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| Titel |
Seismic Constraints on the Mantle Viscosity Structure beneath Antarctica |
| VerfasserIn |
Douglas Wiens, David Heeszel, Richard Aster, Andrew Nyblade, Terry Wilson |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108009
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| Publikation (Nr.) |
 EGU/EGU2015-7738.pdf |
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| Zusammenfassung |
| Lateral variations in upper mantle viscosity structure can have first order effects on glacial
isostatic adjustment. These variations are expected to be particularly large for the Antarctic
continent because of the stark geological contrast between ancient cratonic and
recent tectonically active terrains in East and West Antarctica, respectively. A large
misfit between observed and predicted GPS rates for West Antarctica probably
results in part from the use of a laterally uniform viscosity structure. Although not
linked by a simple relationship, mantle seismic velocities can provide important
constraints on mantle viscosity structure, as they are both largely controlled by
temperature and water content. Recent higher resolution seismic models for the
Antarctic mantle, derived from data acquired by new seismic stations deployed in the
AGAP/GAMSEIS and ANET/POLENET projects, offer the opportunity to use the seismic
velocity structure to place new constraints on the viscosity of the Antarctic upper
mantle.
We use an Antarctic shear wave velocity model derived from array analysis of Rayleigh
wave phase velocities [Heeszel et al, in prep] and examine a variety of methodologies for
relating seismic, thermal and rheological parameters to compute a suite of viscosity models
for the Antarctic mantle. A wide variety of viscosity structures can be derived using various
assumptions, but they share several robust common elements. There is a viscosity
contrast of at least two orders of magnitude between East and West Antarctica at
depths of 80-250 km, reflecting the boundary between cold cratonic lithosphere in
East Antarctica and warm upper mantle in West Antarctica. The region beneath the
Ellsworth-Whitmore Mtns and extending to the Pensacola Mtns. shows intermediate viscosity
between the extremes of East and West Antarctica. There are also significant variations
between different parts of West Antarctica, with the lowest viscosity occurring beneath
the Marie Byrd Land (MBL). The MBL Dome and adjacent coastal areas show
extremely low viscosity (~1018Pa-s) for most parameterizations, suggesting that low
mantle viscosity may produce a very rapid response to ice mass loss in this region. |
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