the rhine glacier, european central alps, at the last glacial maximum |
publisher |
Copernicus Publications |
publishDate |
2018 |
url |
https://doi.org/10.5194/tc-12-2515-2018 https://doaj.org/article/0c23616aaf2342eb99da05c0f7315711 |
genre |
The Cryosphere |
genre_facet |
The Cryosphere |
op_source |
The Cryosphere, Vol 12, Pp 2515-2544 (2018) |
op_relation |
https://www.the-cryosphere.net/12/2515/2018/tc-12-2515-2018.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-12-2515-2018 1994-0416 1994-0424 https://doaj.org/article/0c23616aaf2342eb99da05c0f7315711 |
op_doi |
https://doi.org/10.5194/tc-12-2515-2018 |
container_title |
The Cryosphere |
container_volume |
12 |
container_issue |
8 |
container_start_page |
2515 |
op_container_end_page |
2544 |
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1766216534766649344 |