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https://doi.org/10.5194/egusphere-2024-1893
https://doi.org/10.5194/egusphere-2024-1893
26 Jun 2024
 | 26 Jun 2024

Reconciling Surface Deflections From Simulations of Global Mantle Convection

Conor P. B. O'Malley, Gareth G. Roberts, James Panton, Fred D. Richards, J. Huw Davies, Victoria M. Fernandes, and Sia Ghelichkhan

Abstract. The modern state of the mantle and its evolution on geological timescales is of widespread importance for the Earth sciences. For instance, it is generally agreed that mantle flow is manifest in topographic and drainage network evolution, glacio-eustasy and in the distribution of sediments. There now exists a variety of theoretical approaches to predict histories of mantle convection and its impact on surface deflections.  A general goal is to make use of observed deflections to identify Earth-like simulations and constrain the history of mantle convection. Several important insights into the role of radial and non-radial viscosity variations, gravitation, and the importance of shallow structure already exist. Here we seek to bring those insights into a single framework to elucidate the relative importance of popular modelling choices on predicted instantaneous vertical surface deflections. We start by comparing results from numeric and analytic approaches to solving the equations of motion that are ostensibly parameterised to be as-similar-as-possible. Resultant deflections can vary by ∼10 %, increasing to ∼25 % when viscosity is temperature-dependent. Including self-gravitation and gravitational potential of the deflected surface are relatively small sources of discrepancy. However, spherical harmonic correlations between model predictions decrease dramatically with the excision of shallow structure to increasing depths, and when radial viscosity structure is modified. The results emphasise sensitivity of instantaneous surface deflections to density and viscosity anomalies in the upper mantle. They reinforce the view that a detailed understanding of lithospheric structure is crucial for relating mantle convective history to observations of vertical motions at Earth's surface.

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Journal article(s) based on this preprint

20 Dec 2024
Reconciling surface deflections from simulations of global mantle convection
Conor P. B. O'Malley, Gareth G. Roberts, James Panton, Fred D. Richards, J. Huw Davies, Victoria M. Fernandes, and Sia Ghelichkhan
Geosci. Model Dev., 17, 9023–9049, https://doi.org/10.5194/gmd-17-9023-2024,https://doi.org/10.5194/gmd-17-9023-2024, 2024
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

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We wish to understand how the history of flowing rock within Earth's interior impacts deflection...
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