Polar motions excited by a convecting viscous mantle

The role played by time‐dependent mantle convection on exciting long‐term polar motions is examined by means of a viscous model. For sufficiently low effective viscosity, polar‐wander speeds of 0(1 deg/Myr) would require contributions from the off‐diagonal elements of the inertia tensor, with magnitudes around 10⁵ times smaller than those found in viscoelastic models used for postglacial rebound. Contributions from the large‐scale mantle flow to the angular momentum vector can be comparable to those due to changes in moment of inertia tensor for non‐linear rheology or for young planets. The relative roles of the two contributions depend on the non‐linear rheology of the mantle and its convective vigor.