Germana Carillo The days are getting longer as global temperatures continue to rise. According to research, the melting of global ice sheets and glaciers causes sea level rise, pole-to-equator mass transport, increased Earth oblation and, therefore, an increase in day length
The melting of polar ice caps is causing Earth to rotate more slowly, lengthening days at an “unprecedented” rate.
This finding comes from a study published in the Proceedings of the National Academy of Sciences, showing that water flowing from Greenland and Antarctica is leading to a mass accumulation around the equator. Essentially, the melting ice sheets and global glaciers are raising sea levels, moving mass from the poles to the equator, increasing Earth’s equatorial bulge and lengthening the day.
“It’s like a figure skater spinning with arms close to the body and then extending them,” explains co-author Benedikt Soja from ETH Zurich. “This movement slows the rotation as the masses move away from the axis of rotation, increasing physical inertia.”
Gravitational pull and historical trends
For millennia, the length of a day on Earth has gradually increased by a few milliseconds per century. This increase was largely due to the gravitational pull of the moon, which has slowly been decelerating Earth’s rotation, as well as the glacial isostatic adjustment process—the movement of molten rock in Earth’s mantle towards polar regions, especially in the northern hemisphere. However, the melting ice sheets in the Arctic and Antarctic have also contributed significantly to day length by moving large masses from the poles to the equator. Researchers examined the impact of climate change-induced sea level rise on day length since 1900.
Consequently, Earth’s natural oblate shape, like a slightly flattened sphere bulging at the equator, is becoming even flatter, said Surendra Adhikari, a geophysicist at NASA’s Jet Propulsion Laboratory and one of the study’s authors.
Future projections
By the end of the 21st century, in high-emission scenarios, the impact of climate change alone might surpass the influence of Earth-Moon dynamics. According to the study, the redistribution of mass driven by the melting Greenland and Antarctic ice sheets has occurred at unprecedented rates over the last two decades. Sea level fluctuations have caused the length of Earth’s day to vary between 0.3 and 1.0 milliseconds per century during the 20th century. But since 2000, the day length has increased by about 1.33 milliseconds per century, researchers found.
The day length could increase by another 2.62 milliseconds per century by the end of the 21st century if greenhouse gas emissions continue unchecked, the study says.
Timekeeping challenges
In March, a study published in Nature showed that melting polar ice is altering Earth’s rotation, affecting time measurement. Coordinated Universal Time (UTC) was established as the international standard for timekeeping in 1960. However, UTC might eventually need to incorporate a “negative leap second” due to the planet’s inconsistent rotation spurred by climate change.
If Earth rotates more slowly, the day lengthens by a few milliseconds compared to the standard 86,400 seconds. A significant current factor in this slowing is the moon’s gravitational force acting on the oceans in a process called “tidal friction,” causing a gradual deceleration of 2.40 milliseconds per century over millions of years.
Conclusion
The study concludes that if humanity continues to emit greenhouse gases at a high rate, the effect of a warming climate will outweigh the moon’s gravitational pull by the end of the 21st century.
