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sábado, setembro 24, 2016

Geodetic measurements reveal similarities between post–Last Glacial Maximum and present-day mass loss from the Greenland ice sheet

Shfaqat A. Khan1,*, Ingo Sasgen2, Michael Bevis3, Tonie van Dam4, Jonathan L. Bamber5, John Wahr6,†, Michael Willis7, Kurt H. Kjær8, Bert Wouters9, Veit Helm2, Beata Csatho10, Kevin Fleming11, Anders A. Bjørk8, Andy Aschwanden12, Per Knudsen1 and Peter Kuipers Munneke9

- Author Affiliations

1DTU Space, National Space Institute, Department of Geodesy, Technical University of Denmark, Kgs. Lyngby, Denmark.

2Glaciology Section, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.

3Geodetic Science, Ohio State University, Columbus, OH 43320, USA.

4Faculty of Science, Technology, and Communication, Research Unit of Engineering Sciences, University of Luxembourg, Luxembourg, Luxembourg.

5Bristol Glaciology Centre, University of Bristol, Bristol, U.K.

6Department of Physics and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA.

7Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY 14853, USA.

8Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.

9Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, Netherlands.

10Department of Geology, University at Buffalo, Buffalo, NY 14260, USA.

11Centre for Early Warning Systems Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Potsdam, Germany.

12Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.

↵*Corresponding author. Email: abbas@space.dtu.dk

↵† Deceased.

Science Advances 21 Sep 2016:

Vol. 2, no. 9, e1600931

Fig. 1 Location map.

Locations of the GNET GPS stations (red dots) and RSL observations (green dots). Black curves denote the major drainage basins numbered from 1 to 7; drainage 3 is separated into subbasins 3A and 3B (inset), the latter representing the near field of the KUAQ glacier. The yellow curve shows a reconstruction of the Iceland hot spot track (57, 58). Bathymetry is shown over the ocean and surface elevation over the land/ice (25).


Accurate quantification of the millennial-scale mass balance of the Greenland ice sheet (GrIS) and its contribution to global sea-level rise remain challenging because of sparse in situ observations in key regions. Glacial isostatic adjustment (GIA) is the ongoing response of the solid Earth to ice and ocean load changes occurring since the Last Glacial Maximum (LGM; ~21 thousand years ago) and may be used to constrain the GrIS deglaciation history. We use data from the Greenland Global Positioning System network to directly measure GIA and estimate basin-wide mass changes since the LGM. Unpredicted, large GIA uplift rates of +12 mm/year are found in southeast Greenland. These rates are due to low upper mantle viscosity in the region, from when Greenland passed over the Iceland hot spot about 40 million years ago. This region of concentrated soft rheology has a profound influence on reconstructing the deglaciation history of Greenland. We reevaluate the evolution of the GrIS since LGM and obtain a loss of 1.5-m sea-level equivalent from the northwest and southeast. These same sectors are dominating modern mass loss. We suggest that the present destabilization of these marine-based sectors may increase sea level for centuries to come. Our new deglaciation history and GIA uplift estimates suggest that studies that use the Gravity Recovery and Climate Experiment satellite mission to infer present-day changes in the GrIS may have erroneously corrected for GIA and underestimated the mass loss by about 20 gigatons/year.

Keywords Sea level rise climate change Greenland Ice Sheet GPS glacial isostatic adjustment Last Glacial Maximum

Copyright © 2016, The Authors

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.

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