The axis of the Earth has shifted due to human activity
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Over the course of about two decades, humans have pumped so much water out of the ground that we have shifted the poles of the earth by almost a meter. This is consistent with the polar drift caused by the melting ice of Greenland over the same period.
“Most people would live their lives and not be aware of it [Earth’s] wobbles or the drift,” says Clark Wilson at the University of Texas at Austin. He and his colleagues modeled how changes in the distribution of water across the planet influenced drifting away from the poles.
Part of that polar wander is due to natural causes. Since the Earth is not a perfect sphere, it wobbles like a spinning top several meters per year. The poles also drift due to changes in the distribution of mass around the planet, such as the movement of water due to the seasons.
“There are a number of things that contribute to polar drift, and they all add up,” says Wilson. Reservoir filling and groundwater pumping, as well as the melting of glaciers from climate change and resulting sea level rise, all contribute, though it was not clear what the impact of each specific change was.
Wilson and colleagues modeled the drift using estimates of the amount of groundwater pumped up between 1993 and 2010, totaling about 2,100 gigatons, and the associated rise in sea level, which they estimate at 0.3 millimeters per year.
The polar drift attributed to these changes from groundwater pumping was about 80 centimeters. Wilson says this is mainly due to large aquifers in mid-latitudes, which have the greatest effect on polar drift. The only thing that affected the drift more than changes in groundwater was the recovery of landmasses after the lost weight of melted glaciers from the previous Ice Age.
This in itself has no particular impact on changes in day length or seasons, says Wilson. Although he says knowing the precise location of the axis is essential for any GPS technology to work.
But the finding illustrates just how much water people pumped up, he says Manoocher Shirzaei at Virginia Tech. “The exact number doesn’t really matter,” he says. “The bottom line is that the volume is so gigantic that it could affect Earth’s polar drift.”
Groundwater pumping has accelerated in the 21st century, partly due to droughts caused by climate change, and also due to more crops growing in dry places, Shirzaei says.
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