9526885 Davis The PIs propose to constrain mantle viscosity and ice history from data obtained from project BIFROST (Baseline Inferences of Fennoscandian Rebound Observations, Sea Level and Tectonics). GPS measurements from several permanent networks will be used to determine the three dimensional site velocity to constrain models for mantle viscosity and ice history. Inverse modeling methods will be used to map out allowed combinations of ice and earth models. ***