PhysOrg shares research from ETH Zurich that demonstrates something that should be obvious to anyone who’s played pool. But as the warming Earth makes the ice caps melt, changing the mass at the poles, the Earth’s spin is slowing down.
Climate change is causing the ice masses in Greenland and Antarctica to melt. Water from the polar regions is flowing into the world’s oceans—and especially into the equatorial region.
“This means that a shift in mass is taking place, and this is affecting the Earth’s rotation,” explains Benedikt Soja, Professor of Space Geodesy at the Department of Civil, Environmental and Geomatic Engineering at ETH Zurich.
“It’s like when a figure skater does a pirouette, first holding her arms close to her body and then stretching them out,” Soja says. The initially fast rotation becomes slower because the masses move away from the axis of rotation, increasing physical inertia.
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In the PNAS study, the ETH Zurich researchers show that climate change is also increasing the length of the day by a few milliseconds from its current 86,400 seconds. This is because water is flowing from the poles to lower latitudes and thus slowing down the speed of rotation.
Another cause of this slowdown is tidal friction, which is triggered by the moon. However, the new study comes to a surprising conclusion: if humans continue to emit more greenhouse gases and the Earth warms up accordingly, this would ultimately have a greater influence on the Earth’s rotational speed than the effect of the moon, which has determined the increase in the length of the day for billions of years.
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“For the first time, we present a complete explanation for the causes of long-period polar motion,” says Mostafa Kiani Shahvandi, one of Soja’s doctoral students and lead author of the study. “In other words, we now know why and how the Earth’s axis of rotation moves relative to the Earth’s crust.”
One finding in particular that stands out in their study is that the processes on and in the Earth are interconnected and influence each other. “Climate change is causing the Earth’s axis of rotation to move, and it appears that the feedback from the conservation of angular momentum is also changing the dynamics of the Earth’s core,” Soja explains.
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You can read the team’s research here in PNAS and here in Nature Geoscience.