TerraNeo: Development of a scalable mantle convection code for exascale computing

Simulating the Earth’s mantle convection at full convective vigor on planetary scales is a fundamental challenge in Geodynamics even for state of the art high-performance computing (HPC) systems. Realistic Earth mantle convection simulations can contribute a decisive link between uncertain input parameters, such as the mantle viscosity structure, and testable preconditions, such as dynamic topography. The vertical deflections predicted by such models may then be tested against history of dynamic topography from stratigraphic observations. Considering realistic Earth like Rayleigh numbers (∼ 10⁸ ) a resolution of the thermal boundary layer of 10 − 50 km is necessary considering the volume of the Earth’s mantle.

Simulating Earth’s mantle convection at this level of resolution requires solving sparse indefinite systems with more than 10¹² degrees of freedom, computationally feasible only on exascale HPC systems. This is achievable only by mantle convection codes providing high degrees of parallelism and scalability. Earlier approaches with prototype frameworks using hierarchical hybrid grids (HHG) as solvers for such systems demonstrated the scalability of the underlying concept for future generations of exascale computing systems.

Building up on the TerraNeo project here we report on the progress of utilizing the improved framework HyTeG (Hybrid Tetrahedral Grids) based on matrix-free multigrid solvers in combination with highly efficient parallelisation and scalability. This will allow to solve systems with more than a trillion degrees of freedom on present and future generations of exascale computing systems. We also report on the advances in developing the scalable mantle convection code TerraNeo using the HyTeG framework to realise extreme-scale mantle convection simulations with realistic, Earth like parametrisation and a resolution in the order of ∼ 1km.