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Abstract

This work is concerned with the determination of present-day ice-mass changes and glacial-isostatic adjustment (GIA) in the polar regions from gravity-field data of the satellite mission Gravity Recovery and Climate Experiment (GRACE). Aim is the separation of cryospheric mass changes from the mass redistribution in the Earth’s mantle due to GIA using geophysical modelling and the determination of the contribution of glaciated areas to global sea-level change. This is done by analyzing the time series of monthly GRACE gravity-field solutions with respect to their long-term temporal changes. Filters are developed to optimize the trade-off between noise and spatial resolution in the GRACE gravity fields. Also, a method for the evaluation and combination of GRACE gravity fields from different processing is developed. Forward models of the potential disturbance due to present-day ice-mass changes and GIA are adjusted with respect to the GRACE observations and then used to perform a joint gravity-field inversion for the causative mass changes on and within the Earth. For small spatial scales (e.g. individual drainage basins of glaciers), ambiguities in the solution of this gravimetric inverse problem are reduced by introducing a priori constraints. The relative weight of this information with respect to the GRACE data allows determining the regional spatial resolution of the long-term changes in the GRACE gravity fields. The main region of interest of this work is Antarctica. In addition, investigations concerned with present-day ice-mass changes in Alaska and Greenland are presented, along with results on the gravity-field inversion in terms of the viscosity distribution in the Earth’s mantle under North America.