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| Titel |
Dust from the dark region in the western ablation zone of the Greenland ice sheet |
| VerfasserIn |
I. G. M. Wientjes, R. S. W. Wal, G. J. Reichart, A. Sluijs, J. Oerlemans  |
| 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 ; 5, no. 3 ; Nr. 5, no. 3 (2011-07-22), S.589-601 |
| Datensatznummer |
250002591
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| Publikation (Nr.) |
 copernicus.org/tc-5-589-2011.pdf |
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| Zusammenfassung |
| A dark region tens of kilometres wide is located in the western ablation
zone of the Greenland ice sheet. The dark appearance is caused by higher
amounts of dust relative to the brighter surroundings. This dust has either been deposited recently or was brought
to the surface by melting of outcropping ice. Because the resulting lower albedos may
have a significant effect on melt rates, we analysed surface dust on the ice, also
called cryoconite, from locations in the dark region as well as locations
from the brighter surrounding reference ice with microscopic and geochemical
techniques to unravel its composition and origin. We find that (part of) the
material is derived from the outcropping ice, and that there is little difference
between dust from the dark region and from the reference ice. The
dust from the dark region seems enriched in trace and minor elements that are
mainly present in the current atmosphere because of anthropogenic activity.
This enrichment is probably caused by higher precipitation and lower melt
rates in the dark region relative to the ice marginal zone. The rare earth
elemental ratios of the investigated material are approximately the same for
all sites and resemble Earth's average crust composition. Therefore, the
cryoconite probably does not contain volcanic material. The mineralogical
composition of the dust excludes Asian deserts, which are often found as
provenance for glacial dust in ice cores, as source regions. Consequently,
the outcropping dust likely has a more local origin. Finally, we find
cyanobacteria and algae in the cryoconite. Total Organic Carbon accounts for
up to 5 weight per cent of the cryoconite from the dark region, whereas
dust samples from the reference ice contain only 1 % or less. This
organic material is likely formed in situ. Because of their high light
absorbency, cyanobacteria and the organic material they produce contribute
significantly to the low albedo of the dark region. |
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