Effects of multiple phase transitions in a three-dimensional spherical model of convection in Earth's mantle

摘要: Numerical models of mantle convection that incorporate the major phase changes transition zone reveal an inherently three-dimensional flow pattern, with cylindrical features and linear behave differently in their ability to penetrate 670-km discontinuity. The dynamics are dominated by accumulation cold downwellings into rounded pools above endothermic change at 670 km depth, resulting frequent “avalanches” upper material lower mantle. effect exothermic 400 depth is reduce overall degree layering pushing through change, smaller more avalanches, a wider range morphologies. Large quantities avalanched accumulate coremantle boundary (CMB), region strongly depressed mean temperature base has strong on field, three-distinct regions being visible: (1) mantle, containing characterized high amplitude long wavelength spectrum; (2) midmantle, quasi-cylindrical avalanche conduits low amplitude, broad (3) deep large cold, ultra-red (i.e., wavelength) spectrum. velocity field very different. Flow penetration across wavelength-dependent, easy wavelengths but inhibition short wavelengths. Thus, when comparing numerical seismic tomography, diagnostics based density such as radial correlation function, much sensitive effects transitions than those field. geoid not significantly affected partial layering, because contribution from heterogeneity almost perfectly balanced deflection Avalanches associated lows. However, complex viscosity structure required correctly match sign over slabs Earth.