Reconciling Surface Deflections From Simulations of Global Mantle
Convection
- Conor Patrick O'Malley,
- Gareth G Roberts,
- James Panton,
- Fred D Richards,
- J. Huw Davies,
- Victoria M Fernandes,
- Sia Ghelichkhan
James Panton
School of Earth and Environmental Sciences, Cardiff University
Author ProfileJ. Huw Davies
School of Earth and Ocean Sciences, Cardiff University
Author ProfileAbstract
The modern state of the mantle and its evolution over 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, volcanism,
and in the distribution of sediments. An obvious way to test theoretical
understanding of mantle convection is to compare model predictions with
independent observations. We take a step towards doing so by exploring
sensitivities of theoretical surface deflections generated from a
systematic exploration of global mantle convection simulations. Sources
of uncertainty, model parameters that are crucial for predicting
deflections, and those that are less so, are identified. We start by
quantifying similarities and discrepancies between deflections generated
using numerical and analytical methods that are ostensibly parameterised
to be as-similar-as-possible. Numerical approaches have the advantage of
high spatial resolution, and can capture effects of lateral viscosity
variations. However, treatment of gravity is often simplified due to
computational limitations. Analytic solutions, which leverage propagator
matrices, are computationally cheap, easy to replicate, and can employ
radial gravitation. However, spherical harmonic expansions used to
generate solutions can result in coarser resolution, and the methodology
cannot account for lateral viscosity variations. We quantify the impact
of these factors for predicting surface deflections. We also examine
contributions from radial gravity variations, perturbed gravitational
potential, excised upper mantle, and temperature-dependent viscosity, to
predicted surface deflections. Finally, we quantify effective
contributions from the mantle to surface deflections. The results
emphasise the sensitivity of surface deflections to the upper mantle.21 Oct 2023Submitted to ESS Open Archive 08 Nov 2023Published in ESS Open Archive