Supraglacial streamflow and meteorological drivers from southwest Greenland
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Published:2022-06-14
Issue:6
Volume:16
Page:2245-2263
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ISSN:1994-0424
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Container-title:The Cryosphere
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language:en
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Short-container-title:The Cryosphere
Author:
Muthyala RohiORCID, Rennermalm Åsa K.ORCID, Leidman Sasha Z.ORCID, Cooper Matthew G., Cooley Sarah W., Smith Laurence C., van As DirkORCID
Abstract
Abstract. Greenland ice sheet surface runoff is drained through supraglacial
stream networks. This evacuation influences surface mass balance as well as
ice dynamics. However, in situ observations of meltwater discharge through
these stream networks are rare. In this study, we present 46 discrete
discharge measurements and continuous water level measurements for 62 d
spanning the majority of of the melt season (13 June to 13 August) in 2016 for a 0.6 km2 supraglacial stream catchment in southwest Greenland. The result is
an unprecedentedly long record of supraglacial discharge that captures both
diurnal variability and changes over the melt season. A comparison of
surface energy fluxes to stream discharge reveals shortwave radiation as the
primary driver of melting. However, during high-melt episodes, the
contribution of shortwave radiation to melt energy is reduced by
∼40 % (from 1.13 to 0.73 proportion). Instead, the relative
contribution of longwave radiation, sensible heat fluxes, and latent heat fluxes to
overall melt increases by ∼24 %, 6 %, and 10 %
(proportion increased from −0.32 to −0.08, 0.28 to 0.34, and −0.04 to 0.06)
respectively. Our data also identify that the timing of daily maximum
discharge during clear-sky days shifts from 16:00 local time (i.e., 2 h
45 min after solar noon) in late June to 14:00 in late July and then
rapidly returns to 16:00 in early August. The change in the timing of daily
maximum discharge could be attributed to the expansion and contraction of
the stream network, caused by skin temperatures that likely fell below freezing at night.
The abrupt shift, in early August, in the timing of daily maximum discharge
coincides with a drop in air temperature, a drop in the amount of water temporarily stored in
weathering crust, and a decreasing covariance between stream velocity and
discharge. Further work is needed to investigate if these results can be
transferable to larger catchments and uncover if rapid shifts in
the timing of peak discharge are widespread across Greenland supraglacial streams and
thus have an impact on meltwater delivery to the subglacial system
and ice dynamics.
Funder
Earth Sciences Division
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Water Science and Technology
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