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| Titel |
Multi-modal albedo distributions in the ablation area of the southwestern Greenland Ice Sheet |
| VerfasserIn |
S. E. Moustafa, A. K. Rennermalm, L. C. Smith, M. A. Miller, J. R. Mioduszewski, L. S. Koenig, M. G. Hom, C. A. Shuman |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 9, no. 3 ; Nr. 9, no. 3 (2015-05-07), S.905-923 |
| Datensatznummer |
250116792
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| Publikation (Nr.) |
 copernicus.org/tc-9-905-2015.pdf |
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| Zusammenfassung |
| Surface albedo is a key variable controlling solar radiation absorbed at the
Greenland Ice Sheet (GrIS) surface and, thus, meltwater production. Recent
decline in surface albedo over the GrIS has been linked to enhanced snow
grain metamorphic rates, earlier snowmelt, and amplified melt–albedo feedback
from atmospheric warming. However, the importance of distinct surface types
on ablation area albedo and meltwater production is still relatively
unknown. In this study, we analyze albedo and ablation rates using in situ
and remotely sensed data. Observations include (1) a new high-quality in
situ spectral albedo data set collected with an Analytical Spectral Devices
Inc. spectroradiometer measuring at 325–1075 nm along a 1.25 km transect
during 3 days in June 2013; (2) broadband albedo at two automatic weather
stations; and (3) daily MODerate Resolution Imaging Spectroradiometer (MODIS)
albedo (MOD10A1) between 31 May and 30 August 2012 and 2013. We find that
seasonal ablation area albedos in 2013 have a bimodal distribution, with
snow and ice facies characterizing the two peaks. Our results show that a
shift from a distribution dominated by high to low albedos corresponds to an
observed melt rate increase of 51.5% (between 10–14 July and 20–24
July 2013). In contrast, melt rate variability caused by albedo changes
before and after this shift was much lower and varied between
~10 and 30% in the melting season. Ablation area albedos in
2012 exhibited a more complex multimodal distribution, reflecting a
transition from light to dark-dominated surface, as well as sensitivity to
the so called "dark-band" region in southwest Greenland. In addition to a
darkening surface from ice crystal growth, our findings demonstrate that
seasonal changes in GrIS ablation area albedos are controlled by changes in
the fractional coverage of snow, bare ice, and impurity-rich surface types.
Thus, seasonal variability in ablation area albedos appears to be regulated
primarily as a function of bare ice expansion at the expense of snow,
surface meltwater ponding, and melting of outcropped ice layers enriched
with mineral materials, enabling dust and impurities to accumulate. As
climate change continues in the Arctic region, understanding the seasonal
evolution of ice sheet surface types in Greenland's ablation area is
critical to improve projections of mass loss contributions to sea level
rise. |
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