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 modelling. The modelling component of the project consists of a comprehensive three-dimensional thermo-mechanical 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 modelling 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 modelling to separate the ice mass contribution from the contribution of postglacial isostatic rebound, to separate ice-sheet dynamic changes from inter-annual 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.