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| Titel |
Changing surface–atmosphere energy exchange and refreezing capacity of the lower accumulation area, West Greenland |
| VerfasserIn |
C. Charalampidis, D. Van As, J. E. Box, M. R. van den Broeke, W. T. Colgan, S. H. Doyle, A. L. Hubbard, M. MacFerrin, H. Machguth, C. J. P. P. Smeets |
| 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. 6 ; Nr. 9, no. 6 (2015-11-18), S.2163-2181 |
| Datensatznummer |
250116873
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| Publikation (Nr.) |
 copernicus.org/tc-9-2163-2015.pdf |
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| Zusammenfassung |
We present 5 years (2009–2013) of automatic weather station measurements
from the lower accumulation area (1840 m a.s.l. – above sea level) of the Greenland
ice sheet in the Kangerlussuaq region. Here, the summers of 2010 and 2012
were both exceptionally warm, but only 2012 resulted in a strongly negative
surface mass budget (SMB) and surface meltwater run-off. The observed run-off
was due to a large ice fraction in the upper 10 m of firn that prevented
meltwater from percolating to available pore volume below. Analysis reveals
an anomalously low 2012 summer-averaged albedo of 0.71 (typically ~ 0.78),
as meltwater was present at the ice sheet surface. Consequently,
during the 2012 melt season, the ice sheet surface absorbed 28 % (213 MJ m−2)
more solar radiation than the average of all other years.
A surface energy balance model is used to evaluate the seasonal and
interannual variability of all surface energy fluxes. The model reproduces
the observed melt rates as well as the SMB for each season. A sensitivity
analysis reveals that 71 % of the additional solar radiation in 2012 was
used for melt, corresponding to 36 % (0.64 m) of the 2012 surface
lowering. The remaining 64 % (1.14 m) of surface lowering resulted from
high atmospheric temperatures, up to a +2.6 °C daily average,
indicating that 2012 would have been a negative SMB year at this site even
without the melt–albedo feedback.
Longer time series of SMB, regional temperature, and remotely sensed albedo
(MODIS) show that 2012 was the first strongly negative SMB year, with the
lowest albedo, at this elevation on record. The warm conditions of recent
years have resulted in enhanced melt and reduction of the refreezing capacity
in the lower accumulation area. If high temperatures continue, the current
lower accumulation area will turn into a region with superimposed ice in coming years. |
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