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.”
