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

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

Temperature Northern Hemisphere Reconstruction + measurements scenarios for future IPCC 2001 year AD

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?

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

METHODS: simulations with ECBilt-CLIO global 3D climate model ECBilt (Atmospheric model) –quasi-geostrophic equations –T21 (~5.6° lat-lon), 3 vertical levels 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 coupled H. Renssen

Forcing (2)

Increase in greenhouse gas concentrations in the past 1000 yrs

CO 2 N2ON2O CH 4 Atmospheric concentrations of CO 2, CH 4 and N 2 O following IPCC emission scenarios

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

present-day level level at 2100 AD Simulated Northern Hemisphere annual mean temperature 9k climate0k climate

Temperature difference with AD mean AD

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

IODP ship - RV Joides Resolution

Tertiary pCO 2 pCO2 reconstructions from planktonic foraminiferal boron isotope measurements (Pearson and Palmer 2000) => values lower than 500 ppm throughout the Neogene ?

Sediment observations δ 13 C in benthic foraminifers varying gradients between North Atlantic, South Atlantic, and Southern Ocean are interpreted in terms of the strength of thermohaline overturning benthic δ 13 C data from Wright and Miller 1996, Shackleton + Crowhurst 1997, Billups 2002

(source: Jim Zachos; Schmidt 2003) PETM

PETM in marine core from ODP Leg 208

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

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

Tripati and Elderfield, 2003

Walvis Ridge, Leg 208

Lourens, Sluijs, Kroon and Leg 208 Scientific Party

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

Kvenvolden, 1988 Amount of carbon stored in different compartments

Present-day locations of methane hydrates

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?