HR: 0800h
AN: G41C-0368    [Abstracts]
TI: Numerical Modelling of True Polar Wander
AU: * Paulson, A M
EM: archie.paulson@colorado.edu
AF: University of Colorado, Dept. of Physics P.O. Box 390, Boulder, CO 80309 United States
AU: Zhong, S
EM: szhong@anquetil.colorado.edu
AF: University of Colorado, Dept. of Physics P.O. Box 390, Boulder, CO 80309 United States
AU: Wahr, J
EM: wahr@anquetil.colorado.edu
AF: University of Colorado, Dept. of Physics P.O. Box 390, Boulder, CO 80309 United States
AB: Paleomagnetic data have shown that the Earth's rotation axis may have drifted with respect to hotspots (i.e., true polar wander) for large horizontal distance over tens of millions of years. This true polar wander is caused by mantle convection that has redistributed the Earth's mass to cause changes in its principle inertia axes. Changes in the inertia tensor also raises the possibility of "inertial interchange events", in which the rotation axis reorients through ninety degrees, which have been hypothesized as major events in Earth history. We formulate a finite element model of the complete rotational behavior of the Earth when submitted to changes in its inertia tensor. While the basic theory of polar wander is well-established (e.g., Monk & MacDonald, 1960), the general problem is highly nonlinear. Current solutions of the problem have therefore employed approximations requiring either small excursions of the pole from its initial location as done in studies of post-glacial rebound, or requiring a viscous quasi-fluid approximation (for timescales of millions of years). We develop a solution to the problem in a time-stepping finite element code without recourse to these approximations. The solution involves computation of the response of the rotational bulge to an imposed load which perturbs the rotation axis via changes to the inertia tensor. We may then observe the time-dependent evolution of the bulge's relaxation. With the same model we may observe the regimes of both approximations: small polar motion at short timescales and large polar motion at long timescales. We compare our results to previous work in both regimes. We also consider the question of rates of polar motion, and its behavior during inertial interchange events.
DE: 1239 Earth rotation variations
SC: Geodesy [G]
MN: Fall Meeting 2005