The strength of gravitational core-mantle coupling

TitleThe strength of gravitational core-mantle coupling
Publication TypeJournal Article
Year of Publication2014
AuthorsDavies CJ, Stegman DR, Dumberry M.
JournalGeophysical Research Letters
Date Published2014/06
Type of ArticleArticle
ISBN Number0094-8276
Accession NumberWOS:000339280200015
Keywordsconstraints; 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.

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