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Deeply incised submarine glacial valleys beneath the Greenland ice sheet


The bed topography beneath the Greenland ice sheet controls the flow of ice and its discharge into the ocean. Outlet glaciers move through a set of narrow valleys whose detailed geometry is poorly known, especially along the southern coasts1,2,3. As a result, the contribution of the Greenland ice sheet and its glaciers to sea-level change in the coming century is uncertain4. Here, we combine sparse ice-thickness data derived from airborne radar soundings with satellite-derived high-resolution ice motion data through a mass conservation optimization scheme5. We infer ice thickness and bed topography along the entire periphery of the Greenland ice sheet at an unprecedented level of spatial detail and precision. We detect widespread ice-covered valleys that extend significantly deeper below sea level and farther inland than previously thought. Our findings imply that the outlet glaciers of Greenland, and the ice sheet as a whole, are probably more vulnerable to ocean thermal forcing and peripheral thinning than inferred previously from existing numerical ice-sheet models.

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Figure 1: Bed elevation of the Greenland ice sheet colour-coded between −500 and +2,000 m, with submarine areas in blue.
Figure 2: Bed elevation of Upernavik Isstrøm South, West Greenland.


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This work was performed at the University of California Irvine and the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA, Cryospheric Sciences Program grant NNX12AB86G. CReSIS data products are from NSF grant ANT-0424589 and NASA grant NNX10AT68G. Ice-thinning rates are from NCAR/EOL funded by NSF. SMB data is from M. van den Broeke, University of Utrecht, The Netherlands. The bathymetry data described in Supplementary Information are a product of Grant 2980 from the Gordon and Betty Moore Foundation.

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M.M. developed the algorithm and led the calculations. H.S. assisted in implementing the algorithm. J.M. provided velocity mapping. All authors contributed to the writing of the paper.

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Correspondence to M. Morlighem.

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The authors declare no competing financial interests.

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Morlighem, M., Rignot, E., Mouginot, J. et al. Deeply incised submarine glacial valleys beneath the Greenland ice sheet. Nature Geosci 7, 418–422 (2014).

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