Details

Autor(en) / Beteiligte

• Davies, Christopher J.
• Stegman, Dave R.
• Dumberry, Mathieu

Titel

The strength of gravitational core-mantle coupling

Ist Teil von

• Geophysical research letters, 2014-06, Vol.41 (11), p.3786-3792

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2014

Quelle

Wiley Online Library Journals Frontfile Complete

Beschreibungen/Notizen

• Gravitational coupling between Earth's core and mantle has been proposed as an explanation for a 6 year variation in the length‐of‐day (ΔLOD) signal and plays a key role in the possible superrotation of the inner core. Explaining the observations requires that the strength of the coupling, Γ, falls within fairly restrictive bounds; however, the value of Γ is highly uncertain because it depends on the distribution of mass anomalies in the mantle. We estimate Γ 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 × 1019<Γ<2 × 1020 N m, too small to explain the 6 year ΔLOD signal. This new constraint on Γ has important implications for core‐mantle angular momentum transfer and on the preferred mode of inner core convection. Key Points Gravitational core‐mantle coupling is 2–10 times weaker than previously thought Gravitational coupling is too weak to explain the 6 year length‐of‐day signal Based on LOD constraints, our results suggest an inner core viscosity consistent with recent mineral physics experiments