Analysis of Recent Dynamic Changes of Jakobshavn Isbrae, West Greenland, using a Thermomechanical Model
Jakobshavn Isbrae is a major marine terminating outlet glacier of the western Greenland Ice Sheet, which has been undergoing widespread acceleration and strong mass loss since the disintegration of its floating ice tongue in the late 1990s. The underlying mechanisms are poorly understood despite a w...
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Universität Bremen
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Online Access: | https://media.suub.uni-bremen.de/handle/elib/1240 https://nbn-resolving.org/urn:nbn:de:gbv:46-00105963-16 |
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ftsubbremen:oai:media.suub.uni-bremen.de:Publications/elib/1240 2023-05-15T16:21:12+02:00 Analysis of Recent Dynamic Changes of Jakobshavn Isbrae, West Greenland, using a Thermomechanical Model Analyse der Rezenten Dynamischen Änderungen des Jakobshavn Isbrae, Westgrönland, mittels eines Thermomechanischen Modells Bondzio, Johannes Heinrich Humbert, Angelika Lohmann, Gerrit 2017-06-16 application/pdf https://media.suub.uni-bremen.de/handle/elib/1240 https://nbn-resolving.org/urn:nbn:de:gbv:46-00105963-16 eng eng Universität Bremen FB5 Geowissenschaften https://media.suub.uni-bremen.de/handle/elib/1240 urn:nbn:de:gbv:46-00105963-16 info:eu-repo/semantics/openAccess Bitte wählen Sie eine Lizenz aus: (Unsere Empfehlung: CC-BY) CC-BY Jakobshavn Isbrae Jakobshavn Greenland ice flow modeling ice flow modelling modelling modeling ISSM Ice Sheet System Model climate change calving calving front sea level rise ice dynamics ice glacier outlet glacier 550 550 Earth sciences and geology ddc:550 Dissertation doctoralThesis 2017 ftsubbremen 2022-11-09T07:09:33Z Jakobshavn Isbrae is a major marine terminating outlet glacier of the western Greenland Ice Sheet, which has been undergoing widespread acceleration and strong mass loss since the disintegration of its floating ice tongue in the late 1990s. The underlying mechanisms are poorly understood despite a wealth in observational and modelling studies. This doctoral thesis analyses the dynamic changes of Jakobshavn Isbrae using the Ice Sheet System Model (ISSM), a state-of-the-art finite-element ice flow model. Two missing model features for 1) the modelling the polythermal regime of glaciers and ice sheets, and 2) the dynamic evolution of its horizontal calving front position are designed and implemented into ISSM. A three-dimensional, thermodynamically coupled model of Jakobshavn Isbrae is set up and calibrated using modern observational data products. Low basal drag in the trough under the ice stream requires that its high driving stress is balanced by lateral drag in the shear margins, which allows for high flow velocities, as the ice viscosity is strain-rate-dependent. The developed modules are applied to the glacier model, which captures 90% of the observed changes from 1985 to 2015. Analysis of the model results reveals that calving front retreat is able to trigger widespread inland acceleration due to a rheological ice viscosity drop in the shear margins. Thermal feedbacks contribute 5 to 10% to the total acceleration. The study shows that Jakobshavn Isbrae will continue to contribute to eustatic sea level rise for at least the next century due to ongoing geometry adjustment to the new calving front position. Future fields of research include deriving a suitable calving rate parametrisation for large-scale ice flow models, a material law for temperate ice with a microscopic water content larger than 1%, and technical refinements of the modules developed for this thesis. Doctoral or Postdoctoral Thesis glacier Greenland Ice Sheet Jakobshavn Media SuUB Bremen (Staats- und Universitätsbibliothek Bremen) Greenland |
institution |
Open Polar |
collection |
Media SuUB Bremen (Staats- und Universitätsbibliothek Bremen) |
op_collection_id |
ftsubbremen |
language |
English |
topic |
Jakobshavn Isbrae Jakobshavn Greenland ice flow modeling ice flow modelling modelling modeling ISSM Ice Sheet System Model climate change calving calving front sea level rise ice dynamics ice glacier outlet glacier 550 550 Earth sciences and geology ddc:550 |
