FORWARD AND INVERSE MODELLING OF GPS OBSERVATIONS OF FENNOSCANDIAN GIA G.A. Milne 1, J.X. Mitrovica 2, H.-G. Scherneck 3, J.L. Davis 4, J.M. Johansson 3, H. Koivula 5, M. Vermeer 6 1 Dept. of Geological Sciences, University of Durham, UK 2 Dept. of Physics, University of Toronto, Canada 3 Onsala Space Observatory, Sweden 4 Harvard-Smithsonian Center for Astrophysics, USA 5 Finish Geodetic Institute, Finland 6 Institute of Geodesy, Helsinki University of Technology, Finland

GIA MODEL Earth Forcing Earth Rheology Rotational potential Euler equations Surface loading Ice ICE-3G (Tushingham & Peltier, 1991) FENN+BARENTS (Lambeck et al., 1998) Ocean Sea-level equation Impulse response formalism Linear Maxwell rheology Compressible 1D structure Time-dependent ocean function Near-field water influx

T e (km) Perez-Gussinye et al. (2004)

SUMMARY Data can provide useful information to constrain Fennoscandian ice history. Viscosity inference relatively insensitive to adopted ice model. Data capable of resolving two layers within upper mantle and one layer in lower mantle to a depth of ~1200 km. Remaining residual signal to be explored via: - Dynamic ice models - Lateral earth structure - Neotectonic motions