Researchers said the slowdown of Earth’s inner core could change the length of a day
New Delhi:
A new study has provided “unequivocal evidence” that Earth’s inner core has started to slow its rotation since 2010, compared to the planet’s surface.
The researchers said the slowdown could change the length of a day on Earth by fractions of a second.
Earth’s inner core, a solid sphere made of iron and nickel, is suspended within the liquid outer core (made of molten metals) and anchored in place by gravity. Together, the inner and outer core form one of the planet’s three layers – the other two are the mantle and crust.
Because it is physically inaccessible, researchers generally study the core by analyzing records of waves emitted by earthquakes – seismograms.
“When I first saw the seismograms that suggested this change, I was perplexed,” said John Vidale, professor of Earth Sciences at the University of Southern California, USA.
“But when we found two dozen more observations signaling the same pattern, the result was inevitable. The inner core slowed down for the first time in many decades,” said Vidale, also corresponding author of the study published in the journal Nature.
The slowing of the inner core is hotly debated in the scientific community, with some studies even suggesting that it spins faster than the Earth’s surface.
It is known that the rotation of the inner core is influenced by the magnetic field generated in the outer core and by the gravitational effects on the Earth’s mantle.
However, the inner core is considered to be inverting and receding relative to the surface due to slower rotation than the mantle for the first time in about 40 years.
“Other scientists have recently argued for similar and different models, but our latest study provides the most convincing resolution,” Vidale said.
A study published earlier this year in the journal Nature found that climate change-driven ice melt in Greenland and Antarctica was affecting global timing by slowing the Earth’s rotation.
The author, Duncan Agnew, a geophysicist at the University of California, San Diego, showed that Earth’s liquid core was slowing its rotation. To counter the effects of this, the solid Earth was rotating faster, Agnew said.
However, this has resulted in the need to add fewer ‘leap seconds’ to Coordinated Universal Time (UTC) in recent decades, according to Agnew.
Since 1972, every few years it has been necessary to add a ‘leap second’, due to irregularities in UTC arising from the fact that the Earth does not always rotate at the same speed.
For the latest study, researchers analyzed seismic data recorded from 121 repeat earthquakes – multiple earthquakes occurring in the same location – between 1991 and 2023 in the South Sandwich Islands, a remote archipelago in the South Atlantic Ocean. The islands are prone to violent earthquakes.
Data from twin Soviet nuclear tests between 1971 and 1974, along with multiple French and American nuclear tests from other inner core studies, were also included in the analysis.
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