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| Titel |
Ice age True Polar Wander: raising debates and new analyses |
| VerfasserIn |
Roberto Sabadini, Gabriele Cambiotti, Yanick Ricard |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035030
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| Zusammenfassung |
| Issues related to long time scale instability in the Earth’s rotation, named True Polar Wander
(TPW), have continuously been debated, after the pioneering works of the sixties. Since
Maxwell Earth models with elastic or high viscosity viscoelastic lithospheres predict different
ice-age TPW in the lower mantle viscosity range 1021 - 1022 Pa s, it has been recently
suggested that the observed fluid Love number should be used to describe the initial
equatorial bulge rather than the tidal fluid limit resulting from the viscoelastic modelling
itself. We show that different ice-age TPW predictions have to be expected due to the
dependence of TPW on the Earth’s initial state, characterized by a larger and stress-free
equatorial bulge for the viscoelastic lithosphere, compared to the elastic one, and that there is
no shortcomings or errors in the traditional approach based on the use of tidal Love number
from the model. The use of the observed fluid Love number represents in fact a simplified
attempt to couple the effects on TPW from mantle convection and glacial forcing, by
including the non-hydrostatic flattening due to mantle convection but not its driving part. This
partial coupling freezes in space the non-hydrostatic contribution due to mantle
convection, thus damping the present-day ice-age TPW and forcing the axis of
instantaneous rotation to come back to its initial position when ice ages started. In this
perspective, we discuss the implication of self-consistent convection calculations of the
non-hydrostatic contribution and its impact on the long-term Earth’s rotation stability during
ice-age. We develop a full compressible model, based on the numerical integration in
the radial variable of the momentum and Poisson equations and on the contour
integration in the Laplace domain, which allows us to deal with the non-modal
contribution from continuous radial rheological variations. We quantify the effects
of the compressible rheology, compared to the widely used incompressible ones |
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