The long-term GIA signal at present-day in Scandinavia, northern Europe and the British Isles estimated from GPS and GRACE data

Abstract. The long-term glacial isostatic adjustment (GIA) signal at present-day is constrained via joint inversion of GPS vertical land motion rates and GRACE gravity data for a region encompassing Scandinavia, northern Europe and the British Isles, and the Barents Sea. The best-fit model for the vertical motion signal has a χ2 value of approximately 1 and a maximum posterior uncertainty of 0.3–0.4 mm/yr. An elastic correction is applied to the vertical land motion rates that accounts for present-day changes to terrestrial hydrology as well as recent mass changes of ice sheets and glaciered regions. Throughout the study area, mass losses from Greenland dominate the elastic vertical signal and combine to give an elastic correction of up to +0.5 mm/yr in central Scandinavia. Neglecting to use an elastic correction may thus introduce a small but persistent bias in model predictions of GIA vertical motion even in central Scandinavia where vertical motion is dominated by long-term GIA. The predicted gravity signal is generally less well-constrained than the vertical signal, in part due to uncertainties associated with the correction for contemporary ice mass loss in Svalbard and the Russian Arctic. The GRACE-derived gravity trend is corrected for present-day ice mass loss using estimates derived from the ICESat and CryoSat missions, although a difference in magnitude between GRACE-inferred and altimetry-inferred regional mass loss rates suggests the possibility of a non-negligible GIA response here either from millennial-scale or Little Ice Age GIA.