Implications of high core thermal conductivity on Earth's coupled mantle and core evolution

We assess the effect of high thermal conductivity of Earth's core, which was recently determined to be 2-3 times higher than previously thought, on Earth's thermochemical-magnetic evolution using a coupled model of simulated mantle convection and parameterized core heat balance, following the best fit case of Nakagawa and Tackley (2010). The value of core thermal conductivity has no effect on mantle evolution. The core-mantle boundary heat flow starts high and decreases with time to similar to 13TW, which is below the core adiabatic heat flux for the largest thermal conductivity tested (200W/m/K), meaning that a purely thermal dynamo is not viable. However, gravitational energy release and latent heat associated with inner core growth become important in the last similar to 0.9Gyr and allow continuous geodynamo generation despite high core thermal conductivity, although we estimate a subadiabatic region at the top of the core of the order of hundreds of kilometers.