The thermal conductivity of Earth's lower mantle

Abstract

We assess the thermal conductivity of the Earth's lower mantle anchored on our first-principles calculations of lattice thermal conductivity of MgSiO 3 perovskite. Our calculations agree with measurements of iron-free perovskite at ambient conditions and show a lower pressure dependence compared with other recent calculations. In addition, we show that the effect of iron on the lattice thermal conductivity of silicate perovskite is likely to be small at high temperatures. To provide an assessment of thermal conductivity throughout the lower mantle, we reevaluate existing high-pressure optical absorption data to constrain an upper bound radiative contribution to diffusive heat transfer and examine a composite model for combining thermal conductivity of oxide and perovskite phases in the lower mantle. We find that the overall thermal conductivity of the lower mantle is approximately constant between 2.5 and 3.5W/m/K. These values imply that the mantle has a blanketing effect on heat flow across the core-mantle boundary. Key Points Lattice thermal conductivity of MgSiO3 at high P and T was calculated using DFT Lower mantle radiative and conductive heat transport was assessed Thermal conductivity of lower mantle is low and insensitive to P and T ©2014. American Geophysical Union. All Rights Reserved.