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Melting polar ice is slowing Earth's rotation, increasing daylight hours at an "unprecedented" rate, exacerbating climate warming and negatively affecting space and Earth navigation, a new study shows.

A partially melted glacier in Scoresby Fjord, eastern Greenland.

principle:

Polar ice flows toward the equator, changing Earth's shape and slowing its rotation

The new research results were published in the Proceedings of the National Academy of Sciences on July 15. Surendra Adhikari of NASA's Jet Propulsion Laboratory, one of the authors of the study, told AFP that melted ice water from Greenland and Antarctica at the poles flows to the equator, causing an increase in material around the equator.

"It's like a figure skater spinning with his arms close to his body and then extending them," added Benedict Soja of ETH Zurich, another author of the study. "The initially fast rotation becomes slower because the mass is moved away from the axis of rotation, increasing the physical inertia."

The Earth is usually thought of as a sphere, but it's more accurately called an oblate spheroid, which bulges slightly near the equator. And its shape is constantly changing due to daily tidal changes affecting the oceans and crust, the long-term effects of tectonic plates shifting, and sudden, dramatic changes caused by earthquakes and volcanoes.

The new research is based on observational techniques such as very long baseline interferometry, which allows scientists to measure the difference in time it takes for radio signals from space to reach different points on Earth and use this to infer changes in the direction of the planet and the length of the day.

The new study also used the Global Positioning System (GPS), which can measure Earth's rotation very precisely, to about one hundredth of a millisecond, and compared it with ancient records of solar eclipses dating back thousands of years. GPS can measure Earth's rotation very precisely, to about one hundredth of a millisecond.

predict:

By the end of the 21st century, the impact of global warming will be greater than the moon's gravity

Experts say that if the Earth rotated more slowly, the length of a day would increase by a few milliseconds from the standard 86,400 seconds.

A more important factor currently causing the Earth's slowing down is the gravitational pull of the moon, which exerts a gravitational pull on the oceans known as "tidal friction." Over millions of years, the Earth's rotation has slowed by about 2.4 milliseconds every 100 years.

But new research has come to a surprising conclusion: If humans continue to emit greenhouse gases at a high rate, by the end of the 21st century the impact of global warming will be greater than the influence of the moon's gravity.

From 1900 to today, climate factors have caused daylight hours to lengthen by about 0.8 milliseconds; in the worst-case high-emissions scenario, by 2100, climate factors alone will cause daylight hours to lengthen by 2.2 milliseconds compared to the same baseline.

expert:

There may be a correlation between longer days and more earthquakes

This may not sound like a big deal, and people may not be able to feel it, but Adhikari said it would definitely have a big impact on space and Earth navigation.

Knowing the exact direction of Earth at all times is crucial when humans are trying to communicate with a spacecraft, such as the Voyager probes now traveling far out of the solar system. Even a tiny deviation of a centimeter could result in a deviation of several kilometers when it arrives at its destination.

We live in a high-tech, highly connected world that relies heavily on GPS navigation. Accurate timing is essential for GPS and other communication and navigation systems, and everyone with a smartphone has GPS. These systems use highly accurate atomic time based on certain atomic frequencies.

Since the late 1960s, the world has used Coordinated Universal Time (UTC) to set time zones. UTC relies on atomic clocks, but is still synchronized with the Earth's rotation, which means that at some point a "leap second" needs to be added or subtracted to keep pace with the Earth's rotation.

Some studies have also suggested a correlation between longer days and an increase in earthquakes, said geologist Mustafa Kiani Shahwandi, but he told CNN the link is still speculative and more research is needed to determine if there is a definitive link.

Compiled/written by: Nandu reporter Shi Minglei