Lithosphere thickness and mantle viscosity estimated from joint inversion of GPS and GRACE-derived radial deformation and gravity rates in North America

The Global Positioning System (GPS) and the Gravity Recovery and Climate Experiment (GRACE) have been used to respectively determine the Earth's surface deformation and gravity changes associated with glacial isostatic adjustment, which is caused by ongoing stress release of the viscoelastic ma...

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Bibliographic Details
Published in:Geophysical Journal International
Main Author: Zhao, S.
Format: Text
Language:English
Published: Oxford University Press 2013
Subjects:
Gravity
geodesy and tides
Hudson
Hudson Bay
Online Access:http://gji.oxfordjournals.org/cgi/content/short/194/3/1455
https://doi.org/10.1093/gji/ggt212
Description
Summary:The Global Positioning System (GPS) and the Gravity Recovery and Climate Experiment (GRACE) have been used to respectively determine the Earth's surface deformation and gravity changes associated with glacial isostatic adjustment, which is caused by ongoing stress release of the viscoelastic mantle after removal of the Late Pleistocene ice sheets. Here we present a joint inversion analysis of GPS-derived radial (vertical) deformation and GRACE-derived gravity rates in North America to examine whether the ice sheets (ICE-3G and ICE-5G) and earth models can fit the satellite based observations. The results of joint inversion give an effective lithosphere thickness of 150 km (110–180 km under a statistical confidence level of 80 per cent), an upper-mantle viscosity of 3.7 (2.0–5.0; 90 per cent confidence level) × 1020 Pa s, and a lower-mantle viscosity of 1.9 (1.3–2.6; 90 per cent confidence level) × 1021 Pa s. More sophisticated models such as introducing a transition zone of 400–670 km are not fully resolved with current data sets because there is no significant improvement in fitting observations. Tests of modifying ICE-5G show that a reduction of ice thickness by ∼20 per cent in the area west of Hudson Bay and an increase by ∼40 per cent in the southeast (Quebec region) are required to fit both observed vertical deformation and gravity changes. An additional test from inversion analysis of GRACE-derived geoid rates confirms possible signal loss in the GRACE-derived gravity rates, which could be due to noise reduction methods used in data processing stages.

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