The contribution of glacial isostatic adjustment to relative sea-level rise and land subsidence along the Atlantic coast of Europe

We quantify the contribution of glacial isostatic adjustment (GIA) to land subsidence and sea-level rise along the Atlantic coast of Europe. Using both geologic reconstructions of relative sea-level (RSL) change and geodetic determinations of vertical land motion, we assess GIA model accuracy and determine model parametric uncertainty. Seven ice history models and 440 spherically symmetric Earth viscosity models were used to explore the model parameter space. Our results indicate that the inferred earth model parameters are highly dependent on the barystatic component of the adopted ice sheet model. On the other hand, the modelled RSL output is relatively insensitive to variations in the ice thickness distribution of the Eurasian component of the ice history model. Of the two global ice models considered (ANU and ICE-6G) our results demonstrate the barystatic component of the ANU model to be more accurate. Model uncertainty was determined using data-model misfit values and a Bayesian approach to define a subset of parameter sets (1σ confidence). When considering the model uncertainty, 95 % of the Holocene RSL observations and 93 % of the present-day vertical land motion rates can be explained at this confidence level. Our results support previous work in showing that GIA-related subsidence along the Atlantic coast of Europe is dominated by ice-loading (peripheral bulge) effects and that ocean loading is also important in some areas, such as northwestern France. Using our subset of best-fitting parameter sets, we performed a sea-level budget analysis for the period 1957 to 1997 using data from 10 tide gauges in our study region and find that the sterodynamic signal is the largest contributor at most of the considered tide gauge sites, followed by contributions from GIA and glaciers. The GIA signal dominates the modelled uncertainty at all sites. Of the 10 tide gauge stations considered, the budget is closed at six (to within 2σ uncertainty). The largest residual was found for station Dieppe in northern France, with an unexplained signal of 3.8 ± 0.6 mm/yr, which appears to be related to localized subsidence at the tide gauge site.