MANTLE DYNAMICS AND GEOID GREEN-FUNCTIONS

We compute Green functions relating mantle mass heterogeneities to geoid undulations using both incompressible and radially compressible mantle rheologies. Our results differ from those previously published by Forte and Peltier (1991) and Thoraval, Machetel and Cazenave (1994). This is due to two factors. Instead of taking gravity as constant throughout the mantle, we compute it self-consistently with the radial density profile. Secondly, we show that in the mathematical formulation of the compressible case, stresses are not continuous through a density jump. We then point out that the presence of a surface ocean has no additional effect on the geoid signal associated with internal mantle mass anomalies. We apply this formalism to a geodynamic model of mantle density variations and show that an excellent fit to the observed geoid can be obtained.