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| Titel |
The liquid water balance of the Greenland ice sheet |
| VerfasserIn |
Christian Steger, Carleen Reijmer, Michiel van den Broeke |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250153268
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| Publikation (Nr.) |
 EGU/EGU2017-18220.pdf |
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| Zusammenfassung |
| Mass loss from the Greenland Ice Sheet (GrIS) is an increasingly important contributor to
global sea level rise. During the last decade, the mass loss was dominated by meltwater
runoff. Linking actual runoff from the ice sheet to melt and other forms of liquid water input
at the surface (rainfall and condensation) is however complex, as liquid water may be retained
within the ice sheet due to refreezing and/or (perennial) storage. In the ablation zone on bare
ice, liquid water runs of laterally at the surface, accumulates in supraglacial lakes or enters
the ice sheet’s en- or subglacial hydraulic system via moulins and crevasses. In the higher
elevated accumulation zone, liquid water percolates into the porous firn layer and part
of it may be retained due to refreezing and/or perennial storage in so called firn
aquifers.
In this study, we investigate the liquid water balance of the GrIS focussing on the
role of the firn layer. For this purpose, we ran SNOWPACK, a relatively complex
one-dimensional snow model, on a horizontal resolution of ∼ 11km and for the transient
period of 1960 to 2015. At the snow-atmosphere-interface, the model was forced by
output of the regional atmospheric climate model RACMO2.3. A comparison of
SNOWPACK with in-situ observations (firn density profiles) and remote sensing
data (firn aquifer locations inferred from radar measurements) indicated a good
agreement for most climatic conditions. On a GrIS-wide scale, the modelled surface
mass balance of SNOWPACK exhibits, in combination with ice-discharge data for
ocean-terminating glaciers, an excellent agreement with GRACE data for the period 2003 -
2012.
GrIS-integrated amounts of surface melt reveal a significant positive trend (+11.6Gta−2) in
the second half of the simulation period. Within this interval, the trend in runoff is
larger (+8.3Gta−2) than the one in refreezing (+3.6Gta−2), which results in
an overall decrease of the refreezing fraction. This decrease is for instance less
pronounced in the south-eastern area of the GrIS, where the refreezing fraction
is comparably high (∼ 0.75) due to large amounts of available pore space. This
area also indicates the highest increase in the modelled areal firn aquifer extent
(+343km2 a−1). Generally, many components of the liquid water balance reveal
distinctively different magnitudes and temporal patterns on a local, basin-wide scale. |
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