23 Jan. () –
The rotation of the Earth’s inner core has recently stopped according to a temporal comparative analysis of seismic waves, which suggests a multidecadal variation for this phenomenon.
It is the conclusion of a new study published in Nature Geoscience by Yi Yang and Xiaodong Song of Peking University’s Institute of Theoretical and Applied Geophysics.
It is believed that the differential rotation of the Earth’s inner core with respect to the mantle it occurs under the effects of geodynamics on core dynamics and core-mantle gravitational coupling.
This rotation has been deduced from the temporal changes between repeated seismic waves that should travel the same path through the inner core.
For this new research, Yi Yang and Xiaodong Song analyzed repeated seismic waves from the early 1990s and the authors found that all trajectories that previously showed significant temporal changes have shown few changes over the past decade.
This globally consistent pattern suggests –the authors conclude– “that the rotation of the Earth’s inner core has recently stopped”.
The scientists compared this recent pattern with seismic records in the South Sandwich Islands, in the South Atlantic, which date back to 1964 and appear to be associated with a gradual turning of the inner core as part of an oscillation of approximately seven decadeswith another turning point in the early 1970s.
In his opinion, this multidecadal periodicity coincides with changes in other geophysical observations, especially the length of the day and the magnetic field.
In conclusion, they argue that these observations provide evidence of dynamic interactions between the layers of the Earth, from the deepest interior to the surface, potentially due to gravitational coupling and angular momentum exchange from the core and mantle to the surface.
