Scientists Pin Down Why Earth's Day Length Shifts Every Few Decades

A study in Nature finds that multidecadal changes in Earth's rotation come from deep inside the planet, where gravitational, electromagnetic and topographic coupling compete. Gravitational coupling between the inner core and mantle dominates, while the other two act as a buffer. From the 1970s to 2021 the effect shifted day length by several milliseconds.

• Gravitational coupling between core and mantle dominates rotation changes
• Electromagnetic and topographic coupling buffer those shifts
• From the 1970s to 2021 day length varied by several milliseconds
• Findings rest on statistical models and six decades of observations