Vertical deformation and absolute gravity

Crustal deformation in the Greenland and Antarctic areas is strongly influe nced by both postglacial rebound and contemporary mass redistribution. We e xplore the relationship between the displacement field and the gravitationa l disturbance for a viscoelastic Maxwell Earth with an arbitrary radial vis cosity profile. We seek to determine whether the effects of viscous relaxat ion in the memory of surface mass change can be separated from the effects of present day mass variation by combined measurements of vertical displace ment and absolute gravity when the viscosity profile in the Earth's interio r is unknown. Our conclusion is positive. Specifically, the non-elastic eff ects can be reduced substantially by combined measurements of displacement and gravity change for a Maxwell viscoelastic Earth regardless of its radia l viscosity profile. The underlying physics has nothing to do with the math ematical structure of viscous relaxation modes. Rather, it is due to the fa ct that the non-elastic response of a Maxwell Earth is nearly incompressibl e.