oo C[ / ] 13 o 2 CO [ppmv]

(1)

Alfred Wegener Institute

for Polar and Marine Research Bremerhaven, Germany

The Carbon Cycle during the Pleistocene

Peter K¨ohler

Institute for Applied Geosciences, Darmstadt University of Technology

—

13 November 2007

In cooperation with:

Hubertus Fischer, Alfred Wegener Institute, Bremerhaven, Germany Richard E. Zeebe, University of Hawaii, USA

Guy Munhoven, Universit´e de L`ıege, Belgium

(2)

Outline

The global record of atmospheric CO

₂

EPICA — European Project for Ice Coring in Antarctica The global carbon cycle and the box model BICYCLE

Time-dependent processes: motivations and simulation results Combined scenarios

Open questions

Conclusions

(3)

200 250 300 350

CO

2

[ppmv]

700 400 100 Time [kyr BP]

13C CO₂

10 7 4 1 Time [kyr BP]

1000 1500 2000 Time [yr AD]

2000 198019902000 Time [yr AD]

-8.5 -8.0 -7.5 -7.0 -6.5 -6.0

13

C [

o

/

oo

]

(4)

200 250 300 350

CO

2

[ppmv]

700 400 100 Time [kyr BP]

13C CO₂

10 7 4 1 Time [kyr BP]

1000 1500 2000 Time [yr AD]

2000 198019902000 Time [yr AD]

-8.5 -8.0 -7.5 -7.0 -6.5 -6.0

13

C [

o

/

oo

]

20 y:

seasonal

Point Barrow

Keeling and Whorf, 2005; Keeling et al., 2005.

(5)

200 250 300 350

CO

2

[ppmv]

700 400 100 Time [kyr BP]

13C CO₂

10 7 4 1 Time [kyr BP]

1750 AD

1000 1500 2000 Time [yr AD]

2000 198019902000 Time [yr AD]

-8.5 -8.0 -7.5 -7.0 -6.5 -6.0

13

C [

o

/

oo

]

20 y:

seasonal

1 kyr:

anthrop.

Point Barrow Law Dome

Francey et al., 1998; Trudinger et al., 1999

(6)

200 250 300 350

CO

2

[ppmv]

700 400 100 Time [kyr BP]

13C CO₂

10 7 4 1 Time [kyr BP]

1750 AD

1000 1500 2000 Time [yr AD]

2000 198019902000 Time [yr AD]

-8.5 -8.0 -7.5 -7.0 -6.5 -6.0

13

C [

o

/

oo

]

20 y:

seasonal

1 kyr:

anthrop.

10 kyr:

Holocene

Point Barrow Law Dome

Taylor D.

Smith et al., 1999

(7)

200 250 300 350

CO

2

[ppmv]

700 400 100 Time [kyr BP]

13C CO₂

10 7 4 1 Time [kyr BP]

1750 AD

1000 1500 2000 Time [yr AD]

2000 198019902000 Time [yr AD]

-8.5 -8.0 -7.5 -7.0 -6.5 -6.0

13

C [

o

/

oo

]

20 y:

seasonal

1 kyr:

anthrop.

10 kyr:

Holocene 700 kyr:

glacial/

interglacial

Point Barrow Law Dome

Taylor D.

Vostok

EPICA DC

Petit et al., 1999; Siegenthaler et al., 2005

(8)

Radiative Forcing of Greenhouse Gases — Today

Gas Current Increase Radiative forcing (W m⁻²)

Amount < 1750 1750-2007

H₂O 94 -

CO₂ 383 ppm 105 ppm (38%) 50 1.71

CH₄ 1745 ppb 1045 ppb(150%) 1.1 0.48 N₂O 314 ppb 44 ppb (16%) 1.25 0.16

CFCs 268 ppt 0.31

Preindustrial Greenhouse Forcing 146

Anthropogenic Greenhouse Forcing 2.66 Total Greenhouse Forcing 148.66

Global surface temperature (energy balance without GHG): –18^◦C Global surface temperature (measured in 20th century): +16^◦C Total Greenhouse Forcing (148.66 W/m²) explains ∆T of 34 K.

⇒ Anthropogenic Forcing (2.66 W/m²) explains ∆T of 0.6 K.

