Effects of depth‐dependent thermal expansivity on mantle circulations and lateral thermal anomalies

The influences of depth‐dependent thermal expansivity on the structure of Newtonian thermal convection and lateral thermal anomalies are studied. In an aspect‐ratio ten box the effects of the depth‐dependent expansivity are to produce large aspect‐ratio cells with a few relatively stationary upwellings. The lateral thermal anomalies in the lower mantle are greatly diminished by depth‐dependent expansivity. This together with a decrease in the temperature derivative of seismic velocities in the lower mantle would support the low level of lateral heterogeneities found in recent tomographic studies.