There’s a lot riding on how Earth spins. The planet’s daily rotation around its axis dictates not only our perceptions of time, but also the world’s weather patterns. Since 1988, scientists have been adding occasional “leap seconds” to atomic clocks to compensate for the gradual slowing of Earth’s rotation. But more change could be on the way, writes Charles Q. Choi for LiveScience: Global warming seems to be shifting Earth’s axis.
A new study in Science Advances suggests that as glaciers melt, the redistribution of mass is making Earth shift and spin faster on its axis. The idea that this might be happening isn’t new. In 2002, an oceanographer named Walter Munk noted that though increasing sea levels should hypothetically shift Earth’s axis and make it spin more quickly, evidence of that shift could not be found.
“Munk’s enigma,” as it was called, was a real headscratcher, writes Choi. He explains that melting mountain glaciers and the loss of the ice cap in Antarctica take weight off of the rock that lies beneath. As the rock juts up, the poles become less flat and Earth becomes more round—a shift in the arrangement of mass that should make the planet spin more quickly.
In the latest look at the issue, a team led by Jerry X. Mitrovica at Harvard University found that Munk’s calculations used data that was skewed or too severe, making it difficult to spot the effects he suggested. By adjusting the calculations, they discovered that recent rises in sea levels are in fact contributing to changes in Earth’s axis, as expected.
The results might seem counterintuitive—after all, isn’t Earth's spin slowing down overall instead of speeding up? Kind of. The answer lies inside Earth’s core, co-author Mathieu Dumberry at the University of Alberta says in a press release: “Over the past 3000 years, the core of the Earth has been speeding up a little, and the mantle-crust on which we stand is slowing down,” notes Dumberry. This shift means that time is slowing on the planet’s surface even as it technically spins more quickly.
So what can humans expect as the world alters its spin? Brace yourself for longer days—the team estimates that Earth will gain a whopping six milliseconds per year. You might not notice the difference, but scientists will. And as Mitrovica tells The Washington Post, researchers may soon use Earth’s spin as a way to quantify climate change.