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

Abstract

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). Copyright 2008 by the American Geophysical Union.