Climate change is melting ice in Greenland and Antarctica, shifting water to equatorial regions and affecting the Earth’s rotation, lengthening each day by a few milliseconds. With support from NASA, researchers from ETH Zurich have shown that this effect may surpass the influence of the Moon on the Earth’s rotational speed and is also shifting the Earth’s axis.
Melting polar ice due to climate change is redistributing the Earth’s mass, slowing its rotation and slightly lengthening the days, as highlighted in a study from ETH Zurich. National Aeronautics and Space Administration (NASA)This indicates that humans have a greater influence on the dynamics of Earth’s rotation than previously realized.
Climate change is causing the ice in Greenland and Antarctica to melt. As a result, water from these polar regions is flowing into the world’s oceans, especially in equatorial regions. “This means that there is a change in mass, which is affecting the Earth’s rotation,” explains Benedikt Soja, professor of space geodesy at the School of Civil, Environmental and Geotechnical Engineering at Vancouver University in Canada. ETH Zurich.
“It’s similar to when a figure skater does a pirouette, first bringing their arms close to their body and then extending them,” Soja says. The rotation starts fast and then slows down because the mass moves away from the axis of rotation, increasing physical inertia. In physics, we talk about the law of conservation of angular momentum, and this law also applies to the Earth’s rotation. If the Earth rotates slower, the days get longer. So climate change is also changing the length of days on Earth, albeit very slightly.
Supported by the US space agency NASA, ETH researchers from Soja’s group have published two new studies in the journal. Nature Chemistry and Proceedings of the National Academy of Sciences A study of how climate change affects polar movement and the length of the day (PNAS).
Climate change surpasses the influence of the moon
In a PNAS study, researchers from ETH Zurich report that climate change is also lengthening the length of a day by a few milliseconds from the current length of 86,400 seconds, as water flows from the poles to lower latitudes and the Earth’s rotation slows.
Another cause of the slowdown is tidal friction caused by the Moon. But the new study reaches a surprising conclusion: if humanity continues to emit greenhouse gases and the Earth warms accordingly, it will eventually have a greater impact on the Earth’s rotation speed than the Moon’s influence, which has determined the increase in day length for billions of years. “We humans have a much bigger impact on the Earth than we realise,” Soja concludes. “And so, of course, we have a big responsibility for the Earth’s future.”
The Earth’s axis of rotation is off
But the changes in Earth’s surface and interior mass caused by melting ice do more than just change the Earth’s rotation rate and the length of its day. As researchers have shown: Nature Chemistrythey also change the axis of rotation, meaning that the point where the axis actually meets the Earth’s surface moves. Researchers can observe this polar movement, which, on longer time frames, amounts to about 10 meters per 100 years. It is not only the melting of ice sheets that plays a role here, but also movements that take place inside the Earth: deep in the Earth’s mantle, rocks become viscous due to high pressure, which causes displacements over long periods of time. Also, the liquid metal in the Earth’s outer core has heat flows that are responsible for both the creation of the Earth’s magnetic field and the changes in its mass.
In the most comprehensive modeling to date, Soja and his team have shown how polar motion arises from separate processes in the core, mantle, and surface climate. Their work was recently published in the journal Nature. Nature Chemistry“For the first time, we present a complete explanation for the causes of long-term polar motion,” says Mostafa Kiani Shavandi, one of Soja’s doctoral students and lead author of the study. “In other words, we know why and how the Earth’s axis moves relative to the crust.”
A particularly striking finding from their study was that Nature ChemistryProcesses on and inside the Earth are interconnected and affect each other. “Climate change is shifting the Earth’s axis of rotation, and feedback from the conservation of angular momentum seems to be changing the dynamics of the Earth’s core as well,” explains Soja. Kiani Shahvandi adds that “ongoing climate change is also affecting deep processes inside the Earth, and may have a greater impact than previously assumed.” However, these effects are small and unlikely to pose a risk, so there is little need to worry.
Fusion of physical laws and artificial intelligence
In their study on polar motion, the researchers used something called a physics-based neural network, which is a new artificial intelligence A technique by which (AI) researchers apply the laws and principles of physics to develop particularly powerful and reliable algorithms. Machine LearningKiani Sharvandi was supported by Siddhartha Mishra, professor of mathematics at ETH Zurich, an expert in the field and the 2023 recipient of the Rösler Prize, the university’s highest-funded research award.
Algorithms developed by Kiani Chavandi make it possible for the first time to record all the different influences on the Earth’s surface, mantle and core and model their interactions. The calculations show how the Earth’s poles have moved since 1900. These model values match very well with historical astronomical observations and actual data provided by satellites over the past 30 years, and also allow predictions for the future.
Important for space travel
“Even if the Earth’s rotation changes only slowly, we need to take this effect into account when navigating space, for example, when landing a space probe on another planet,” Soja says. A deviation of just one centimeter on Earth can grow to hundreds of meters over long distances. “Otherwise, it would be impossible to land in a specific crater. Mars” he says.
References:
“The Increasing Impact of Climate Change on Photoperiod Changes” by Mostafa Kiani Shahvandi, Surendra Adhikari, Mathieu Danbury, Siddhartha Mishra, and Benedict Soja, 15 July 2024 Proceedings of the National Academy of Sciences.
Translation: 10.1073/pnas.2406930121
“Contributions of Core, Mantle, and Climatological Processes to the Earth’s Polar Motion”, Mostafa Kiani Shahvandi, Surendra Adhikari, Mathieu Danbury, Sadegh Modiri, Robert Heinkelmann, Harald Schuh, Siddhartha Mishra, Benedict Soja, 12 July 2024, Nature Chemistry.
DOI: 10.1038/s41561-024-01478-2
