Time Rate of Change of Gravity in North America and Greenland due to Post Glacial Rebound and Other Tectonic Movements

In the process to regain isostatic equilibrium following the Last Glacial Maximum, the Earths crust is experiencing continuous uplift and/or subsidence, a phenomenon called Glacial Isostatic Adjustment (GIA). We determine the time rate of change of gravity (g-dot) due to GIA by estimating it directly from a Least-Squares adjustment of an integrated gravity network covering the continent. Observation equations are created based on historical relative gravity measurements and the network is constrained using g-dot values obtained from absolute gravity measurements. Recognizing that gravity variation is also influenced by other significant continuous geophysical processes (tides, tidal load and hydrology), such effects are removed by correcting all gravity measurements at the pre-adjustment stage. Results are presented in the form of a g-dot map and demonstrate that Canadas National Gravity Data Base (NGDB), with its over 50-year-long history, can provide us with useful constraints for the evaluation/verification and refinement of post-glacial rebound models.