Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
© Author(s) 2008. This work is distributed
under the Creative Commons Attribution 3.0 License.
14 Jul 2008
Review status
This discussion paper has been under review for the journal The Cryosphere (TC). The manuscript was not accepted for further review after discussion.
Applicability of the Shallow Ice Approximation inferred from model inter-comparison using various glacier geometries
M. Schäfer1, O. Gagliardini1, F. Pattyn2, and E. Le Meur1 1LGGE, CNRS, UJF-Grenoble, BP 96, 38402 Saint-Martin d'Hères Cedex, France
2Laboratoire de Glaciologie, ULB, Bruxelles, Belgium
Abstract. This paper presents an inter-comparison of three different models applied to various glacier geometries. The three models are built on different approximations of the Stokes equations, from the well known Shallow Ice Approximation (SIA) to the full-Stokes (FS) solution with an intermediate higher-order (HO) model which incorporates longitudinal stresses. The studied glaciers are synthetic geometries, but two of them are constructed so as to mimic a valley glacier and a volcano glacier. For each class of glacier, the bedrock slope and/or the aspect ratio are varied. First, the models are compared in a diagnostic way for a fixed and given geometry. Here the SIA surface velocity can overestimate the FS velocity by a factor of 5 to a factor of 10. Then, the free surface is allowed to evolve and the time-dependent evolution of the glacier is studied. As a result, the difference between the models decreases, but can still be as large as a factor of 1.5 to 2. This decrease can be explained by a negative feedback for the SIA which overestimates velocities.

Citation: Schäfer, M., Gagliardini, O., Pattyn, F., and Le Meur, E.: Applicability of the Shallow Ice Approximation inferred from model inter-comparison using various glacier geometries, The Cryosphere Discuss., 2, 557-599, doi:10.5194/tcd-2-557-2008, 2008.
M. Schäfer et al.
M. Schäfer et al.


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