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FORWARD AND INVERSE MODELLING OF GPS OBSERVATIONS FROM FENNOSCANDIA

FORWARD AND INVERSE MODELLING OF GPS OBSERVATIONS FROM FENNOSCANDIA. 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

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FORWARD AND INVERSE MODELLING OF GPS OBSERVATIONS FROM FENNOSCANDIA

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  1. FORWARD AND INVERSE MODELLING OF GPS OBSERVATIONS FROM FENNOSCANDIA G.A. Milne1, J.X. Mitrovica2, H.-G. Scherneck3, J.L. Davis4, J.M. Johansson3, H. Koivula5, M. Vermeer6 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

  2. BASELINE INFERENCES FOR FENNOSCANDIAN REBOUND OBSERVATIONS SEA LEVEL AND TECTONICS • Apply GPS to observe the present-day deformation field in Fennoscandia. • Employ observations to: (1) Infer GIA model parameters. (2) Estimate secular height shift of geoid. (3) Examine importance of neotectonic processes.

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

  4. SUMMARY ● Forward modelling shows: (1) FENN+BARENTS ice model produces significantly better fit compared to ICE-3G. (2) Viscosity inference relatively insensitive to ice model. (3) GIA model can account for most of observed signal. ● Inverse modelling shows: (1) Depth sensitivity to viscosity is site dependent. (2) Data can resolve two-layer upper mantle structure and a lower mantle layer to a depth of ~1200 km. ● Residual signal to be explored further: (1) Neotectonics. (2) Dynamic ice models. (3) Lateral variations in earth structure.

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