Glacial isostatic adjustment model with composite 3-D Earth rheology for Fennoscandia

We find that sea level data can be explained with our ice model and with information on mantle rheology from laboratory experiments, heatflow and seismology and a pure olivine rheology above 400 km. Moreover, laterally heterogeneous models provide a significantly better fit to relative sea level data than the VM2 viscosity, for our ice model as well as for the ICE-5G model that is based on the VM2 profile. The new ice model gives different constraints on mantle rheology than the ICE-5G model, indicating a possible bias towards mantle viscosity in the latter or shortcomings in our ice model. Present-day uplift rates for a dry rheology are close to GPS observed uplift rate for certain combinations of grain size and temperature fields. Sea level data show a preference for a wet olivine rheology, but in that case uplift rates are too low for all grain sizes and temperature fields. The difficulty to fit sea level data and uplift rate data simultaneously can not be resolved by varying creep parameters below 400 km. Uncertainties in the flow law and the neglect of other materials in the upper mantle, as well as the neglect of flow in the crust could affect our conclusions.