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Class 10, Stable isotopes
- 2. November 24 Brief (15-minute) summaries of project topics. (1) What are the most important features of the modern climate in your region? (2) What proxies are available in your region, over the time interval specified? How are they related to climate? and (3) How different were past climates from modern conditions? Why is that important?
- 3. S TA B L E I S OTO P E S I N PA L E O C L I M ATO LO GY
- 4. Isotopes are elements with the same number of protons but varying numbers of neutrons.
- 5. Stable isotopes are either not radioactive or decay so slowly that their half-lives cannot be measured.
- 6. Stable isotopes have the same chemical properties but don’t have the same atomic mass.
- 7. O16 O18
- 8. Stable isotopes of oxygen O16 99.76% O18 0.2% O17 0.04%
- 9. Photograph: David Sifry SMOW standard mean ocean water
- 11. Fractionation
- 23. “heavy”
- 24. “heavy” “light”
- 25. O18 O16
- 26. O18 O16 small
- 29. “more positive” δO18 = “heavy” = “enriched” for example, ocean water
- 30. “more negative” δO18 = “light” = “depleted” for example, glacial ice
- 31. Source: Jouzel et al., Journal of Geophysical Research, 1994
- 32. Source: Jouzel et al., Journal of Geophysical Research, 1994 “light” “heavy”
- 35. paleothermometer
- 36. Source: Bowen and Revenaugh, Water Resources Research, 2003 δO18 in precipitation
- 37. Source: Bowen and Wilkinson, Geology, 2002 δO18 in precipitation
- 38. The “amount effect”: The greater the amount of rainfall, the lower the δO18 of the rainfall. (i.e., more negative)
- 40. O18 O18 O18 O18O16 O16 O16 O16O16 O16 O16 “more negative” δO18 = “light” = “depleted”
- 42. O18 O18 O18 O18O16 O16 O16 O16 “more positive” δO18 = “heavy” = “enriched”
- 43. Source: Shanahan et al., Science, 2009 less O18 more negative “depleted” more O18 more positive “enriched”