1. Modern and Ancient Precipitation  18 O and  D Gradients on the Tibetan Plateau - or - When did the Plateau Plateau? Pratigya J. Polissar 1, Katherine H. Freeman 1, David B. Rowley 2, Brian S. Currie 3 1 The Pennsylvania State University, University Park PA 2 The University of Chicago, Chicago IL 3 Miami 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. Rowley (2007)

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

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

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

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

10. Paleowater  18 O and  D  18 O carb : lacustrine, pedogenic, cement New Approach: paired  18 O carb and  D organic

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 Polissar et al. (in prep.) Modern

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

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

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

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)

21. Seawater  18 O Billups & Schrag (2003) –16 –8 0 8 16 24 ~  D seawater

22. Paired  18 O carb and  D organic ModernAncient Polissar & Freeman (in prep.); Polissar et al. (in review)

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