Meandering Path of Earth's Spin Axis
The animation – based on data used in a July 2024 NASA-funded study – shows polar motion, a phenomenon that results from the combined action of several physical processes that broadly shift the distribution of mass around the globe or create forces in its mantle and core that cause the planet to wobble as it rotates. These changes cause the spin axis to meander over time.
The blue line starts at the position of the spin axis near the North Pole in 1900, the first year polar motion data was collected, and tracks it until 2023. The spin axis now sits about 30 feet (10 meters) from where it was in 1900, in the direction of Canada's Baffin Bay. Around 2000, the axis took a sudden eastward turn, which researchers at NASA's Jet Propulsion Laboratory in Southern California in a 2016 study attributed to faster melting of the Greenland and Antarctic ice sheets and groundwater depletion in Eurasia.
Surendra Adhikari, a JPL geophysicist who co-authored that study, used measurements from the International Earth Rotation and Reference Systems Service to create the animation.
Adhikari and collaborators from Switzerland, Canada, and Germany found in a July 2024 paper in Nature Geoscience that about 90% of repeated oscillations in polar motion between 1900 and 2018 could be explained by large-scale mass redistribution at Earth's surface due to the melting of ice sheets and glaciers and the depletion of aquifers. It also found that nearly all of the long-term, non-repeating drift of the axis was due to dynamics in the mantle.