Study finds melting ice caps slow Earth's spin

WASHINGTON — As far as the climate crisis goes, time is of the essence.

Now, a study released on Monday showed that the melting of polar ice caps is causing our planet to spin more slowly, increasing the length of days at an "unprecedented" rate.

The paper, published in Proceedings of the National Academy of Sciences, showed that water flowing from Greenland and Antarctica is resulting in more mass around the equator, co-author Surendra Adhikari of NASA's Jet Propulsion Laboratory told Agence France-Presse.

"It's like when a figure skater does a pirouette, first holding her arms close to her body and then stretching them out," co-author Benedikt Soja of ETH Zurich said.

"The initially fast rotation becomes slower because the masses move away from the axis of rotation, increasing physical inertia."

Earth is commonly thought of as a sphere, but it is more accurate to call it an "oblate spheroid" that bulges somewhat around the equator.

Moreover, its shape is constantly changing, from the impacts of daily tides that affect the oceans and crusts to long-term effects from the drift of tectonic plates and abrupt violent shifts caused by earthquakes and volcanoes.

The paper relied on observational techniques like Very Long Baseline Interferometry, where scientists can measure the difference in time it takes for radio signals from space to reach different points on Earth, and use that to infer variations in the planet's orientation and length of day.

It also used the Global Positioning System, which measures the Earth's rotation very precisely, to about 100th of a millisecond, and even looked at ancient eclipse records going back millennia.

If the Earth turns more slowly, then the length of the day increases by a few milliseconds from the standard measure of 86,400 seconds.

A significant cause of the slowdown is the gravitational pull of the moon, which pulls on the oceans in a process called "tidal friction" that has caused a gradual deceleration of 2.4 milliseconds per century over millions of years.

But the new study comes to a surprising conclusion that, if humans continue to emit greenhouse gases at a high rate, the effect of a warming climate will be greater than that of the moon's pull by the end of the 21st century, Adhikari said.

Agencies via Xinhua