The Markowitz wobble represents a quasi-decadal oscillation in the polar motion record with typical timescales of around 30 years. Despite doubts on its true existence and the causes of its variations, Kiani Shahvandi, et al. (2024a) have demonstrated that not only this wobble is real, but also its causes are rooted in the barystatic and core dynamics processes.

Barystatic processes represent the mass variations in continental-ocean system due to melting of polar icesheets and global glaciers, as well as variations in Terrestrial Water Storage (TWS). The latter proved to be the most satisfactory explanation for the Markowitz wobble, although as mentioned there is a secondary contribution due to the core dynamics. Kiani Shahvandi, et al. (2024a) argued that this contribution represents the dynamic response of the core to surface mass variations, a profound and striking discovery that can further our understanding of the climate and more broadly, the Earth system as a whole.

Kiani Shahvandi, et al. (2024b) also showed that the TWS induces decadal oscillations in the length of day and coefficient of ellipticity. Although the amplitude of these oscillations is less than one tenth of a milliseconds, they are projected to increase in the coming decades.

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