The study, recently published in the Geophysical Research Letters, has found that wells tapping underground water aquifers have redistributed enough of the Earth’s mass to affect its spin.
Between 1993 and 2010, humans pumped around 2,150 gigatons of groundwater, the equivalent of raising the ocean level by 6 millimeters. That caused the planet’s poles to shift about 80 centimeters (31.5 inches) to the east, roughly in the direction of Russia's Novaya Zemlya.
Scientists had previously discovered in 2016 that polar motion was affected by how water is stored on the planet. However, its impact had not been directly quantified.
"Earth's rotational pole actually changes a lot," said geophysicist Ki-Weon Seo of Seoul National University in South Korea, in a news release. "Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole."
"Observing changes in Earth's rotational pole is useful for understanding continent-scale water storage variations," Seo said. "Polar motion data are available from as early as the late 19th century. So, we can potentially use those data to understand continental water storage variations during the last 100 years. Were there any hydrological regime changes resulting from the warming climate? Polar motion could hold the answer."
Other events can also cause the planet’s pole to change its location, including powerful earthquakes and large meteor strikes, both of which alter the shape of the Earth’s crust. Each year, the pole shifts several meters.
The scientists isolated ground water pumping as the cause by running different models that included different phenomena, and only arrived at a solution when groundwater was accounted for.
"I'm very glad to find the unexplained cause of the rotation pole drift," he added. "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."
Climate change is affecting this as well. As the planet warms and more and more polar and glacial ice melts, it changes where that water is distributed on the planet and causes the sea level to rise.