Three Decades of Repeated Absolute Gravity Measurements at the Finnish Antarctic Research Station Aboa

Abstract Absolute gravity time series from Antarctica are used to study the viscoelastic gravity change and deformation due to Glacial Isostatic Adjustment (GIA) after the Holocene deglaciation. Here we present the three-decades long absolute gravity (AG) time series at the Finnish Antarctic Research Station Aboa. A gravity increase of nearly 50 $$\upmu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> Gal is observed. Comparisons of the gravity trend with the land uplift observed in the Aboa GPS station time series and with GIA model predictions show that GIA can’t explain the observed gravity increase. We use satellite gravimetry and altimetry, GPS measurements, and modelling to interpret the gravity increase. A regional mass increase around Aboa is observed with satellite gravimetry. Satellite altimetry shows positive surface elevation change in the region over the last three decades. GPS-based surface elevation change measurements in the vicinity of Aboa also point to increase snow and ice volume. Increased precipitation in Dronning Maud Land in the 2000s is noted in the literature. Modelling of the direct attraction due to added mass on the ice sheet around Aboa yields gravity change comparable to what is observed in the time series. Consequently the apparent explanation to the gravity increase is the positive mass balance of the seasonal snow close to the gravity laboratory and of the surrounding ice sheet. Increased direct attraction and elastic ground deformation overshadow the viscoelastic GIA signal in the absolute gravity time series. Conversely, absolute gravity time series at Aboa can be used as an independent observation of the mass increase.