Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
doi:10.5194/tc-2016-285
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
02 Jan 2017
Review status
This discussion paper is under review for the journal The Cryosphere (TC).
Hypsometric amplification and routing moderation of Greenland ice sheet meltwater release
Dirk van As1, Andreas Bech Mikkelsen2, Morten Holtegaard Nielsen3, Jason Box1, Lillemor Claesson Liljedahl4, Katrin Lindbäck5, Lincoln Pitcher6, and Bent Hasholt2 1Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350 Copenhagen, Denmark
2Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen, Denmark
3Marine Science & Consulting, Peder Lykkes Vej 8, 4. th, 2300 Copenhagen, Denmark
4Svensk Kärnbränslehantering AB, Research and Safety Assessment, Box 250, SE-101 24 Stockholm, Sweden
5Norwegian Polar Institute, Framsentret, Postboks 6606, Langnes, 9296 Tromsø, Norway
6Department of Geography, University of California – Los Angeles, Los Angeles, California, USA 90095
Abstract. Concurrent ice sheet surface runoff and proglacial discharge monitoring are essential for understanding Greenland ice sheet meltwater release. We use an updated, well-constrained river discharge time series from Watson River in southwest Greenland, with an accurate, observation-based ice sheet surface mass balance model of the ca. 12,000 km2 ice sheet area feeding the river. For the 2006–2015 decade, we find that the large, factor of three range in interannual variability is for ca. 56 % caused by hypsometric amplification through ice sheet area increase with elevation. A good match between river discharge and ice sheet surface meltwater production is found after introducing elevation-dependent transit delays that moderate diurnal variability in meltwater release by a factor of 10–20. The routing lag time increases with ice sheet elevation and attains values in excess of one week for the upper reaches of the runoff area at ca. 1800 m above sea level. These multi-day routing delays yield that the highest proglacial discharge levels, and thus overbank flooding events, are more likely to occur after multi-day melt episodes. Finally, we conclude that there is little evidence of meltwater storage in or release from the en- and subglacial environments based on the unprecedented good match between ice sheet runoff and proglacial discharge.

Citation: van As, D., Bech Mikkelsen, A., Holtegaard Nielsen, M., Box, J., Claesson Liljedahl, L., Lindbäck, K., Pitcher, L., and Hasholt, B.: Hypsometric amplification and routing moderation of Greenland ice sheet meltwater release, The Cryosphere Discuss., doi:10.5194/tc-2016-285, in review, 2017.
Dirk van As et al.
Dirk van As et al.
Dirk van As et al.

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Short summary
Ice sheet melt and proglacial river monitoring are essential for understanding Greenland ice sheet meltwater release. For a large ice sheet area in southwest Greenland, meltwater production is for ca. 56 % amplified by the shape of the ice sheet (it flattens with elevation as opposed to mountain glaciers), and more so in other regions of the ice sheet. It takes up to one week for meltwater to escape the ice sheet. There is no evidence of meltwater storage in or under the ice sheet.
Ice sheet melt and proglacial river monitoring are essential for understanding Greenland ice...
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