Download
slide1 n.
Skip this Video
Loading SlideShow in 5 Seconds..
David Schneider and Eric Steig PowerPoint Presentation
Download Presentation
David Schneider and Eric Steig

David Schneider and Eric Steig

119 Vues Download Presentation
Télécharger la présentation

David Schneider and Eric Steig

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Isotopic Records in US-ITASE Cores: A preliminary report WAIS Workshop September, 2003 David Schneider and Eric Steig University of Washington

  2. Annual mean Accumulation at US-ITASE Sites (cm^3 water-equivalent) Figure courtesy Dixon, Kaspari, Spikes.

  3. δ18O From 2001-5

  4. 2001-5 δ18O Dating of ice core: Based on summer sulphate and isotopic peaks.

  5. Climatology (1982-1999) of temperature and δ18O at 2001-5 δ18O = .19*T - 26‰ r = .92

  6. Mean annual temperature- δ18O relationship?

  7. Mean annual temperature- δ18O relationship? T δ18O

  8. δ18O record at 2000-1 (near proposed WAIS deep core)

  9. Temperature variability at 2000-1 and 2001-5

  10. Isotopic variability at 2000-1 and 2001-5

  11. Interannual temperature variability in Antarctica

  12. Isotopes from 2000-1 and reconstructed PC’s of Antarctic temperature r = .40 winter r = .28 annual

  13. Two cores are better than one r = .37 annual; .39 winter R-pc1 annual mean Linear combination of 01-5 and 00-1

  14. Three cores are better than two r = .54 annual; .52 winter R-pc1 annual mean Linear combination of 01-5 and 00-1 and Law Dome

  15. Summary: • The cores can be well-dated with summer sulphate peaks, corroborated by isotopic annual cycles • Isotopic records exhibit a robust climatological relationship with the seasonal temperature cycle; a spatial relationship can be obtained once more cores are analyzed.

  16. Summary: • The cores can be well-dated with summer sulphate peaks, corroborated by isotopic annual cycles • Isotopic records exhibit a robust climatological relationship with the seasonal temperature cycle; a spatial relationship can be obtained once more cores are analyzed. • The temporal isotopic-temperature slope appears to be much smaller than the traditional Dansgaard spatial slope (~0.2 vs ~0.64). • On seasonal to interannual timescales, temperatures at sites 2001-5 and 2000-1 are well correlated

  17. Summary: • The cores can be well-dated with summer sulphate peaks, corroborated by isotopic annual cycles • Isotopic records exhibit a robust climatological relationship with the seasonal temperature cycle; a spatial relationship can be obtained once more cores are analyzed. • The temporal isotopic-temperature slope appears to be much smaller than the traditional Dansgaard spatial slope (~0.2 vs ~0.64). • On seasonal to interannual timescales, temperatures at sites 2001-5 and 2000-1 are well correlated • However, annual mean isotopic values are not well-correlated with annual mean temperatures at the site or between sites but the two cores agree better with Law Dome than with each other.

  18. Summary: • The cores can be well-dated with summer sulphate peaks, corroborated by isotopic annual cycles • Isotopic records exhibit a robust climatological relationship with the seasonal temperature cycle; a spatial relationship can be obtained once more cores are analyzed. • The temporal isotopic-temperature slope appears to be much smaller than the traditional Dansgaard spatial slope (~0.2 vs ~0.64). • On seasonal to interannual timescales, temperatures at sites 2001-5 and 2000-1 are well correlated • However, annual mean isotopic values are not well-correlated with annual mean temperatures at the site or between sites. • Larger-scale measures of temperature variability (i.e. PC’s) show a better correlation with isotopic ratios than local T or circulation patterns alone. • Preliminary correlations of three ice cores with leading PC’s of Antarctic temperatures suggests ice core-based temperature reconstructions may agree well with station-based temperature reconstructions. • Rather than having conflicting information, these cores probably have complimentary information.

  19. Multiple parameters in core 2001-5 T δ18O H2O2 SO42- 2002 1992 1982 Figure courtesy Dixon

  20. Mean annual accumulation and δ18O at 2000-1 r = .21

  21. Ongoing work: • Continue isotopic measurements on ITASE cores (21 sites!!) • More calibration exercises • Better understanding/interpretation of controls on interannual variability in isotopic ratios • Reconstruction of last 200-500 years of Antarctic climate variability

  22. Annual mean temperature -60 -50 -40 -30 -20 °C from AVHRR

  23. Monthly (1982-1999) regression between local temperature and δ18O at 2001-5 r = .59

  24. Climatology of temperature- δ18O at 2000-1 r = .92

  25. Mean annual temperature- δ18O at 2000-1 δ18O T r = .30

  26. Power spectra: 2000-1 Annual cycle Semiannual cycle

  27. Depth-age scales for 01-5

  28. Power spectra: 2001-5 Annual cycle Semiannual cycle

  29. Significant low-frequency variability?

  30. Something about Hercules Dome (2002-4) • Could be easier than WAIS to relate to large-scale variability • But is the accumulation rate too low?

  31. Spatial temperature-elevation relationship

  32. What determines isotopic ratios in an ice core? • Temperature when precipitation forms • Traditional to use mean annual surface temperature • May be better idea to use inversion temperature

  33. What determines isotopic ratios in an ice core? • Temperature when precipitation forms • Traditional to use mean annual surface temperature • May be better idea to use inversion temperature • Timing of accumulation events; amount of precipitation • Temperature of source (place of evaporation) • Distance/pathway from source to deposition site

  34. Multiple parameters in core 2001-5 Figure by Dixon