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Earth's Rotation Slowing Due to Melting Ice Could Impact Timekeeping, Study Finds

Earth's Rotation Slowing Due to Melting Ice Could Impact Timekeeping, Study Finds

March 28, 2024

A new study published in Nature suggests human-driven climate change is slowing the Earth's rotation, potentially impacting how we measure time.

The research, led by Scripps Institution of Oceanography geophysicist Duncan Agnew, attributes the slowdown to melting ice sheets in Greenland and Antarctica. As massive glaciers lose ice, Earth's mass distribution changes, shifting more mass towards the equator. This shift, similar to a figure skater extending their arms, creates a slight rotational deceleration.

Earth's Rotation Slowing Due to Melting Ice Could Impact Timekeeping, Study Finds

Melting ice counteracts the effect

While Earth's rotation has naturally sped up in recent decades due to core dynamics, melting ice counteracts this effect. The study predicts this could delay the need for a "negative leap second" – an extra second subtracted from clocks to maintain synchronization with Earth's rotation – by up to three years.

Earth's Rotation Slowing Due to Melting Ice Could Impact Timekeeping, Study Finds

"Leap seconds" have been implemented since 1972 to adjust for Earth's  irregular rotation.  Previously, concerns focused on adding leap seconds due to Earth's speeding rotation.  This research suggests the first potential need for a negative leap second due to a slowing Earth.

Affecting Earth's rotation

"It's remarkable that human activity is measurably affecting Earth's rotation," said Agnew. "This highlights the unprecedented nature of climate change and its far-reaching consequences."

Earth's Rotation Slowing Due to Melting Ice Could Impact Timekeeping, Study Finds

The study emphasizes that melting ice is just one factor influencing Earth's rotation. Tidal friction caused by the Moon and internal fluid dynamics within the planet's core also play a role.

This research underscores the complex interplay between human activity and Earth's natural systems, with potential implications for future timekeeping practices.