1. The Deuterium Excess record from the Siple Dome ice core Annalisa Schilla, James White, Eric Steig, Ed Brook

2. Overview Regional variation among Antarctic deuterium excess records Extra-Antarctic/Pacific climate signal in Siple Dome deuterium excess A Holocene precession signal in the Ross Sea region?

3. Background Deuterium excess is defined as: d=δD-8*δ 18 O (indexed to MWL) Measure of kinetic fractionation, primarily SST (actual T change?) Distinct signal from raw isotopes

4. Various Antarctic Moisture Sources Modified from Vimeux et al., 2001

5. Pacific as Siple Moisture Source Region GCM and simple model results: coastal sites have > contribution from proximal ocean basin Siple Dome moisture is dominated throughout the year by Pacific sources, from ~30ºS to the sea ice edge Delaygue et al., 2000 Siple Dome

6. Siple d vs. Pacific Records Siple d shares variability on several timescales with Pacific records

7. Other sources of d variability?

8. Low-latitude and high-latitude?

9. Millennial-scale Spectra

10. Climate Change vs. Elevation?

11. Siple Dome vs. Taylor Dome

12. Precession at Siple Dome? Moisture flux during (a) 1980 (normal year) and (b) 1982 (El Nino year). From Cullather et al., 1996. Did ENSO variability really increase in the mid-Holocene (e.g., per Clement et al., 2000, Rodbell et al. 1999, Moy et al. 2000)? a) b) Siple Dome Taylor Dome

13. Summary Deuterium excess varies dramatically across Antarctica  various moistures source regions Moisture source region for Siple participates in global climate changes separately from Antarctica at a variety of timescales Siple-Taylor isotope divergence through Holocene  a precession signal?