Understanding past climates

Dick KroonDepartment of Paleoecology and Paleoclimatology

Faculty of Earth and Life SciencesVrije 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 HemisphereReconstruction + measurements scenarios

for future

1000 1200 1400 1600 1800 2000 2100

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

Atmospheric CH4 and CO2 concentrations

500

550

600

650

700

750

-9000 -8000 -7000 -6000 -5000 -4000 -3000 -2000 -1000 0

year

CH

4 c

onc

[ppb

v]

260

265

270

275

280

285

CO

2 c

onc

[ppm

v]

CH4 CO2

Forcing (2)

Increase in greenhouse gasconcentrationsin the past 1000 yrs

CO2

N2OCH4

Atmospheric concentrations ofCO2, CH4 and N2Ofollowing IPCC emissionscenarios

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

Northern Hemispheric annual mean temperature

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

-9000 -8000 -7000 -6000 -5000 -4000 -3000 -2000 -1000 0

time [yr]

°C

present-day level

level at 2100 AD

Simulated Northern Hemisphere annual mean temperature

9k climate 0k climate

Temperature difference with 1000-1750 AD mean

2070-3000 AD

Methane hydrate instability possibly amplifiedmillennial-scale climate change during the last glacial

Methane and δ18O in Greenland ice cores

IODP ship - RV Joides Resolution

Tertiary pCO2

pCO2 reconstructions from planktonic foraminiferal boron isotope measurements (Pearson

and Palmer 2000)

=> values lower than 500 ppm throughout the Neogene ?

Intensification of N Hem Glaciation

Mid Miocene Antarctic Glaciation

-0.5

0

0.5

1

1.5

13 C

(‰

VP

DB

)C benthic

0 4 8 12 16 20 24 28

2

Eq. Atlantic

N Atlantic

Southern Ocean

Eq. Pacific

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

(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 13C in all reservoirs• pronounced dissolution of carbonate• 1 to 8°C increase in ocean temperatures (18O, Mg/Ca)

0

1

2

3

4

5

6

10 15 20 25 30

G. ruber pinkG. ruber whiteG. sacculiferG. sacculifer with sacN. dutertreiP. obliquiloculataG. conglobatusG. inflataG. truncatulinoidesG. hirsutaG. crassiformisall species

18O calcification temperature (oC)

Mg/Ca= 0.38± 0.02 exp (0.09±0.003)*T)

Anand et al., Paleoceanography,

2003.

Mg/Ca in planktonic foraminifera

Tripati and Elderfield, 2003

Walvis Ridge, Leg 208

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

293.60 294.10 294.60 295.10 295.60 296.10

ODP Site 1263depth (mcd)

-0.500

0.000

0.500

1.000

1.500

2.000

2.500

bulk measurements

A. soldadoensis

Lourens, Sluijs, Kroon en Leg 208 Scientific Party

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?