Observing Gravity Change in the Fennoscandian Uplift Area with the Hanover Absolute Gravimeter

The Nordic countries Norway, Sweden, Finland and Denmark are a key study region for research of glacial isostasy. In addition, such research offers a unique opportunity for absolute gravimetry to show its capability as a geodetic tool for geophysical research. Within a multi-national cooperation, annual absolute gravity measurements have been performed in Fennoscandia by IfE since 2003. For the Hanover gravimeter FG5-220, overall accuracy of +/- 30 nm/s(2) is indicated for a single station determination. First results of linear gravity changes are derived for ten stations in the central and southern part of the uplift area. Comparing with the rates predicted by glacial rebound modelling, the gravity trends of the absolute measurements differ by 3.8 nm/s(2) per year (root-mean-square discrepancy) from the uplift model. The mean difference between observed and predicted rates is 0.8 nm/s(2) per year only. A proportionality factor of -1.63 +/- A 0.20 nm/s(2) per mm has been obtained, which describes the mean ratio between the observational gravity and height rates.