Although it has long being disputed whether the dynamics of the Earth’s core plays a role in the variations of Earth’s rotation, Kiani Shahvandi, et al. (2024a) have demonstrated that core dynamics contributes to the polar motion in terms of a small secular trend, as well as quasi-decadal oscillations with amplitudes much smaller than that of terrestrial water storage.  

Similarly, Kiani Shahvandi, et al. (2024b) have shown that in order to close the budget of secular trend observed in the length of day record since 1935, it is necessary to account for a significant contribution from the fluid motion at the top of the core. In fact, even though the contribution of core to polar motion is secondary to barystatic processes, it is primary in the variations in the length of day.

References

Kiani Shahvandi, M., Adhikari, S., Dumberry, M., Modiri, S., Heinkelmann, R., Schuh, H., Mishra, S., Soja, B. (2024a). Contributions of core, mantle and climatological processes to Earth’s polar motion. Nature Geoscience, 17: 705-710, https://doi.org/10.1038/s41561-024-01478-2

Kiani Shahvandi, M., Adhikari, S., Dumberry, M., Mishra, S., Soja, B.  (2024b). The increasingly dominant role of climate change on length of day variations. Proceedings of the National Academy of Sciences, 121: e2406930121, https://doi.org/10.1073/pnas.2406930121