Articles | Volume 8, issue 5
https://doi.org/10.5194/gmd-8-1275-2015
https://doi.org/10.5194/gmd-8-1275-2015
Methods for assessment of models
 | 
04 May 2015
Methods for assessment of models |  | 04 May 2015

A stabilized finite element method for calculating balance velocities in ice sheets

D. Brinkerhoff and J. Johnson

Abstract. We present a numerical method for calculating vertically averaged velocity fields using a mass conservation approach, commonly known as balance velocities. This allows for an unstructured grid, is not dependent on a heuristic flow routing algorithm, and is both parallelizable and efficient. We apply the method to calculate depth-averaged velocities of the Greenland Ice Sheet, and find that the method produces grid-independent velocity fields for a sufficient parameterization of horizontal plane stresses on flow directions. We show that balance velocity can be used as the forward model for a constrained optimization problem that can be used to fill gaps and smooth strong gradients in InSAR velocity fields.

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Short summary
We present a novel numerical method for computing velocity fields in ice sheets using the principle of mass conservation, and show that, for suitable smoothing of flow directions, the velocity converges to a unique solution under grid refinement. We use this method as the forward model in a constrained optimization problem, and use these so-called balance velocities to seamlessly fill in gaps between satellite-based velocity observations.