Gravimetric and magnetic anomalies produced by dissolution-crystallization at the core mantle boundary

Abstract:

Using the unique magnetic and gravity datasets provided by CHAMP and GRACE satellites, a correlation
between magnetic and gravity field temporal variations have been reported. On a time scale of few years to a decade, both field variations may be linked to changes at the top of the core. We propose that the topography of the core mantle boundary (CMB) is in a dynamic equilibrium state mainly controlled by a dissolution/crystallization process of the mantle silicate rocks in the liquid alloy of the core. Subsequent to the continuous changes in topography at the CMB, we show that anomalies of hundreds of nGal and tens of nT/yr² can be produced by the corresponding mass redistribution and the secondary flows generated by the dynamic pressure. Numerical models and both gravimetric and magnetic anomalies suggest a rate of centimeters per year for changes in topography at the CMB.