A new inference of mantle viscosity based upon joint inversion of convection and glacial isostatic adjustment data

We present new profiles of mantle viscosity derived on the basis of non-linear, Occam-style joint inversions of an extensive set of data associated with mantle convection and glacial isostatic adjustment (GIA). The convection related observables include satellite-derived free-air gravity harmonics, the geodetically inferred excess ellipticity of the CMB and tectonic plate motions. The GIA constraints involve two classes of observables previously shown to be relatively insensitive to errors in the late Pleistocene ice history: the so-called Fennoscandian relaxation spectrum (FRS) and a set of site-specific decay times determined from the postglacial sea-level history in Hudson Bay and Sweden. The inverted viscosity profiles show a significant, three orders of magnitude, increase from the upper mantle (mean value of ∼4×1020 Pa s) to a high-viscosity (>1023 Pa s) peak at 2000 km depth, followed by a reduction toward the core-mantle boundary.