Fig. 2: Thermal conductivities of the Earth’s outer shell: 40 km-thick lithosphere, upper mantle (40–410 km), upper MTZ (410–520 km), and lower MTZ (520–660 km).
From: Olivine’s high radiative conductivity increases slab temperature by up to 200K
Our calculated mantle adiabat53,54 assumes a potential temperature of \(1619 \ {K}\). The solid curves represent the \(\varLambda\) profiles used in our study, while the dashed and dashed-dotted curves indicate the \(\varLambda\) profiles reported in the literature. The \(P\), \(T\) dependence of \({\varLambda }_{{rad}}^{{Ol}}\) is shown in Fig. S5. 1. (solid black) total thermal conductivity computed as \(\varLambda={\varLambda }_{{lat}}+{\varLambda }_{{rad}}\). The grey shaded area represents the uncertainty in \(\varLambda\) estimates. 2. (solid red) radiative thermal conductivity \({\varLambda }_{{rad}}\) computed from: olivine[this study] (UM), wadsleyite36 (upper MTZ), and ringwoodite36 (lower MTZ). The red shaded area represents the \(\pm 30\%\) uncertainty in \({\varLambda }_{{rad}}^{{Ol}}\) estimates from LH-DAC measurements37,38,39. 3. (solid blue) lattice thermal conductivity \({\varLambda }_{{lat}}\) profile computed from: olivine55,68 (UM) and ringwoodite45 (MTZ). The blue shaded area represents \(\pm 15\%\) uncertainty in \({\varLambda }_{{lat}}^{{Ol}}\) estimates from Time-Domain Thermo-Reflectance (TDTR) measurements45,68. 4. (dashed black) total thermal conductivity \({\varLambda }_{{tot}}^{{Hof}1999}\), with \({\varLambda }_{{rad}}^{{Hof}1999} \sim 0.35\) \(W\) \({m}^{-1}\) \({K}^{-1}\) ref. 27. 5. (dashed-dotted crimson) radiative thermal conductivity \({\varLambda }_{{rad}}^{{Hof}2005}\), ref. 28. 6. (dashed crimson) radiative thermal conductivity \({\varLambda }_{{rad}}^{G\&A2019}\), ref. 35. 7. (coral diamonds) radiative thermal conductivity for the crystallographic directions a and c \({\varLambda }_{{rad}}^{Sha1979}\), ref. 25. Note that our estimated \({\varLambda }_{{rad}}\) (profile 2, solid red) rapidly increases in the lithosphere (linear \(T\) gradient \(35\) \(K/{km}\)) and flattens in the sub-lithospheric mantle (adiabatic \(T\) gradient \(\sim \!0.5\) \(K/{km}\)54).
