What things influence the wobble of the earth's axis?

There are many components that have been detected at the scale of 1/1000 of a second of arc. 

         Source                                   Approximate Period
_____________________________________________________________________________

Seasonal, airmass, ice and water shifts................Annual period

Chandler Wobble: random impulses of unknown origin
                 that are damped by earth's elasticity..14 months

Electromagnetic coupling of the core/mantle boundary.... decade

Variations in sea level................................. century

Tidal friction.......................................... thousand years

Continental Drift and 'unrest'.......................... Million years
The amplitudes run from 1/1000 of a second of arc to tens of degrees.
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All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the
NASA IMAGE/POETRY Education and Public Outreach program.