Subglacial hydrology of the Icelandic ice caps: Outburst floods and ice dynamics
Continuous GPS measurements on three broad and gently sloping temperate ice-cap outlets in southern and western Vatnajökull, southeast Iceland, and in northern Hofsjökull, central Iceland, are the subject of this thesis. The measurements show events of increased ice velocity and how jökulhlaups (gla...
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Format: | Doctoral or Postdoctoral Thesis |
Language: | English |
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Bergur Einarsson
2018
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Online Access: | https://hdl.handle.net/20.500.11815/696 |
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ftopinvisindi:oai:opinvisindi.is:20.500.11815/696 2023-05-15T16:21:43+02:00 Subglacial hydrology of the Icelandic ice caps: Outburst floods and ice dynamics Vatnafræði íslenskra jökla: Jökulhlaup og flæði íss Einarsson, Bergur Tómas Jóhannesson Jarðvísindadeild (HÍ) Faculty of Earth Sciences (UI) Verkfræði- og náttúruvísindasvið (HÍ) School of Engineering and Natural Sciences (UI) Háskóli Íslands University of Iceland 2018-05-23 111 https://hdl.handle.net/20.500.11815/696 en eng Bergur Einarsson Bergur Einarsson, 2018, Subglacial hydrology of the Icelandic ice caps: Outburst floods and ice dynamics, PhD dissertation, Faculty of Earth Science, University of Iceland, 111 pp. 9789935930699 https://hdl.handle.net/20.500.11815/696 info:eu-repo/semantics/openAccess Jöklar Jöklarannsóknir Jökulhlaup Vatnafræði Vatnafar Mælingar Doktorsritgerðir info:eu-repo/semantics/doctoralThesis 2018 ftopinvisindi https://doi.org/20.500.11815/696 2022-11-18T06:51:36Z Continuous GPS measurements on three broad and gently sloping temperate ice-cap outlets in southern and western Vatnajökull, southeast Iceland, and in northern Hofsjökull, central Iceland, are the subject of this thesis. The measurements show events of increased ice velocity and how jökulhlaups (glacial outburst floods) affect glacier motion. Interpretation of these events, with the aid of other available hydrological and glaciological data, such as discharge time series from proglacial rivers and runoff modelling calibrated with mass balance measurements, sheds light on the time-dependent development of the subglacial hydraulic system of the ice cap outlets, and its interaction with ice motion. Motion events unrelated to jökulhlaups are observed: (i) during the early melt season, (ii) contemporaneous with events of increased surface melt or rain, and (iii) during the emptying of supraglacial slush ponds. Events of slower movement than late winter velocities are also observed, prior to early-melt-season motion events and in the wake of motion events during the height of the melt season. We interpret these events, with the aid of runoff modelling on the glacier and estimates of longitudinal stress-gradient coupling lengths, as being induced by hydrological forcing on basal slip. Lack of response in movement to certain runoff pulses and the characteristics of the diurnal variation in measured proglacial discharge indicate the development in the ablation zone of a fast, efficient subglacial hydraulic system early in the summer. The passing of a jökulhlaup and high subglacial groundwater flow do not disturb this development. Three GPS campaigns to measure jökulhlaups have been carried out over known jökulhlaup paths in two outlets from Vatnajökull ice cap, Skaftárjökull and Skeiðarárjökull. Two slowly rising jökulhlaups from Grímsvötn and two rapidly rising jökulhlaups from the western and eastern Skaftá cauldrons were captured in these campaigns, with maximum discharge ranging from 240 to 3300m3 s-1. Glacier ... Doctoral or Postdoctoral Thesis glacier Hofsjökull Ice cap Iceland Vatnajökull Opin vísindi (Iceland) Skaftá ENVELOPE(-17.933,-17.933,63.783,63.783) Skaftárjökull ENVELOPE(-17.833,-17.833,64.167,64.167) Skeiðarárjökull ENVELOPE(-17.208,-17.208,64.056,64.056) Vatnajökull ENVELOPE(-16.823,-16.823,64.420,64.420) |
institution |
Open Polar |
collection |
Opin vísindi (Iceland) |
op_collection_id |
ftopinvisindi |
language |
English |
topic |
Jöklar Jöklarannsóknir Jökulhlaup Vatnafræði Vatnafar Mælingar Doktorsritgerðir |
spellingShingle |
Jöklar Jöklarannsóknir Jökulhlaup Vatnafræði Vatnafar Mælingar Doktorsritgerðir Einarsson, Bergur Subglacial hydrology of the Icelandic ice caps: Outburst floods and ice dynamics |
topic_facet |
Jöklar Jöklarannsóknir Jökulhlaup Vatnafræði Vatnafar Mælingar Doktorsritgerðir |
description |
Continuous GPS measurements on three broad and gently sloping temperate ice-cap outlets in southern and western Vatnajökull, southeast Iceland, and in northern Hofsjökull, central Iceland, are the subject of this thesis. The measurements show events of increased ice velocity and how jökulhlaups (glacial outburst floods) affect glacier motion. Interpretation of these events, with the aid of other available hydrological and glaciological data, such as discharge time series from proglacial rivers and runoff modelling calibrated with mass balance measurements, sheds light on the time-dependent development of the subglacial hydraulic system of the ice cap outlets, and its interaction with ice motion. Motion events unrelated to jökulhlaups are observed: (i) during the early melt season, (ii) contemporaneous with events of increased surface melt or rain, and (iii) during the emptying of supraglacial slush ponds. Events of slower movement than late winter velocities are also observed, prior to early-melt-season motion events and in the wake of motion events during the height of the melt season. We interpret these events, with the aid of runoff modelling on the glacier and estimates of longitudinal stress-gradient coupling lengths, as being induced by hydrological forcing on basal slip. Lack of response in movement to certain runoff pulses and the characteristics of the diurnal variation in measured proglacial discharge indicate the development in the ablation zone of a fast, efficient subglacial hydraulic system early in the summer. The passing of a jökulhlaup and high subglacial groundwater flow do not disturb this development. Three GPS campaigns to measure jökulhlaups have been carried out over known jökulhlaup paths in two outlets from Vatnajökull ice cap, Skaftárjökull and Skeiðarárjökull. Two slowly rising jökulhlaups from Grímsvötn and two rapidly rising jökulhlaups from the western and eastern Skaftá cauldrons were captured in these campaigns, with maximum discharge ranging from 240 to 3300m3 s-1. Glacier ... |
author2 |
Tómas Jóhannesson Jarðvísindadeild (HÍ) Faculty of Earth Sciences (UI) Verkfræði- og náttúruvísindasvið (HÍ) School of Engineering and Natural Sciences (UI) Háskóli Íslands University of Iceland |
format |
Doctoral or Postdoctoral Thesis |
author |
Einarsson, Bergur |
author_facet |
Einarsson, Bergur |
author_sort |
Einarsson, Bergur |
title |
Subglacial hydrology of the Icelandic ice caps: Outburst floods and ice dynamics |
title_short |
Subglacial hydrology of the Icelandic ice caps: Outburst floods and ice dynamics |
title_full |
Subglacial hydrology of the Icelandic ice caps: Outburst floods and ice dynamics |
title_fullStr |
Subglacial hydrology of the Icelandic ice caps: Outburst floods and ice dynamics |
title_full_unstemmed |
Subglacial hydrology of the Icelandic ice caps: Outburst floods and ice dynamics |
title_sort |
subglacial hydrology of the icelandic ice caps: outburst floods and ice dynamics |
publisher |
Bergur Einarsson |
publishDate |
2018 |
url |
https://hdl.handle.net/20.500.11815/696 |
long_lat |
ENVELOPE(-17.933,-17.933,63.783,63.783) ENVELOPE(-17.833,-17.833,64.167,64.167) ENVELOPE(-17.208,-17.208,64.056,64.056) ENVELOPE(-16.823,-16.823,64.420,64.420) |
geographic |
Skaftá Skaftárjökull Skeiðarárjökull Vatnajökull |
geographic_facet |
Skaftá Skaftárjökull Skeiðarárjökull Vatnajökull |
genre |
glacier Hofsjökull Ice cap Iceland Vatnajökull |
genre_facet |
glacier Hofsjökull Ice cap Iceland Vatnajökull |
op_relation |
Bergur Einarsson, 2018, Subglacial hydrology of the Icelandic ice caps: Outburst floods and ice dynamics, PhD dissertation, Faculty of Earth Science, University of Iceland, 111 pp. 9789935930699 https://hdl.handle.net/20.500.11815/696 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/20.500.11815/696 |
_version_ |
1766009701528502272 |