- 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

GRIP and GISP2 (Central Greenland) ; North GRIP

Les forages glaciaires au GROENLAND

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

The last deglaciation d = D - 8 * 18 O

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

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

Severinghaus et al. (Nature, 1998) Severinghaus and Brook (Science, 1999) Rapid 15 N changes caused by thermal and gravitational processes Combined use of 15 N / 14 N and 40 Ar/ 36 Ar 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. CH 4, CO 2 ….) with rapid temperature change Method also useful for Antarctica (Cf Caillon et al., Science, 2003 who inferred the timing between CO 2 and temperature change at Termination 3

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

Rapid changes in the North Atlantic

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 dicebergs Risque de surprise climatique dans un climat plus chaud (apport deau douce à travers des précipitations

Geographical extension of rapid changes

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

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

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

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

Greenland / Antarctica

Blunier and Brook, Science, 2001 Corrélations Nord-Sud De à ans

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

Caillon et al., unpublished Le sud se réchauffe avant le Nord sur toute la dernière période glaciaire avec une avance de ~2000 ans.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 lintensité de la circulation thermohaline dans lhémisphère Nord. Corrélations Nord-Sud Étude de la transition 5d/5c ( ans)

Raisbeck et al., Goldschmidt Conference, 2002 The 10 Be 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. Small events / Large events ? Interesting modelling approach of Johnsen and Stocker, Paleoceanography, 2003

High resolution Vostok CH 4 record shows millennial-scale variability during MIS 6 and MIS8 (periods of 2 to 7 kyr) : Delmotte et al., In prep, Chappellaz, Euresco, 2003 Detailed water isotope profiles combined with high resolution methane measurements should allow to extend the record of D/O events to previous glacials

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