Constraining deep mantle thermal evolution by linking geodynamic modelling, absolute plate motions and normal mode seismology

The frequency of geomagnetic field reversals varies on time scales of tens of millions of years, reflecting mantle-controlled changes in outer core flow that sustains the geodynamo. Accurate knowledge of lateral heat flow variations across the core–mantle boundary (CMB) and their evolution over geologic time is therefore fundamental to understanding the long-term geodynamo behaviour.

Here, we aim at generating robust predictions of lower mantle thermal evolution based on compressible high-resolution mantle circulation models (MCM). By assimilating 410 million years of plate motion history, which coincides roughly with two mantle overturns, the time span of geologically-informed structure above the CMB covers the Cretaceous normal superchron and beyond. To estimate uncertainties in lower mantle thermal evolution, we will employ systematic variations of model parameters, with a focus on uncertainties in the underlying absolute plate motion reference frame. Appraisal of the MCMs will be performed by predicting seismic data that can be compared to observations. Long-period normal mode data are particularly suited in this context, as they provide global constraints. In addition, splitting functions show high sensitivity to variations in the absolute reference frame. The realistic histories of mantle thermal evolution and CMB heat flux that we aim for in this project can in future be linked to geodynamo models and thus be used to predict time-series of Earth's magnetic field behaviour.