Climate change is changing the Earth at its very core, a new study suggests.
As polar and glacial ice melts due to global warming, water that was once concentrated at the top and bottom of the globe is being redistributed towards the equator. The extra mass around the center of the Earth slows its rotation, which in turn has a lengthening effect on our days.
A new study provides more evidence of this dynamic and further suggests that changes in the planet’s ice have been profound enough to affect Earth’s axis – the invisible line at its center around which it spins. Together, these displacements are causing reactions below the surface, affecting the fluids that move in the Earth’s molten core.
The findings were published in two journals, Nature Geoscience and Proceedings of the National Academy of Sciences, last week.
The studies, along with similar research published in March, suggest that humans have tampered with fundamental elements of the planet’s physical properties — a process that will continue long after global temperatures have stabilized and the melting of ice sheets has caught up. a balance.
“You can add the rotation of the Earth to this list of things that humans have completely touched,” said an author of the two new studies, Benedikt Soja, an assistant professor of space geodesy at ETH Zurich in Switzerland.
The change in Earth’s rotation is significant enough that it could one day rival the impact of tidal forces caused by the moon, Soja said — if carbon emissions continue at extreme levels.
In general, the speed of the Earth’s rotation depends on the shape of the planet and where its mass is distributed – factors governed by several countervailing forces.
Scientists often offer a comparison to a skater spinning on ice: when skaters spin with their arms outstretched, their spin will be slower. But if skaters’ arms are kept tight, they spin faster.
Similarly, the friction of ocean tides from the moon’s gravitational pull slows the Earth’s rotation. Historically, this has had the biggest impact on the planet’s rotation rate, Soja said.
Meanwhile, the slow recovery of the Earth’s crust in some high-latitude regions after the removal of the Ice Age glaciers works in the opposite direction, speeding up the planet’s rotation.
Both of these processes have long been predictable influences on the Earth’s angular velocity.
But now, the rapid melting of ice due to global warming is becoming a powerful new force. If humans continue to pollute the planet with carbon emissions, Soja said, the impact of ice loss could surpass that of the moon.
“In worst-case scenarios, then yes, climate change would become the most dominant factor,” he said.
A fourth important factor affecting the Earth’s rotation is the movement of fluid within its core. Scientists have long understood that this can speed up or slow down the planet’s rotation – a trend that can shift in 10- to 20-year intervals. Right now, the core is temporarily causing the Earth’s rotation to speed up a bit, counteracting the slowdown due to climate change.
Climate change also appears to be affecting the Earth’s core, as a result of ice melting and shifts in the planet’s spin axis.
The researchers behind the new study built a 120-year model of polar motion, or how the axis shifts over time. They found that changes in the distribution of mass on the planet due to melting ice likely contribute to small fluctuations in polar motion.
Soja estimated that climate change is most likely responsible for 1 meter of change over 10 years.
The research further suggests that the movement of molten rock inside the Earth adjusts to changes in its axis and rotation speed – a feedback process in which the Earth’s surface affects its interior.
“The rotation changes a bit and that, we believe, can have an indirect effect on the bottom line,” Soja said. “That’s something that’s not very easy or impossible to measure directly because we can’t go down there.”
The findings have implications for how humans keep time and for how we position satellites in space.
“If you want to fly a new mission to Mars, for example, we really need to know what the Earth’s condition is exactly in space, and if that changes, we could make a navigation error or a mistake,” Soya said.
A 1-meter shift in Earth’s axis, for example, could mean a spacecraft misses its target by 100 or 1,000 meters when it reaches Mars.
As for timekeeping, research published in March suggested that climate change has delayed the need to add a “negative leap second” to Coordinated Universal Time to keep the world’s clocks in line with Earth’s rotation.
Duncan Agnew, a geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego, who led that earlier study, said the new research “fits in very well” with his own work.
“It extends the result further into the future and looks at more than one climate scenario,” Agnew said, adding that although Soja and his co-authors took a different approach, they reached a result similar to his.
“Multiple discoveries are almost the rule in science — this is another case,” Agnew said.
Thomas Herring, a professor of geophysics at the Massachusetts Institute of Technology who was not involved in either study, said the new research could really provide insight into how changes in the Earth’s surface can affect what’s going on. inside.
“For feedback between surface and core processes, I find it plausible,” Herring said in an email, explaining that “large-scale” processes at the surface can “penetrate into the core of the liquid.”