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Localization of the gravity field and the signature of glacial rebound

Simons, Mark and Hager, Bradford H. (1997) Localization of the gravity field and the signature of glacial rebound. Nature, 390 (6659). pp. 500-504. ISSN 0028-0836. doi:10.1038/37339.

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The negative free-air gravity anomaly centred on Hudson Bay, Canada, shows a remarkable correlation with the location of the Laurentide ice sheet, suggesting that this gravity anomaly is the result of incomplete post-glacial rebound. This region, however, is also underlain by higher-than-average mantle seismic velocities, suggesting that the gravity low might result instead from dynamic topography associated with convective downwellings. Here we analyse the global gravity field as a simultaneous function of geographic location and spectral content. We find that the Hudson Bay gravity low is unique, with anomalously high amplitude in the spectral band where the power from the Laurentide ice load is greatest and the relaxation times predicted for viable models of viscous relaxation are longest. We estimate that about half of the Hudson Bay gravity anomaly is the result of incomplete post-glacial rebound, and derive a mantle viscosity model that explains both this gravity signature and the characteristic uplift rates for the central Laurentide and Fennoscandian regions. This model has a jump in viscosity at 670 km depth, comparable to that in dynamic models of the geoid highs over subducted slabs, but lacks a low-viscosity asthenosphere, consistent with a higher viscosity in the upper mantle beneath shields than in oceanic regions.

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Simons, Mark0000-0003-1412-6395
Hager, Bradford H.0000-0002-5643-1374
Additional Information:© 1997 Macmillan Publishers Ltd. Received 27 January 1997; Accepted 23 September 1997. We thank M. Fang, M. Gurnis and S. Zhong for constructive discussions, as well as J. X. Mitrovica for a thorough review. This work was supported by NASA.
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Issue or Number:6659
Record Number:CaltechAUTHORS:20130610-102157743
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38876
Deposited By: Tony Diaz
Deposited On:24 Jun 2013 23:04
Last Modified:09 Nov 2021 23:40

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