|Title||The strength of gravitational core-mantle coupling|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Davies CJ, Stegman DR, Dumberry M.|
|Journal||Geophysical Research Letters|
|Type of Article||Article|
|Keywords||constraints; dynamics; earths inner-core; geodynamic data; growth; length; models; nutation observations; outer core; rotation|
Gravitational coupling between Earth's core and mantle has been proposed as an explanation for a 6 year variation in the length-of-day (Delta LOD) signal and plays a key role in the possible superrotation of the inner core. Explaining the observations requires that the strength of the coupling, Gamma, falls within fairly restrictive bounds; however, the value of Gamma is highly uncertain because it depends on the distribution of mass anomalies in the mantle. We estimate Gamma from a broad range of viscous mantle flow models with density anomalies inferred from seismic tomography. Requiring models to give a correlation larger than 70% to the surface geoid and match the dynamic core-mantle boundary ellipticity inferred from Earth's nutations, we find that 3 x 10(19) < Gamma < 2 x 10(20) N m, too small to explain the 6 year Delta LOD signal. This new constraint on Gamma has important implications for core-mantle angular momentum transfer and on the preferred mode of inner core convection.