Study links Earth's inner core gravity to decade-scale day-length shifts

Researchers analyzed length-of-day (LOD) records from 1964 to 2019, after removing known effects from the atmosphere, oceans, tides and surface mass changes, to isolate multidecadal variations. They modeled these residual variations using torque equations that account for gravitational pull from the inner core alongside electromagnetic and topographic coupling at the core-mantle boundary, finding that gravitational torque from the inner core contributes to the slow, multidecadal changes in how long a day lasts.