As ice melts, water levels rise, which changes the Earth’s rotation in a small way. This phenomenon could change the way we measure time.
The blue planet in slow motion? According to a study in the scientific journal Nature published Wednesday March 27, the Earth is currently rotating less quickly due to global warming. A phenomenon imperceptible to humans, but which could have consequences on our way of measuring time.
Melting ice to blame
Gilles Dawidowicz, vice-president of the Astronomical Society of France, explains to BFMTV that “the rotational movement of the Earth, which accelerates in normal times”, is currently faced with a “counter-phenomenon” of slowing down of our planet faster than expected, “linked to global warming”.
How to explain this phenomenon? Concretely, global warming leads to the melting of the ice pack at the North Pole and the South Pole, a well-known phenomenon, but which has multiple consequences. Among them, researchers note that the melted ice reaches all of the seas and oceans of the planet, which then increases the mass of the Earth at the equator.
The change remains “tiny”, assures BFMTV Christian Bizouard, astronomer at the Paris observatory, in charge of monitoring the rotation of the Earth, it is of the order of “milliseconds or in fractions of milliseconds in hundreds of years”.
The slowing effect of melting ice was suggested at the end of the 19th century and has been calculated since the 1950s, reports Duncan Agnew from Agence France-Presse (AFP). “But the novelty of my work is to show the extent of the impact of melting ice on the rotation of the Earth. A change never seen before,” he says.
Consequences on universal time
This slowdown is imperceptible to humans, but it is detected by the international clock which has been responsible since 1967 for defining universal international time, regularly updated and used in particular to make digital services and such as satellite navigation work uniformly.
UTC time is linked to astronomical time which is calculated with the Earth’s rotation speed. Problem, this rotation is not constant. Scientists must therefore regularly make corrections.
“Sometimes, we add leap seconds, for example 23h59min and 60 seconds,” explains Gilles Dawidowicz.
Take a second off?
With the slowing of the Earth’s rotation, a new difficulty appears for scientists.
“Perhaps, in a few years, we will have to subtract a second”, which would be unprecedented, indicates the vice-president of the Astronomical Society of France.
“It’s going to be a bit like what we feared from the Y2K bug,” he adds, in other words, a leap into the unknown which worries the scientific community, while today’s society is increasingly dependent on more about computerization.
“I would not recommend being on a plane at that time,” Demetrios Matsakis, former chief scientist of the United States Naval Observatory, told AFP. took part in the work.
The slowdown is such that it could postpone the possible reduction of a second until 2029, according to the results of the study. Without the effects of global warming, it would undoubtedly have had to be added in 2026.
This delay is, however, rather welcome for metrologists, since it gives them “more time to decide if 2035 is the best date to eliminate the leap second, or if it should be abandoned before then”, reacted Patrizia Tavella, from International Bureau of Weights and Measures (BIPM), in a commentary attached to the study.
