Vertical deformation and absolute gravity

Crustal deformation in the Greenland and Antarctic areas is strongly influenced by both postglacial rebound and contemporary mass redistribution. We explore the relationship between the displacement field and the gravitational disturbance for a viscoelastic Maxwell Earth with an arbitrary radial viscosity profile. We seek to determine whether the effects of viscous relaxation in the memory of surface mass change can be separated from the effects of present day mass variation by combined measurements of vertical displacement and absolute gravity when the viscosity profile in the Earth's interior is unknown. Our conclusion is positive. Specifically, the non-elastic effects can be reduced substantially by combined measurements of displacement and gravity change for a Maxwell viscoelastic Earth regardless of its radial viscosity profile. The underlying physics has nothing to do with the mathematical structure of viscous relaxation modes. Rather, it is due to the fact that the non-elastic response of a Maxwell Earth is nearly incompressible.