Combination of geodetic space observations for estimating cryospheric mass changes and their impact on Earth rotation

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Redistribution and motion of masses in the Earth System cause Earth rotation variations. While the integral excitation mechanism is observed by geometric space techniques with high accuracy, the separation into the individual contributions from the subsystems of the Earth remains a challenge. Especially the estimation of the cryospheric mass effect is afflicted with large uncertainties due to the fact that no reliable geophysical models of the cryosphere exist and due to the lack of precise geodetic observations. Since 2002 gravity field changes of the Earth can be observed precisely by the satellite mission GRACE (Gravity Recovery and Climate Experiment). The separation in particular of the underlying ice mass changes poses a special challenge because of the spatial distribution of the ice masses of the Earth and the postglacial land uplift. Since 2003 and 2010 respectively ice height changes can be observed by the altimeter satellite ICESat (Ice, Cloud, and land Elevaion Satellite) and CryoSat-2 with high accuracy. By the transformation into ice mass changes the ice dynamic and density has to be considered. Within this project for the first time geometric and gravimetric space observations are combined for estimating the cryospheric mass effect. Due to the combination of the different geodetic space observations the weaknesses of the individual processing strategies can be compensated and the technique specific strengths can be optimal accounted. The new improved findings give information about how strong polar motion is influenced by the increasing ice melting and the involved sea level rise and what consequences this polar motion has on the mean annual temperature of the Earth. Due to assimilation of the geodetic estimated angular momenta the geophysical models of the cryosphere could be improved.