Plume heat flow in a numerical model of mantle convection with moving plates

Abstract

Abstract Self-consistent numerical models are presented for a two-dimensional thermal convection with moving plates to estimate the heat flow transported by hot upwelling plumes in both internally and basally heated mantle. The plume heat flow depends on the internal heating rate and convective regimes but does not exceed 30% of basal heat flow when the plates rigidly move as observed on the Earth; the fraction of plume heat flow to basal heat flow becomes higher when the lithosphere behaves as a stagnant lid or as a mechanically not so strong plate. When estimated from the dynamic topography of plume-swells above hot upwelling plumes, the plume heat flow appears to be only a small fraction of the real plume heat flow. As a whole, the apparent plume heat flow estimated from dynamic topography remains only a few percent of the total heat flow on the surface boundary, the value observed for the Earth, even when the basal heating rate exceeds 50% of the total heating rate. Such a high fraction of basal heating rate is necessary for the amplitude of topography above hot upwelling plumes to become comparable to the value observed for the Earth, too. It is necessary to reexamine the earlier inference that the heat released from the core manifests itself as plume heat flow in the Earth.