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The heat flux across the core–mantle boundary (CMB) is a fundamental variable for Earth evolution and internal dynamics. Seismic tomography provides access to seismic heterogeneities in the lower mantle, which can be related to present-day thermal heterogeneities. Alternatively, mantle convection models can be used to either infer past CMB heat flux or to produce statistically realistic CMB heat flux patterns in self-consistent models. Mantle dynamics modifies the inertia tensor of the Earth, which implies a rotation of the Earth with respect to its spin axis, a phenomenon called true polar wander (TPW). This rotation must be taken into account to link the dynamics of the mantle to the dynamics of the core. In this study, we explore the impact of TPW on the CMB heat flux over long timescales (∼1 Gyr) using two recently published mantle convection models: one model driven by a plate reconstruction and a second that self-consistently produces a plate-like behaviour. We compute the geoid in both models to correct for TPW. In the plate-driven model, we compute a total geoid and a geoid in which lateral variations of viscosity and density are suppressed above 350 km depth. An alternative to TPW correction is used for the plate-driven model by simply repositioning the model in the original paleomagnetic reference frame of the plate reconstruction. The average TPW rates range between 0.4 and 1.8° Myr -1 , but peaks up to 10° Myr -1 are observed. We find that in the plate-driven mantle convection model used in this study, the maximum inertia axis produced by the model does not show a long-term consistency with the position of the magnetic dipole inferred from paleomagnetism. TPW plays an important role in redistributing the CMB heat flux, notably at short timescales (≤10 Myr). Those rapid variations modify the latitudinal distribution of the CMB heat flux, which is known to affect the stability of the magnetic dipole in geodynamo simulations. A principal component analysis (PCA) is computed to obtain the dominant CMB heat flux pattern in the different cases. These heat flux patterns are representative of the mantle convection cases studied here and can be used as boundary conditions for geodynamo models. [ABSTRACT FROM AUTHOR]

Heat flux across the core-mantle boundary (CMB) is an important variable of Earth's thermal evolution and dynamics. Seismic tomography provides access to seismic heterogeneities in the lower mantle, which can be related to present-day thermal heterogeneities. Alternatively, mantle convection models can be used to either infer past CMB heat flux or to produce statistically realistic CMB heat flux patterns in self-consistent models. Mantle dynamics modifies the inertia tensor of the Earth, which implies a rotation of the Earth with respect to its spin axis, a phenomenon called true polar wander (TPW). This rotation must be taken into account to link the dynamics of the mantle to the dynamics of the core. In this study, we use two recently published mantle convection models to explore the impact of TPW on the CMB heat flux over long timescales (~ 1 Gyr). One of the mantle convection models is driven by a plate reconstruction, while the other self-consistently produces a plate-like behavior. We compute the geoid in both models to correct for TPW. In the plate-driven model, we compute a total geoid and a geoid in which lateral variations of viscosity and temperature are suppressed above 350 km depth. We show that TPW plays an important role in redistributing the CMB heat flux, notably at short time scales (≤ 10 Myr). Those rapid variations modify the latitudinal distribution of the CMB heat flux, which is known to affect the stability of the magnetic dipole in geodynamo simulations. A principal component analysis (PCA) is computed to obtain the dominant CMB heat flux pattern in the different cases. These heat flux patterns can be used as boundary conditions for geodynamo models as representative of the mantle convection cases studied here. We note that the geoids produced by the two models are widely different from each other and from the observed present-day geoid. Work thus still needs to be done to improve the computation of the geoid in mantle convection models related to plate-tectonics. [ABSTRACT FROM AUTHOR]

The core-mantle boundary (CMB) heat flux is an important variable of Earth's thermal evolution and dynamics. Seismic tomography enables access to seismic heterogeneities in the lower mantle, which can be related to present-day thermal heterogeneities. Alternatively, mantle convection models can be used to either infer the past CMB heat flux or to produce statistically realistic CMB heat flux distributions in self-consistent models. Mantle dynamics modifies the inertia tensor of the Earth, which implies a rotation of the Earth with respect to its rotation axis called True Polar Wander (TPW). This rotation has to be taken into account if mantle dynamics is to be linked to core dynamics. In this study, we explore the TPW and the CMB heat flux produced by a self-consistent mantle convection model. The geoid is also computed and investigated in order to determine the driving mechanism of TPW. This model includes continents, dense chemical piles at the bottom of the shell and plate-like behavior, providing the possibility to link TPW and the CMB heat flux with plate tectonics. A principal component analysis (PCA) of the CMB heat flux is computed to obtain the dominant heat flux patterns. The model shows a geoid dominated by upper mantle structures. Subduction zones and continents are correlated with positive geoid anomalies, about 20 times larger than the observed geoid anomalies. Chemical piles are mostly correlated with negative geoid anomalies because of the anti-correlation between the positions of subducting slabs and the piles. TPW thus tends to lock continents and subduction zones close to the equator, while chemical piles are shifted towards higher latitudes. The positive CMB heat flux anomalies are mostly located at low latitudes because of the equatorial slabs. The dominant heat flux patterns obtained by the PCA largely reflect the supercontinent cycle captured by the model, providing CMB heat flux patterns representative of the supercontinent formation and dispersal. [ABSTRACT FROM AUTHOR]