EPSS Colloquium winter-2019

The viscosity structure of Earth's deep mantle affects the thermal evolution of Earth, the ascent of mantle upwellings, sinking of subducted oceanic lithosphere, and the mixing of compositional heterogeneities in the mantle. Modeling the long-wavelength dynamic geoid allows us to constrain the radial viscosity profile of the mantle. I will discuss new solutions for the mantle viscosity structure and its uncertainty based on a suite of joint whole-mantle tomographic models of both S- and P-wave velocity as well as density. The resulting density variations in the lowermost mantle span scenarios in which the net buoyancy of the Large Low Shear Velocity Provinces (LLSVPs) appears to be primarily controlled by temperature, as well as those in which the LLSVPs represent intrinsically dense material. Finally, I will show results from kinematically-constrained mantle convection models with idealized viscosity profiles and make a comparison between emergent large-scale structures and structures observed in seismic tomography.