Abstract
Length-of-Day (LOD) measurements represent variations in the angular momentum of the solid Earth (crust and mantle). There is a known ~6-year LOD signal suspected to be due to core-mantle coupling. If it is, then the core flow associated with the 6-year LOD signal may also deform the mantle, causing a 6-year signal in the deformation of the Earth’s surface. Stacking of Global Positioning System (GPS) data is found to contain a ~6-year radial deformation signal. We inverted the deformation signal for the outer core’s flow and equivalent angular momentum changes, finding good agreement with the LOD signal in some cases. These results support the idea of subdecadal core-mantle coupling, but are not robust. Interpretation of the results must also take into account methodological limitations. Gravitational field changes resulting from solid Earth deformation were also computed and found to be smaller than the errors in the currently available data.
Highlights
There is a ~6-year LOD signal that remains after removing the effects of the oceans and atmosphere[1]
Results were compared with this expectation, and gravitational field changes resulting from solid Earth deformation were computed
The ΔLODatmosphere accounts for atmospheric angular momentum (AAM) variations and was computed as[9]: ΔLODatmosphere =
Summary
There is a ~6-year LOD signal that remains after removing the effects of the oceans and atmosphere[1] Both the fluid outer core[4] and the solid inner core[5] have been suggested as causes for the signal. This study aimed to 1) Test the idea that the ~6-year LOD signal is due to angular momentum exchange between the solid Earth and outer core, and 2) Demonstrate the viability of a novel approach to investigating the core’s rotation: the inversion of crustal deformation data. We analyzed the spectrum of 523 stacked GPS radial time series, and found there is a global ~6-year deformation signal (Fig. 1). Fang et al.[7] detailed how pressure anomalies below the core-mantle boundary (CMB) deform the solid Earth. The ~6-year LOD signal was isolated and used to derive a time series of equivalent solid Earth angular momentum changes ΔLMC. Results were compared with this expectation, and gravitational field changes resulting from solid Earth deformation were computed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
