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Article Dans Une Revue Geophysical Journal International Année : 2020

The limited contribution from outer core dynamics to global deformations at the Earth’s surface

N Gillet
M Dumberry
  • Fonction : Auteur
Séverine Rosat

Résumé

Planetary scale interannual deformations of the Earth's surface, of millimetric amplitude, have recently been related to both geomagnetic field changes and motion within the fluid outer core. We calculate the temporal variations of the dynamical pressure at the surface of the core associated with core flow models inverted from geomagnetic observations. From these we compute predictions of the changes in Earth's topography in response to elastic deformations in the mantle. We show that at decadal periods, the predicted changes in Earth's topography are at most of the order of 0.3 mm. Focused at interannual periods between 4 and 9.5 yr, the predicted topography variations are smaller than 0.05 mm, at least an order of magnitude smaller than the reported observations. These amplitudes are only weakly sensitive to the choice of hypothesis used to reconstruct fluid motions at the core surface. We conclude that surface deformations induced by dynamical pressure changes in the core are below the detection level at present-day. Alternative geophysical sources must be sought to explain the observed millimetric interannual variations of the planetary scale topography, and its associated gravity variations. We currently see no justification for a physical relationship between interannual fluctuations of the geomagnetic Downloaded from
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Dates et versions

hal-02949229 , version 1 (25-09-2020)

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N Gillet, M Dumberry, Séverine Rosat. The limited contribution from outer core dynamics to global deformations at the Earth’s surface. Geophysical Journal International, 2020, ⟨10.1093/gji/ggaa448⟩. ⟨hal-02949229⟩
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