Assessing the current Evolution of the Greenland Ice Sheet

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The objective of the project is to contribute to a more accurate assessment of the current evolution of the Greenland ice sheet and its major drainage basins from a combination of observational data and glaciological modeling. The modeling component of the project consists of a comprehensive three-dimensional thermomechanical ice-sheet model, a surface melt and runoff model, and a model to calculate balance velocities, with further input from a regional atmospheric climate model and a visco-elastic self-gravitating solid Earth model. The modeling will primarily yield the long-term ice sheet and bedrock evolution as well as the surface mass balance over the last few decades.The observational data come from the time-dependent geoid from GRACE, altimetry from ICESat and ERS-1/ERS-2/ENVISAT, optical data from ASTER, SAR data from ERS-1/2, ENVISAT and TerraSAR, and ground-based GPS data. These data will provide snapshots of surface elevation changes, gravity changes, surface velocity, and surface accumulation rate over the duration of the measurement platforms.The project relies on a strong interaction between observational analyses and modeling to separate the ice mass contribution from the contribution of postglacial isostatic rebound, to separate ice-sheet dynamic changes from interannual surface mass balance changes, and to separate long-term ice-dynamic changes from short-term flow fluctuations. The result will be an improved estimate of the present-day contribution of the Greenland ice sheet to global sea-level change and a better understanding of the various contributions to current ice mass changes and their associated uncertainties.