Overview
- The study led by Donald Argus and published Thursday found the annual oscillation of Earth’s centre of mass is roughly half the size estimated eight years earlier, based on a refined analysis of long‑term observations.
- Researchers combined ground GPS data with orbital tracking of low‑Earth‑orbit satellites and removed elastic displacements caused by changing water and ice loads to reduce measurement bias.
- Seasonal mass shifts in snow, rivers and the oceans drive the motion: March snow in North America and Eurasia moves the centre about 3 millimetres north, April Amazon water storage shifts it about 2.2 millimetres south, and August–October Pacific changes produce the largest ocean contribution.
- The new result agrees with GRACE‑FO gravity observations and matters for precise satellite navigation, mapping reference frames and elevation measurements, and NASA plans to continue the gravity record with the GRACE‑C mission targeted for late 2028.
- The change reflects improved measurement and modeling rather than a sudden physical change in Earth, and continued monitoring will help keep commercial and scientific systems—such as shipping logistics, precision farming and climate records—accurate to the millimetre scale.