(which is in agreement with observations during the last 150 years)

(9)

Radiative Forcing of Greenhouse Gases — LGM

Agent Radiative forcing

(W m⁻²) Preindustrial Greenhouse Gases +146 Anthropogenic Greenhouse Gases +2.66

LGM

GHG (CO₂ +CH₄ +N₂O) –2.8

Dust –1.4

Ice sheets (Albedo) –3.0

Vegetation (Albedo) –1.2

LGM sum –8.4

⇒ Anthropogenic GHG forcing is of the same order but opposite sign than GHG foring during LGM.

(10)

The global record of atmospheric CO

₂

EPICA — European Project for Ice Coring in Antarctica

The global carbon cycle and the box model BICYCLE

Time-dependent processes: motivations and simulation results Combined scenarios

Open questions

Conclusions

(11)

EPICA drilling sites:

Dome C (EDC): low accumulation rate; long time series (∼8 glacial cycles) Dronning Maud Land (EDML): high accumulation rate, high resolution

(12)

Kohnen station in Dronning Maud Land

(13)

Drilling team 2005/06 with last section of EDML (from 2774 m depth)

(14)

Scientific lab in Kohnen station

(15)

200 250 300 350

CO

2

[ppmv]

700 400 100 Time [kyr BP]

13C CO₂

10 7 4 1 Time [kyr BP]

1750 AD

1000 1500 2000 Time [yr AD]

2000 198019902000 Time [yr AD]

-8.5 -8.0 -7.5 -7.0 -6.5 -6.0

13

C [

o

/

oo

]

20 y:

seasonal

1 kyr:

anthrop.

10 kyr:

Holocene 700 kyr:

glacial/

interglacial

Point Barrow Law Dome

Taylor D.

Vostok

EPICA DC

(16)

The EPICA challenge

Predicting pCO₂ prior to Vostok (Wolff et al., 2004, 2005, EOS) 8 contributions: from regression analysis to full carbon cycle model

-450 -420 -390 -360

D(o /oo)

EDC D

1 5

7 9

11 13

15 17

MIS

0 500 1000

dust(ppbv) 1500

EDC dust

700 600 500 400 300 200 100 0

Time (kyr BP)

160 200 240 280

pCO2(ppmv)

Vostok pCO

₂

I II

III

?

IV

EPICA, 2004; Petit et al., 1999

(17)

The EPICA challenge

Predicting pCO₂ prior to Vostok (Wolff et al., 2004, 2005, EOS) 8 contributions: from regression analysis to full carbon cycle model

-450 -420 -390 -360

D(o /oo)

EDC D

1 5

7 9

11 13

15 17

MIS

0 500 1000

dust(ppbv) 1500

EDC dust

700 600 500 400 300 200 100 0

Time (kyr BP)

160 200 240 280

pCO2(ppmv)

Vostok pCO

₂

EDC pCO

₂

I II

III IV

V VI

VII

EPICA, 2004; Petit et al., 1999 Siegenthaler et al., 2005

(18)

The EPICA challenge

Our contribution to the EPICA challenge:

Carbon cycle model simulations based on results for Termination I

-450 -420 -390 -360

D(o /oo)

EDC D

Termination I

1 5

7 9

11 13

15 17

MIS

0 500 1000

dust(ppbv) 1500

EDC dust

700 600 500 400 300 200 100 0

Time (kyr BP)

160 200 240 280

pCO2(ppmv)

Vostok pCO

₂

EDC pCO

₂

I II

III IV

V VI

VII

EPICA, 2004; Petit et al., 1999 Siegenthaler et al., 2005

(19)

Atmospheric carbon during Termination I

Interprete the temporal evolution of atmospheric CO₂, δ¹³C, ¹⁴C records

by carbon cycle simulations.

