Abstract
Global water transport between oceans and continents during the transition from glacial to interglacial times has been enormous. The viscoelastic solid Earth has been responding to this unloading of large ice masses with a rise of the land masses, in a process termed glacial isostatic adjustment. In addition, significant changes in the land/ocean water distribution occur at present. As both present-day changes in the ice/water thickness and glacial isostatic adjustment affect space geodetic measurements, it is difficult to untangle the relative contributions of these two processes. Here we combine gravity measurements and geodetic data of surface movement with a data-assimilating model of ocean bottom pressure to simultaneously estimate present-day water transport and glacial isostatic adjustment. We determine their separate contributions to movements in the geocentre, which occur in response to changes in the Earth’s mass distribution, with uncertainties below 0.1 mm yr−1. According to our estimates, mass losses between 2002 and 2008 in Greenland, Alaska/Yukon and West Antarctica are 104±23, 101±23 and 64±32 Gt yr−1, respectively. Our estimates of glacial isostatic adjustment indicate a large geocentre velocity of −0.72±0.06 mm yr−1 in the polar direction. We conclude that a significant revision of the present estimates of glacial isostatic adjustments and land–ocean water exchange is required.
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Acknowledgements
Part of this work was carried out at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA), and financially supported through NASA’s International Polar Year, GRACE Science Team and MEaSUREs (through a project led by V. Zlotnicki in JPL) programmes. We thank Z. Altamimi, S. Bettadpur, J. Davis, I. Fukumori, F. Landerer, J. Ries, R. Riva, D. Salstein, M. Tamisiea and J. Wahr for discussions and help, and Y. Xu for editorial assistance. The figures are prepared using the GMT graphics package (Wessel and Smith, EOS, 1991).
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X.W. formulated the project, conducted the inverse analysis and wrote the paper. M.B.H. produced the JPL GPS time series and participated in work formulation. H.S. and B.L.A.V. provided the viscoelastic deformation code and contributed to forward modelling of GIA. R.S.G. participated in work formulation and worked on consistency of gravity and polar-wander data. E.R.I. provided the IJ05 model and contributed to work formulation. D.D., A.W.M. and S.E.O. contributed to GPS data processing. All authors read the manuscript and discussed the results.
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Wu, X., Heflin, M., Schotman, H. et al. Simultaneous estimation of global present-day water transport and glacial isostatic adjustment. Nature Geosci 3, 642–646 (2010). https://doi.org/10.1038/ngeo938
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DOI: https://doi.org/10.1038/ngeo938
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