Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
The Cryosphere, 10, 597-611, 2016
https://doi.org/10.5194/tc-10-597-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
15 Mar 2016
Modelled glacier dynamics over the last quarter of a century at Jakobshavn Isbræ
Ioana S. Muresan1, Shfaqat A. Khan1, Andy Aschwanden2, Constantine Khroulev2, Tonie Van Dam3, Jonathan Bamber4, Michiel R. van den Broeke5, Bert Wouters4,5, Peter Kuipers Munneke5, and Kurt H. Kjær6 1Department of Geodesy, DTU Space, Technical University of Denmark, Kgs. Lyngby, Denmark
2Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA
3University of Luxembourg, Faculty of Science, Technology and Communication (FSTC), Research Unit of Engineering Sciences, Luxembourg, Luxembourg
4University of Bristol, School of Geographical Sciences, Bristol, UK
5Institute for Marine and Atmospheric research Utrecht (IMAU), Utrecht University, the Netherlands
6Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark
Abstract. Observations over the past 2 decades show substantial ice loss associated with the speed-up of marine-terminating glaciers in Greenland. Here we use a regional three-dimensional outlet glacier model to simulate the behaviour of Jakobshavn Isbræ (JI) located in western Greenland. Our approach is to model and understand the recent behaviour of JI with a physical process-based model. Using atmospheric forcing and an ocean parametrization we tune our model to reproduce observed frontal changes of JI during 1990–2014. In our simulations, most of the JI retreat during 1990–2014 is driven by the ocean parametrization used and the glacier's subsequent response, which is largely governed by bed geometry. In general, the study shows significant progress in modelling the temporal variability of the flow at JI. Our results suggest that the overall variability in modelled horizontal velocities is a response to variations in terminus position. The model simulates two major accelerations that are consistent with observations of changes in glacier terminus. The first event occurred in 1998 and was triggered by a retreat of the front and moderate thinning of JI prior to 1998. The second event, which started in 2003 and peaked in the summer 2004, was triggered by the final break-up of the floating tongue. This break-up reduced the buttressing at the JI terminus that resulted in further thinning. As the terminus retreated over a reverse bed slope into deeper water, sustained high velocities over the last decade have been observed at JI. Our model provides evidence that the 1998 and 2003 flow accelerations are most likely initiated by the ocean parametrization used but JI's subsequent dynamic response was governed by its own bed geometry. We are unable to reproduce the observed 2010–2012 terminus retreat in our simulations. We attribute this limitation to either inaccuracies in basal topography or to misrepresentations of the climatic forcings that were applied. Nevertheless, the model is able to simulate the previously observed increase in mass loss through 2014.

Citation: Muresan, I. S., Khan, S. A., Aschwanden, A., Khroulev, C., Van Dam, T., Bamber, J., van den Broeke, M. R., Wouters, B., Kuipers Munneke, P., and Kjær, K. H.: Modelled glacier dynamics over the last quarter of a century at Jakobshavn Isbræ, The Cryosphere, 10, 597-611, https://doi.org/10.5194/tc-10-597-2016, 2016.
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We use a regional 3-D outlet glacier model to simulate the behaviour of Jakobshavn Isbræ (JI) during 1990–2014. The model simulates two major accelerations in 1998 and 2003 that are consistent with observations. We find that most of the JI retreat during the simulated period is driven by the ocean parametrization used, and the glacier's subsequent response, which is largely governed by bed geometry. The study shows progress in modelling the temporal variability of the flow at JI.
We use a regional 3-D outlet glacier model to simulate the behaviour of Jakobshavn Isbræ (JI)...
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