Climate change is slowing down the Earth’s rotation.

Melting polar ice due to climate change is redistributing Earth’s mass, slowing its rotation and lengthening the day slightly, ETH Zurich-backed studies have shown. NASAThis suggests a greater human influence on the Earth’s rotational dynamics than previously recognized.

Climate change is melting ice in Greenland and Antarctica. As a result, water from these polar regions is flowing into the world’s oceans – especially into the equatorial region. “This means a shift in mass, and this affects the Earth’s rotation,” explains Benedikt Soja, professor of space geodesy at the Department of Civil, Environmental and Geomatics Engineering at ETH Zurich.

“It’s like when a figure skater dances to music, she first brings her arms together and then extends them,” says Suga. The initially fast rotation becomes slower because the masses are moving away from the axis of rotation, increasing physical inertia. In physics, we talk about the law of conservation of angular momentum, and this same law also governs the rotation of the Earth. If the Earth rotates more slowly, the days get longer. So climate change also changes the length of a day on Earth, albeit only slightly.

With support from NASA, researchers at the Swiss Federal Institute of Technology in Zurich from the SOGA group have published two new studies in scientific journals. Natural Sciences and Geology And Proceedings of the National Academy of Sciences (PNAS) On how climate change affects polar motion and day length.

Climate change goes beyond the moon’s influence

In a study published in the Proceedings of the National Academy of Sciences, researchers at the Swiss Federal Institute of Technology in Zurich showed that climate change is also causing the day to be a few milliseconds longer than its current 86,400 seconds. That’s because water is flowing from the poles to lower latitudes, slowing the rotation.

Another reason for the slowdown is tidal friction, which is driven by the moon. But the new study comes to a surprising conclusion: If humans continue to emit more greenhouse gases, and the Earth warms as a result, this could eventually have a greater effect on the Earth’s rotation than the moon, which has been driving the length of the day for billions of years. “Humans have a greater impact on our planet than we realize,” Soja concludes, “and this naturally places a greater responsibility on us for the future of our planet.”

The Earth’s axis of rotation is shifting

However, shifts in mass on and within the Earth’s surface caused by melting ice do not only change the Earth’s rotation speed and the length of the day: as researchers explain in Natural Sciences and GeologyIt also changes the axis of rotation. This means that the points where the axis of rotation actually meets the Earth’s surface move. Researchers can observe this polar movement, which over longer periods of time amounts to about ten meters per hundred years. Not only does the melting of ice sheets play a role here, but also movements that occur in the Earth’s interior. Deep in the Earth’s mantle, where rocks become viscous due to high pressure, displacements occur over long periods of time. There are also convection flows in the liquid metal in the Earth’s outer core, which are responsible for generating the Earth’s magnetic field and leading to shifts in mass.

In the most comprehensive model yet, Soga and his team have now shown how polar motion arises from individual processes in the core, in the mantle, and from the climate at the surface. Their study was recently published in the journal Natural Sciences and Geology“For the first time, we provide a complete explanation for the causes of long-term polar motion,” says Mostafa Kiani Shahvandi, a doctoral student at SOGA 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 stands out in particular in their study: Natural Sciences and Geology: The processes that take place on and within the Earth are interconnected and affect each other. “Climate change is causing the Earth’s axis of rotation to shift, and the feedbacks resulting from the conservation of angular momentum also seem to be changing the dynamics of the Earth’s core,” explains Suga. “Continuing climate change may therefore even affect processes deep within the Earth, and the extent of these effects is greater than previously assumed,” adds Kiani Shahwandi. However, there is no cause for concern, as these effects are minor and unlikely to pose a threat.

The laws of physics combined with artificial intelligence

In their study of polar motion, the researchers used what are known as physics-informed neural networks. These are new networks artificial intelligence (Artificial Intelligence) The methods by which researchers apply the laws and principles of physics to develop particularly powerful and reliable algorithms. Machine learningKiani Shahwandi was supported by Siddhartha Mishra, a professor of mathematics at ETH Zurich, who in 2023 received the Rössler Prize from ETH Zurich, the university’s highest research award, and is a specialist in this field.

The algorithms developed by Kiani Shahvandi have made it possible for the first time to record all the different influences on the Earth’s surface, mantle, and core, and to model their possible interactions. The result of the calculations shows how the Earth’s rotational poles have moved since 1900. The values ​​of these models are in excellent agreement with the real data provided by astronomical observations in the past and satellites over the past 30 years, which means that they can also predict the future.

Important for space travel

“Even if the Earth’s rotation changes only slowly, this effect must be taken into account when navigating in space – for example, when sending a space probe to land on another planet,” says Suga. Even a slight deviation of just one centimeter on Earth can grow to a deviation of hundreds of meters over vast distances. “Otherwise, it would not be possible to land in a specific crater on the Earth’s surface. Mars,” He says.

References:

“The increasingly dominant role of climate change on day length changes” by Mustafa Kiani Shahwandi, Surendra Adhikari, Matthew Dompieri, Siddhartha Mishra, and Benedict Soja, July 15, 2024, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2406930121

“Contributions of core, mantle, and climate processes to the Earth’s poles” by Mostafa Kiani Shahwandi, Surendra Adhikari, Matthew Dompieri, Sadiq Modiri, Robert Heinkelmann, Harald Schuh, Siddhartha Mishra, and Benedict Soja, July 12, 2024, Natural Sciences and Geology.
doi: 10.1038/s41561-024-01478-2