spellingShingle |
Jakobshavn Isbrae Jakobshavn Greenland ice flow modeling ice flow modelling modelling modeling ISSM Ice Sheet System Model climate change calving calving front sea level rise ice dynamics ice glacier outlet glacier 550 550 Earth sciences and geology ddc:550 Bondzio, Johannes Heinrich Analysis of Recent Dynamic Changes of Jakobshavn Isbrae, West Greenland, using a Thermomechanical Model |
topic_facet |
Jakobshavn Isbrae Jakobshavn Greenland ice flow modeling ice flow modelling modelling modeling ISSM Ice Sheet System Model climate change calving calving front sea level rise ice dynamics ice glacier outlet glacier 550 550 Earth sciences and geology ddc:550 |
description |
Jakobshavn Isbrae is a major marine terminating outlet glacier of the western Greenland Ice Sheet, which has been undergoing widespread acceleration and strong mass loss since the disintegration of its floating ice tongue in the late 1990s. The underlying mechanisms are poorly understood despite a wealth in observational and modelling studies. This doctoral thesis analyses the dynamic changes of Jakobshavn Isbrae using the Ice Sheet System Model (ISSM), a state-of-the-art finite-element ice flow model. Two missing model features for 1) the modelling the polythermal regime of glaciers and ice sheets, and 2) the dynamic evolution of its horizontal calving front position are designed and implemented into ISSM. A three-dimensional, thermodynamically coupled model of Jakobshavn Isbrae is set up and calibrated using modern observational data products. Low basal drag in the trough under the ice stream requires that its high driving stress is balanced by lateral drag in the shear margins, which allows for high flow velocities, as the ice viscosity is strain-rate-dependent. The developed modules are applied to the glacier model, which captures 90% of the observed changes from 1985 to 2015. Analysis of the model results reveals that calving front retreat is able to trigger widespread inland acceleration due to a rheological ice viscosity drop in the shear margins. Thermal feedbacks contribute 5 to 10% to the total acceleration. The study shows that Jakobshavn Isbrae will continue to contribute to eustatic sea level rise for at least the next century due to ongoing geometry adjustment to the new calving front position. Future fields of research include deriving a suitable calving rate parametrisation for large-scale ice flow models, a material law for temperate ice with a microscopic water content larger than 1%, and technical refinements of the modules developed for this thesis. |
author2 |
Humbert, Angelika Lohmann, Gerrit |
format |
Doctoral or Postdoctoral Thesis |
author |
Bondzio, Johannes Heinrich |
author_facet |
Bondzio, Johannes Heinrich |
author_sort |
Bondzio, Johannes Heinrich |
title |
Analysis of Recent Dynamic Changes of Jakobshavn Isbrae, West Greenland, using a Thermomechanical Model |
title_short |
Analysis of Recent Dynamic Changes of Jakobshavn Isbrae, West Greenland, using a Thermomechanical Model |
title_full |
Analysis of Recent Dynamic Changes of Jakobshavn Isbrae, West Greenland, using a Thermomechanical Model |
title_fullStr |
Analysis of Recent Dynamic Changes of Jakobshavn Isbrae, West Greenland, using a Thermomechanical Model |
title_full_unstemmed |
Analysis of Recent Dynamic Changes of Jakobshavn Isbrae, West Greenland, using a Thermomechanical Model |
title_sort |
analysis of recent dynamic changes of jakobshavn isbrae, west greenland, using a thermomechanical model |
publisher |
Universität Bremen |
publishDate |
2017 |
url |
https://media.suub.uni-bremen.de/handle/elib/1240 https://nbn-resolving.org/urn:nbn:de:gbv:46-00105963-16 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
glacier Greenland Ice Sheet Jakobshavn |
genre_facet |
glacier Greenland Ice Sheet Jakobshavn |
op_relation |
https://media.suub.uni-bremen.de/handle/elib/1240 urn:nbn:de:gbv:46-00105963-16 |
op_rights |
info:eu-repo/semantics/openAccess Bitte wählen Sie eine Lizenz aus: (Unsere Empfehlung: CC-BY) |
op_rightsnorm |
CC-BY |
_version_ |
1766009214624333824 |