Smith et al., 1999; Monnin et al., 2001;

Stuiver et al., 1998; Hughen et al., 2004

-7.0 -6.8 -6.6 -6.4 -6.2

13 C[o / oo]

Interval I II III IV H1 BA YD 13

C

180 200 220 240 260 280

pCO2[ppmv]

pCO

₂

20 18 16 14 12 10 GISP2 Age [kyr BP]

0 100

200 300 400 500

14 C[o /oo]

14

C

(20)

The global record of atmospheric CO

₂

EPICA — European Project for Ice Coring in Antarctica The global carbon cycle and the box model BICYCLE

Time-dependent processes: motivations and simulation results Combined scenarios

Open questions

Conclusions

(21)

THC

The global

carbon cycle

60 PgC/yr 60 PgC/yr

1 PgC/yr 10 PgC/yr

ATMOSPHERE (600 PgC)

ROCK

TERR. BIOSPHERE (2200 PgC)

0.8 PgC/yr

0.2 PgC/yr

DEEP OCEAN (38000 PgC)

SEDIMENT

soft tissues | hard shells marine biosphere SURFACE OCEAN (700 PgC)

preindustrial reservoir sizes and annual fluxes

(22)

Carbonate System in the Ocean

Dissolved Inorganic Carbon (DIC) = CO₂ + HCO⁻₃ + CO⁼₃

Atmosphere

CO₂ + H₂0 ⇀↽^K¹ HCO⁻₃ + H⁺ ⇀↽^K² CO⁼₃ + 2H⁺

1% 89% 10%

m

^K⁰

CO2(g)

m

CO2(g)

Ocean

K0, K1, K2 = f(temperature,salinity,depth)

after Zeebe and Wolf-Gladrow, 2001

(23)

000000 000000 000000 000000 000000 000000 000000 000000 000000

111111 111111 111111 111111 111111 111111 111111 111111 111111

00000 00000 00000 00000 00000 00000 00000 00000 00000

11111 11111 11111 11111 11111 11111 11111 11111 11111 0000

0000 1111 1111

00000000 00000000 00000000 11111111 11111111 11111111

Box model of the Isotopic Carbon cYCLE BICYCLE

Rock

C3

FS SS

NW W D

C4

Atmosphere

Atlantic Indo−Pacific

Sediment SO

Biosphere

mediate inter−

surface

deep

water carbon

K¨ohler, et al., 2005, Global Biogeochemical Cycles.

(24)

000000 000000 000000 000000 000000 000000 000000 000000 000000

111111 111111 111111 111111 111111 111111 111111 111111 111111

00000 00000 00000 00000 00000 00000 00000 00000 00000

11111 11111 11111 11111 11111 11111 11111 11111 11111 0000

0000 1111 1111

00000000 00000000 00000000 11111111 11111111 11111111

Box model of the Isotopic Carbon cYCLE BICYCLE

Rock

C3

FS SS

NW W D

C4

Atmosphere

Sediment SO

Biosphere

water carbon

Prognostic variables:

10 oceanic boxes: DIC,

7 terrestrial boxes: C, 13C, 14C 1 atmospheric box:

14C, ALK, PO4, O2 13C,

CO2, 13C, 14C

(25)

000000 000000 000000 000000 000000 000000 000000 000000 000000

111111 111111 111111 111111 111111 111111 111111 111111 111111

00000 00000 00000 00000 00000 00000 00000 00000 00000

11111 11111 11111 11111 11111 11111 11111 11111 11111 0000

0000 1111 1111

00000000 00000000 00000000 11111111 11111111 11111111

Box model of the Isotopic Carbon cYCLE BICYCLE

Rock

C3

FS SS

NW W D

C4

Atmosphere

Sediment SO

Biosphere

water carbon

Prognostic variables:

10 oceanic boxes: DIC,

7 terrestrial boxes: C, 13C, 14C 1 atmospheric box:

14C, ALK, PO4, O2 13C,

CO2,

DIC + ALK −> CO2, HCO3, CO3, 13C, 14C

pH

(26)

The global record of atmospheric CO

₂

EPICA — European Project for Ice Coring in Antarctica The global carbon cycle and the box model BICYCLE

Time-dependent processes: motivations and simulation results

Combined scenarios Open questions

Conclusions

(27)

Overall objective and procedure for time-dependent simulations

Novelty:

• BICYCLE runs forward in time (no inverse studies)

• Transient simulations based on and forced with available paleo records

Three steps:

1. Which time-dependent processes were changing the carbon cycle on glacial/interglacial timescales?

2. How can we prescribe / force these processes in BICYCLE?

3. What are the impacts on CO₂?

(28)

Time-dependent processes:

Which How What ?

