Preprints
https://doi.org/10.5194/egusphere-2023-1507
https://doi.org/10.5194/egusphere-2023-1507
09 Aug 2023
 | 09 Aug 2023

Increasing numerical stability of mountain valley glacier simulations: implementation and testing of free-surface stabilization in Elmer/Ice

André Löfgren, Thomas Zwinger, Peter Råback, Christian Helanow, and Josefin Ahlkrona

Abstract. This paper concerns a numerical stabilization method for free-surface ice flow called the free-surface stabilization algorithm (FSSA). In the current study, the FSSA is implemented into the numerical ice-flow software Elmer/Ice and tested on synthetic two-dimensional (2D) glaciers, as well as on the real-world glacier of Midtre Lovénbreen, Svalbard. For the synthetic 2D cases it is found that the FSSA method increases the largest stable time-step size at least by a factor of ten for the case of a gently sloping ice surface (3°), and by at least a factor of five for cases of moderately to steeply inclined surfaces (6° to 12°) . Furthermore, the FSSA method increases the overall accuracy for all surface slopes. The largest stable time-step size is found to be smallest for the case of a low sloping surface, despite having overall smaller velocities. For Midtre Lovénbreen the FSSA method doubles the largest stable time-step size, however, the accuracy is in this case slightly lowered in the deeper parts of the glacier, while it increases near edges. The implication is that the non-FSSA method might be more accurate at predicting glacier thinning, while the FSSA method is more suitable for predicting future glacier extent. A possible application of the larger time-step sizes allowed for by the FSSA is for spin-up simulations, where relatively fast changing climate data can be incorporated on short time scales, while the slowly changing velocity field is updated over larger time scales.

André Löfgren, Thomas Zwinger, Peter Råback, Christian Helanow, and Josefin Ahlkrona

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André Löfgren, Thomas Zwinger, Peter Råback, Christian Helanow, and Josefin Ahlkrona
André Löfgren, Thomas Zwinger, Peter Råback, Christian Helanow, and Josefin Ahlkrona

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Short summary
This paper investigates a stabilization method for free-surface flows in the context of glacier simulations. Previous applications of the stabilization on ice flows have only considered simple ice-sheet benchmark problems; in particular the method has not been tested on real-world glacier domains. This work addresses this shortcoming by demonstrating that the stabilization works well also in this case, and increases stability and robustness without negatively impacting computation times.