Abstract
SUMMARY We outline a linearized rotational stability theory for predicting the time dependence of true polar wander (TPW) on a Maxwell viscoelastic body in response to mantle convective loading. The new theory is based on recent advances in ice age rotation theory. A comparison between predictions based on the new theory and analytic expressions for equilibrium (infinite-time) TPW on planetary models with elastic lithospheres demonstrates that the linearized theory can, in the case of loading at mid-latitudes, predict TPW of over 20° to better than 5 per cent accuracy. We present predictions of TPW for loading with periodic and net ramp-up time histories. Moreover, we compare the time dependence of TPW under assumptions consistent with the canonical equilibrium stability theory adopted in most previous analyses of convection-induced TPW, and a stability theory that includes two effects that have not been considered in previous geophysical analyses: (1) the so-called ‘remnant rotational bulge’ associated with the imperfect reorientation of the rotational bulge due to the presence of an elastic lithosphere; and (2) a stable (over the timescale of the forcing) excess ellipticity. As a first application of the new theory, we consider recent inferences of rapid (order 1 Myr) TPW motion of amplitude 10°–20° during the Late Cretaceous. We conclude that excursions of this amplitude and timescale are physically implausible.
Highlights
The stability of the Earth’s rotation vector in response to thermal convective motions in the mantle has been, and remains, the subject of active debate within the geophysical and geological literature
In this case, the system will have a memory of its initial state, and the ultimate result is that the final equilibrium pole position (Fig. 1B5) will reflect a balance between loading and what Willemann (1984) and Matsuyama et al (2006) called the ‘remnant rotational bulge’
Within this range of true polar wander (TPW) we explore the full complexity of the time dependence of the TPW
Summary
The stability of the Earth’s rotation vector in response to thermal convective motions in the mantle has been, and remains, the subject of active debate within the geophysical and geological literature. The deviation from scenario 1A arises because elastic stresses that develop in the (initially unstressed) lithosphere in response to the perturbed centrifugal potential will impose a permanent restoring force on the rotation vector That is, in this case, the system will have a memory of its initial state, and the ultimate result is that the final equilibrium pole position (Fig. 1B5) will reflect a balance between loading and what Willemann (1984) and Matsuyama et al (2006) called the ‘remnant rotational bulge’. It would only stabilize the rotation pole in response to forcings with timescales less than the relaxation time of the high viscosity lithosphere In this regard, it would act, as in the terminology of Tsai & Stevenson (2007), as a low pass TPW filter. We begin with a summary of the linearized theory of rotational stability
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
