Estimation of PGR Induced Absolute Gravity Changes at Greenland GNET Stations

An important subject in the climate debate is the study of the major ice sheets mass balance. Knowledge of the mass balance provides understanding of changes in the relative sea-level (RSL). Several methods are used for mass balance studies but they are associated with large uncertainties. One reason for the uncertainty is the presence of the postglacial rebound (PGR) signal in the geodetic data used for mass balance estimates. Estimates of the PGR signal can be obtained by modelling and then being subtracted from the data to eliminate its influence. In this study, the PGR gravity signal will be investigated through modelling. The modelling of seven different scenarios shows that the PGR gravity signal in Greenland is less then 1 mu Gal/year (1 mu Gal=10 nm/s(2)). Repeated absolute gravity (AG) measurements at selected Greenland network (GNET) GPS sites were initiated in 2009. These data will in the future help constrain PGR and present-day ice mass changes. The data is collected with an A10 absolute gravimeter, which has an accuracy of 10 mu Gal (manufacturer specification). Here we will evaluate themodelled PGR gravity signal at selected GNET sites and conclude that the signal is significantly smaller then the gravity instruments accuracy and a long time is needed to detect it. Also, it can be expected that the elastic signal will be larger and other data like GPS is needed to separate the viscous and elastic signal.