Gravity Changes in the Fennoscandian Uplift Area to be Observed by GRACE and Absolute Gravimetry

Gravity changes due to the glacial isostatic adjustment in Fennoscandia entails a temporal geoid variation of about 3 mm and a gravity change of about 10 μGal over five years (linear trend) in the centre of the land uplift area. This gravity change can be observed by absolute gravimetry with an accuracy of lb 1 - 2 μGal and by GRACE with a geoid accuracy at the few mm level for long wavelengths. Since 2003, annual absolute gravity measurements have been intensified to improve the knowledge about the land uplift, about its accuracy and its spatial structure. Independently, relative gravimetry, tide gauge observations and GPS measurements are carried out by various institutions in dedicated campaigns or during their routine work. All Nordic countries contribute in different ways to the project (preparation of the sites, campaigns, collection of auxiliary data, computations and analyses). The main result of the project will be reduced point-wise gravity observations, which are combined with GPS height observations to derive an independent, spatially and temporally smoothed model of the geoid change. It can be compared with the land uplift determined from the GRACE data, i.e., gound-truth for the satellite measurements.