HR: 17:30h
AN: G34A-07    [Abstracts]
TI: Decadal Variations in Earth Rotation and Mechanisms of Core-Mantle Coupling
AU: * Mound, J
EM: jon@sphere.physics.utoronto.ca
AF: University of Toronto, Dept. Physics, Toronto, ON M5S 1A7 Canada
AU: Buffett, B
EM: buffett@geosci.uchicago.edu
AF: University of Chicago, Dept. Geophysical Sciences, Chicago, IL 60637 United States
AB: Lengthy observational records have enabled the detection of decadal variations in both the orientation and magnitude of the rotation of the solid Earth. Rotational variations that do not arise from a forcing external to the planet as a whole represent interaction between the mantle and some other subsystem of the Earth (the atmosphere, oceans, outer or inner core). Changes in mantle rotation correspond to a change in angular momentum and require the application of a torque. The observed decadal rotational variations likely involve interaction with the core. Study of rotational variations can thus provide information on the dynamics of the core, that is the motions associated with the changing angular momentum, and the mechanisms of core-mantle coupling, that is the processes which produce the torque. Decadal changes in the magnitude of solid Earth rotation, observed as changes in length-of-day, are generally considered to arise due to torsional oscillations of the fluid core. This view is based on estimates of core angular momentum, constrained by geomagnetic secular variation data, that correlate well with the length-of-day time series. The orientation of solid Earth rotation also varies on decadal timescales and this data series has been found to correlate with the length-of-day time series suggesting that torsional oscillations and core-mantle interactions may also be responsible for decadal variations in polar motion. Core-mantle coupling can occur through electromagnetic, topographic and gravitational mechanisms. This study uses a torsional oscillation model to investigate these coupling mechanisms in order to estimate both their magnitude and spectral signature and compares the results with observed properties of rotational variations.
DE: 8115 Core processes (1507)
DE: 1213 Earth's interior--dynamics (8115, 8120)
DE: 1239 Rotational variations
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting