Together with collaborators Max Rudolph at Portland State University and Carolina Lithgow-Bertelloni at University College London, we used a novel inversion framework to detect the presence of an increase in viscosity in the Earth's mid mantle.
As Science magazine put it:
A mysterious mid-mantle slowdown
The viscosity of Earth's deep interior plays a key role in mediating plate tectonics. Rudolph et al. combined several geophysical data sets to model the viscosity of the mantle. Mantle viscosity abruptly increases below 1000 km. The increase could explain the stalling of subducting slabs and the deflections of hot upwelling plumes around this depth. Although the viscosity increase explains some recent unexpected observations, the origin of the jump itself remains a mystery.
Science, this issue p. 1349"
Links to media coverage:
Link to the University of Maryland press release: https://cmns.umd.edu/news-events/features/3353
Link to the paper: Rudolph_Lekic_LB