Mantle Viscosity in Fennoscandia from GRACE and an Ensemble of 3-D Thermo-mechanically Coupled Ice Sheet Models
Abstract
The Gravity Recovery and Climate Experiment (GRACE) satellite mission allows among others identification of solid Earth processes such as glacial isostatic adjustment (GIA). We use the latest release of monthly GRACE solutions from several analysis centers to determine the long-term mass change in Fennoscandia, which shows a clear GIA signature. In the next step, we apply the viscoelastic normal-mode method to determine the best-fitting combination of a radial (1-D) viscosity profile and lithospheric thickness for Fennoscandia from these mass change signals. For surface loading, we use a high variance subset of ice sheet histories from a large calibrated ensemble of glaciological model runs. The calibration set for the ensemble include relative sea-level records, present-day vertical velocities, and geologically inferred ice margin chronologies for the past 30 ka. GSM (Glacial Systems Model) parameters subject to the Bayesian calibration account (in part) for uncertainties in ice physics, climate forcing, and ice-ocean interactions. Independent of the ice sheet model, the results generally agree with earlier results using GRACE and newer results based upon relative sea level and GPS data. Lithospheric thickness in Fennoscandia is found to lie between 90 and 160 km - with a preference to thicker values. Upper mantle viscosity is about [4-7] × 1020 Pa s. Lower mantle viscosity cannot be clearly resolved.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.G11A1055S
- Keywords:
-
- 0726 Ice sheets;
- CRYOSPHEREDE: 1207 Transient deformation;
- GEODESY AND GRAVITYDE: 1236 Rheology of the lithosphere and mantle;
- GEODESY AND GRAVITYDE: 8162 Rheology: mantle;
- TECTONOPHYSICS