The melting of polar ice leads to a change in the planet’s rotation speed, which in turn affects the global calculation of time, a study from the University of California showed, reports the scientific journal Nature. Geophysicists from the University of California have found evidence that the slowing rotation of the Earth’s core, combined with the melting of the Antarctic and Greenland glaciers, will lead to the fact that in 2029, humanity will have to shorten, rather than increase, the length of the day for the first time.
According to the results of the study, melting ice in the Arctic and Antarctic affects the rotation of the earth: it leads to the flow of large volumes of water into the oceans, which causes a redistribution of water mass and a slight change in the speed of rotation of the planet. Accelerated melting of ice in Greenland and Antarctica, measured using satellite gravimetry, has caused the Earth’s angular velocity to decrease in less time than before.
This will create a never-before-seen challenge for computer network synchronization and may require changes to UTC (Universal Time) sooner than planned. Global warming is already affecting global timekeeping, the article says.
Recall that since 1972, leap seconds have been periodically added to the universal time scale UTC, which are additional seconds periodically added to the UTC scale on June 30 or December 31 by the International Earth Rotation Service. This happened when humanity began to use atomic clocks to measure the length of the day and determine the speed of rotation of the Earth.
Since then, 27 leap seconds have been added to the scale, the last of which was added to UTC in December 2016. Calculations carried out by the researchers show that humanity will have to subtract a leap second from UTC for the first time in 2029, given how the Earth’s rotation is affected by the nature of the movement of rocks in its core, as well as the process of melting polar glaciers.
The researchers came to this conclusion when analyzing how various processes in the Earth’s interior and on its surface affect the speed of the planet’s rotation around its axis and the length of the day. In the past, scientists believed that the length of the day on Earth was gradually increasing, which was associated with a slowdown in its rotation as a result of gravitational interactions between our planet and the Moon. Recently, this situation has become significantly more complicated after geophysicists discovered that the rotation speeds of the Earth’s surface and its inner core are different. It turned out that the speed of the nucleus around its axis is not a constant value, which significantly affects the length of the day.
Calculations have shown that the typical length of a day is affected not only by how much the Earth’s rotation accelerates as a result of the work of geophysical processes in its core that are still unknown to us, but also by the speed at which the glaciers of Greenland and Antarctica are melting. Their disappearance leads to a redistribution of mass from the poles towards the planet’s equator, as a result of which the Earth’s rotation slows down further.
Taking this factor into account in the calculations led to the conclusion that by 2029 humanity will have to introduce a negative leap second into the Coordinated Universal Time (UTC) scale for the first time, and global warming will delay this moment by 3 years. This will give the IT industry additional time to make changes to the operation of the Internet and communication systems that will be necessary to reduce, rather than increase, the length of the day, the researcher concluded.
Throughout the history of the Earth, its rotation has slowed down. About 1.4 billion years ago, a day lasted 18 hours and 41 minutes, but in the age of dinosaurs, a day lasted only 23 hours. This is a fairly slow process – so slow that Earth’s day is only 0.047 seconds longer than at the end of the Bronze Age.
Recently, however, the Earth has been bucking this trend due to the rotation of the planet’s liquid outer core, and is actually speeding up the process of time passing. According to Scientific American, it’s likely that scientists would have had to eliminate the leap second much sooner if climate change had not been an issue, but warming ice caps have delayed this unprecedented decision—delayed, but not avoided.
“There used to be no negative leap second, and leap seconds themselves have always been a problem for people managing computer networks,” Scientific American reports. “Given that many critical systems rely on accurate timekeeping. “Having to include a negative leap second would have been a bigger problem because they never had to do it.”
Since 1972, scientists have added 27 extra seconds to the clock – sometimes with disastrous results. Website crashes, technical service outages, airline booking glitches and financial market instability are just a few of the problems, and companies like Google and Meta have even invented a technique called “splash dab” that essentially distributes the added second during the day. What happens if scientists subtract the leap second remains to be seen.
Today the planet rotates at a speed of 24 hours a day. But from a geological point of view, this is a surprisingly new phenomenon. During the Mesozoic era (252–66 million years ago), the world rotated on its axis every 23 hours. And 1.4 billion years ago—a billion years before life actually began on Earth—a day lasted only 18 hours and 41 minutes.
The rotation of the Earth is most influenced by the only natural satellite of the Earth – the Moon, which was formed in the fiery days of the Hadean eon. When the Moon formed (likely from debris from Earth’s collision with the ancient planet Theia), it was only 14,000 miles from Earth. This is 17 times closer than it is today, and this proximity caused the Earth to spin faster. Since then, the Moon has gradually moved some distance away from its parent planet. This means that days on Earth should get longer and longer, but it’s not that simple.
For decades, some scientists have theorized that for about a billion years (between 2 and 1 billion years ago), the length of Earth’s day actually remained at about 19 hours, ignoring the suggestion that the length of Earth’s days increased until the Moon moved into its modern orbit. This long period of time, reminiscent of the mid-Proterozoic era, is affectionately known to scientists as the “boring billion” because “little” happened on Earth.
Now scientists from the Chinese Academy of Sciences and Australia’s Curtin University say they have figured out why the Earth has stopped increasing its length of day. Using newly collected data—especially through cyclostratigraphy, where researchers use patterns in sediments to study climate cycles caused by astronomical events—and conducting statistical analysis, the scientists found that fluctuations in Earth’s atmosphere at the time created enough counteracting forces to counteract any changes day lengths caused by the gravitational influence of the Moon. The results were published Monday in the journal Nature Geoscience.
Mitchell and Kirscher, Natural Geosciences, 2023.
Illustration of how the Sun’s accelerating torque and the Moon’s decelerating torque could balance each other over nearly 1 billion years.
The start of this pause coincides with the so-called Great Oxidation Event, when Earth temporarily saw oxygen levels rise and create an ozone layer before levels dropped again. This change in the atmosphere could enhance the effect of solar atmospheric tides, which then offset the influence of the Moon. It is possible that this pause delayed the origins of life on Earth, as early photosynthetic bacteria may have taken more days to reach enough oxygen to support more complex life.