7/30/2019 Asa's AGU poster
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Ice Sheet Hydrologic Network Examinedwith In Situ River
Discharge from Nested Watersheds in Greenland
sa K. Rennermalm1, A. B. Mikkelsen2, L.C. Smith3, V. W. Chu3, S.
E. Moustafa1, M R. van den Broeke4, Bent Hasholt21Rutgers
University, 2University of Copenhagen, 3University of California
Los Angeles, 4Utrecht University
1. INTRODUCTIONGreenland surface meltwater created on the ice
sheet peripheryand interior surfaces is routed to its margin
through a complexhydrologic network including storage in firn
layers, glaciallakes, streams, and transport pathways through
moulins,crevasses, and other conduits. However, development
andfunctioning of this network is still unclear, partly because of
lack of observational data. In this study, we contrast in situ
icesheet river discharge losses observed at two nested,
andoverlapping drainage basins of difference sizes (~64km 2
and~9,750 km 2) within the Akuliarusiarsuup Kuua (AK) River
watershed (a.k.a. Watson River) in Southwest Greenland
between 2008 and 2012. By analyzing timing, magnitude andextent
of ice sheet surface melting and river discharge insmaller
watersheds nested within larger watersheds, better understanding is
obtained of how scale, space, and timeinfluence storages and export
of meltwater. The rich dataset for the AK River watershed provides
unique insights intodevelopment and functioning of the hydrological
network for one of Greenlands largest land terminating glaciers
.
C43C-0616
4. RESULTS
Discharge: Time series of river discharge were made by
relatingoccasional measurements of river discharge to continuously
monitoredwater depth with a rating curve.Discharge was determined
with thevelocity-area method, and water depthwas calculated from
measurements of atmospheric and water pressure usingSolinst
pressure transducers.
5. CONCLUSIONS
The nested watershed approach provides a method toinvestigate
ice sheet meltwater source area
The importance of ice sheet melt below 850 has declinedfrom 2008
to 2012
In 2009 to 2012 the m ajority of meltwater originated fromhigher
elevations
This agree with satellite remote sensing observations of
expanding ice sheet melt area in recent years
Contact: [email protected]
2. STUDY SITE
3. METHODS
The study was undertakenfor two nested drainagewatersheds of
differencesizes:1) AkuliarusiarsuupKuua (AK) River drainage basin
(~64km 2)collecting meltwater fromthe ice margin2) Watson River
drainage
basin (~9,750 km 2)collecting meltwater fromthe ice margin and
theinterior ice sheet.The AK River is a subwatershed of the
WatsonRiver.
Nested watershed approach:Hydrologic observations of water
export from sub watersheds areassumed representative for similar
elevation bands within the larger catchment. Sub watersheddischarge
is upscaled to match therepresentative area of the larger
basin.
The upper reaches of the nested sub watershed is at 850 m a.s.l.
This marks the boundary for Watson River watersheds ice margin. Sub
watershed elevationdistribution lacks some of low elevations that
are manifested in the Watson icemargin drainage watershed (
