Humans have used enough groundwater to change the tilt of the earth

Rampant extraction of groundwater for drinking and irrigation is changing the distribution of water on the planet, changing the tilt of the planet, according to a comprehensive new study.

This discovery underscores the dramatic Impact of human activity on the earth.

Humans derive most of their drinking water from natural underground reservoirs called aquifer. Researchers calculate that between 1993 and 2010, they removed a total of 2,150 gigatons of groundwater. That’s enough to fill 860 million Olympic pools.

A new study published June 15 in the journal Geophysical Research Letters says that all water movement has moved the Earth’s tilt 31.5 inches to the east.

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Many people might imagine the shape of the Earth to be a perfect sphere, but it is not. It is oblate, with high mountains and deep ocean trenches, and unevenly distributed mass, making the planet resemble a lumpy potato. The whole thing is also spinning like a spinning top, and if you move enough mass from one place to another, the planet will wobble as it spins.

“I liken it to a softball in water,” said James Famiglietti, a hydrologist at Arizona State University who was not involved in the study. “When a softball or baseball gets wet, it becomes waterlogged, and when you throw it, it wobbles in a weird way. That’s what’s happening here.”

The axis of rotation, the imaginary line along which the planet rotates, is known as the Earth’s pole of rotation. The poles are tilted about 23.5 degrees with respect to the plane of the orbit around the Sun, which is why we have seasons. According to Ki-Weon Seo, a geophysicist at Seoul National University and lead author of the study, the exact position of the poles can change dramatically as the planet wobbles, a phenomenon called “polar motion.” .

“It changes every second. About 10 meters a year,” Seo said. “Wind, [ocean] All kinds of mass changes, such as ocean currents, atmospheric pressure, and glaciers, can cause polar motion. “

However, it is only recently that scientists have realized how much human activity can cause polar motion.

A 2016 study demonstrated that climate-induced changes in water mass distribution can cause a shift in the Earth’s poles. However, the activity examined in that study did not fully explain the observed polar motion.

Based on 17 years of observations, Seo and his colleagues used a computer model to simulate which hydrological sources have the greatest impact on the Earth’s tilt. To Seo’s surprise, the modeled polar drift matched observations only when groundwater pumping was included.

“We have a lot of dams and a lot of reservoirs on land too, so at first I thought it should be very important,” Seo said. “But that’s not really the case. After including groundwater effects, we were finally able to explain everything.” [of the] observation. “

Changes in the Earth’s tilt are too small to affect weather or seasons, Seo said. But a team of scientists has found that polar drift can be used to estimate the impact of groundwater pumping on sea-level rise.

As water is pumped up from the ground to irrigate crops and meet the world’s freshwater needs, water eventually flows into the world’s oceans through rivers and other pathways. The researchers found that from 1993 to 2010, groundwater pumping transferred enough mass to contribute 0.24 inches to global sea level rise.

“Pumping groundwater is one of the few operational decisions you can make about how to slow the rate of sea level rise,” Famiglietti said. “We have a real impact on this planet, and we need to better manage our planet’s resources.”