The response of a glacier to a surface disturbance: a case study on Vatnajökull ice cap, Iceland
In the course of a tremendous outburst flood (jökulhlaup) following the subglacial eruption in Vatnajökull, Iceland, in October 1996, a depression in the surface of the ice cap was created as a result of ice melting from the walls of a subglacial tunnel. The surface depression was initially approxim...
Published in: | Annals of Glaciology |
---|---|
Main Authors: | , , |
Format: | Article in Journal/Newspaper |
Language: | unknown |
Published: |
International Glaciological Society
2000
|
Subjects: | |
Online Access: | https://nrl.northumbria.ac.uk/id/eprint/38036/ https://doi.org/10.3189/172756400781819914 |
id |
ftunivnorthumb:oai:nrl.northumbria.ac.uk:38036 |
---|---|
record_format |
openpolar |
spelling |
ftunivnorthumb:oai:nrl.northumbria.ac.uk:38036 2023-05-15T13:29:25+02:00 The response of a glacier to a surface disturbance: a case study on Vatnajökull ice cap, Iceland Aðalgeirsdóttir, Guðefinna Gudmundsson, Hilmar Björnsson, Helgi 2000 https://nrl.northumbria.ac.uk/id/eprint/38036/ https://doi.org/10.3189/172756400781819914 unknown International Glaciological Society Aðalgeirsdóttir, Guðefinna, Gudmundsson, Hilmar and Björnsson, Helgi (2000) The response of a glacier to a surface disturbance: a case study on Vatnajökull ice cap, Iceland. Annals of Glaciology, 31. pp. 104-110. ISSN 0260-3055 F800 Physical and Terrestrial Geographical and Environmental Sciences Article PeerReviewed 2000 ftunivnorthumb https://doi.org/10.3189/172756400781819914 2022-09-25T06:09:12Z In the course of a tremendous outburst flood (jökulhlaup) following the subglacial eruption in Vatnajökull, Iceland, in October 1996, a depression in the surface of the ice cap was created as a result of ice melting from the walls of a subglacial tunnel. The surface depression was initially approximately 6 km long, 800 m wide and 100 m deep. This ˚canyon" represents a significant perturbation in the geometry of the ice cap in this area where the total ice thickness is about 200–400 m. We present results of repeated measurements of flow velocities and elevation changes in the vicinity of the canyon made over a period of about 2 years. The measurements show a reduction in the depth of the canyon and a concomitant decrease in surface flow towards it over time. By calculating the transient evolution of idealized surface depressions using both analytical zeroth- and first-order theories, as well as the shallow-ice approximation (SIA) and a finite-element model incorporating all the terms of the momentum equations we demonstrate the importance of horizontal stress gradients at the spatial scale of this canyon. The transient evolution of the canyon is calculated with a two-dimensional time-dependent finite-element model with flow parameters (the parameters A and n of Glen’s flow law) that are tuned towards an optimal agreement with measured flow velocities. Although differences between measured and calculated velocities are comparable to measurement errors, the differences are not randomly distributed. The model is therefore not verified in detail. Nevertheless the model reproduces observed changes in the geometry over a 15 month time period reasonably well The model also reproduces changes in both velocities and geometry considerably better than an alternative model based on the SIA. Article in Journal/Newspaper Annals of Glaciology glacier Ice cap Iceland Vatnajökull Northumbria University, Newcastle: Northumbria Research Link (NRL) Vatnajökull ENVELOPE(-16.823,-16.823,64.420,64.420) Annals of Glaciology 31 104 110 |
institution |
Open Polar |
collection |
Northumbria University, Newcastle: Northumbria Research Link (NRL) |
op_collection_id |
ftunivnorthumb |
language |
unknown |
topic |
F800 Physical and Terrestrial Geographical and Environmental Sciences |
spellingShingle |
F800 Physical and Terrestrial Geographical and Environmental Sciences Aðalgeirsdóttir, Guðefinna Gudmundsson, Hilmar Björnsson, Helgi The response of a glacier to a surface disturbance: a case study on Vatnajökull ice cap, Iceland |
topic_facet |
F800 Physical and Terrestrial Geographical and Environmental Sciences |
description |
In the course of a tremendous outburst flood (jökulhlaup) following the subglacial eruption in Vatnajökull, Iceland, in October 1996, a depression in the surface of the ice cap was created as a result of ice melting from the walls of a subglacial tunnel. The surface depression was initially approximately 6 km long, 800 m wide and 100 m deep. This ˚canyon" represents a significant perturbation in the geometry of the ice cap in this area where the total ice thickness is about 200–400 m. We present results of repeated measurements of flow velocities and elevation changes in the vicinity of the canyon made over a period of about 2 years. The measurements show a reduction in the depth of the canyon and a concomitant decrease in surface flow towards it over time. By calculating the transient evolution of idealized surface depressions using both analytical zeroth- and first-order theories, as well as the shallow-ice approximation (SIA) and a finite-element model incorporating all the terms of the momentum equations we demonstrate the importance of horizontal stress gradients at the spatial scale of this canyon. The transient evolution of the canyon is calculated with a two-dimensional time-dependent finite-element model with flow parameters (the parameters A and n of Glen’s flow law) that are tuned towards an optimal agreement with measured flow velocities. Although differences between measured and calculated velocities are comparable to measurement errors, the differences are not randomly distributed. The model is therefore not verified in detail. Nevertheless the model reproduces observed changes in the geometry over a 15 month time period reasonably well The model also reproduces changes in both velocities and geometry considerably better than an alternative model based on the SIA. |
format |
Article in Journal/Newspaper |
author |
Aðalgeirsdóttir, Guðefinna Gudmundsson, Hilmar Björnsson, Helgi |
author_facet |
Aðalgeirsdóttir, Guðefinna Gudmundsson, Hilmar Björnsson, Helgi |
author_sort |
Aðalgeirsdóttir, Guðefinna |
title |
The response of a glacier to a surface disturbance: a case study on Vatnajökull ice cap, Iceland |
title_short |
The response of a glacier to a surface disturbance: a case study on Vatnajökull ice cap, Iceland |
title_full |
The response of a glacier to a surface disturbance: a case study on Vatnajökull ice cap, Iceland |
title_fullStr |
The response of a glacier to a surface disturbance: a case study on Vatnajökull ice cap, Iceland |
title_full_unstemmed |
The response of a glacier to a surface disturbance: a case study on Vatnajökull ice cap, Iceland |
title_sort |
response of a glacier to a surface disturbance: a case study on vatnajökull ice cap, iceland |
publisher |
International Glaciological Society |
publishDate |
2000 |
url |
https://nrl.northumbria.ac.uk/id/eprint/38036/ https://doi.org/10.3189/172756400781819914 |
long_lat |
ENVELOPE(-16.823,-16.823,64.420,64.420) |
geographic |
Vatnajökull |
geographic_facet |
Vatnajökull |
genre |
Annals of Glaciology glacier Ice cap Iceland Vatnajökull |
genre_facet |
Annals of Glaciology glacier Ice cap Iceland Vatnajökull |
op_relation |
Aðalgeirsdóttir, Guðefinna, Gudmundsson, Hilmar and Björnsson, Helgi (2000) The response of a glacier to a surface disturbance: a case study on Vatnajökull ice cap, Iceland. Annals of Glaciology, 31. pp. 104-110. ISSN 0260-3055 |
op_doi |
https://doi.org/10.3189/172756400781819914 |
container_title |
Annals of Glaciology |
container_volume |
31 |
container_start_page |
104 |
op_container_end_page |
110 |
_version_ |
1766000583764869120 |