Physics (without ocean circulation) 1 Temperature

2 Sea level / salinity

3 Gas exchange / sea ice Ocean circulation

4 NADW formation

5 Southern Ocean ventilation Biogeochemistry

6 Marine biota / iron fertilisation 7 Terrestrial carbon storage

8 CaCO₃ chemistry

(29)

1 Temperature

Simulation with the climate model CCSM3 LGM–Preindustrial: light blue: –(2-4)K

Otto-Bliesner et al., 2006

(30)

Time-dependent processes:

Which How (T I) What (ppmv) ?

Physics (without ocean circulation)

1 Temperature +(3–5) K +30 !

2 Sea level / salinity

4 NADW formation

8 CaCO₃ chemistry

(31)

2 Sea Level / Salinity

Sea level rose during Termination I by 125 m; salinity dropped by 3%

50 100 150 200 250 300 350

Longitude [^o]

-90 -60 -30 0 30 60 90

Latitude[o ]

Area flooded from LGM to present

Bathymetry from Scripps Institiute of Oceanography from ICE-5G, Peltier, 2004

(32)

Time-dependent processes:

2 Sea level / salinity +125 m –15 !

4 NADW formation

8 CaCO₃ chemistry

(33)

3 Gas Exchange / Sea Ice

Annual mean sea ice area shrunk by ∼50% (Termination I)

Dynamics coupled to temperature in the high latitude surface boxes

Arctic (present): The Cryosphere Today (www) Antarctic (LGM) Gersonde et al., 2005

(34)

3 Gas Exchange / Sea Ice

Model comparions came to ambiguous results

Box models: full sea ice cover in SO reduces CO₂ General Circulation Models: only small changes

Archer et al., 2003 BICYCLE

(35)

3 Gas Exchange / Sea Ice

BICYCLE: Sea ice change in N and S N is sink for CO₂; S is source for CO₂

S as in box models, but N dominates over S

700 600 500 400 300 200 100 0 Time (kyr BP)

250 260 270 280

CO 2(ppmv)

S only (90% coverage) S only (60% coverage) S only (30% coverage) N and S

Archer et al., 2003 BICYCLE

(36)

Time-dependent processes:

3 Gas exchange / sea ice –50% –15 ?

Ocean circulation 4 NADW formation

8 CaCO₃ chemistry

(37)

4 North Atlantic Deep Water (NADW) Formation

Conveyor belt Changes in Atlantic THC

Rahmstorf, 2002

(38)

4 North Atlantic Deep Water (NADW) Formation

Preindustrial circulation: World Ocean Circulation Experiment (WOCE) data Temporal changes: NADW reduce from 16 Sv to 10 Sv (0 Sv)

Box model of the Isotopic Carbon cYCLE

BICYCLE

100 m

1000 m

DEEP SURFACE

MEDIATEINTER−

Rock

carbon

water

C3

FS SS

NW W D

C4

Atmosphere

Sediment

40°N

50°N 40°S 40°S

SO

Biosphere

16

22 5

10 1

4 16

9 6

3 30

9 16

20 1

18 19

15

6

9 9

16

12 5 2 1

3

Circulation after Ganachaud & Wunsch, 2000

(39)

Time-dependent processes:

Ocean circulation

4 NADW formation +6 Sv +15 !

8 CaCO₃ chemistry

(40)

4 Indirect effects of shutdown of NADW (not in BICYCLE)

Additionally, a NADW shutdown would lead to cooling in Eurasia Temperature anomalies simulated with climate model ECBILT-CLIO

K¨ohler et al., 2005, Climate Dynamics (after Knutti et al., 2004)

(41)

4 Indirect effects of shutdown of NADW (not in BICYCLE)

Reduction of marine export production (blue) in North Atlantic by 50%

Schmittner, 2005

(42)

4 Indirect effects of shutdown of NADW (not in BICYCLE)

Cooling leads to southwards shift of treeline (LPJ-DGVM) Competing effect of soil respiration and vegetation growth

275 280 285 290 295 300

CO 2 (ppmv)

CO₂ fert. feedbacks off CO₂ fert feedbacks on

230 235 240 245 250

CO 2 (ppmv)

