The influence of post-perovskite strength on the Earth's mantle thermal and chemical evolution

We have investigated the influence of post-perovskite (ppv) viscosity on mantle convective dynamics and stirring efficiency, using numerical modeling and simple analytical theory.Our results show that the strength of ppv has a dramatic influence on convective dynamics. The presence of a weak ppv enhances heat transfer across the bottom thermal boundary layer, resulting in higher temperatures, lower mantle viscosities and considerably larger convective velocities. This leads to a significant increase in stirring efficiencies with decreasing the ppv strength, by at least one order of magnitude.In addition, using a simple parameterized convection evolution that includes the influence of ppv, coupled to a mixing model, we show that during the long term history of the Earth's mantle, the presence of ppv yields systematically hotter thermal evolution and more efficient convective stirring.Such a strong effect of ppv strength on mantle stirring efficiency suggests that the influence of ppv phase must be considered when interpreting both geochemical and geophysical observations.

► We study the influence of ppv strength on mantle convective mixing. ► Weaker ppv yields higher temperatures and convective velocities. ► We derived scalings for stirring and convective heat transfer with ppv. ► Weak ppv can increase stirring efficiency by at least a factor 10 ► ppv must be taken into account for interpreting surface observations.