Forty-three years of absolute gravity observations of the Fennoscandian postglacial rebound in Finland

• Published in: Journal of Geodesy
• Main Authors: Bilker-Koivula, Mirjam, Mäkinen, Jaakko, Ruotsalainen, Hannu, Näränen, Jyri, Saari, Timo
• Other Authors: National Land Survey of Finland, Maanmittauslaitos
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer 2021
• Subjects: Absolute gravimetry; Postglacial rebound; Gravity trend; Glacial isostatic adjustment; Fennoscandia; Finland; Fennoscandian
• Online Access: http://hdl.handle.net/10138/326166

Postglacial rebound in Fennoscandia causes striking trends in gravity measurements of the area. We present time series of absolute gravity data collected between 1976 and 2019 on 12 stations in Finland with different types of instruments. First, we determine the trends at each station and analyse the effect of the instrument types. We estimate, for example, an offset of 6.8 μgal for the JILAg-5 instrument with respect to the FG5-type instruments. Applying the offsets in the trend analysis strengthens the trends being in good agreement with the NKG2016LU_gdot model of gravity change. Trends of seven stations were found robust and were used to analyse the stabilization of the trends in time and to determine the relationship between gravity change rates and land uplift rates as measured with global navigation satellite systems (GNSS) as well as from the NKG2016LU_abs land uplift model. Trends calculated from combined and offset-corrected measurements of JILAg-5- and FG5-type instruments stabilized in 15 to 20 years and at some stations even faster. The trends of FG5-type instrument data alone stabilized generally within 10 years. The ratio between gravity change rates and vertical rates from different data sets yields values between − 0.206 ± 0.017 and − 0.227 ± 0.024 µGal/mm and axis intercept values between 0.248 ± 0.089 and 0.335 ± 0.136 µGal/yr. These values are larger than previous estimates for Fennoscandia.