Researchers led by Ki-Weon Seo say earth's rotation shifted after groundwater loss between 1993 and 2010 nudged Earth’s rotational pole about 31.5 inches. The 2023 study in Geophysical Research Letters estimated that humans depleted about 2,150 gigatons of groundwater during that period.
Seo, a geophysicist at Seoul National University, said the redistribution of groundwater has the largest impact on the drift of Earth’s rotational pole among climate-related causes. The study also estimated that the water loss added about 6.24 millimeters, or 0.24 inches, to global sea level.
Seo's Rotational Pole Study
The researchers modeled observed changes in Earth’s rotational pole and tested different water-redistribution scenarios. The scenario that best matched the observed drift included 2,150 gigatons of groundwater depletion, with much of the pumping tied to irrigation and human use.
Seo said, "Earth’s rotational pole actually changes a lot" and added, "Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole." He also said, "I’m very glad to find the unexplained cause of the rotation pole drift."
Groundwater Loss In Western North America
The study pointed to heavy groundwater depletion in western North America and northwestern India as especially important to the modeled drift. A 2026 Journal of Geodesy reappraisal using the WaterGAP hydrological model found that terrestrial water storage plays a significant role in polar motion across different timescales.
Surendra Adhikari, a research scientist at NASA’s Jet Propulsion Laboratory, said, "They’ve quantified the role of groundwater pumping on polar motion" and added, "and it’s pretty significant."
Earth's Rotation And Sea Level
Seo also said, "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 study ties a human water-use pattern to a measurable change in the planet’s spin axis and to a documented contribution to sea-level rise.
For readers trying to understand the practical takeaway, the study’s number is the point: groundwater pumping from 1993 to 2010 was large enough, in the model the researchers found best, to move Earth’s rotational pole by 31.5 inches. That puts a precise figure on a process that is usually invisible at ground level.
