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| Titel |
How accurately do we know interannual variations of surface mass balance and firn volume in Antarctica? |
| VerfasserIn |
Martin Horwath, Michiel R. van den Broeke, Jan T. M. Lenaerts, Stefan R. M. Ligtenberg, Benoît Legrésy, Fabien Blarel |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078774
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| Zusammenfassung |
| Knowing the interannual variations in the Antarctic ice sheet net snow accumulation, or
surface mass balance (SMB), is essential for analyzing and interpreting present-day
observations. For example, accumulation events like the one in East Antarctica in 2009
(Shepherd et al. 2012, Science, doi: 10.1126/science.1228102) challenge our ability to
interpret observed decadal-scale trends in terms of long-term changes versus natural
fluctuations. SMB variations cause changes in the firn density structure, which need to be
accounted for when converting volume trends from satellite altimetry into mass
trends.
Recent assessments of SMB and firn volume variations mainly rely on atmospheric modeling
and firn densification modeling (FDM). The modeling results need observational validation,
which has been limited by now. Geodetic observations by satellite altimetry and satellite
gravimetry reflect interannual firn volume and mass changes, among other signals like
changes in ice flow dynamics. Therefore, these observations provide a means of validating
modeling results over the observational period.
We present comprehensive comparisons between interannual volume variations from
ENVISAT radar altimetry (RA) and firn densification modeling (FDM), and between
interannual mass variations from SMB modeling by the regional atmospheric climate model
RACMO2 and GRACE satellite gravimetry. The comparisons are performed based on time
series with approximately monthly sampling and with the overlapping period from 2002 to
2010. The RA-FDM comparison spans the spatial scales from 27 km to the continental
scale. The mass comparison refers to the regional (drainage basin) and continental
scale.
Overall, we find good agreement between the interannual variations described by the models
and by the geodetic observations. This agreement proves our ability to track and understand
SMB-related ice sheet variations from year to year. The assessment of differences between
modeling and observations allows us to quantify upper bounds on the uncertainties of the
results from either technique. Moreover, the joint analysis of the four techniques aids in
attributing the remaining discrepancies to deficits in individual techniques. These analyses
may guide further improvements in observing and modeling SMB-related ice sheet
variations. |
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