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| Titel |
Greenland ice sheet albedo feedback: thermodynamics and atmospheric drivers |
| VerfasserIn |
J. E. Box, X. Fettweis, J. C. Stroeve, M. Tedesco, D. K. Hall, K. Steffen |
| 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 ; 6, no. 4 ; Nr. 6, no. 4 (2012-08-08), S.821-839 |
| Datensatznummer |
250003694
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| Publikation (Nr.) |
 copernicus.org/tc-6-821-2012.pdf |
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| Zusammenfassung |
| Greenland ice sheet mass loss has accelerated in the past
decade responding to combined glacier discharge and surface
melt water runoff increases. During summer, absorbed solar
energy, modulated at the surface primarily by albedo, is the
dominant factor governing surface melt variability in the ablation
area. Using satellite-derived surface albedo with calibrated regional
climate modeled surface air temperature and surface downward solar
irradiance, we determine
the spatial dependence and quantitative impact of the ice
sheet albedo feedback over 12 summer periods beginning in 2000. We find
that, while albedo feedback defined by the change in net solar shortwave flux
and temperature over time is positive over 97% of the ice sheet, when
defined using paired annual anomalies, a second-order negative feedback is
evident over 63% of the accumulation area. This negative feedback damps
the accumulation area response to warming due to a positive correlation
between snowfall and surface air temperature anomalies. Positive
anomaly-gauged feedback concentrated in the ablation area accounts for more
than half of the overall increase in melting when satellite-derived melt
duration is used to define the timing when net shortwave flux is sunk into
melting. Abnormally strong anticyclonic circulation, associated
with a persistent summer North Atlantic Oscillation extreme
since 2007, enabled three amplifying mechanisms to maximize the
albedo feedback: (1) increased warm (south) air advection along the
western ice sheet increased surface sensible heating that in
turn enhanced snow grain metamorphic rates, further reducing
albedo; (2) increased surface downward shortwave flux,
leading to more surface heating and further albedo reduction;
and (3) reduced snowfall rates sustained low albedo,
maximizing surface solar heating, progressively lowering
albedo over multiple years. The summer net infrared and solar radiation for the
high elevation accumulation area approached positive values
during this period. Thus, it is reasonable to expect 100% melt area over
the ice sheet within another similar decade of warming. |
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