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| Titel |
Changes in the firn structure of the western Greenland Ice Sheet caused by recent warming |
| VerfasserIn |
S. Peña, I. M. Howat, P. W. Nienow, M. R. Broeke, E. Mosley-Thompson, S. F. Price, D. Mair, B. Noël, A. J. Sole |
| 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 (2015-06-11), S.1203-1211 |
| Datensatznummer |
250116810
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| Publikation (Nr.) |
 copernicus.org/tc-9-1203-2015.pdf |
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| Zusammenfassung |
| Atmospheric warming over the Greenland Ice Sheet during the
last 2 decades has increased the amount of surface meltwater production,
resulting in the migration of melt and percolation regimes to higher
altitudes and an increase in the amount of ice content from refrozen
meltwater found in the firn above the superimposed ice zone. Here we present
field and airborne radar observations of buried ice layers within the
near-surface (0–20 m) firn in western Greenland, obtained from campaigns
between 1998 and 2014. We find a sharp increase in firn-ice content in the
form of thick widespread layers in the percolation zone, which decreases the
capacity of the firn to store meltwater. The estimated total annual ice
content retained in the near-surface firn in areas with positive surface
mass balance west of the ice divide in Greenland reached a maximum of
74 ± 25 Gt in 2012, compared to the 1958–1999 average of 13 ± 2 Gt,
while the percolation zone area more than doubled between 2003 and 2012.
Increased melt and column densification resulted in surface lowering
averaging −0.80 ± 0.39 m yr−1 between 1800 and 2800 m in the
accumulation zone of western Greenland. Since 2007, modeled annual melt and
refreezing rates in the percolation zone at elevations below 2100 m surpass
the annual snowfall from the previous year, implying that mass gain in the
region is retained after melt in the form of refrozen meltwater. If current
melt trends over high elevation regions continue, subsequent changes in firn
structure will have implications for the hydrology of the ice sheet and
related abrupt seasonal densification could become increasingly significant
for altimetry-derived ice sheet mass balance estimates. |
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