Humans drew so much groundwater since 1993 that Earth's spin axis tilted 31.5 inches, a Seoul team published the math in Geophysical Research Letters three decades later in 2023

Every time a farmer in California’s Central Valley or India’s Punjab region pumps water from underground to irrigate crops, something happens far above, at the level of the planet’s own spin. According to a 2023 study titled ‘Drift of Earth's Pole Confirms Groundwater Depletion as a Significant Contributor to Global Sea Level Rise 1993–2010,’ published in Geophysical Research Letters and led by geophysicist Ki-Weon Seo of Seoul National University, humans pumped enough groundwater between 1993 and 2010 to cause Earth’s rotational pole to shift about 31.5 inches (80 centimeters) eastward.

What exactly moved and how
According to the study, researchers estimate that approximately 2,150 gigatons of groundwater were extracted over the 17-year period. That water didn’t just get used and forgotten; it ended up in rivers, oceans, and the atmosphere, physically redistributing mass around the planet. The study also finds that this redistribution amounts to more than 6 millimeters (about 0.24 inches) of global sea level rise.

It's like shifting the weight on a spinning top. When mass moves around on a rotating body, the axis of rotation shifts. Earth is not different. But when scientists modeled polar drift with only ice sheets and glaciers, the simulation didn't match what satellites actually observed, the study says. The model fit the observations from the real world only when researchers included the entire 2,150-gigaton groundwater redistribution; otherwise, the model was off by 78.5 centimeters, or roughly 4.3 centimeters of drift per year.


“Earth's rotational pole actually changes a lot,” Seo said, according to an AGU press release, “among climate-related causes, the redistribution of groundwater has the largest impact on the drift of the rotational pole.”

The 2016 discovery that made all of this possible
Until fairly recently, it was not possible to link groundwater pumping to polar motion. According to a landmark 2016 paper, titled ‘Climate-driven polar motion: 2003–2015,’ published in Science Advances by Surendra Adhikari and Erik Ivins of NASA's Jet Propulsion Laboratory, changes in terrestrial water storage, along with shifts in the global cryosphere, explained nearly the entire direction and amplitude of Earth’s observed polar drift between 2003 and 2015. That research set the stage for the link between large-scale water flow and the Earth’s spin, a connection the 2023 research was then able to build on and quantify.

Adhikari, who was not involved in the 2023 study, provided comments on its findings. According to the AGU press release accompanying the research, he said: “This is a nice contribution and an important documentation for sure. They’ve quantified the role of groundwater pumping on polar motion, and it’s pretty significant.”

Where the pumping happened matters
Not all groundwater extraction impacts the pole in the same way. Reallocating water from mid-latitudes has the strongest leverage on the spin axis, according to the study. According to the AGU press release, the most significant groundwater redistribution during the study period occurred in western North America and northwestern India, both of which lie in sensitive mid-latitude zones. This puts places like California and the High Plains in sharp focus for Americans. The aquifers that power American agriculture are among the largest contributors to this shift.

Why this matters beyond the numbers
Seo’s team is looking backward now. According to the Geophysical Research Letters study, polar motion records date back to the late 19th century, which means scientists could potentially tap historical orientation data to reconstruct groundwater depletion trends in the past, reading water history from the wobble of the planet itself.

There is a policy element, too. Countries that slow groundwater depletion, especially in mid-latitude areas, could theoretically slow polar drift, the AGU press release adds. However, the researchers caution that this would require large-scale, sustained conservation efforts.

Seo offered a candid reflection on his own findings during the AGU press release: “I'm very glad to find the unexplained cause of the rotation pole drift. On the other hand, as a resident of Earth and a father, I'm concerned and surprised to see that pumping groundwater is another source of sea-level rise.”

The pole is naturally displaced several meters every year by various forces, so this alone won’t send the seasons spiraling. But it does mean that when you water a field in Kansas or irrigate a rice paddy in Punjab, you are, in the most literal sense, moving the planet.