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Discussion papers
https://doi.org/10.5194/se-2019-73
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/se-2019-73
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 23 Apr 2019

Research article | 23 Apr 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Solid Earth (SE).

The impact of rheological uncertainty on dynamic topography predictions: Gearing up for dynamic topography models consistent with observations

Ömer F. Bodur and Patrice F. Rey Ömer F. Bodur and Patrice F. Rey
  • EarthByte Group, School of Geosciences, The University of Sydney, NSW 2006, Australia

Abstract. Much effort has been given on extracting the dynamic component of the Earth’s topography, which is driven by density heterogeneities in the mantle. Seismically mapped density anomalies have been used as an input into mantle convection models to predict the present-day mantle flow and stresses applied on the Earth’s surface, resulting in dynamic topography. However, mantle convection models give dynamic topographies generally larger by a factor of ∼2 compared to dynamic topographies estimated from residual topography after extraction of the isostatically compensated topography. Our 3D thermo-mechanical numerical experiments suggest that this discrepancy can be explained by the use of a viscosity model, which doesn’t account for non-linear viscosity behaviour. In this paper, we numerically model the dynamic topography induced by a spherical density anomaly embedded into the mantle. When we use non-linear viscosities, our numerical models predict dynamic topographies lesser by a factor of ∼2 than those derived from numerical models using isoviscous rheology. This reduction in dynamic topography is explained by either the formation of a low viscosity channel beneath the lithosphere, or a decrease in thickness of the mechanical lithosphere due to induced local reduction in viscosity. Furthermore, we show that uncertainties related to activation volume and fluid activity, lead to variations in dynamic topography of about 20 %.

Ömer F. Bodur and Patrice F. Rey
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Ömer F. Bodur and Patrice F. Rey
Ömer F. Bodur and Patrice F. Rey
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Latest update: 19 Jul 2019
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Short summary
Giant assemblages of hot and cold rocks in deep Earth dynamically change the elevation of continents and bathymetry of oceans. Predicted amplitudes of those motions are notably higher than observations. Our models suggest that this can be related to oversimplification of viscosities of rocks (i.e. resistance to flow) in the models. Moreover, the uncertainty in viscosity of the Earth's interior produces 20% deviation in topography, giving clues on how to produce realistic dynamic Earth models.
Giant assemblages of hot and cold rocks in deep Earth dynamically change the elevation of...
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