For centuries, human actions had little effect on the Earth’s motions, ie its rotation speed and axis.
These motions were driven primarily by the moon’s gravitational pull and internal processes in the core and mantle.
But now, the melting of the ice sheets caused by human activity is interfering with these natural movements.
A new study reveals that Earth’s spin axis is “shifting” due to climate change and the planet’s internal dynamics.
Researchers at ETH Zurich have used the latest AI models to better understand polar motion, which is the movement of the Earth’s spin axis relative to the crust.
The study predicts that if greenhouse gas emissions continue to rise, they will eventually overwhelm the long-term influence of the moon’s tidal force. For billions of years, the moon has determined the continued lengthening of our days.
“We humans have a greater impact on our planet than we realize. And this of course places great responsibility on us for the future of our planet”, said Benedikt Soja, Professor of Space Geodesy in the Department of Civil, Environmental and Geomatic Engineering at ETH Zurich.
Lengthening of days
Two recent studies have examined a surprising link between the melting of the ice caps, the wobble of the planet and the length of our days.
Melting ice at the poles redistributes mass toward the equator, slowing the Earth’s rotation. Water travels from the poles to the equator, upsetting the Earth’s balance.
As ice melts on Earth’s surface, it slows the planet’s rotation and lengthens the day. The ETH Zurich research shows that the deceleration takes a little longer than our days – just a few milliseconds compared to the typical 86,400 seconds.
In physics, there is a law called conservation of angular momentum. It basically says that a spinning object likes to keep spinning at the same rate unless something forces it to change. Even the rotation of the Earth follows this rule. The melting of the ice redistributes the mass, and this displacement, according to the law, slows down the rotation of the Earth.
“That means there’s a mass shift happening and it’s affecting the Earth’s rotation,” Soja explained.
Impact on the Earth’s core
Researchers also studied why and how the Earth’s axis moves gradually over long periods. The team used physics-informed neural networks to create the most comprehensive model to date, explaining how motions within the Earth’s core, mantle and surface climate all contribute to polar motion.
Both studies highlight the complex web of interactions within the Earth. Events at the surface, such as the melting of ice, can have consequences deep within the core and vice versa.
“Climate change is causing Earth’s spin axis to move, and it appears that feedback from conservation of angular momentum is also changing the dynamics of Earth’s core,” Soja explained.
“Ongoing climate change may affect processes deep within the Earth and have a greater scope than previously assumed,” added Kiani Shahvandi, the study’s lead author and PhD student, in the press release.
They emphasize that these fundamental changes are very small and are not a cause for concern. However, this research provides valuable insights into the complex ways climate change is affecting our planet.
Both studies were published in Nature Geoscience AND Proceedings of the National Academy of Sciences (PNAS) magazine.
ABOUT THE EDITOR
Mrigakshi Dixit Mrigakshi is a science journalist who enjoys writing about space exploration, biology and technological innovations. Her work has been featured in popular publications including Nature India, Supercluster, The Weather Channel and Astronomy magazine. If you have any pixies in mind, please don’t hesitate to email her.