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

Abstract

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.

Basin Mass Changes in Finland From GRACE: Validation and Explanation

“…The absolute gravity time series at Metsähovi station spanning ∼40 years from 1980 to 2019 were recently published by Bilker‐Koivula et al. (2021). We adopt the absolute gravity data measured during the GRACE era to verify the GRACE‐derived TWS change.…”

“…The Metsähovi Geodetic Research Station (shown as the red star in Figure 1), subordinated to the Finnish Geospatial Research Institute (FGI), is a stable part of the global network of geodetic core stations within the Global Geodetic Observing System. The absolute gravity time series at Metsähovi station spanning ∼40 years from 1980 to 2019 were recently published by Bilker-Koivula et al (2021). We adopt the absolute gravity data measured during the GRACE era to verify the GRACE-derived TWS change.…”

Search for variability in Newton’s constant using local gravitational acceleration measurements

“…Some examples of these are enumerated in D21, and include tides, polar motion of the Earth, instrumental effects related to the speed of light, gradient height and vertical transfer, etc. Other possibilities include environment effects such as post-glacial rebound [18] or water table changes [19]. A detailed modeling of these additional systematics is beyond the scope of this work.…”

Data Quality Assessment of Time-Variable Surface Microgravity Surveys in the Southeastern Tibetan Plateau

“…Terrestrial gravimetry is usually divided into relative gravimetry and absolute gravimetry [8][9][10][11][12][13]. For decades, with rapid improvement of different high-accuracy gravimeters and development of dense gravity survey networks, repeated surface gravity observations have been available to study geoscientific problems such as crustal deformation [14][15][16], groundwater change [17,18], oil, gas, and mineral exploration [19], glacier mass change [20], volcanoes [21][22][23], and earthquake precursor research [24][25][26][27][28][29][30].…”