TY - JOUR
T1 - Hypsometric amplification and routing moderation of Greenland ice sheet meltwater release
AU - van As, Dirk
AU - Mikkelsen, Andreas Bech
AU - Nielsen, Morten Holtegaard
AU - Box, Jason E.
AU - Liljedahl, Lillemor Claesson
AU - Lindbäck, Katrin
AU - Pitcher, Lincoln
AU - Hasholt, Bent
N1 - Publisher Copyright:
© Author(s) 2017.
PY - 2017/6/9
Y1 - 2017/6/9
N2 - Concurrent ice sheet surface runoff and proglacial discharge monitoring are essential for understanding Greenland ice sheet meltwater release. We use an updated, wellconstrained 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
2 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 elevationdependent 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 ∼1800m 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 multiday 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.
AB - Concurrent ice sheet surface runoff and proglacial discharge monitoring are essential for understanding Greenland ice sheet meltwater release. We use an updated, wellconstrained 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
2 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 elevationdependent 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 ∼1800m 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 multiday 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.
UR - http://www.scopus.com/inward/record.url?scp=85020656238&partnerID=8YFLogxK
U2 - 10.5194/tc-11-1371-2017
DO - 10.5194/tc-11-1371-2017
M3 - Article
VL - 11
SP - 1371
EP - 1386
JO - Cryosphere
JF - Cryosphere
SN - 1994-0416
IS - 3
ER -