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Modern and Ancient Precipitation d18O and dD Gradients on the Tibetan Plateau - When did the Plateau Plateau?

This study investigates the d18O and dD gradients of modern and ancient precipitation on the Tibetan Plateau to determine the timing of plateau formation. It examines Cenozoic climate evolution data and stable isotope paleoaltimetry, and analyzes modern precipitation patterns and moisture sources. The study concludes that the topographic barrier to atmospheric circulation in the south has existed since the Eocene, and the present topography in the central and southern plateau largely developed during the Miocene. The findings have implications for understanding moisture sources and trajectories on the northern plateau.

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Modern and Ancient Precipitation d18O and dD Gradients on the Tibetan Plateau - When did the Plateau Plateau?

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  1. Modern and Ancient Precipitation d18O and dD Gradients on the Tibetan Plateau- or -When did the Plateau Plateau? Pratigya J. Polissar1, Katherine H. Freeman1, David B. Rowley2, Brian S. Currie3 1The Pennsylvania State University, University Park PA 2The University of Chicago, Chicago IL 3Miami University, Oxford OH

  2. Cenozoic Climate Evolution data from Kroon et al. (1991) Quade & Cerling (1995) Clift et al. (2002) Ma et al. (1998) Donghuai et al. (1998) Guo et al.(2002, 2004) Clift (2006)

  3. Plateau Evolution

  4. Stable Isotope Paleoaltimetry

  5. Stable Isotope Paleoaltimetry Rowley (2007)

  6. Modern Precipitation Gradient Polissar et al. (in review)

  7. Modern Precipitation Gradient Polissar et al. (in review)

  8. Moisture Source Westerly SW Monsoon after Tian (2007)

  9. Modern Isotope Gradient Determined by: • Moisture source • Rainout (airmass trajectory) • Moisture recycling

  10. Paleowater d18O and dD • d18Ocarb: lacustrine, pedogenic, cement • New Approach: paired d18Ocarb and dDorganic

  11. Paleopreciptation Sites Quade et al. (1995); Garzione et al. (2000) ; Dettman et al. (2003); Currie et al. (2005); Cyr et al. (2005); Graham et al. (2005); Rowley & Currie (2006); deCelles et al. (2007); Rieser et al. (2008)

  12. Modern Modern Polissar et al. (in prep.)

  13. Miocene Miocene Polissar et al. (in prep.)

  14. Oligocene Oligocene Polissar et al. (in prep.)

  15. Eocene Eocene Polissar et al. (in prep.)

  16. Observations • Modern and past gradients are similar • Miocene precipitation isotopes more negative on plateau, no change at edge

  17. Conclusions • Topographic barrier to S-N atmospheric circulation has existed since Eocene • Present topography in south and central plateau largely developed by Miocene

  18. Implications • S. Tibet paleoaltimetry works • N. Tibet more complicated - mixed moisture source • similar gradient present throughout Cenozoic despite changing latitude and elevation • Essential to understand moisture sources and trajectories on N. plateau

  19. Acknowledgements Canadian Institute for Advanced Research U.S.-National Science Foundation Penn. State Organic Geochemistry Lab (esp. Denny Walizer)

  20. Seawater d18O –16 –8 0 ~ dDseawater 8 16 24 Billups & Schrag (2003)

  21. Paired d18Ocarb and dDorganic Modern Ancient Polissar & Freeman (in prep.); Polissar et al. (in review)

  22. Cenozoic Cenozoic Polissar et al. (in prep.)

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