Investigating changes in basal conditions of Variegated Glacier prior to and during its 1982–1983 surge
Variegated Glacier (Alaska) is known to surge periodically after a sufficient amount of cumulative mass balance is reached, but this observation is difficult to link with changes in the basal conditions. Here, using a 10-yr dataset, consisting of surface topography and surface velocity observations...
Main Authors: | , , , |
---|---|
Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2011-08-01
|
Series: | The Cryosphere |
Online Access: | http://www.the-cryosphere.net/5/659/2011/tc-5-659-2011.pdf |
id |
doaj-08f74dda68c445b1a6944a84ad6961b3 |
---|---|
record_format |
Article |
spelling |
doaj-08f74dda68c445b1a6944a84ad6961b32020-11-24T21:33:28ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242011-08-015365967210.5194/tc-5-659-2011Investigating changes in basal conditions of Variegated Glacier prior to and during its 1982–1983 surgeM. Jay-AllemandF. Gillet-ChauletO. GagliardiniM. NodetVariegated Glacier (Alaska) is known to surge periodically after a sufficient amount of cumulative mass balance is reached, but this observation is difficult to link with changes in the basal conditions. Here, using a 10-yr dataset, consisting of surface topography and surface velocity observations along a flow line for 25 dates, we have reconstructed the evolution of the basal conditions prior to and during the 1982–1983 surge. The model solves the full-Stokes problem along the central flow line using the finite element method. For the 25 dates of the dataset, the basal friction parameter distribution is inferred using the inverse method proposed by Arthern and Gudmundsson (2010). This method is here slightly modified by incorporating a regularisation term in the cost function to avoid short wavelength changes in the friction parameter. Our results indicate that dramatic changes in the basal conditions occurred between 1973 to 1983. Prior to the surge, periodic changes can be observed between winter and summer, with a regular increase of the sliding from 1973 to 1982. During the surge, the basal friction decreased dramatically and an area of very low friction moved from the upper part of the glacier to its terminus. Using a more complex friction law, these changes in basal sliding are then interpreted in terms of basal water pressure. Our results support that dramatic changes took place in the subglacial drainage system of Variegated Glacier, moving from a relatively efficient drainage system prior to the surge to an inefficient one during the surge. By reconstructing the water pressure evolution at the base of the glacier it is possible to propose a scenario for the hydrological history leading to the occurrence of a surge.http://www.the-cryosphere.net/5/659/2011/tc-5-659-2011.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
M. Jay-Allemand F. Gillet-Chaulet O. Gagliardini M. Nodet |
spellingShingle |
M. Jay-Allemand F. Gillet-Chaulet O. Gagliardini M. Nodet Investigating changes in basal conditions of Variegated Glacier prior to and during its 1982–1983 surge The Cryosphere |
author_facet |
M. Jay-Allemand F. Gillet-Chaulet O. Gagliardini M. Nodet |
author_sort |
M. Jay-Allemand |
title |
Investigating changes in basal conditions of Variegated Glacier prior to and during its 1982–1983 surge |
title_short |
Investigating changes in basal conditions of Variegated Glacier prior to and during its 1982–1983 surge |
title_full |
Investigating changes in basal conditions of Variegated Glacier prior to and during its 1982–1983 surge |
title_fullStr |
Investigating changes in basal conditions of Variegated Glacier prior to and during its 1982–1983 surge |
title_full_unstemmed |
Investigating changes in basal conditions of Variegated Glacier prior to and during its 1982–1983 surge |
title_sort |
investigating changes in basal conditions of variegated glacier prior to and during its 1982–1983 surge |
publisher |
Copernicus Publications |
series |
The Cryosphere |
issn |
1994-0416 1994-0424 |
publishDate |
2011-08-01 |
description |
Variegated Glacier (Alaska) is known to surge periodically after a sufficient amount of cumulative mass balance is reached, but this observation is difficult to link with changes in the basal conditions. Here, using a 10-yr dataset, consisting of surface topography and surface velocity observations along a flow line for 25 dates, we have reconstructed the evolution of the basal conditions prior to and during the 1982–1983 surge. The model solves the full-Stokes problem along the central flow line using the finite element method. For the 25 dates of the dataset, the basal friction parameter distribution is inferred using the inverse method proposed by Arthern and Gudmundsson (2010). This method is here slightly modified by incorporating a regularisation term in the cost function to avoid short wavelength changes in the friction parameter. Our results indicate that dramatic changes in the basal conditions occurred between 1973 to 1983. Prior to the surge, periodic changes can be observed between winter and summer, with a regular increase of the sliding from 1973 to 1982. During the surge, the basal friction decreased dramatically and an area of very low friction moved from the upper part of the glacier to its terminus. Using a more complex friction law, these changes in basal sliding are then interpreted in terms of basal water pressure. Our results support that dramatic changes took place in the subglacial drainage system of Variegated Glacier, moving from a relatively efficient drainage system prior to the surge to an inefficient one during the surge. By reconstructing the water pressure evolution at the base of the glacier it is possible to propose a scenario for the hydrological history leading to the occurrence of a surge. |
url |
http://www.the-cryosphere.net/5/659/2011/tc-5-659-2011.pdf |
work_keys_str_mv |
AT mjayallemand investigatingchangesinbasalconditionsofvariegatedglacierpriortoandduringits19821983surge AT fgilletchaulet investigatingchangesinbasalconditionsofvariegatedglacierpriortoandduringits19821983surge AT ogagliardini investigatingchangesinbasalconditionsofvariegatedglacierpriortoandduringits19821983surge AT mnodet investigatingchangesinbasalconditionsofvariegatedglacierpriortoandduringits19821983surge |
_version_ |
1725953019071168512 |