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

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.