1. Ice Cores and the WAIS What we’ve learned What we still need to accomplish Eric Steig University of Washington

4. Conclusions It is important that we drill deep ice. It is important that we drill more than one new intermediate to deep ice core (but fewer than 23) in the WAIS. It is important where we drill.

5. Why? Low frequency climate variability is not understood.

6. Why? Low frequency climate variability is not understood but is the fundamental to the climate change debate (“does recent warming exceed the range of “natural variability”?). -->Ice cores provide the best low frequency information we have (need ice cores). -->To assess climate change (at any frequency) we need to get the spatial patterns right (>>1 core). -->To get the spatial patterns right we need to get the cross-dating right (it matters where we drill).

7. Modeled pattern of millennial-scale climate change Vellinga and Wood, 2002

8. “Patterns of variability” hypothesis

9. Deep ice cores Vellinga and Wood, 2002

10. Well dated deep ice cores Byrd Siple Dome

13. Byrd and Siple Coherence, Holocene

14. Steig and Alley, 2002, Annals

15. Papers since 2002 on the GISP2/WAIS relationship Ganopolski and Ramstorff, 2002 - Science Wunsch, 2003 - Quaternary Science Reviews Schmittner et al., 2003 - QSR Huybers, 2003 - QSR Stocker and Johnson, 2003 - QSR Chaing, Battisti et al., 2004 - Paleoceanography Roe and Steig, 2004 - Journal of Climate Brook et al., in review - QSR

16. Huybers, 2003, QSR Coherence of temperature Phase of temperature Coherence Of CH 4

17. Siple, GISP2 Coherence, Glacial

18. Byrd vs SDM White & Brook

19. Z500 PCs vs. T

20. US ITASE Cores in West Antarctica 34 33 47 22 Accumulation (water equiv cm/year)

21. RAW xsSO4 (RED) AND ssSO4 (GREEN) CONCENTRATIONS FROM 1800-2002 AD

23. Conclusions It is important that we drill deep ice -- because the dating quality is not yet good enough. The new WAIS core will offer significantly improved dating precision. It is important that we drill more than one new intermediate to deep ice core (but fewer than 23) in the WAIS -- because there are clearly spatial differences within WAIS. It is important where we drill. We will still need deep core east of the divide, in the Amundsen and/or Weddell drainages to capture the full spatial characteristics of low frequency climate variability.