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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 6 | Copyright
The Cryosphere, 11, 2773-2782, 2017
https://doi.org/10.5194/tc-11-2773-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 05 Dec 2017

Research article | 05 Dec 2017

Satellite-derived submarine melt rates and mass balance (2011–2015) for Greenland's largest remaining ice tongues

Nat Wilson1,2, Fiammetta Straneo3,a, and Patrick Heimbach4 Nat Wilson et al.
  • 1MIT-WHOI Joint Program in Oceanography/Applied Ocean Science and Engineering, Cambridge, Massachusetts, USA
  • 2Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
  • 3Physical Oceanography Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
  • 4Jackson School of Geosciences and Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, Texas, USA
  • anow at: Scripps Institution of Oceanography, UCSD, La Jolla, CA, USA

Abstract. Ice-shelf-like floating extensions at the termini of Greenland glaciers are undergoing rapid changes with potential implications for the stability of upstream glaciers and the ice sheet as a whole. While submarine melting is recognized as a major contributor to mass loss, the spatial distribution of submarine melting and its contribution to the total mass balance of these floating extensions is incompletely known and understood. Here, we use high-resolution WorldView satellite imagery collected between 2011 and 2015 to infer the magnitude and spatial variability of melt rates under Greenland's largest remaining ice tongues – Nioghalvfjerdsbræ (79 North Glacier, 79N), Ryder Glacier (RG), and Petermann Glacier (PG). Submarine melt rates under the ice tongues vary considerably, exceeding 50m a−1 near the grounding zone and decaying rapidly downstream. Channels, likely originating from upstream subglacial channels, give rise to large melt variations across the ice tongues. We compare the total melt rates to the influx of ice to the ice tongue to assess their contribution to the current mass balance. At Petermann Glacier and Ryder Glacier, we find that the combined submarine and aerial melt approximately balances the ice flux from the grounded ice sheet. At Nioghalvfjerdsbræ the total melt flux (14.2±0.96km3 a−1w.e., water equivalent) exceeds the inflow of ice (10.2±0.59km3 a−1w.e.), indicating present thinning of the ice tongue.

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We estimate submarine melt rates from ice tongues in northern Greenland using WorldView satellite imagery. At Ryder Glacier, melt is strongly concentrated around regions where subglacier channels likely enter the fjord. At the 79 North Glacier, we find a large volume imbalance in which melting removes a greater quantity of ice than is replaced by inflow over the grounding line. This leads us to suggest that a reduction in the spatial extent of the ice tongue is possible over the coming decade.
We estimate submarine melt rates from ice tongues in northern Greenland using WorldView...
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