Temperate ice permeability, stability of water veins and percolation of internal meltwater
Abstract In temperate glacier ice, in situ, besides water veins, there are water lenses, on grain boundaries more or less perpendicular to the direction of maximum pressure p 1 (at the grain scale). Geometry of veins is developed. Grains are modelled as equal tetrakaidecahedra. The stress and temper...
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Cambridge University Press (CUP)
1996
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Online Access: | http://dx.doi.org/10.1017/s0022143000004068 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000004068 |
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crcambridgeupr:10.1017/s0022143000004068 2024-03-03T08:46:05+00:00 Temperate ice permeability, stability of water veins and percolation of internal meltwater Lliboutry, L. 1996 http://dx.doi.org/10.1017/s0022143000004068 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000004068 en eng Cambridge University Press (CUP) Journal of Glaciology volume 42, issue 141, page 201-211 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1996 crcambridgeupr https://doi.org/10.1017/s0022143000004068 2024-02-08T08:34:04Z Abstract In temperate glacier ice, in situ, besides water veins, there are water lenses, on grain boundaries more or less perpendicular to the direction of maximum pressure p 1 (at the grain scale). Geometry of veins is developed. Grains are modelled as equal tetrakaidecahedra. The stress and temperature fields around a vein at a smaller, microscopic scale are estimated and the water discharge by a Vein is calculated. The time-derivative of the cross-sectional area S of a vein is governed neither by energy dissipation in the water nor by plasticity, but by capillarity effects and salinity. A “vasodilator threshold” p d for water pressure p w in the veins is defined. Normally, P w < P d , then S has a stable value, the same for any orientation of the vein, and the microscopic temperature is uniform. The coefficient of permeability is proportional to ( P d - p w ) −4 , and thus a true Darcy law does not hold. As an application, the percolation of internal meltwater is studied; in an upper boundary layer about 2 m thick this meltwater flows upwards, because in the bulk of the glacier p w is very close to P 1 , whereas it is zero at the surface. When, exceptionally, p w > p d , S increases irreversibly. Whether it leads to the formation of “worm-holes” is discussed. Article in Journal/Newspaper Journal of Glaciology Cambridge University Press Journal of Glaciology 42 141 201 211 |
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Open Polar |
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Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
spellingShingle |
Earth-Surface Processes Lliboutry, L. Temperate ice permeability, stability of water veins and percolation of internal meltwater |
topic_facet |
Earth-Surface Processes |
description |
Abstract In temperate glacier ice, in situ, besides water veins, there are water lenses, on grain boundaries more or less perpendicular to the direction of maximum pressure p 1 (at the grain scale). Geometry of veins is developed. Grains are modelled as equal tetrakaidecahedra. The stress and temperature fields around a vein at a smaller, microscopic scale are estimated and the water discharge by a Vein is calculated. The time-derivative of the cross-sectional area S of a vein is governed neither by energy dissipation in the water nor by plasticity, but by capillarity effects and salinity. A “vasodilator threshold” p d for water pressure p w in the veins is defined. Normally, P w < P d , then S has a stable value, the same for any orientation of the vein, and the microscopic temperature is uniform. The coefficient of permeability is proportional to ( P d - p w ) −4 , and thus a true Darcy law does not hold. As an application, the percolation of internal meltwater is studied; in an upper boundary layer about 2 m thick this meltwater flows upwards, because in the bulk of the glacier p w is very close to P 1 , whereas it is zero at the surface. When, exceptionally, p w > p d , S increases irreversibly. Whether it leads to the formation of “worm-holes” is discussed. |
format |
Article in Journal/Newspaper |
author |
Lliboutry, L. |
author_facet |
Lliboutry, L. |
author_sort |
Lliboutry, L. |
title |
Temperate ice permeability, stability of water veins and percolation of internal meltwater |
title_short |
Temperate ice permeability, stability of water veins and percolation of internal meltwater |
title_full |
Temperate ice permeability, stability of water veins and percolation of internal meltwater |
title_fullStr |
Temperate ice permeability, stability of water veins and percolation of internal meltwater |
title_full_unstemmed |
Temperate ice permeability, stability of water veins and percolation of internal meltwater |
title_sort |
temperate ice permeability, stability of water veins and percolation of internal meltwater |
publisher |
Cambridge University Press (CUP) |
publishDate |
1996 |
url |
http://dx.doi.org/10.1017/s0022143000004068 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000004068 |
genre |
Journal of Glaciology |
genre_facet |
Journal of Glaciology |
op_source |
Journal of Glaciology volume 42, issue 141, page 201-211 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000004068 |
container_title |
Journal of Glaciology |
container_volume |
42 |
container_issue |
141 |
container_start_page |
201 |
op_container_end_page |
211 |
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1792501961880240128 |