Time-dependent rotational stability of dynamic planets with elastic lithospheres
Abstract
True polar wander (TPW), a reorientation of the rotation axis relative to the solid body, is driven by mass redistribution on the surface or within the planet and is stabilized by two aspects of the planet's viscoelastic response: the delayed viscous readjustment of the rotational bulge and the elastic stresses in the lithosphere. The latter, following Willemann (1984), is known as remnant bulge stabilization. In the absence of a remnant bulge, the rotation of a terrestrial planet is said to be inherently unstable. Theoretical treatments have been developed to treat the final (equilibrium) state in this case and the time-dependent TPW toward this state, including nonlinear approaches that assume slow changes in the inertia tensor. Moreover, remnant bulge stabilization has been incorporated into both equilibrium and linearized, time-dependent treatments of rotational stability. We extend the work of Ricard et al. (1993) to derive a nonlinear, time-dependent theory of TPW that incorporates stabilization by both the remnant bulge and viscous readjustment of the rotational bulge. We illustrate the theory using idealized surface loading scenarios applied to models of both Earth and Mars. We demonstrate that the inclusion of remnant bulge stabilization reduces both the amplitude and timescale of TPW relative to calculations in which this stabilization is omitted. Furthermore, given current estimates of mantle viscosity for both planets, our calculations indicate that departures from the equilibrium orientation of the rotation axis in response to forcings with timescale of 1 Myr or greater are significant for Earth but negligible for Mars.
Additional Information
© 2013 American Geophysical Union. Received 18 Jun. 2013 Accepted 14 Dec. 2013 Accepted article online 16 Dec. 2013 Published online 28 Jan. 2014. We thank two anonymous reviewers for their comprehensive and constructive reviews. We acknowledge funding from Harvard University and the Canadian Institute for Advanced Research. This work is also supported in part by the M. Hildred Blewett Fellowship of the American Physical Society, www.aps.org.Attached Files
Published - jgre20195.pdf
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Additional details
- Eprint ID
- 46111
- Resolver ID
- CaltechAUTHORS:20140606-080028558
- Harvard University
- Canadian Institute for Advanced Research (CIAR)
- American Physical Society M. Hildred Blewett Fellowship
- Created
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2014-06-06Created from EPrint's datestamp field
- Updated
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2021-11-10Created from EPrint's last_modified field