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The dynamics of the Earth’s inner core: Convection and differential rotation

Authors

Tkalčić,  Hrvoje
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Wang,  Sheng
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Muir,  Jack
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Waszek,  Lauren
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Bodin,  Thomas
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Belonoshko,  Anatoly
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Mattesini,  Maurizio
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Moresi,  Louis
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

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Citation

Tkalčić, H., Wang, S., Muir, J., Waszek, L., Bodin, T., Belonoshko, A., Mattesini, M., Moresi, L. (2023): The dynamics of the Earth’s inner core: Convection and differential rotation, XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) (Berlin 2023).
https://doi.org/10.57757/IUGG23-3132


Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5020574
Abstract
Earth’s inner core structure, evolution and current thermal state remain enigmatic. Recent papers on its differential rotation relative to the mantle spurred much interest. However, significant matters arise from analysing the travel times of the subset of repetitive earthquakes from the South Sandwich Islands region to Alaska—the dataset recently used to infer the 70-year differential rotation cycle. 17 of 24 doublets were discarded from the previous dataset. This selective approach is at odds with the principle that all data (already deemed legitimate doublets in earlier studies) are useful in small data sets to inform the solution. Another problematic approach has been to use a fixed parameterisation—a highly subjective choice. We revisit this problem using Bayesian transdimensional inference. Alternative models of the differential rotation also explain the observed data, but, like all proposed models (Bayesian or Frequentist), they are not required by the data.Several hypotheses involving a thermally-convecting inner core have been proposed: a simple, high-viscosity, translational mode or a classical, lower-viscosity, plume-style convection. We use state-of-the-art seismic imaging to probe the inner core’s outermost shell for its compressional speed and compare it with recently-developed attenuation maps. The pattern emerging in the resulting tomograms is interpreted with recent data on iron’s viscosity as the inner core surface manifestation of thermal convection, with a positive correlation between compressional speed and attenuation. The internally driven inner-core convection is a plausible model that explains many observations for the inner core, including distinct anisotropy in the innermost inner core.