FAST TRACK PAPER: Inference of mantle viscosity from GRACE and relative sea level data

Details FAST TRACK PAPER: Inference of mantle viscosity from GRACE and relative sea level data FAST TRACK PAPER: Inference of mantle viscosity from GRACE and relative sea level data

Nov 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007geoji.171..497p&link_type=abstract

Geophysical Journal International, Volume 171, Issue 4, pp. 497-508.

Astronomy and Astrophysics

Astronomy

49

Inversion, Mantle Viscosity, Post-Glacial Rebound, Time-Varying Gravity

Scientific paper

Gravity Recovery And Climate Experiment (GRACE) satellite observations of secular changes in gravity near Hudson Bay, and geological measurements of relative sea level (RSL) changes over the last 10000 yr in the same region, are used in a Monte Carlo inversion to infer-mantle viscosity structure. The GRACE secular change in gravity shows a significant positive anomaly over a broad region (>3000 km) near Hudson Bay with a maximum of ~2.5 μGalyr-1 slightly west of Hudson Bay. The pattern of this anomaly is remarkably consistent with that predicted for postglacial rebound using the ICE-5G deglaciation history, strongly suggesting a postglacial rebound origin for the gravity change. We find that the GRACE and RSL data are insensitive to mantle viscosity below 1800 km depth, a conclusion similar to that from previous studies that used only RSL data. For a mantle with homogeneous viscosity, the GRACE and RSL data require a viscosity between 1.4 × 1021 and 2.3 × 1021 Pas. An inversion for two mantle viscosity layers separated at a depth of 670km, shows an ensemble of viscosity structures compatible with the data. While the lowest misfit occurs for upper- and lower-mantle viscosities of 5.3 × 1020 and 2.3 × 1021 Pas, respectively, a weaker upper mantle may be compensated by a stronger lower mantle, such that there exist other models that also provide a reasonable fit to the data. We find that the GRACE and RSL data used in this study cannot resolve more than two layers in the upper 1800 km of the mantle.

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