Melting ice caps put the need for bizarre 'negative leap second' on hold
Earth's increasing rate of spin may require us to actually skip over a second of time in the coming years, but the effects of global warming appear to be delaying that need, for now.
Researchers found that Earth’s rotation is slowing down ever so slightly due to global warming melting the polar ice caps.
If this slowing trend continues, it may delay the need for officials to consider a “negative leap second” by next decade.
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The issue: Earth's core is a (relative) slowpoke
Earth doesn’t rotate on its axis at a constant rate. Several factors work together to influence our spinning rock in space by slightly speeding up or slowing down its rate of rotation.
Our planet’s inner core spins independently from the hard outer crust on which we live. Scientists have found that our inner core is generally slowing down over time. As it slows, the angular momentum lost from the core is being directly transferred to the mantle and crust, causing the outer layers of the planet to speed up.
This has caused our days to shorten in recent years, with June 29, 2022 being our shortest day recorded in more than 60 years.
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Climate change is also playing a role in our planet’s spin, according to a paper recently published in Nature by a scientist with the Scripps Institute at the University of California San Diego.
“Imagine a skater spinning on the ice,” Duncan Agnew, the author of the paper, told the Natural History Museum. “If they hold their arms out, their spinning is slower, but if they bring them into their body, then they speed up. This demonstrates the conservation of angular momentum, a principle which applies to all spinning objects including the Earth.”
“As polar ice melts, the water spreads out over the whole ocean, causing the same effect as the skater spreading their arms out – the Earth slows down,” Agnew explained. “More rapid melting would slow the Earth more rapidly, opposing the overall speedup of the planet that has been seen in recent years.”
Leap days and leap seconds spare our calendars and clocks
The ability to measure time with incredible precision is a testament to how far human technology has come over the past few centuries.
It’s all the more impressive when you consider that our very concept of time depends on Earth’s precise movements—which turn out not to be all that precise. We adjust for these imprecisions with leap days and leap seconds.
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Earth takes about 365.25 days to complete one revolution around the Sun. We account for the extra one-quarter of a day by adding a leap day on February 29 every four years to keep our calendars in sync.
Officials also occasionally add a leap second to the clock to account for irregularities in Earth’s rotation on its axis, which add up to make days very slightly shorter than 24 hours.
Adding one second to the clock keeps precise time measured by scientists roughly in sync with solar time. The last official leap second occurred at 23:59:60 UTC on December 31, 2016.
However, due to the recent increases in the rotation rate of Earth's crust, sometime in the next few years official may need to actually remove a second, by applying a “negative leap second” to the clock.
The slow-down caused by the melting of polar ice appears to be offsetting this effect, though. As a result, Agnew's research shows that the need for this “negative leap second” may have been delayed by up to three years.
Effects of a negative leap second
It’s easier for tiny devices and massive systems alike to add one second than it is to remove one second from the clock. If this negative leap second becomes a necessity, it could have major ripple effects on computer networks around the world.
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The last such threat to global computer networks likely was the so-called Y2K (Year 2000) Bug—the problem that operating systems and programs couldn't properly handle flipping from the year 1999 to the year 2000.
Despite the fact that it’s become the butt of jokes in recent years, the Y2K issue was a legitimate threat to many computer systems. Engineers spent countless hours of labour fixing code to ensure it didn’t cause an issue.
The fact that no systems collapsed at the turn of the millennium is a testament to their hard work. Today’s crop of engineers may have a similar chance to flex their abilities if a negative leap second is required in the not-so-distant future.
Editor's note: A previous version of this article stated that the melting of polar ice was speeding up Earth's rotation, possibly making a "negative leap second" necessary by the end of the decade. However, the research referenced indicates that melting polar ice is actually slowing Earth's rotation. This slowing due to global warming has offset some of the increase in rotation seen in recent years due to other sources, which has delayed the need for a "negative leap second" by a few years. The article has been corrected. We apologize for any confusion.
(Header image courtesy of Unsplash.)
