Climate change is changing how we keep time

Climate change is changing how we keep time

Science News reports:

Climate change may be making it harder to know exactly what time it is.

The rapid melting of the ice sheets atop Greenland and Antarctica, as measured by satellite-based gravitational measurements, is shifting more mass toward Earth’s waistline. And that extra bulge is slowing the planet’s rotation, geophysicist Duncan Agnew reports online March 27 in Nature. That climate change–driven mass shift is throwing a new wrench into international timekeeping standards.

The internationally agreed-upon coordinated universal time, or UTC, is set by atomic clocks, but that time is regularly adjusted to match Earth’s actual spin. Earth’s rotation isn’t always smooth sailing — the speed of the planet’s spin changes depending on a variety of factors, including gravitational drag from the sun and the moon, changes to the rotation speed of Earth’s core, friction between ocean waters and the seafloor, and shifts in the planet’s distribution of mass around its surface. Even earthquakes can affect the spin: The magnitude 9.1 earthquake in Indonesia in 2004, for example, altered the land surface in such a way that it caused Earth to rotate a tiny bit faster, says Agnew, of the Scripps Institution of Oceanography in La Jolla, Calif. [Continue reading…]

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