On the effect of a low viscosity asthenosphere on the temporal change of the geoid—A challenge for future gravity missions

Marquart, Gabriele; Steinberger, Bernhard; Niehuus, K.

doi:10.1016/j.jog.2005.04.006

Cited by 8 publications

(7 citation statements)

References 40 publications

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“…These kernels are close to those computed in studies based on the best fitting between the observed geoid and the one induced by mantle density heterogeneities derived from tomography and/or geodynamic models (e.g. Steinberger 2000; Marquart et al 2205). These studies assumed a Newtonian viscous stratified mantle.…”

Section: Degree N Viscous Geoid and Topography Kernelssupporting

confidence: 84%

Dynamic mantle density heterogeneities and global geodetic observables

Greff-Lefftz

Métivier

Besse

2010

Geophysical Journal International

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S U M M A R YWe investigate the influence of mantle dynamics on low degree deformations of the Earth at geological timescale. We first compute surface deformations, and discuss the analytical form of the tangential surface displacement induced by internal loads, in a reference frame related to the centre of mass of the planet. We use the theoretical Love numbers formalism since the Earth has a viscoelastic behaviour at geological timescale.Then we quantify degree-one and degree-two deformations induced by upwelling domes and subducted plates sinking into the mantle. We use a simple model in which the slabs are modelled as blobs diving vertically through the mantle, and in which the domes are assumed to be stable over the last 120 Ma. Their location is modelled from seismic tomography within the lower mantle. The temporal evolutions of the J 2 gravitational potential coefficient and of the geocentre motion are plotted since 120 Ma.We find that:(1) The mantle density heterogeneities within the mantle can explain the present-day nonhydrostatic flattening of the Earth. However they vary at a too slow timescale to significantly perturb theJ 2 coefficient.(2) Although there is a significant discrepancy of about a few hundred metres between the centre of figure and the centre of mass of the Earth, the secular variation of the geocentre motion is one order of magnitude smaller than the one induced by surface loads.

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Section: Degree N Viscous Geoid and Topography Kernelssupporting

confidence: 84%

Dynamic mantle density heterogeneities and global geodetic observables

Greff-Lefftz

Métivier

Besse

2010

Geophysical Journal International

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“…Our degree 2 kernel for VR = 40 (solid line) is close to the degree 2 geoid kernel computed in studies based on the best fit between the observed geoid and the one induced by mantle density heterogeneities derived from tomography and/or geodynamic models (e.g. Ricard et al 1993a; Steinberger 2000; Marquart et al 2005). So, we will use this viscosity ratio for our reference model.…”

Section: Viscoelasto‐gravitational Deformations and Mantle Density supporting

confidence: 76%

Length of day variations due to mantle dynamics at geological timescale

Greff-Lefftz

2011

Geophysical Journal International

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S U M M A R YThe geological evolution of length of day (LOD) variations is mainly controlled by the frictional tidal torque responsible for the secular slowdown of the Earth's rotation and for the receding of the Moon. Superimposed on this variation, which has existed since the early history of the planet, there are, at shorter timescales (less than 1 Myr), LOD perturbations induced by the glaciation-deglaciation cycles. In this paper, we investigate the influence of mantle dynamics on LOD at the geological timescale. We use the complete non-linear equations to compute the influence of mantle density heterogeneities on the angular velocity of the rotation, that is to say on the LOD. We discuss the degree zero coefficient of the spherical harmonic expansion of the mantle mass anomaly, which is strongly dependent on the conservation of mass of the Earth.We first compute the effects induced by upwelling domes and subducted plates sinking into the mantle, which are known to induce geological variations in the orientation of the rotation axis with respect to a fixed terrestrial frame (the so-called True Polar Wander). We find that the time-variable mantle density heterogeneities associated with the large-scale pattern of plate tectonic motions since 120 Ma and with the upwelling domes can perturb LOD by about 0.4 µs per year, that is, with an order of magnitude smaller than the effects induced by the last deglaciation. Superimposed on this linear trend, we show that there are fluctuations around 0.1-0.2 s Myr −1 on a timescale of a few tens of millions of years.We then combine a spherical model of mantle circulation with solutions for the equations governing the rotation of a viscous planet, to improve the constraint of mantle mass conservation.Finally, we compare our results with other effects.

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“…It is important to remember that a thin ultra-low viscosity layer is invisible to post-glacial rebound viscosity computation due to the channel flow effect (Cathles, 1975) or to the geoid variation (Marquart et al, 2005). Therefore the occurrence of such a layer cannot be excluded a priori.…”

Section: The Decoupling In the Upper Asthenospherementioning

confidence: 99%