Constraint of GIA in Northern Europe with Geological RSL and VLM Data

In this study, we focus on better constraint of the long term glacial isostatic adjustment (GIA) signal at present-day, and its role as a contributor to total present-day rates of change. The main study area extends from the coastal regions of northern Europe to Scandinavia. Both Holocene relative sea level (RSL) data as well as vertical land motion (VLM) data are incorporated as constraints in a semi-empirical GIA model. Specifically, 70 geological rates of GIA-driven RSL change are inferred from Holocene data; peak RSL fall is indicated in central Scandinavia and the northern British Isles where past ice sheets were thickest, RSL rise is indicated in the southern British Isles and along the northern European coastline. Rates of vertical land motion from GPS at 108 sites provide an additional measure of regional GIA deformation. Within the study area, the geological RSL data complement the spatial gaps of the VLM data and vice versa; both datasets are inverted in a semi-empirical GIA model to yield updated estimates of regional present-day GIA deformations. A regional validation is presented for the North Sea, where the GIA signal may be complicated by lateral variations in Earth structure and existing predictions of regional and global GIA models are discrepant. The model validation in the North Sea region indicates that geological data are needed to fit independent estimates of GIA-related RSL change inferred from tide gauge rates, suggesting that the geological rates provide an important additional constraint of present-day GIA.