Polar ice is melting and changing the Earth's rotation. It's messing with time itself

CNN
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One day in the next two years, every person in the world will lose a second of their time. Exactly when that will happen is affected by humans, according to New studylike Melting polar ice Change The rotation of the Earth and the change in time itself.

The hours and minutes that dictate our days are determined by the Earth's rotation. But this rotation is not constant; It can change very slightly, depending on what is happening on the Earth's surface and In essence, molten.

These sometimes imperceptible changes mean that the world's clocks need to be adjusted by “leap seconds”, which may seem small but can have a huge impact on computing systems.

A lot of seconds have been added over the years. But after a long period of slowing down, the Earth's rotation is now accelerating due to changes in its core. For the first time ever, a second must be taken off.

“A negative leap second has never been added or tested, so the problems it can create are unprecedented,” Patricia Tavella, a member of the Time Division at the International Bureau of Weights and Measures in France, wrote in an article accompanying the study. .

But exactly when this will happen is affected by global warming, according to the study published Wednesday in the journal Nature. The report found that the melting of polar ice is delaying the leap second by three years, pushing it from 2026 to 2029.

“Part of knowing what will happen in global timekeeping… depends on understanding what is happening with the greenhouse effect,” said Duncan Agnew, a professor of geophysics at the University of California San Diego and an author of the study.

Before 1955, a second was defined as a specific fraction of the time it takes the Earth to rotate once relative to the stars. Then came the era of highly accurate atomic clocks, which proved to be a more stable way of determining the physical second.

Since the late 1960s, the world has begun using Coordinated Universal Time (UTC) to designate time zones. Coordinated Universal Time (UTC) is based on atomic clocks but still keeps pace with the planet's rotation.

But since the rotation speed is not constant, the two time scales slowly diverge. This means that a “leap second” must be added every now and then to bring it back into alignment.

Changes in the Earth's long-term rotation are dominated by tidal friction on the ocean floor, which slows down its rotation. newly, Effects of melting polar iceAgnew said climate change, driven by humans burning fossil fuels that are warming the planet, has become a significant factor. As ocean ice melts, the melted water moves from the poles toward the equator, and then farther Slows down the speed of Earth's rotation.

Ted Scambos, a glaciologist at the University of Colorado Boulder who was not involved in the study, describes the process like an ice skater spinning with his arms above his head. When they lower their arms toward their shoulders, their rotation slows down.

The melting of polar ice “was significant enough to significantly affect the rotation of the entire Earth in an unprecedented way,” Agnew said. “To me, the fact that humans have changed the Earth's rotation is kind of amazing.”

But while melting ice may slow Earth's rotation, there's another factor at play when it comes to global timekeeping, according to the report: processes occurring in the Earth's core.

Planet The liquid core rotates independently of its solid outer shell. If the heart slows down, the crust hardens It's accelerating to maintain momentum, and that's what's happening right now, Agnew said.

Very little is known about what is happening approximately 1,800 miles below the Earth's surface, and it is not clear why the speed of the core changes. “It's basically unpredictable,” Agnew said.

But what is clear, according to the study, is that although the melting of polar ice is exerting a slowing effect, the Earth's overall rotation is accelerating. This means that the world will soon need to roll out a second one for the first time.

“A second doesn't sound like much,” Agnew says, but computing systems intended for activities like stock exchange transactions must be accurate to a thousandth of a second.

Many computer systems have programs that enable them to add a second, but few have the ability to subtract one. Humans would need to reprogram computers, increasing the possibility of error.

“No one really expected that the Earth would accelerate to the point where we might have to remove a leap second,” Agnew said.

“What's important” about the study is that it shows that “changes from the Earth's core are now trending larger than trends in ice loss from the poles — even though ice loss has been increasing,” said Scambos, a glaciologist at the University of Colorado Boulder. in the past decade.”

“It's a 'wow' moment for some computer applications,” he told CNN, but for most people life will continue as usual.

For Agnew, the findings could be a powerful tool to connect people to the ways humans are changing the planet.

“Being able to say that so much ice has melted that it has actually changed the Earth's rotation by a measurable amount, I think gives you the sense of, OK, this is big.”