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The Ice Isotope Record from Siple Dome, Antarctica

The Ice Isotope Record from Siple Dome, Antarctica. A. Schilla, J.W.C. White, R. Alley, M. Bender, E. Brook, E. Steig, K. Taylor. Regional Similarities. Broad Antarctic Climate Signal: Siple fits. Regional Similarities. Broad Antarctic Climate Signal: Siple fits

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The Ice Isotope Record from Siple Dome, Antarctica

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  1. The Ice Isotope Record from Siple Dome, Antarctica A. Schilla, J.W.C. White, R. Alley, M. Bender, E. Brook, E. Steig, K. Taylor

  2. Regional Similarities.... • Broad Antarctic Climate Signal: Siple fits

  3. Regional Similarities.... • Broad Antarctic Climate Signal: Siple fits • ~ Similar A1-A7 warm events (after Blunier and Brook, 2001), but timing and relative magnitudes differ A1 A2 A5 A3 A6 A4 A7 ? ?

  4. Regional Similarities.... • Siple and Byrd: agree very well for at least last ~10ka

  5. Regional Variation.... • Milankovitch cycle strengths seem to vary among cores

  6. Regional Variation.... • Milankovitch cycle strengths seem to vary among cores • Timing of termination differs among cores

  7. Regional Variation.... • Milankovitch cycle strengths seem to vary among cores • Timing of termination differs among cores • Rapid event at termination in Siple ice

  8. Regional Variation.... • Neither core has a final age-model yet • Siple and Taylor: opposed throughout Holocene?  At least for last ~6ka

  9. What Does Siple Dome Tell Us About WAIS?

  10. What did WAIS Look Like During the LIG? • Siple Dome Ice  Inconclusive • Drop in isotopes + “funny” gases at ~100ka  Siple Dome overrun by ice from higher up on ice sheet??

  11. How Long has Siple Been a Dome? • Siple and the surrounding Ice Streams have probably existed for ≥ 100ka From: http://igloo.gsfc.nasa.gov/wais/ismap2.jpg

  12. Elevation Changes Between Byrd and Siple Dome? • Relative Holocene elevation change between Siple and Byrd could only be ~50m (Δ‰ only ~0.5; with a lapse rate of ~ -1‰/100m) barring a very precise coordination of elevation and associated climate change

  13. Divergence Across the Ross Ice Shelf • Opposition between Siple and Taylor  storm track modulation by ENSO/ASL??

  14. ASL/ENSO Influence.... b) a) • 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)?

  15. Dating Issues.... • Age relationship between Taylor Dome and Siple, Byrd is crucial for picking apart ENSO/ASL story • Were Siple and Taylor opposed only for late Holocene, or for entire Holocene? • How much dating room is there with Taylor?

  16. Summary • WAIS during LIG: Siple Dome ice = inconclusive • Siple Dome and surrounding ice streams ≥ 100ka • Siple and Byrd either have very little relative elevation change, or Byrd climate and elevation change ~ cancelled out • Taylor and Siple ages are key to Taylor-Siple Holocene story, and therefore part of the Holocene ENSO story

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