Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 9, 2549-2562, 2016
https://doi.org/10.5194/gmd-9-2549-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Model description paper
27 Jul 2016
Comparison of adjoint and nudging methods to initialise ice sheet model basal conditions
Cyrille Mosbeux1,2, Fabien Gillet-Chaulet1,2, and Olivier Gagliardini1,2 1CNRS, LGGE, 38041 Grenoble, France
2Univ. Grenoble Alpes, LGGE, 38401 Grenoble, France
Abstract. Ice flow models are now routinely used to forecast the ice sheets' contribution to 21st century sea-level rise. For such short term simulations, the model response is greatly affected by the initial conditions. Data assimilation algorithms have been developed to invert for the friction of the ice on its bedrock using observed surface velocities. A drawback of these methods is that remaining uncertainties, especially in the bedrock elevation, lead to non-physical ice flux divergence anomalies resulting in undesirable transient effects. In this study, we compare two different assimilation algorithms based on adjoints and nudging to constrain both bedrock friction and elevation. Using synthetic twin experiments with realistic observation errors, we show that the two algorithms lead to similar performances in reconstructing both variables and allow the flux divergence anomalies to be significantly reduced.

Citation: Mosbeux, C., Gillet-Chaulet, F., and Gagliardini, O.: Comparison of adjoint and nudging methods to initialise ice sheet model basal conditions, Geosci. Model Dev., 9, 2549-2562, https://doi.org/10.5194/gmd-9-2549-2016, 2016.
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Short summary
Model projections of ice sheet contribution to 21st century sea level rise are greatly affected by initial conditions. Solutions have been developed to infer the friction of the ice on its bedrock using observed surface velocities. A drawback of these methods is that remaining uncertainties, especially in the bedrock elevation, lead to non-physical ice flux divergence anomalies. Here, we compare two different solutions able to infer both bedrock friction and elevation with good performance.
Model projections of ice sheet contribution to 21st century sea level rise are greatly affected...
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