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| Titel |
Comparing a thermo-mechanical Weichselian Ice Sheet reconstruction to reconstructions based on the sea level equation: aspects of ice configurations and glacial isostatic adjustment |
| VerfasserIn |
P. Schmidt, B. Lund, J.-O. Näslund, J. Fastook |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 5, no. 1 ; Nr. 5, no. 1 (2014-05-26), S.371-388 |
| Datensatznummer |
250115274
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| Publikation (Nr.) |
 copernicus.org/se-5-371-2014.pdf |
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| Zusammenfassung |
In this study we compare a recent reconstruction of the Weichselian Ice Sheet
as simulated by the University of Maine ice sheet model (UMISM) to two
reconstructions commonly used in glacial isostatic adjustment (GIA)
modelling: ICE-5G and ANU (Australian National University, also known as
RSES). The UMISM reconstruction is carried out on a regional scale based on
thermo-mechanical modelling, whereas ANU and ICE-5G are global models based
on the sea level equation. The three models of the Weichselian Ice Sheet are
compared directly in terms of ice volume, extent and thickness, as well as in
terms of predicted glacial isostatic adjustment in Fennoscandia.
The three reconstructions display significant differences. Whereas UMISM and
ANU includes phases of pronounced advance and retreat prior to the last
glacial maximum (LGM), the thickness and areal extent of the ICE-5G ice
sheet is more or less constant up until the LGM. During the post-LGM
deglaciation phase ANU and ICE-5G melt relatively uniformly over the entire
ice sheet in contrast to UMISM, which melts preferentially from the edges,
thus reflecting the fundamental difference in the reconstruction scheme.
We find that all three reconstructions fit the present-day uplift rates over
Fennoscandia equally well, albeit with different optimal earth model
parameters. Given identical earth models, ICE-5G predicts the fastest
present-day uplift rates, and ANU the slowest. Moreover, only for ANU can
a unique best-fit model be determined. For UMISM and ICE-5G there is
a range of earth models that can reproduce the present-day uplift rates
equally well. This is understood from the higher present-day uplift rates
predicted by ICE-5G and UMISM, which result in bifurcations in the best-fit
upper- and lower-mantle viscosities.
We study the areal distributions of present-day residual surface velocities
in Fennoscandia and show that all three reconstructions generally
over-predict velocities in southwestern Fennoscandia and that there are large
differences in the fit to the observational data in Finland and northernmost
Sweden and Norway. These difference may provide input to further enhancements
of the ice sheet reconstructions. |
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