Arctic ice is melting and changing the Earth’s rotation. It’s tampering with time itself

By | March 27, 2024

One day in the next few years, everyone in the world will lose a second of their time. Exactly when that will happen will be influenced by humans, according to a new study, as melting Arctic ice alters the Earth’s rotation and changes time itself.

The hours and minutes that define our days are determined by the rotation of the Earth. But that rotation is not constant; it can change very slightly depending on what happens on the Earth’s surface and in the molten core.

These almost imperceptible changes sometimes mean that the world’s clocks need to be adjusted by a “leap second,” which may sound small but can have a big impact on computer systems.

Many seconds have been added over the years. But after a long trend of slowing, Earth’s rotation is now accelerating due to changes in its core. For the first time, a second one must be removed.

“A negative leap second has never been added or tested, so the problems it could cause are without precedent,” Patrizia Tavella, member of the Time Department of the International Bureau of Weights and Measures in France, wrote in an article accompanying the study. .

But exactly when this will happen will be influenced by global warming, according to the study published Wednesday in the journal Nature. Melting Arctic ice will delay the leap second by three years, pushing it from 2026 to 2029, the report found.

“Part of figuring out what’s going to happen in global timekeeping … depends on understanding what’s happening with global warming,” said Duncan Agnew, a professor of geophysics at the University of California San Diego and author of the study.

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

Beginning in the late 1960s, the world began using Coordinated Universal Time (UTC) to set time zones. UTC relies on atomic clocks, but still keeps pace with the planet’s rotation.

But because the rotation speed is not constant, the two time scales slowly diverge. This means adding a ‘leap second’ every now and then to bring them back into line.

Long-term changes in the Earth’s rotation are dominated by the friction of the tides on the ocean floor, which slows its rotation. Recently, the effects of melting Arctic ice, caused by people burning fossil fuels that warm the planet, have become a major factor, Agnew said. As the ice in the ocean melts, meltwater moves from the poles toward the equator, further slowing the rate of Earth’s rotation.

Ted Scambos, a glaciologist at the University of Colorado Boulder who was not involved in the study, describes the process as a figure skater spinning with his arms above his head. As they bring their arms to their shoulders, their rotation slows down.

The melting of polar ice “has been large enough to noticeably affect the rotation of the entire Earth in a way that is unprecedented,” Agnew said. “To me, the fact that humans have caused the Earth’s rotation to change is quite astonishing.”

Flowing water from melting ice in Scoresby Fjord, Greenland, on August 12, 2023. - Olivier Morin/AFP/Getty ImagesFlowing water from melting ice in Scoresby Fjord, Greenland, on August 12, 2023. - Olivier Morin/AFP/Getty Images

Flowing water from melting ice in Scoresby Fjord, Greenland, on August 12, 2023. – Olivier Morin/AFP/Getty Images

But while melting ice may be slowing Earth’s rotation, the report says there is another factor at play when it comes to global timekeeping: processes in the Earth’s core.

The planet’s liquid core rotates independently of the solid outer shell. As the core slows down, the solid shell speeds up to maintain momentum, Agnew said, and that’s what’s happening right now.

Very little is known about what happens about 3,000 kilometers below the Earth’s surface, and it is not clear why the core’s speed changes. “It’s fundamentally unpredictable,” Agnew said.

But what is clear, according to the research, is that despite the fact that the melting of the polar ice is acting as a slowing influence, the Earth’s rotation is generally accelerating. This means that the world will soon have to subtract a second for the first time.

“A second doesn’t seem like a lot,” Agnew said, but computer systems set up for activities such as stock market transactions must be accurate to within a thousandth of a second.

Many computer systems have software that allows them to add a second, but few have the ability to subtract one. People will have to reprogram computers, which creates the risk of errors.

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

Scambos, the glaciologist from the University of Colorado Boulder, said the “big problem” with the study is that it shows that “changes from the Earth’s core are now greater than trends in ice loss from the poles — even though ice loss has increased. in the last decade.”

“It’s a ‘yikes’ moment for some computer applications,” he told CNN, but for most people life will continue as normal.

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

“If you can say that so much ice has melted that it has measurably changed the rotation of the Earth, I think you get the feeling: OK, this is a big problem.”

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