Hypsometric amplification and routing moderation of Greenland ice sheet meltwater release
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 the Watson River in southwest Greenland, with an accurate, observation-based ice sh...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-06-01
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| Series: | The Cryosphere |
| Online Access: | http://www.the-cryosphere.net/11/1371/2017/tc-11-1371-2017.pdf |
| Summary: | 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
the
Watson River in southwest Greenland, with an accurate, observation-based ice
sheet surface mass balance model of the ∼ 12 000 km<sup>2</sup> ice
sheet area feeding the river. For the 2006–2015 decade, we find a large range of a factor of 3 in interannual variability in discharge. The amount of
discharge is amplified ∼ 56 % by the ice sheet's hypsometry,
i.e., 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 1 week for the upper
reaches of the runoff area at ∼ 1800 m above sea level. These
multi-day routing delays ensure that the highest proglacial discharge levels
and thus overbank flooding events are more likely to occur after multi-day
melt episodes. Finally, for the Watson River ice sheet catchment, we find no
evidence of meltwater storage in or release from the en- and subglacial
environments in quantities exceeding our methodological uncertainty, based on
the good match between ice sheet runoff and proglacial discharge. |
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| ISSN: | 1994-0416 1994-0424 |