16 Aug 2023
 | 16 Aug 2023
Status: this preprint is open for discussion.

On the impact of true polar wander on heat flux patterns at the core-mantle boundary

Thomas Frasson, Stéphane Labrosse, Henri-Claude Nataf, Nicolas Coltice, and Nicolas Flament

Abstract. 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.

Thomas Frasson et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • EC1: 'Comment on egusphere-2023-1782', Juliane Dannberg, 21 Aug 2023 reply
    • AC3: 'Reply on EC1', Thomas Frasson, 28 Sep 2023 reply
  • RC1: 'Comment on egusphere-2023-1782', Anonymous Referee #1, 06 Sep 2023 reply
    • AC1: 'Reply on RC1', Thomas Frasson, 28 Sep 2023 reply
  • RC2: 'Comment on egusphere-2023-1782', Bernhard Steinberger, 22 Sep 2023 reply
    • AC2: 'Reply on RC2', Thomas Frasson, 28 Sep 2023 reply
      • RC3: 'Reply on AC2', Bernhard Steinberger, 28 Sep 2023 reply

Thomas Frasson et al.

Data sets

CMB heat flux PCA results Thomas Frasson, Stéphane Labrosse, Henri-Claude Nataf, Nicolas Coltice, Nicolas Flament

Thomas Frasson et al.


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Short summary
Heat flux heterogeneities at the bottom of Earth's mantle plays an important role in the dynamic of the underlying core. Here, we study how these heterogeneities are affected by the global rotation of the Earth called true polar wander (TPW), which has to be considered to relate mantle dynamics with core dynamics. We find that TPW can greatly modify the large scales of the heat flux heterogeneities, notably at short time scales. We provide representative maps of these heterogeneities.