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| Titel |
New insights on Mantle Convection and Ice Age True Polar Wander |
| VerfasserIn |
Roberto Sabadini, Gabriele Cambiotti, Yanick Ricard |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048573
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| Zusammenfassung |
| True Polar Wander (TPW), the slow motion of the Earth rotation axis with respect to the
mantle, is due to perturbations of the inertia of the planet resulting from internal
and surface mass rearrangements. It is generally taken as evidence of Ice Sheet
melting and Mantle Convection. Owing to the ability of rotational bulge to relax and
readjust to perturbations of rotation axis on timescales T of 1 - 100kyr, TPW
studies often assume that rotational bulge readjusts instantaneously to the Myr
timescale of mantle convection, implying the coincidence between the Earth rotation
axis and the Maximum Inertia Direction of Mantle Convection (MC-MID). This
approximation is herein overcome and our new linearized treatment of the Earth’s
rotation shows that such an approximation missed a fundamental aspect of TPW
dynamics, namely the stabilizing effect due to the bulge from mantle convection
being smaller than the rotational bulge. Such a smallness inhibits the viscoelastic
readjustment of rotational bulge by increasing the timescale T to values comparable to
those of mantle convection. With respect to previous estimates, TPW rates from
mantle convection are now reduced and sizeable offsets of degrees are obtained
between the axis of rotation and the MC-MID for realistic viscosity profiles of the
mantle. These new findings impact the interpretation of present-day TPW data
in terms of the relative contribution from Mantle Convection and from Ice Ages.
Furthermore, they allow to estimate the degree-2 Stokes coefficients C21 and S21 of
the present-day geoid anomalies in a self-consistent way with TPW dynamics. |
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