195 200 205 210 215

CO 2 (ppmv)

0 1000 2000 3000 Simulation time (yr) 175

180 185 190 195 200

CO 2 (ppmv)

1 kyr BP

13 kyr BP

21 kyr BP 17 kyr BP

K¨ohler et al., 2005, Climate Dynamics

(43)

Time-dependent processes:

Ocean circulation

4 NADW formation +6 Sv +15 !/? (off)

8 CaCO₃ chemistry

(44)

5 Southern Ocean Ventilation

How to explain ∆δ¹³C(PRE-LGM)=+1.2/^◦_◦◦ in deep Southern Ocean?

SO mixing reduced by 2/3 coupled to SO SST = f(EDC δD)

Different hypotheses on the physical cause behind it (work in progress)

20 18 16 14 12 10 Time [kyr BP]

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

13

C in deep SO [

o

/

oo

]

SO stratification breakdown

at 17 kyr BP no SO stratification breakdown

Hodell et al, 2003 K¨ohler, et al., 2005, Global Biogeochemical Cycles

(45)

Time-dependent processes:

Ocean circulation

5 Southern Ocean ventilation +20 Sv +35 o

Biogeochemistry

8 CaCO₃ chemistry

(46)

6 Marine Biota / Iron fertilisation

Marine biological productivity might be Fe limited

in high nitrate low chlorophyll (HNLC) areas (Martin, 1990)

surface nitrate (µmol kg⁻¹) (Conkright et al, 1994)

(47)

6 Marine Biota / Iron fertilisation

Aeolian dust input to Antarctica LGM export production:

+ 20% (12 PgC yr⁻¹) Dust/iron input is reduced before rise in CO₂ starts

Monnin et al., 2001;

R¨othlisberger et al., 2002

Interval I II III IV

180 200 220 240 260

CO 2[ppmv]

EPICA Dome C CO₂

20 18 16 14 12 10

GISP2 age [kyr BP]

0 10 20 30 40 50 nss-Ca2+ [ppb]

EPICA Dome C nss-Ca²⁺

iron limitation no iron limitation

(48)

Time-dependent processes:

Ocean circulation

Biogeochemistry

6 Marine biota / iron fertilisation –2 PgC yr⁻¹ +20 ? 7 Terrestrial carbon storage

8 CaCO₃ chemistry

(49)

7 Terrestrial carbon storage

Model and data-based estimates range from 300 to 800 PgC Example from LPJ-DGVM (Preindustrial–LGM)

K¨ohler et al., 2005, Climate Dynamics

(50)

Time-dependent processes:

Ocean circulation

Biogeochemistry

6 Marine biota / iron fertilisation –2 PgC yr⁻¹ +20 ? 7 Terrestrial carbon storage +500 PgC –15 ! 8 CaCO₃ chemistry

(51)

8 Carbonate compensation

Dissolution / accumulation of CaCO₃ depends on deep ocean [CO²₃⁻ ]

Zeebe and Westbroeck, 2003

(52)

8 Carbonate compensation

Anomalies in deep ocean [CO²₃⁻ ] caused by carbon cycle variations relax to initial state with an e-folding time τ of 1.5 to 6 kyr

100 80 60 40 20 0

Depth (cm) -20

-10 0 10 20 30

CO 32- (molkg-1 )

-20 -10 0 10 20 30

CO 32- (molkg-1 )

25 20 15 10 5

Time (cal kyr BP)

= 6.0 kyr

= 1.5 kyr

8.314 CkyrBP 9.4calkyrBP 3.314 CkyrBP 3.5calkyrBP

τ = 6.0 kyr:

process-based sediment model

(Archer et al., 1997) τ = 1.5 kyr:

reconstruction of deep ocean [CO²₃⁻ ]

(Marchitto et al., 2005)

after Marchitto et al., 2005

(53)

Time-dependent processes:

Ocean circulation

Biogeochemistry

6 Marine biota / iron fertilisation –2 PgC yr⁻¹ +20 ? 7 Terrestrial carbon storage +500 PgC –15 !

8 CaCO₃ chemistry τ=1.5 kyr +20 ?

(54)

Time-dependent processes:

