The goal of the project is a new and comprehensive estimate of the long-term ice mass balance of Antarctica and its major ice drainage basins and the corresponding sea level contribution with unprecedented accuracy. This shall be achieved by combining various types of observations and modelling. The observational fundament are time-variable gravity field data from GRACE, surface elevation and elevation-change data from ICESat and ERS-1/ERS-2/ENVISAT and surface flow data from satellite synthetic aperture radar (SAR) . The modelling fundament is thermo-mechanical ice sheet modelling which provides a long-term dynamic ice mass history and aids modeling of glacial-isostatic adjustment (GIA). GIA modelling and atmospheric modelling of snow accumulation will also be incorporated in the project. The project involves thorough analyses of observational data, the implementation of elaborate methods of combining complementary observations, and strong interactions between observational analyses and modelling. This approach shall meet the project’s challenges: Namely, to account for the specific spatio-temporal resolutions and specific sensitivities of the individual observation and modelling methods, to separate ice mass balance signals from GIA signals as well as from atmospheric and oceanographic signals, to separate inter annual ice mass variations from the long-term ice mass balance, and to realistically assess uncertainties.