Dynamic significance of long-wave density gradients due to heat generation within the mantle

Abstract

[1] We give a new solution of the Boussinesq equations of motion describing flow driven by internal heat generation within a plane horizontal layer of viscous but thermally non-conducting fluid. The solution models the central region of a long mantle convection cell, excluding the cold plate and slab, and gives the coupled velocity and temperature fields in terms of the heating rate and material properties. Interaction of the buoyantly-driven flow with internal heat generation creates a long-wave, horizontal density gradient. Scaled to the mantle, the predicted amplitude of that gradient appears too small to observe seismically with current methods, but the corresponding flow speeds are comparable with those observed. To assume that mantle flow is driven purely by currently observable density differences may therefore be to ignore a large part of the forcing.