Deep Earth Core Dynamics Drive Decadal Shifts in Day Length
A new study in Nature identifies gravitational, electromagnetic, and topographic coupling between Earth’s inner core and mantle as the primary drivers of multidecadal changes in the length of a day. Researchers Huifeng Zhang and Mathieu Dumberry found that gravitational torque from the inner core primarily influences these shifts, while the other two mechanisms act as buffers. These deep interior interactions have altered the day’s length by several milliseconds between the early 1970s and 2021, offering new constraints on the physical properties of Earth’s deep layers.