Earth days will grow at an unprecedented rate as polar ice melts: ScienceAlert

It is well known that time is of the essence when it comes to the climate crisis.

Melting polar ice caps are slowing our planet’s rotation, causing days to lengthen at an “unprecedented” rate, a study released Monday showed.

The paper published in Proceedings of the National Academy of SciencesThe study showed that water flowing from Greenland and Antarctica is adding mass around the equator, co-author Surendra Adhikari of NASA’s Jet Propulsion Laboratory told AFP.

“It’s similar to what happens when a figure skater performs a pirouette, first holding her arms close to her body and then extending them,” added co-author Benedikt Soja of the Swiss Federal Institute of Technology in Zurich.

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

The Earth is generally thought of as a sphere, but it is more accurate to call it an “oblate spheroid” that bulges somewhat around the equator, somewhat like a satsuma.

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

The paper relied on observational techniques such as very long baseline interferometry, where scientists can measure the difference in how long it takes radio signals from space to reach different points on Earth, and use that to infer differences in the planet’s orientation and the length of the day.

He also used GPS, which measures the Earth’s rotation very accurately, to within one hundredth of a thousandth of a second, and even looked at ancient eclipse records dating back thousands of years.

Implications for space travel

If the Earth rotated more slowly, the length of a day would increase by a few milliseconds from the standard measurement of 86,400 seconds.

The most important reason for the current slowdown is the gravitational pull of the moon, which pulls on the oceans in a process called “tidal friction” and has caused a gradual slowdown of 2.40 milliseconds per century over millions of years.

But the new study comes to a surprising conclusion: If humans continue to emit greenhouse gases at high rates, the warming effect will be greater than the moon’s gravitational pull by the end of the 21st century, Adhikari said.

Between 1900 and today, climate has caused days to lengthen by about 0.8 milliseconds—and in the worst-case scenario of high emissions, climate alone would be responsible for about 2.2 milliseconds longer days by 2100, compared to the same baseline.

This may not seem like a big deal, and it’s certainly not something humans can comprehend.

But “there are definitely a lot of implications for space and terrestrial navigation,” Adhikari said.

Knowing the exact direction of the Earth at any given moment is crucial when trying to communicate with a spacecraft, such as the Voyager probes now outside our solar system, where even a slight deviation of one centimeter can end up being kilometers away by the time it reaches its destination.

© AFP