The influence of melting polar ice on the Earth’s rotation is named

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

These almost imperceptible changes sometimes mean that the world clock must be adjusted by “leap seconds,” which may seem tiny but can have a big impact on computing systems.

Many seconds have been added over the years. But after a long trend of slowing, the Earth’s rotation is now speeding up due to changes in its core. For the first time in history, it will be necessary to film a second, CNN notes.

“The negative leap second has never been added or tested, so the problems it could create are without precedent,” wrote Patricia Tavella, a time officer at the International Bureau of Weights and Measures in France, in an article accompanying the study.

But exactly when that happens is influenced by global warming, according to a study published Wednesday in the journal Nature. Melting polar ice is delaying leap second by three years, pushing it back from 2026 to 2029, the report says.

“Part of figuring out what will happen in global timing… depends on understanding what’s happening with the global warming 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 certain fraction of the time it takes the Earth to complete one revolution relative to the stars. Then came the era of highly accurate atomic clocks, which proved to be a much more stable way of determining the physical second.

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

But since the rotation speed is not constant, the two time scales gradually diverge. This means that a “leap second” needs to be added from time to time to bring them back into line.

Changes in the Earth’s rotation over the long term were determined by the friction of the tides on the ocean floor, which slowed its rotation. Recently, the effects of melting polar ice caps caused by humans burning fossil fuels to warm the planet have become a significant factor, Agnew said. When ice melts in the ocean, meltwater moves from the poles to the equator, further slowing the Earth’s rotation rate.

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 raised above his head. When they lower their arms to 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,” notes Duncan Agnew. “To me, the fact that human beings caused the rotation of the Earth to change is kind of amazing.”

But while melting ice may be slowing the Earth’s rotation, according to the report, there is another factor influencing global timing: processes in the Earth’s core.

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

Very little is known about what happens approximately 1,800 miles below the Earth’s surface, and it is unclear why the core’s speed changes. “It’s fundamentally unpredictable,” Agnew states.

But what is clear, according to the study, is that while melting polar ice has a slowing effect, overall the Earth’s rotation is accelerating. This means the world will soon need to subtract a second for the first time.

“A second doesn’t sound like much,” Agnew notes, but computing systems set up for operations such as the stock market must be accurate to the 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 need to reprogram their computers, leading to a potential bug.

“Nobody really expected the Earth to accelerate to such an extent that we might have to remove the leap second,” says Duncan Agnew.

Scambos, a glaciologist at the University of Colorado Boulder, emphasizes that the “big significance” of the study is that it shows that “changes in the Earth’s core are currently trending larger than trends in ice loss from the poles—even though that ice loss has increased over the past decade

“It’s unfortunate for some computer applications,” he told CNN, but for most people life will continue as usual.

Agnew said the findings could be a powerful tool for educating people about how humans are changing the planet.

“To be able to say that so much ice melted that it actually changed the rotation of the Earth by a measurable amount, I think lets you know that this is a big deal.”