EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Geometric Controls of Fjord Glacier Dynamics

Thomas Frank1, Henning Åkesson2,3, Basile de Fleurian4,5, and Kerim H Nisancioglu4,5
Thomas Frank et al.
  • 1Department of Physical Geography, Stockholm University, Stockholm, Sweden
  • 2Department of Geological Sciences, Stockholm University, Stockholm, Sweden
  • 3Bolin Center for Climate Research, Stockholm, Sweden
  • 4Department of Earth Science, University of Bergen, Bergen, Norway
  • 5Bjerknes Center for Climate Research, Bergen, Norway

Retreat of marine outlet glaciers and ice shelves may initiate depletion of inland ice and lead to ice loss that by far exceeds what would be expected from ocean and atmospheric warming alone. Many marine outlet glaciers draining large parts of past and present ice masses have shown non-linear and variable retreat rates, with adjacent glaciers sometimes showing a highly different response to the same large-scale climate forcing. This suggests that individual glacier characteristics play a dominant role in governing retreat.

There is widespread evidence that the dynamic glacier adjustment to an external forcing is highly influenced by fjord topography. However, whether this stabilizes the glacier, or promotes enhanced retreat, depends on the shape of the fjord. So far, no rigorous, systematic assessment of the exact influence of certain geometric features such as overdeepenings or embayments has been undertaken in a model framework that incorporates all relevant processes in a 3D layout.

Here, we analyze a multitude of topographic settings and scenarios using the Ice Sheet System Model (ISSM), which accounts for all relevant physics in a 3D framework. Using artificial fjord geometries, we investigate glacier-topography interaction and quantify the modeled glacier response directly in relation to topographic features.

In light of our modeled topographic influence on glacier retreat, we consider whether we reliably can extrapolate observations from a few well-monitored glaciers to those less studied. Furthermore, we discuss implications for past and future ice sheet mass loss and associated sea-level rise. Finally, a deeper understanding of processes at the glacier front improves confidence in the climate signal derived from the deglacial landscape, as glacier-proximal landforms can more confidently be linked to climate.

How to cite: Frank, T., Åkesson, H., de Fleurian, B., and Nisancioglu, K. H.: Geometric Controls of Fjord Glacier Dynamics, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-838,, 2019.

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Display material version 1 – uploaded on 05 May 2020
  • CC1: Comment on EGU2020-838, Matt Trevers, 08 May 2020

    Hi Thomas,

    Thanks for a really nice presentation.

    May I ask how you initialise the model? If you ran a spinup into a steady state, it would presumably result in a different glacier geometry for the different fjord configurations.

    The videos in the powerpoint didn't work for me. Is there any chance you might be able to upload them separately?


    • AC1: Reply to CC1, Thomas Frank, 08 May 2020

      Hi Matt,

      thank you! We created a reference steady-state glacier in a fjord without any geometric perturbations and then "teleported" it into a fjord with a different geometry, while filling potential voids (under the glacier in the depression and on the side for the embayment) with ice or "cutting out" ice if we introduce bottlenecks or bumps. Then, we let the glacier relax for 50 yrs which results in all glaciers across all geometries having a volume change dV/dt<0.5%. So all runs start from a glacier that is as similar as possible, but of course, during the relaxation, some adjustments occur that lead to some differences before the retreat. Since this is a consequence of fjord geometry by itself, we do not see it as problematic for the retreat experiments.

      Strange that you can't see the videos.. but here is a link were you should be able to download them individually:

      If you have more questions, do not hesitate to ask.