The human footprint greatly modifies the planet. What happens when water is extracted from the ground and moved to other places? Well: the extraction of water tilted the Earth. So much so, that it tilted almost 80 centimeters eastward between 1993 and 2010 alone. The research is in Geophysical Research Letters.
It was estimated that humans pumped 2,150 gigatons of groundwater between 1993 and 2010. Equivalent to more than 6 millimeters of sea level rise, between 1993 and 2010. At the Earth’s rotation pole (around which the planet revolves) is the track. It moves during a process called polar motion. The distribution of water on the planet affects how the mass is distributed.
Like adding a little weight to a spinning top, the Earth rotates a little differently as the water moves. “The Earth’s rotation pole actually changes a lot,” Ki-Weon Seo said in a statement. He is a geophysicist at Seoul National University who led the study. “The redistribution of groundwater has the biggest impact on the drift of the rotation pole.”
The ability of water to change the Earth’s rotation was discovered in 2016. Researchers modeled the observed changes in Earth’s rotational pole drift and water movement.
“I am very happy to find the unexplained cause of the rotation pole drift,” Seo said. “It is surprising to see that groundwater pumping is another source of sea level rise.” The location of groundwater matters by how much polar drift could change. Redistributing water from mid-latitudes has a greater impact on the rotation pole.
Reducing groundwater depletion rates could alter the change in drift. But only if such conservation approaches are sustained for decades.
The pole of rotation typically shifts several meters in about a year. Changes due to groundwater pumping do not risk changing seasons. But on geologic time scales, polar drift can have an impact on climate. If water extraction tilted the Earth, it would be wise to look into the past. Tracking polar movement could hold the answer about what is coming in the future.