Coupling the Dynamics of Earth's Core and Mantle / Core-Mantle-Coup

• Applicants: Professor Hans-Peter Bunge, Ph.D.; Dr. Johannes Wicht
• Subject Area: Geophysics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 521319093

Ever since the pioneering work of Glatzmaier et al.1999, it is understood that Earth's mantle exerts critical control on the dynamo action in the liquid iron core. The amount and pattern of core heat loss through the Core-Mantle Boundary (CMB) effects the magnetic field strength, geometry, and dynamics, including its reversal rate. Here we propose to take advantage of recent dramatic progress in mantle convection and dynamo simulations capabilities to investigate this first-order process of core and mantle coupling over a time span of 100 million years, ranging from the enigmatic Cretaceous Normal Superchron (CNS) to present-day. The well-documented increase in reversal rate from only very few reversals during the CNS to about 4 per Myr. today provides important constraints for both dynamo and mantle dynamics. Our mantle convection simulations will exploit state-of-the-art geodynamic data-assimilation techniques through the adjoint method in high resolution models, applying more than 670 million grid points for discretizing Earth's mantle, to retrodict global mantle flow back in time and to track the amplitude and pattern of core heat loss across the CMB. Geologic constraints on past dynamic topography will help to inform the selection of optimal geodynamic modeling parameters employed forthe mantle flow trajectories. Next to isochemical dynamic Earth models in pyrolite composition we will bring new thermo-chemical adjoint techniques to bear, in order to retrodict mantle flow under the assumption of large dynamically isolated mantle domains, in particular the LLSVPs. State-of-the-art dynamo simulations at different parameter combinations will explore the impact of different CMB heat flux pattern on the geodynamo. Whether or not the pattern from the etrodictions will yield the observed reversal rate will allow dismissing unrealistic model assumptions. Unraveling the mantle influences on the core dynamo will enable us to exploit the rich paleomagnetic record for understanding Earth’s deep dynamics.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2404: Reconstructing the deep dynamics of planet Earth over geologic time (DeepDyn)
• International Connection: Australia
• Cooperation Partner: Dr. Sia Ghelichkhan