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Model links Earth’s core forces to millisecond-scale changes in day length
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Gravitational torque best matches multidecadal rotation changes
A peer-reviewed Nature study published September 23 found that gravitational coupling between Earth’s inner core and mantle best reproduced observed multidecadal changes in day length from 1964 to 2019. The model attributes fluctuations of several milliseconds mainly to gravitational torque, with electromagnetic and topographic forces acting in opposition. This offers a testable explanation for changes already linked to exchanges of angular momentum between the core and mantle, but it depends on indirect reconstructions of inner-core rotation and fluid-core flow rather than direct measurements of the proposed forces.
Nature News — Gravitational tug-of-war inside Earth is changing the length of our days · Nature — Competing torques couple Earth’s core and mantle