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Mass changes and flow in the Earth's mantle causes the Earth's crust not only to move vertically, but also horizontally and to tilt, and produce a major stress in the lithosphere. Here we use a gravimetric approach to model sub-lithosphere horizontal stress in the Earth's mantle and its temporal changes caused by geodynamical movements like mantle convection in Fennoscandia. The flow in the mantle is inferred from tectonics and convection currents carrying heat from the interior of the Earth to the crust. The result is useful in studying how changes of the stress influence the stability of crust. The outcome of this study is an alternative approach to studying the stress and its change using forward modelling and the Earth's viscoelastic models. We show that the determined horizontal stress using a gravimetric method is consistent with tectonics and seismic activities. In addition, the secular rate of change of the horizontal stress, which is within 95 kPa/year, is larger outside the uplift dome than inside. [ABSTRACT FROM AUTHOR]

Abstract: The crustal thickness can be determined based on gravimetric–isostatic and seismic models. Modelling crustal thickness by a gravimetric–isostatic model suffers from some problems. The isostatic assumption for compensating the topographic potential is incomplete, as there are other effects which should be considered. Using the isostatic hypothesis for determining the depth of crust causes some disturbing signals, non-isostatic effects, which influence the crustal thickness determination. Isostatic and non-isostatic compensations are the main issues in this paper. We present three methods to overcome the problem due to the disturbing signals, namely the approach by truncating the spherical harmonic approach, determination of non-isostatic correction using a seismic crustal thickness model (e.g., CRUST2.0) and combination of isostatic and seismic models by applying a least-squares adjustment method. The estimated results of the non-isostatic effects varies between −65.2 and 391.8mGal in Fennoscandia. The root mean squares difference of the crustal thickness obtained from the gravimetric–isostatic model and CRUST2.0 is improved up to six times (from 6.15 to 0.97km) when the non-isostatic effects are considered. [Copyright &y& Elsevier]

Abstract: Atmospheric masses play an important role in precise downward continuation and validation of satellite gravity gradiometry data. In this paper we present two alternative ways to formulate the atmospheric potential. Two density models for the atmosphere are proposed and used to formulate the external and internal atmospheric potentials in spherical harmonics. Based on the derived harmonic coefficients, the direct atmospheric effects on the satellite gravity gradiometry data are investigated and presented in the orbital frame over Fennoscandia. The formulas of the indirect atmospheric effects on gravity anomaly and geoid (downward continued quantities) are also derived using the proposed density models. The numerical results show that the atmospheric effect can only be significant for precise validation or inversion of the GOCE gradiometric data at the mE level. [Copyright &y& Elsevier]

Precise gravity measurements have been repeatedly observed in Fennoscandia since the 1960-ties, first by relative gravimeters, then by absolute gravimeters, for studying the temporal change of gravity related with the on-going glacial isostatic adjustment (GIA). The results of such studies are vital for understanding GIA processes and tuning GIA and Earth structure models. This study uses monthly repeated data from the twin satellite mission GRACE for 164 months between 2003 and 2016 for estimating the temporal change of surface gravity, its ratio (f) to the land uplift rate as well as the upper mantle density related with the viscous mass flow in the mantle. The maximum negative change of gravity is estimated to −1.8 μGal/yr, and f is estimated to −0.172 ± 0.018 μGal/mm. The solutions for f from the three independent techniques (relative, absolute and satellite gravity observations) were found to agree statistically without significant biases, and they were merged in a joint solution to −0.166 ± 0.004 μGal/mm, corresponding to a mean upper mantle mass flow density of 3402.5 ± 95 kg/m3, which decreases towards the uplift center. • Applying GRACE data to model upper mantle density and surface gravity change • Comparing the results with relative and absolute gravity observations • A combined solution for the above-mentioned ratio is presented in this study. [ABSTRACT FROM AUTHOR]