6 Marine biota / iron fertilisation –2 PgC yr⁻¹ +20 ? 7 Terrestrial carbon storage +500 PgC –15 !

8 CaCO₃ chemistry τ=1.5 kyr +20 ?

Sum +75

Sum (without sea ice) +90

Vostok (incl. Holocene rise) +103

(55)

The global record of atmospheric CO

₂

EPICA — European Project for Ice Coring in Antarctica The global carbon cycle and the box model BICYCLE

Time-dependent processes: motivations and simulation results Combined scenarios

Open questions

Conclusions

(56)

Atmospheric carbon during Termination I

Interprete the temporal evolution of atmospheric CO₂, δ¹³C, ¹⁴C records

by carbon cycle simulations.

Stuiver et al., 1998; Hughen et al., 2004

-7.0 -6.8 -6.6 -6.4 -6.2

13 C[o / oo]

C

180 200 220 240 260 280

pCO2[ppmv]

pCO

₂

20 18 16 14 12 10 GISP2 Age [kyr BP]

0 100

200 300 400 500

14 C[o /oo]

14

C

(57)

Atmospheric carbon during Termination I

Not only the amplitudes but also the timing of the changes in CO₂, δ¹³C,

14C seems to be appropriate.

Stuiver et al., 1998; Hughen et al., 2004 K¨ohler et al., 2005,

Global Biogeochemical Cycles

-7.0 -6.8 -6.6 -6.4 -6.2

13 C[o / oo]

C

180 200 220 240 260 280

pCO2[ppmv]

pCO

₂

20 18 16 14 12 10 GISP2 Age [kyr BP]

0 100

200 300 400 500

14 C[o /oo]

20 18 16 14 12 10 GISP2 Age [kyr BP]

0 100

200 300 400 500

14 C[o /oo]

14

C

(58)

The EPICA challenge

Working hypothesis:

Our findings for Termination I are of general nature.

Approach:

Use same assumptions and extend forcing data set back in time.

-450 -420 -390 -360

D(o /oo)

EDC D

1 5

7 9

11 13

15 17

MIS

0 500 1000

dust(ppbv) 1500

EDC dust

700 600 500 400 300 200 100 0

Time (kyr BP)

160 200 240 280

pCO2(ppmv)

Vostok pCO₂ EDC pCO₂

I II

III IV

V VI

VII

(59)

0 20 40 60 80 100

IRD(%) (a)

5 10 15

SST(o C)

(b)

5 4 3 2

18 O(o /oo)

(c)

0 -1 -2

18 O(o /oo)

(d)

-15 -10 -5 0

T(K)

(e)

1.0 0.5 0.0

18 O(o /oo)

(f)

-100 -50 0

sealevel(m)

(g)

-450 -420 -390 -360

D(o /oo)

(h)

1 5

7 9

11 13

15 17

500 400 300 200 100 0

Feflux(gm-2 yr-1 )

(i)

700 600 500 400 300 200 100 0

Time (kyr BP)

180 200 220 240 260 280

CO2(ppmv)

700 600 500 400 300 200 100 0

Time (kyr BP)

180 200 220 240 260 280 300

CO2(ppmv)

(j)

S6.0k S1.5k S0.0k

I II

III IV

V VI

VII VIII

a: Heinrich b: N-SST c: NADW d: EQ-SST

e: NH ∆T

f: deep sea ∆T g: sea level

h: SO SST i: Fe fert.

j: CO₂

K¨ohler and Fischer, 2006, Climate of the Past

(60)

The EPICA challenge

800 700 600

180 200 220 240 260 280 300

CO2(ppmv) S6.0k

S1.5k S0.0k

800 700 600

180 200 220 240 260 280 300

CO2(ppmv)

(a)

VII

"VIII"

17

600 500 400

180 200 220 240 260 280 300

CO2(ppmv)

600 500 400

180 200 220 240 260 280 300

CO2(ppmv)

(b)

V VI

11 13

15

400 300 200

180 200 220 240 260 280 300

CO2(ppmv)

400 300 200

180 200 220 240 260 280 300

CO2(ppmv)

(c)

III IV

7 9

200 100 0

Time (kyr BP) 180

200 220 240 260 280 300

CO2(ppmv)

