Humanity ’s groundwater pumping has altered Earth’s tilt

While spinning on its axis, Earth wobbles like an off-kilter top. Sloshing molten iron in Earth’s core, melting ice, ocean currents, and even hurricanes can all cause the poles to wander. Now, scientists have found that a significant amount of the polar drift results from human activity: pumping groundwater for drinking and irrigation. “The very way the planet wobbles is impacted by our activities,” says Surendra Adhikari, a geophysicist at NASA’s Jet Propulsion Laboratory and an expert on Earth’s rotation who was not involved in the study. “It is, in a way, mind boggling.” Imagine spinning a basketball on your finger. If you can keep the ball balanced, it will spin evenly along its axis. But add a little bit of weight to one part of the ball or remove it from another, and the ball will rapidly become unbalanced, wobbling and shifting its spin axis. Earth’s spin axis also wobbles, its North Pole tracing out a roughly 10-meter-wide circle every year or so. The center of this wobble also drifts over the long term; lately, it has been tilting in the direction of Iceland by about 9 centimeters per year. Clark R. Wilson, a geophysicist at the University of Texas at Austin, and his colleagues thought the removal of tens of gigatons of groundwater each year might affect the drift. But they knew it could not be the only factor. “There’s a lot of pieces that go into the final budget for causing polar drift,” Wilson says. The scientists bui...
Source: ScienceNOW - Category: Science Source Type: news