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The effect of GIA models on mass-balance estimates in Antarctica

Riccardo Riva, Brian Gunter, Bert Vermeersen, Roderik Lindenbergh and Hugo Schotman Department of Earth Observation and Space Systems (DEOS) Delft University of Technology GRACE Science Team Meeting, Potsdam, 17 October 2007. The effect of GIA models on mass-balance estimates in Antarctica.

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The effect of GIA models on mass-balance estimates in Antarctica

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  1. Riccardo Riva, Brian Gunter, Bert Vermeersen, Roderik Lindenbergh and Hugo Schotman Department of Earth Observation and Space Systems (DEOS) Delft University of Technology GRACE Science Team Meeting, Potsdam, 17 October 2007 The effect of GIA models on mass-balance estimates in Antarctica

  2. Introduction • Glacial Isostatic Adjustment (GIA): • Ice model (ice distribution at LGM, melting history) • Earth model (lithospheric thickness, mantle viscosity, lateral variations) • Secular geoid changes: • Surface mass variations • Internal mass redistribution (GIA, seismo-tectonic processes,…) • Antarctic mass variability: • Snow accumulation up to 2000 Gt/yr • Predicted unbalance up to 200 Gt/yr

  3. IJ05 by Ivins and James (2006): for Antarctica mainly from geological data free from a specific Earth model local constraints on total ice melt earlier and gradual deglaciation ice melting in East Antarctica mainly along the coast ICE-5G by Peltier (2004): for the whole Earth mainly from sea-level data tied to Earth model VM2 global constraints on total ice melt later and sudden deglaciation ice melting also on internal East Antarctica Ice models: IJ05 and ICE-5G

  4. Antarctic eustatic sea-level rise from LGM

  5. Ice load at 21 kyr before present (LGM) IJ05 ICE-5G

  6. Ice load at 11 kyr before present IJ05 ICE-5G

  7. Ice load at 7 kyr before present IJ05 ICE-5G

  8. Present-day GIA IJ05 ICE-5G

  9. RL04 GSM mass variability (2006-2003)

  10. GIA-corrected GRACE GRACE - IJ05 GRACE - ICE-5G

  11. GIA variability I: IJ05 Max: 90 Gt/yr (litho 65, UM 1021, LM 4x1021) Min: 40 Gt/yr (litho 120, UM 1021, LM 1023)

  12. GIA variability II: ICE-5G Max: 150 Gt/yr (litho 65, UM 1021, LM 1022) Min: 25 Gt/yr (litho 120, UM 1020, LM 1021)

  13. GIA variability III: upper vs. lower mantle viscosityand lithospheric thickness

  14. GIA: northern hemisphere contribution Ice model: ICE-5G Earth model: VM2 Mass change: 17 Gt/yr

  15. Antarctic mass change estimates • IJ05: 82 ± 25 Gt/yr • ICE-5G: 105 ± 64 Gt/yr • GRACE: 44 ± 20 Gt/yr • GRACE - IJ05: -38 ± 32 Gt/yr (0.10 mm/yr e.s.l.) • GRACE - ICE-5G: -61 ± 67 Gt/yr (0.15 mm/yr e.s.l.)

  16. Conclusions • Antarctic ice mass loss derived from GRACE is in the range 0-120 Gt/yr, (0-3 mm/yr e.s.l.) depending on the GIA model (40-170 Gt/yr). • Due to different ice distribution and deglaciation history, IJ05 and ICE-5G have very different GIA signatures, especially regarding their response to mantle viscosity. • Peak GIA values are mostly smaller than GRACE values, but GIA total mass change can still be larger due to its positiveness. • GIA due to ice loads in the northern hemisphere, though locally small, represents and important contribution to the total mass change.

  17. GIA: West vs. East Antarctica

  18. Leakage I

  19. Leakage II

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