Earth’s Inner Core ‘Unambiguously’ Slowing Down, Study Finds
A new study has found "unambiguous evidence" that Earth's inner core began slowing its rotation in 2010 compared to the planet’s surface. Researchers suggest this change could alter the length of a day on Earth by fractions of a second.
The Earth's inner core is a solid sphere composed of iron and nickel, suspended within the liquid outer core of molten metals and held in place by gravity. Together with the mantle and crust, these form the Earth's three layers. Due to its inaccessibility, researchers study the core by analyzing seismic waves from earthquakes.
John Vidale, a professor of Earth Sciences at the University of Southern California and the study's corresponding author, noted that initial seismogram data hinted at the change. Additional observations confirmed that the inner core had indeed slowed down for the first time in decades.
This finding is controversial within the scientific community, as some studies have suggested the inner core rotates faster than the Earth's surface. The spin of the inner core is influenced by the magnetic field from the outer core and gravitational effects within the mantle.
The latest study indicates that the inner core is reversing its direction relative to the surface due to rotating slower than the mantle for the first time in about 40 years. Vidale asserts that their study provides the most convincing resolution to this debate.
Earlier this year, another study in the journal Nature found that climate change-driven melting of ice in Greenland and Antarctica was also affecting Earth's rotation. Geophysicist Duncan Agnew from the University of California San Diego showed that the Earth’s liquid core was slowing down, causing the solid Earth to rotate faster. This has led to fewer 'leap seconds' being added to Coordinated Universal Time (UTC) in recent decades. Since 1972, leap seconds have been periodically added due to irregularities in Earth's rotation.
The latest study examined seismic data from 121 repeating earthquakes between 1991 and 2023 in the South Sandwich Islands, a region prone to violent earthquakes. Data from Soviet nuclear tests between 1971 and 1974, and multiple French and American nuclear tests, were also included in the analysis.
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