The effect of continents on mantle convective stirring

Abstract

[1] We have investigated the influence of continental lids on mantle convective stirring efficiency using numerical experiments and analytical theory at infinite Prandtl number with strong temperature dependence of viscosity. Differences between oceans and continents are accounted for by imposing heterogeneous surface boundary conditions for temperature and velocity. We measure the convective stirring efficiency using mixing times and Lyapunov exponent distribution. We quantify systematically the influence of the Rayleigh number, the horizontal extent of continental lids and the rheology on mantle convective stirring efficiency. The presence of continents increases the mantle temperature and therefore reduces mantle viscosity. This in turn leads to an increase of convective vigor and results in a drastic enhancement (3–6 fold, and possibly up two orders of magnitude increase) of mantle convective stirring efficiency.