Investigating Surface Gravity and Height Variations due to Glacial Isostatic Adjustment: Insights from GRACE and GRACE-FO Data in Fennoscandia and Canada

Precise gravity measurements have been consistently collected in Fennoscandia and Canada since the 1960s and 1990s, respectively, using relative gravimeters and later employing absolute gravimeters (e.g., FG5 and A10 absolute gravimeters) to establish gravity reference system and study temporal changes in gravity, e.g. associated with ongoing glacial isostatic adjustment (GIA). In this study, we utilized monthly data from GRACE and GRACE Follow-on, spanning 2003 to 2023, to estimate temporal variations in surface gravity changes, their relationship with land uplift rates, and to determine the upper mantle density associated with viscous mass flow in the mantle. The main focus of this paper is Canada; however, the results will be compared with our previous studies in Fennoscandia. We used the ICE-6G_D land uplift model for Canada and the NKG2016LU regional land uplift model for Fennoscandia for this purpose. The satellite gravimetry results were compared with terrestrial absolute gravity observations collected at 43 stations across Canada and Fennoscandia, respectively.

The results derived from GRACE and GRACE Follow-on data show that the ratio between surface gravity and height changes is −0.152 ± 0.010 μGal/mm in Canada and −0.156 ± 0.016 μGal/mm in Fennoscandia aligning closely with findings from terrestrial gravity observations. These values correspond to upper mantle densities of approximately 3736 ± 239 kg/m³ and 3641 ± 382 kg/m³ in Canada and Fennoscandia, respectively. In addition, the results were combined with terrestrial absolute gravimetry results. These findings highlight the importance of satellite gravimetry data and are crucial for GIA modeling and the Earth’s interior parameters.