The melting of Earth’s ice caps in Greenland and Antarctica is causing the oceans to swell near the equator, altering the speed at which Earth rotates. According to a new paper published today in Proceedings of the National Academy of Sciences, climate change is causing Earth to spin more slowly, thus increasing the length of a day.
A single rotation of our planet takes 24 hours and constitutes a day. A few milliseconds added to that 24-hour period could cause problems for global time-keeping, digital infrastructure and the accuracy of GPS satellites orbiting the planet. The researchers also said it could have consequences for space travel.
Shift In Mass
The more water from the polar regions flows into the world’s oceans— particularly into equatorial areas—the more significant the drag factor on the speed at which Earth rotates, says the paper.
“This means that a shift in mass is taking place, and this is affecting the Earth’s rotation,” said 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.” As mass moves away from the axis of rotation, physical inertia increases and the initially fast rotation becomes slower.
Melting And The Moon
There are 86,400 seconds in any 24-hour rotation, a figure governed by the moon. Its gravitational pull is slowing the Earth’s rotation—a process called tidal braking—which is increasing the length of our day by 2.3 milliseconds per century, according to the BBC. The moon uses Earth’s rotational energy to take it into an orbital path slightly farther away. In about 200 million years, the moon will be farther from Earth, which will turn more slowly, and the length of a day could reach 25 hours.
That’s a natural process. Climate change isn’t—and it could have a more significant effect than the moon, say the researchers. “We humans have a greater impact on our planet than we realize, and this naturally places great responsibility on us for the future of our planet,” said Soja.
Axis Change
In a second paper in Nature Geoscience, the same researchers also show that climate change is slowing the planet’s rate of rotation and its angle. Exactly where the axis of rotation meets Earth’s surface moves by about 30 feet (10 meters) per hundred years. According to the paper, that’s down to both the melting of the ice caps and the motion within Earth’s interior. “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,” said Soja.
The researchers used AI to calculate how the Earth’s rotational poles have moved since 1900, which matches observations by astronomers and satellites.
Inner Core
It comes just weeks after another team of researchers suggested that the slight increase in the length of a day may be because Earth’s inner core has been slowing down for 14 years. A sphere of solid iron-nickel about 3,000 miles below the surface, Earth’s inner core is about the same size as the moon and surrounded by an outer core of liquid iron-nickel outer core. It generates Earth’s magnetic field.
Using seismic data from earthquakes and nuclear tests, researchers found that Earth’s inner core has been slowing down in relation to the planet’s surface since 2010. The paper concludes that the slowing is the result of the churning of the liquid iron outer core and gravitational tugs from parts of the mantle.
