Breaking the seal at Grímsvötn, Iceland
Abstract Of several problems associated with theoretical explanations of the jökulhlaups which emerge from the outlet glacier Skeiðarárjökull of the ice cap Vatnajökull in southeast Iceland, the mechanism of flood initiation is one that has hitherto defied explanation. We provide such an explanation...
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Language: | English |
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Cambridge University Press (CUP)
1999
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Online Access: | http://dx.doi.org/10.1017/s0022143000001362 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000001362 |
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crcambridgeupr:10.1017/s0022143000001362 2024-03-03T08:44:38+00:00 Breaking the seal at Grímsvötn, Iceland Fowler, A. C. 1999 http://dx.doi.org/10.1017/s0022143000001362 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000001362 en eng Cambridge University Press (CUP) Journal of Glaciology volume 45, issue 151, page 506-516 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1999 crcambridgeupr https://doi.org/10.1017/s0022143000001362 2024-02-08T08:47:47Z Abstract Of several problems associated with theoretical explanations of the jökulhlaups which emerge from the outlet glacier Skeiðarárjökull of the ice cap Vatnajökull in southeast Iceland, the mechanism of flood initiation is one that has hitherto defied explanation. We provide such an explanation based on a careful analysis of the classical Nye-Röthlisberger model; near the subglacial lake Grímsvötn, the hydraulic potential gradient is towards the lake, and there is therefore a catchment boundary under the ice, whose location depends on the subglacial meltwater drainage characteristics. As the conditions for a flood approach, we show that the water divide migrates towards the lake, while at the same time the lake pressure increases. When the hydraulic potential gradient towards the lake is low and the refilling rate is slow, the seal will "break" when the catchment boundary reaches the lake, while the lake level is still below flotation pressure, whereas if refilling is rapid, flotation can be achieved before a flood is initiated. This theory can thus explain why the seal is normally broken when the lake level at Grímsvötn is still some 60 m below flotation level. In addition, we are able to explain why the jökulhlaup following the 1996 eruption did not occur until flotation level was achieved, and we show how the cyclicity and magnitude of jökulhlaups can be explained within this theory. Article in Journal/Newspaper glacier Ice cap Iceland Journal of Glaciology Vatnajökull Cambridge University Press Vatnajökull ENVELOPE(-16.823,-16.823,64.420,64.420) Skeiðarárjökull ENVELOPE(-17.208,-17.208,64.056,64.056) Journal of Glaciology 45 151 506 516 |
institution |
Open Polar |
collection |
Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
spellingShingle |
Earth-Surface Processes Fowler, A. C. Breaking the seal at Grímsvötn, Iceland |
topic_facet |
Earth-Surface Processes |
description |
Abstract Of several problems associated with theoretical explanations of the jökulhlaups which emerge from the outlet glacier Skeiðarárjökull of the ice cap Vatnajökull in southeast Iceland, the mechanism of flood initiation is one that has hitherto defied explanation. We provide such an explanation based on a careful analysis of the classical Nye-Röthlisberger model; near the subglacial lake Grímsvötn, the hydraulic potential gradient is towards the lake, and there is therefore a catchment boundary under the ice, whose location depends on the subglacial meltwater drainage characteristics. As the conditions for a flood approach, we show that the water divide migrates towards the lake, while at the same time the lake pressure increases. When the hydraulic potential gradient towards the lake is low and the refilling rate is slow, the seal will "break" when the catchment boundary reaches the lake, while the lake level is still below flotation pressure, whereas if refilling is rapid, flotation can be achieved before a flood is initiated. This theory can thus explain why the seal is normally broken when the lake level at Grímsvötn is still some 60 m below flotation level. In addition, we are able to explain why the jökulhlaup following the 1996 eruption did not occur until flotation level was achieved, and we show how the cyclicity and magnitude of jökulhlaups can be explained within this theory. |
format |
Article in Journal/Newspaper |
author |
Fowler, A. C. |
author_facet |
Fowler, A. C. |
author_sort |
Fowler, A. C. |
title |
Breaking the seal at Grímsvötn, Iceland |
title_short |
Breaking the seal at Grímsvötn, Iceland |
title_full |
Breaking the seal at Grímsvötn, Iceland |
title_fullStr |
Breaking the seal at Grímsvötn, Iceland |
title_full_unstemmed |
Breaking the seal at Grímsvötn, Iceland |
title_sort |
breaking the seal at grímsvötn, iceland |
publisher |
Cambridge University Press (CUP) |
publishDate |
1999 |
url |
http://dx.doi.org/10.1017/s0022143000001362 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000001362 |
long_lat |
ENVELOPE(-16.823,-16.823,64.420,64.420) ENVELOPE(-17.208,-17.208,64.056,64.056) |
geographic |
Vatnajökull Skeiðarárjökull |
geographic_facet |
Vatnajökull Skeiðarárjökull |
genre |
glacier Ice cap Iceland Journal of Glaciology Vatnajökull |
genre_facet |
glacier Ice cap Iceland Journal of Glaciology Vatnajökull |
op_source |
Journal of Glaciology volume 45, issue 151, page 506-516 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000001362 |
container_title |
Journal of Glaciology |
container_volume |
45 |
container_issue |
151 |
container_start_page |
506 |
op_container_end_page |
516 |
_version_ |
1792500115660865536 |