Heat Transport Scaling in Earth's Mantle-Plate System: Understanding Core Heat Flow and the Effect of Continents

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

Tackley EAR-0229504 Understanding how the heat fluxes at Earth's surface and core-mantle-boundary (CMB) scale with the relevant parameters is essential to understanding the thermal evolution of the mantle and core. This two-year project involves focused studies of two important but presently ill-determined aspects of heat transport, using the tool of numerical modeling. The first aspect is how CMB heat flux scales in the presence of plate tectonics. This is important because constraints from geodynamo energetics on the heat flow through the CMB indicate that the likely heat flow is much higher than that measured by buoyancy fluxes of observed hotspots, suggesting that other modes of core heat removal are important. It is thought that these other modes are most likely 'slab warming' (warming of cold subducted slabs resting above the CMB), and 'stealth plumes' (plumes that do not generate an observable signature at the surface). The relevant scalings in the presence of plate tectonics and strongly variable interior viscosity are not known, and will be the first focus of this investigation. The second aspect is the effect of continents on surface heat flow. Continents have a "thermal blanketing" effect which affects the scaling of heat flux (Nu) with Rayleigh number (Ra). However, the effect of continents on this scaling has not been quantified, with previous parameterized thermal evolution models simply reducing the standard Nu-Ra scaling in proportion to the fractional surface area covered by continents. Establishing the scaling of surface heat flow, internal temperature and velocities with continental (width, Biot number) and standard convective parameters will be the second focus of this project.