Elmer/Ice News

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Best of both worlds: SIA and full-Stokes

Written by Thomas Zwinger on .

In a recent article in the Journal of Computational Physics, Ahlkrona et al. present a method (ISCAL - Ice  Sheet  Coupled Approximation Levels) implemented in Elmer/Ice that uses an error estimate to identify areas where the shallow ice approximation (SIA) can and cannot be deployed. According to this estimate, those regions, where the shallowness assumption prevails can be switched to a - compared to the full-Stokes solution - extremely cheap SIA (simply by replacing the matrix entries in the system matrix of the linearized and discretized full-Stokes problem. In their article the authors demonstrate a reduction of CPU time by ISCAL on an in size reduced real world case of up to 75% compared to a full-Stokes simulation run of the same problem.

Ahlkrona, J., P. Lötstedt, N. Kirchner, and T. Zwinger, 2016. Dynamically coupling the non-linear Stokes equations with the shallow ice approximation in glaciology: Description and first applications of the ISCAL method. J. Comp. Phys., 308, 1-19, doi:10.1016/j.jcp.2015.12.025.

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Elmer/Ice @ AGU2015

Written by Olivier Gagliardini on .

aguDon't miss the 9 presentations using Elmer/Ice at the next AGU!

Monday, 14 December 2015 - Moscone South - Poster Hall - 08:00 - 12:20
- C11B-0761: Triggers for the Collapse of Ice Shelves in Antarctica: Investigating Compressive Arch Failure with Numerical Models, Alex Huth and Benjamin Smith

Thursday, 17 December 2015 - Moscone West - 3007
- 10:50 - 11:05: C42A-03: Influence of an Increasing Surface Melt Over Decadal Timescales on Land Terminating Outlet Glaciers, Olivier Gagliardini, Mauro Werder and Gaël Durand

Friday, 18 December 2015 - Moscone South - Poster Hall - 08:00 - 12:20
- C51C-0736: Simulating Ice-Flow and Calving on Store Glacier, West Greenland, with a 3D Full Stokes Model, Joe Todd, Poul Christoffersen, Thomas Zwinger, Adrian Luckman and Doug Benn
- C51C-0730: Quantifying Uncertainty in Inferred Viscosity and Basal Shear Stress Over Ice Streams, David Lilien, Ian Joughin and Benjamin Smith

Friday, 18 December 2015 - Moscone West - 3005
- 13:55 - 14:10: C53E-02: Improvement of Basal Conditions in Wilkes Land, East Antarctica, Using Data Assimilation, Cyrille Mosbeux, Fabien Gillet-chaulet and Olivier Gagliardini
- 14:25 - 14:40: C53E-04: The Friction Law Stress Exponent under Pine Island Glacier from 15 Years of Surface Elevation and Velocity Measurements (Invited), Fabien Gillet-chaulet, Gaël Durand, Olivier Gagliardini, Cyrille Mosbeux, Jeremie Mouginot, Frederique Remy and Catherine Ritz
- 14:55 - 15:10: C53E-06: Stability of Barnes Ice Cap, Baffin Island, Canada, Adrien Gilbert and others.
- 16:15 - 16:30: C54B-02: The influence of subtemperate sliding on the formation of temperate ice in ice stream margins, Marianne Haseloff, Christian Schoof and Olivier Gagliardini
- 17:00 - 17:15: C54B-05: Explicit Numerical Modeling of Heat Transfer in Glacial Channels, Alexander Jarosch and Thomas Zwinger

 

 

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Vesfonna Ice Cap: Mass-balance/elevation feedback

Written by Thomas Zwinger on .

Vestfonna cross sectionFull two-way coupling between mass-balance models and ice flow models brings along substantial technical challenges. In this paper the authors examine some coupling effects for the Vestfonna ice cap, Nordaustlandet, Svalbard, by analyzing the impacts of different coupling intervals on mass-balance and sea-level rise (SLR) projections. They show that neglecting the topographic feedback in the coupling leads to underestimations of 10–20% in SLR projections on century timescales in our model. Fast-flowing outlet glaciers decrease in impacting SLR due to their deceleration and reduced mass flux as they thin and retreat from the coast. By introduction of a method to estimate errors introduced by different coupling schemes it is shown that parameterizing mass-balance adjustment for changes in topography using lapse rates is a cost-effective reasonably accurate alternative to full coupling.

 

Schäfer M., M. Möller, T. Zwinger and J.C. Moore, 2015. Dynamic modelling of future glacier changes: mass-balance/elevation feedback in projections for the Vestfonna ice cap, Nordaustlandet, Svalbard. Journal of Glaciology, 61, 1121-1136 doi:10.3189/2015JoG14J184.

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