200 100 0

Time (kyr BP) 180

200 220 240 260 280 300

CO2(ppmv)

(d)

I II

1 5

(61)

The EPICA challenge

800 700 600

180 200 220 240 260 280 300

CO2(ppmv) S6.0k

S1.5k S0.0k

800 700 600

180 200 220 240 260 280 300

CO2(ppmv)

(a)

VII

"VIII"

17

600 500 400

180 200 220 240 260 280 300

CO2(ppmv)

600 500 400

180 200 220 240 260 280 300

CO2(ppmv)

(b)

V VI

11 13

15

400 300 200

180 200 220 240 260 280 300

CO2(ppmv)

400 300 200

180 200 220 240 260 280 300

CO2(ppmv)

(c)

III IV

7 9

200 100 0

Time (kyr BP) 180

200 220 240 260 280 300

CO2(ppmv)

200 100 0

Time (kyr BP) 180

200 220 240 260 280 300

CO2(ppmv)

(d)

I II

1 5

1. Terminations I, III, IV, V

(62)

The EPICA challenge

800 700 600

180 200 220 240 260 280 300

CO2(ppmv) S6.0k

S1.5k S0.0k

800 700 600

180 200 220 240 260 280 300

CO2(ppmv)

(a)

VII

"VIII"

17

600 500 400

180 200 220 240 260 280 300

CO2(ppmv)

600 500 400

180 200 220 240 260 280 300

CO2(ppmv)

(b)

V VI

11 13

15

400 300 200

180 200 220 240 260 280 300

CO2(ppmv)

400 300 200

180 200 220 240 260 280 300

CO2(ppmv)

(c)

III IV

7 9

200 100 0

Time (kyr BP) 180

200 220 240 260 280 300

CO2(ppmv)

200 100 0

Time (kyr BP) 180

200 220 240 260 280 300

CO2(ppmv)

(d)

I II

1 5

1. Terminations I, III, IV, V 2. Maximum peaks

(63)

The EPICA challenge

800 700 600

180 200 220 240 260 280 300

CO2(ppmv) S6.0k

S1.5k S0.0k

800 700 600

180 200 220 240 260 280 300

CO2(ppmv)

(a)

VII

"VIII"

17

600 500 400

180 200 220 240 260 280 300

CO2(ppmv)

600 500 400

180 200 220 240 260 280 300

CO2(ppmv)

(b)

V VI

11 13

15

400 300 200

180 200 220 240 260 280 300

CO2(ppmv)

400 300 200

180 200 220 240 260 280 300

CO2(ppmv)

(c)

III IV

7 9

200 100 0

Time (kyr BP) 180

200 220 240 260 280 300

CO2(ppmv)

200 100 0

Time (kyr BP) 180

200 220 240 260 280 300

CO2(ppmv)

(d)

I II

1 5

3. Timing inconsistencies

(64)

The EPICA challenge

800 700 600

180 200 220 240 260 280 300

CO2(ppmv) S6.0k

S1.5k S0.0k

800 700 600

180 200 220 240 260 280 300

CO2(ppmv)

(a)

VII

"VIII"

17

600 500 400

180 200 220 240 260 280 300

CO2(ppmv)

600 500 400

180 200 220 240 260 280 300

CO2(ppmv)

(b)

V VI

11 13

15

400 300 200

180 200 220 240 260 280 300

CO2(ppmv)

400 300 200

180 200 220 240 260 280 300

CO2(ppmv)

(c)

III IV

7 9

200 100 0

Time (kyr BP) 180

200 220 240 260 280 300

CO2(ppmv)

200 100 0

Time (kyr BP) 180

200 220 240 260 280 300

CO2(ppmv)

(d)

I II

1 5

3. Timing inconsistencies

Solutions:

A: Synchronisation errors?

B: Missing processes?

C: Are our findings for Termination I

of general nature?

