Understanding past climates

1. Understanding past climates Dick Kroon Department of Paleoecology and Paleoclimatology Faculty of Earth and Life Sciences Vrije Universiteit Amsterdam

2. Why is IODP useful for society? Paleoclimatology provides a framework for understanding our climate system and may even lead to climate prediction or not.

3. IPCC2001 Temperature Northern Hemisphere Reconstruction + measurements scenarios for future year AD 1000 1200 1400 1600 1800 2000 2100

4. A geological framework (and thus IODP) is needed to put current anthropogenic warming into a context of climate history.This is necessary to provide answers to the following questions: • How unique is the current warming as a response to greenhouse gases? Has it happened before? • Which feedbacks operate during an extreme warming event?

5. Why is the current anthropogenic warming dangerous? modeling experiments to predict the future: with long-term changes in insolation and greenhouse gas concentrations H. Renssen and modeling group

6. METHODS: simulations with ECBilt-CLIOglobal 3D climate model • ECBilt (Atmospheric model) • quasi-geostrophic equations • T21 (~5.6° lat-lon), 3 vertical levels coupled • CLIO 3°x 3° lat-lon • Ocean general circulation model • Primitive equations – free surface • 20 vertical levels • Sea-ice model • Thermodynamics and dynamics • 3 layers snow-ice model + leads H. Renssen

8. Forcing (2)

9. Increase in greenhouse gas concentrations in the past 1000 yrs

10. Atmospheric concentrations of CO2, CH4 and N2O following IPCC emission scenarios CO2 N2O CH4

11. Not taken into account: • Volcanism • Changes in solar activity • High-frequency changes in greenhouse gases • in period 9,000-250 yr BP • Melting of Laurentide Ice Sheet

12. Simulated Northern Hemisphere annual mean temperature level at 2100 AD present-day level 9k climate 0k climate

13. Temperature difference with 1000-1750 AD mean 2070-3000 AD

14. Methane and δ18O in Greenland ice cores Methane hydrate instability possibly amplified millennial-scale climate change during the last glacial

16. IODP ship - RV Joides Resolution

19. Tertiary pCO2 pCO2 reconstructions from planktonic foraminiferal boron isotope measurements (Pearson and Palmer 2000) => values lower than 500 ppm throughout the Neogene ?

20. Sediment observations δ13C in benthic foraminifers varying gradients between North Atlantic, South Atlantic, and Southern Ocean are interpreted in terms of the strength of thermohaline overturning benthic δ13C data from Wright and Miller 1996, Shackleton + Crowhurst 1997, Billups 2002

21. PETM (source: Jim Zachos; Schmidt 2003)

23. PETM in marine core from ODP Leg 208

24. Evidence for methane hydrate instability during PETM: • 3‰ excursion in 13C in all reservoirs • pronounced dissolution of carbonate • 1 to 8°C increase in ocean temperatures (18O, Mg/Ca) PETM

25. Mg/Ca in planktonic foraminifera Mg/Ca= 0.38± 0.02 exp (0.09±0.003)*T) Anand et al., Paleoceanography, 2003.

26. Tripati and Elderfield, 2003

27. Walvis Ridge, Leg 208

28. Lourens, Sluijs, Kroon and Leg 208 Scientific Party

29. What is a gas hydrate? Crystalline solid constituting of gas molecules, usually methane, surrounded by a cage of water molecules

31. Amount of carbon stored in different compartments Kvenvolden, 1988

32. Present-day locations of methane hydrates

33. IODP gives the paleoclimate community the opportunity to make an attempt to find the cause of this event, and others, as well as the consequences of rapid greenhouse warming. • PETM scenario is analogue for our future climate. Studying this event and others may tell us what may happen with our future climate. Is methane a potential source for a positive feedback?