CSEDI: Core-Mantle Interactions and the Polar Motion of the Earth

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Weijia Kuang0079998 The investigators plan to expand the Kuang-Bloxham geodynamo model to investigate in detail the dynamical couplings between the Earth's core (including the solid inner core) and its solid mantle, and the angular momentum variation of the solid Earth. They will focus on the equatorial components of the angular momentum that excite the polar motion (variation of the rotation axis of the solid Earth; past studies on this subject have all been dealing with the axial component related to the length-of-day). Geophysical excitations of the "secular" polar motion as well as polar motion of time scales shorter than a few years have been largely understood. On the intermediate time scales, a particularly large undulation known as the Markowitz wobble in the polar motion with a quasi-periodicity of about 30 years and an amplitude as large as 30 milliarcseconds has long been observed but remains a mystery to date. However, the time scale and amplitude of this wobble suggest that the core-mantle coupling may be a possible cause. This project has two parts. First is the modification of the existing 3-dimensional, self-consistent dynamo model to include the hydrostatic elliptic mantle, the hydrostatic elliptic solid inner core and the couplings of the solid Earth. Then, the investigators will use the modified geodynamo model to evaluate core-mantle interactions within the geodynamo simulation. Of particular interest, they plan to investigate the contributions of electromagnetic, topographic and gravitational (between the inner core and the mantle) energy on the equatorial angular momentum exchange between the core and mantle. The proposed research shall be carried out among the PI, Dr. Weijia Kuang, at the University of Maryland, Baltimore County (leading effort in geodynamo simulation) and collaborators Dr. Lanbo Liu of the University of Connecticut (mantle structure and dynamics) and Dr. Benjamin Chao of NASA's Goddard Space Flight Center (Earth rotation dynamics).