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  4. Analysis of Recent Dynamic Changes of Jakobshavn Isbrae, West Greenland, using a Thermomechanical Model
 
Zitierlink URN
https://nbn-resolving.de/urn:nbn:de:gbv:46-00105963-16

Analysis of Recent Dynamic Changes of Jakobshavn Isbrae, West Greenland, using a Thermomechanical Model

Veröffentlichungsdatum
2017-06-16
Autoren
Bondzio, Johannes Heinrich  
Betreuer
Humbert, Angelika  
Gutachter
Lohmann, Gerrit  
Zusammenfassung
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.
Schlagwörter
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
Institution
Universität Bremen  
Fachbereich
Fachbereich 05: Geowissenschaften (FB 05)  
Dokumenttyp
Dissertation
Zweitveröffentlichung
Nein
Sprache
Englisch
Dateien
Lade...
Vorschaubild
Name

00105963-1.pdf

Size

24.47 MB

Format

Adobe PDF

Checksum

(MD5):ba8770e2ade4829df36216fe18feb26c

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