GRACE Detection of Transient Mass Redistributions During a Mineral Phase Transition in the Deep Mantle

Abstract The temporal evolution of the core‐mantle boundary (CMB) is of critical importance in elucidating the dynamic interactions between the fluid core and the solid mantle, but remains largely unknown. To investigate corresponding mass redistributions, we analyze GRACE satellite and Satellite Laser Ranging (SLR) measurements of the 2003–2015 space‐time variations of the Earth's gravity field and search for transient gravity changes at large spatial scales. We detect an anomalous North‐South oriented gravity signal in the Eastern Atlantic Ocean in January 2007, evolving at timescales of few years and less. We show that this signal cannot be fully explained by surface water mass redistributions, and probably originates, at least partly, from the D” layer. We suggest it could reflect temporal changes in the depth of the perovskite to post‐perovskite phase boundary within vertically moving thermal heterogeneities at the base of lower mantle upwellings, creating decimetric CMB topography changes over 2 years.