The dynamics of a subglacial salt wedge
Marine-terminating glaciers, such as those along the coastline of Greenland, often release meltwater into the ocean in the form of subglacial discharge plumes. Though these plumes can dramatically alter the mass loss along the front of a glacier, the conditions surrounding their genesis remain poorl...
Published in: | Journal of Fluid Mechanics |
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Format: | Article in Journal/Newspaper |
Language: | English |
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Cambridge University Press
2020
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Online Access: | https://doi.org/10.1017/jfm.2020.308 https://ora.ox.ac.uk/objects/uuid:6f4130e2-6fcc-4883-91fe-ce46e398e90f |
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ftuloxford:oai:ora.ox.ac.uk:uuid:6f4130e2-6fcc-4883-91fe-ce46e398e90f 2024-10-06T13:48:53+00:00 The dynamics of a subglacial salt wedge Wilson, EA Wells, AJ Hewitt, IJ Cenedese, Claudia 2020-05-21 https://doi.org/10.1017/jfm.2020.308 https://ora.ox.ac.uk/objects/uuid:6f4130e2-6fcc-4883-91fe-ce46e398e90f eng eng Cambridge University Press doi:10.1017/jfm.2020.308 https://ora.ox.ac.uk/objects/uuid:6f4130e2-6fcc-4883-91fe-ce46e398e90f https://doi.org/10.1017/jfm.2020.308 info:eu-repo/semantics/openAccess Journal article 2020 ftuloxford https://doi.org/10.1017/jfm.2020.308 2024-09-06T07:47:36Z Marine-terminating glaciers, such as those along the coastline of Greenland, often release meltwater into the ocean in the form of subglacial discharge plumes. Though these plumes can dramatically alter the mass loss along the front of a glacier, the conditions surrounding their genesis remain poorly constrained. In particular, little is known about the geometry of subglacial outlets and the extent to which seawater may intrude into them. Here, the latter is addressed by exploring the dynamics of an arrested salt wedge – a steady-state, two-layer flow system where salty water partially intrudes a channel carrying fresh water. Building on existing theory, we formulate a model that predicts the length of a non-entraining salt wedge as a function of the Froude number, the slope of the channel and coefficients for interfacial and wall drag. In conjunction, a series of laboratory experiments were conducted to observe a salt wedge within a rectangular channel. For experiments conducted with laminar flow (Reynolds number Re < 800), good agreement with theoretical predictions are obtained when the drag coefficients are modelled as being inversely proportional to Re. However, for fully turbulent flows on geophysical scales, these drag coefficients are expected to asymptote toward finite values. Adopting reasonable drag coefficient estimates for this flow regime, our theoretical model suggests that typical subglacial channels may permit seawater intrusions of the order of several kilometres. While crude, these results indicate that the ocean has a strong tendency to penetrate subglacial channels and potentially undercut the face of marine-terminating glaciers. Article in Journal/Newspaper glacier Greenland ORA - Oxford University Research Archive Greenland Journal of Fluid Mechanics 895 |
institution |
Open Polar |
collection |
ORA - Oxford University Research Archive |
op_collection_id |
ftuloxford |
language |
English |
description |
Marine-terminating glaciers, such as those along the coastline of Greenland, often release meltwater into the ocean in the form of subglacial discharge plumes. Though these plumes can dramatically alter the mass loss along the front of a glacier, the conditions surrounding their genesis remain poorly constrained. In particular, little is known about the geometry of subglacial outlets and the extent to which seawater may intrude into them. Here, the latter is addressed by exploring the dynamics of an arrested salt wedge – a steady-state, two-layer flow system where salty water partially intrudes a channel carrying fresh water. Building on existing theory, we formulate a model that predicts the length of a non-entraining salt wedge as a function of the Froude number, the slope of the channel and coefficients for interfacial and wall drag. In conjunction, a series of laboratory experiments were conducted to observe a salt wedge within a rectangular channel. For experiments conducted with laminar flow (Reynolds number Re < 800), good agreement with theoretical predictions are obtained when the drag coefficients are modelled as being inversely proportional to Re. However, for fully turbulent flows on geophysical scales, these drag coefficients are expected to asymptote toward finite values. Adopting reasonable drag coefficient estimates for this flow regime, our theoretical model suggests that typical subglacial channels may permit seawater intrusions of the order of several kilometres. While crude, these results indicate that the ocean has a strong tendency to penetrate subglacial channels and potentially undercut the face of marine-terminating glaciers. |
format |
Article in Journal/Newspaper |
author |
Wilson, EA Wells, AJ Hewitt, IJ Cenedese, Claudia |
spellingShingle |
Wilson, EA Wells, AJ Hewitt, IJ Cenedese, Claudia The dynamics of a subglacial salt wedge |
author_facet |
Wilson, EA Wells, AJ Hewitt, IJ Cenedese, Claudia |
author_sort |
Wilson, EA |
title |
The dynamics of a subglacial salt wedge |
title_short |
The dynamics of a subglacial salt wedge |
title_full |
The dynamics of a subglacial salt wedge |
title_fullStr |
The dynamics of a subglacial salt wedge |
title_full_unstemmed |
The dynamics of a subglacial salt wedge |
title_sort |
dynamics of a subglacial salt wedge |
publisher |
Cambridge University Press |
publishDate |
2020 |
url |
https://doi.org/10.1017/jfm.2020.308 https://ora.ox.ac.uk/objects/uuid:6f4130e2-6fcc-4883-91fe-ce46e398e90f |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
glacier Greenland |
genre_facet |
glacier Greenland |
op_relation |
doi:10.1017/jfm.2020.308 https://ora.ox.ac.uk/objects/uuid:6f4130e2-6fcc-4883-91fe-ce46e398e90f https://doi.org/10.1017/jfm.2020.308 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1017/jfm.2020.308 |
container_title |
Journal of Fluid Mechanics |
container_volume |
895 |
_version_ |
1812176963660414976 |