Past climate changes : general presentation and tools Antarctic ice cores : from Byrd to Vostok

1. Past climate changes : general presentation and tools • Antarctic ice cores : from Byrd to Vostok • Greenland ice cores : from Camp Century to GRIP/GISP2 • Historical overview • GRIP and GISP 2 rapid changes • Dating strategy Isotope :temperature • Dating strategy • Rapid changes in the North Atlantic • Geographical extension of rapid cahnges • Greenland / Anatarctica • - The 8.2 K event • - Ongoing projects : EPICA, North GRIP and others

2. GRIP and GISP2 (Central Greenland) ; North GRIP

3. Les forages glaciaires au GROENLAND

4. Below 2700 m (~ 100 000 years) the two profiles diverge due to ice flow disturbances

5. The last deglaciation d = dD - 8 * d18O

7. D0 8 D0 12 The glacial period : the Dansgaard / Oeschger events

8. Review of independent temperature estimates : Jouzel (1999) Differences largely due to seasonality (Krinner et al., 1997 ; Werner et al., 2000)

9. Rapid 15N changes caused by thermal and gravitational processes Combined use of 15N /14N and 40Ar/ 36Ar isotopic ratios allows precise estimate of the associated temperature change Comparison of the ice and gas records allow direct estimate of the firn thickness and of the gas age/ ice age difference Direct comparison of gas records (e.g. CH4, CO2 ….) with rapid temperature change Method also useful for Antarctica (Cf Caillon et al., Science, 2003 who inferred the timing between CO2 and temperature change at Termination 3 Severinghaus et al. (Nature, 1998) Severinghaus and Brook (Science, 1999)

11. North GRIP 20 19 18 40Ar and 15N measurements combined with a firn model allow precise estimates of Tsite :10°C (18 and 20), 15°C (19) ; Landais et al. (In preparation)

12. Rapid changes in the North Atlantic

13. Découverte de variations climatiques rapides dans le passé ( ~ 10°C en quelques décennies) Groenland, atlantique nord, continents.. Modifications du cycle hydrologique liées à la décharge massive d’icebergs Risque de surprise climatique dans un climat plus chaud (apport d’eau douce à travers des précipitations

16. Geographical extension of rapid changes

17. Lake sediments in Bavaria, Germany ; von Grafensteinet al., Scienc, 2001

18. French cave 200 km from the ocean Genty et al. Nature, 2003

20. Hulu Cave, East of Nanjing (China) :Wang et al. (Science, 2001)

22. Dongge cave, Guizhou Province : Yuan et al. (Science, 2004)

23. Greenland / Antarctica

25. Corrélations Nord-Sud De 10 000 à 90 000 ans Blunier and Brook, Science, 2001

26. 8.2 K event : a rapid event cooling during a warm period The day after tomorrow

28. Corrélations Nord-Sud Étude de la transition 5d/5c (108 000 ans)  Le sud se réchauffe avant le Nord sur toute la dernière période glaciaire avec une avance de ~2000 ans. Rôle important joué par la circulation océanique et l’intensité de la circulation thermohaline dans l’hémisphère Nord. Caillon et al., unpublished

29. Raisbeck et al., Goldschmidt Conference, 2002 The 10Be peak straddles event 10, exactly as seen in the GRIP core. This implies that, within our ability to resolve, which we presently estimate as 200 years, the GRIP and EPICA climaterecords at this time are synchronous. Interesting modelling approach of Johnsen and Stocker, Paleoceanography, 2003 Small events / Large events ?

30. Detailed water isotope profiles combined with high resolution methane measurements should allow to extend the record of D/O events to previous glacials High resolution Vostok CH4 record shows millennial-scale variability during MIS 6 and MIS8 (periods of 2 to 7 kyr) : Delmotte et al., In prep , Chappellaz , Euresco, 2003

31. Bender.M., Malaizé, B., Orchado, J., Sowers, T, Jouzel, J Geophysical Monograph , 1999