Long‐term true polar wander of the Earth including the effects of convective processes in the mantle and continental drift

SUMMARY Long‐term true polar wander (TPW) of the Earth was examined by taking into account the effects of simplified convective processes in the Earth's mantle and continental drift. The TPW, for a given viscoelastic earth model, is wholly determined by both the magnitude of non‐forcing elements of moment of inertia ( I 11 , I 22 and I 33 ) and I 12 element of product of inertia, and the rates for forcing elements, d I 13 /d t and d I 23 /d t . The forcing rates are largely related to time‐dependent convective processes in the mantle and also continental drift. In this study, I examined the TPW on a convecting mantle with oscillating moments of inertia, inferred from a convective process of alternating degree‐one and degree‐two structure changes of mantle convection by Zhong et al . (2007). In the phase for a relatively hydrostatic Earth, corresponding to largely degree‐one planform, the predicted TPW is sensitive to the viscosity structure of the mantle, particularly to the lithospheric viscosity structure, and its magnitude may be larger than ∼30° even for the forcing rates with ∼10 30  kg m 2  Myr −1 related to continental drift (Dickman 1979). In the phase for a non‐hydrostatic Earth characterized by largely degree‐two planform such as for the present‐day, however, the TPW is less sensitive to the viscosity structure, and its magnitude may be ∼10° at most. These results may provide quantitative constraints on examining relationship between rheological structure and convective processes in the mantle, continental drift and TPW.