Core‐mantle boundary topography estimated from numerical simulations of instantaneous mantle flow

Core‐mantle boundary (CMB) topography is estimated from numerical simulations of instantaneous mantle flow in a three‐dimensional spherical shell geometry. Density anomaly models of the Earth's mantle are derived from geodynamic models constrained principally by seismic tomography results. To account for the small (±∼1.5 km) CMB topographic relief inferred from recent seismological results, lateral viscosity variations in the mantle, compositionally dense piles in the deep mantle, and a low‐viscosity D″ layer are all required for the numerical models. Low‐viscosity subducting slabs in the lower mantle serve to reduce the topographic amplitude below high‐velocity regions (i.e., the circum‐Pacific belt). The existence of dense piles may cause the local topographic depressions even below low‐velocity regions (i.e., the South Pacific and Atlantic Africa regions).