Time-variable gravity anomaly arising from dynamical mass transport in the outer core and core-mantle interaction

The geomagnetic field has been generated and maintained by convective flow in the Earth's outer core through much of the Earth's history. The core convection varies on time scales of a few decades and longer. This process contributes to time-variable gravity mainly in two ways: (1) redistributing small density anomalies within the entire outer core, and (2) producing varying non-hydrostatic pressure loading on the core-mantle boundary (CMB). The combined gravity effect shall be displayed at the Earth's surface. Our previous studies indicate that the density anomalies in the core alone could produce a time-variable gravity signal observable at the Earth's surface. However, the effect of mantle deformation depends not only on the core pressure field on the CMB, but also the properties of the mantle. It is therefore necessary to understand the net effect via our MoSST core dynamics model. To achieve this, we add two "plug-in" modules to the system: one for gravity variation due to density anomalies in the core, and one on mantle deformation due to pressure field on the CMB. This study shall help identify the geophysical contributors to the time-variable gravity observed at the Earth's surface, thus facilitating multidisciplinary studies of core dynamics and interactions of the core with other components of the Earth.