(65)

Terminations I-VIII

combined simulation vs. ice core data

∼20 ppmv per Termination are missing

VIII VII VI V IV III II I Number of Termination

0 10 20 30 40 50 60 70 80 90 100 110 120 130

CO 2rise(ppmv)

Vostok and EDC data scenario S1.5K

sum of one-at-a-time sum of all-but-one

Vostok pre-Vostok

(66)

Terminations I-VIII

combined simulation vs. ice core data

Termination VI, VII: smaller contributions from OCEAN CIRCULATION and SST

VIII VII VI V IV III II I Number of Termination

0 10 20 30 40 50 60 70 80 90 100 110 120 130

CO 2rise(ppmv)

Vostok and EDC data scenario S1.5K

sum of one-at-a-time sum of all-but-one

Vostok pre-Vostok

(67)

pH

pH from δ¹¹B in surface waters of equatorial Atlantic only pH reconstruction available so far

700 600 500 400 300 200 100 0 Time (kyr BP)

8.1 8.15

8.2 8.25 8.3 8.35

pH

S6.0k S1.5k S0.0k

1 5

7 9

11 13

15 17

pH from H¨onisch & Hemming 2005

(68)

The global record of atmospheric CO

₂

EPICA — European Project for Ice Coring in Antarctica The global carbon cycle and the box model BICYCLE

Time-dependent processes: motivations and simulation results Combined scenarios

Open questions

Conclusions

(69)

Missing processes

• process-based sediment model (work in progress)

• riverine input of continental weathering

THC

The global carbon cycle

60 PgC/yr 60 PgC/yr

1 PgC/yr 10 PgC/yr

ATMOSPHERE (600 PgC)

ROCK

TERR. BIOSPHERE (2200 PgC)

0.8 PgC/yr

0.2 PgC/yr

DEEP OCEAN (38000 PgC)

SEDIMENT

soft tissues | hard shells marine biosphere SURFACE OCEAN (700 PgC)

(70)

Continental Weathering

Two effects of continental weathering:

1. a sink for atmospheric CO₂

2. a source of HCO⁻₃ and alkalinity to the ocean

For steady state conditions :

riverine input = sedimentation output

Changes in the riverine input lead to changes in the sedimentation output (carbonate compensation) until a new equlibrium with equal input and output is established.

For investigations under changing climates (either 21st century or LGM) one would need :

1. a climate model coupled to a model of continenal weathering 2. riverine inputs in an ocean carbon cycle model (incl sediments)

(71)

Continental Weathering II

Two different processes:

• Carbonate weathering: C supply from atmosphere and continental crust

• Silicate weathering: C supply from atmospheric CO₂ only

⇒: Outgassing from ocean. Changes in alkalinity are more important than for the changes in the C budget itself.

(Munhoven 1997)

(72)

Continental Weathering III

Work on changes in continental weathering during the last 20 000 yr:

• Munhoven 2002: CO₂ changes by 6 to 12 ppmv

• Jones et al 2002: CO₂ changes by less than 6 ppmv

Shortcomings:

• Weathering: underlying lithology (incl resolution)

• Carbon cycle: simplified model

(73)

The global record of atmospheric CO

₂

EPICA — European Project for Ice Coring in Antarctica The global carbon cycle and the box model BICYCLE

Time-dependent processes: motivations and simulation results Combined scenarios

Open questions

Conclusions

(74)

Take Home Messages

1. There are reasonable data- and model-based evidences which processes were influencing the global carbon cycle on glacial/interglacial timescales.

2. The way how they are treated in a model depends on its architecture.

Prescribing climate (box models) vs. internally calculated climate variability (climate models). More important is the agreement with paleo data sets.

3. Not only the amplitudes, but also the timing of changes need to be addres- sed to quantify what impacts individual processes have on CO₂.

4. Simulation results are always model-dependent, but the amplitudes of individual contributions can be estimated with simple models such as BICYCLE.

5. Are our findings for Termination I of general nature?

(75)

Take Home Messages

(76)

Take Home Messages

(77)

Take Home Messages

(78)

Take Home Messages

(79)

Take Home Messages

(80)

Future δ¹³C data might verify or falsify our approach.

200 250 300 350

CO 2[ppmv]

700 400 100 Time [kyr BP]

13C CO₂

10 7 4 1 Time [kyr BP]

1750 AD

1000 1500 2000 Time [yr AD]

2000 198019902000 Time [yr AD]

-8.5 -8.0 -7.5 -7.0 -6.5 -6.0

13 C[o / oo]