The Southern Ocean Decoupling Hypothesis

(1)

Alfred Wegener Institute

for Polar and Marine Research Bremerhaven, Germany

Carbon cycle and the Mid Pleistocene Transition:

The Southern Ocean Decoupling Hypothesis

Peter K¨ohler

Berger Symposium on Climate Change, Louvain-la-Neuve, Belgium — May 2008

In cooperation with:

Hubertus Fischer, Climate and Environmental Physics, University of Bern, Switzerland

B¨arbel H¨onisch, Lamont Doherty Earth Observatory of Columbia University, New York, USA Richard Bintanja, KNMI (Royal Netherlands Meteorological Institute), De Bilt, Netherlands

(2)

Outline

The data The model

The EPICA Time Window

The Southern Ocean Decoupling Hypothesis Other Theories

Take-home messages

(3)

Paleo Reconstructions — Climate

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) 5

4 3

LR0418 O(o /oo)

A

^MIS¹³⁵⁷⁹¹¹¹³¹⁵¹⁷¹⁹²¹²³²⁵²⁷²⁹³¹³³³⁵³⁷³⁹⁴¹⁴³⁴⁵⁴⁷⁴⁹⁵¹⁵³⁵⁵⁵⁷⁵⁹⁶¹⁶³⁶⁵

100-kyr MPT

40-kyr

10¹ 2 5 10² 2 5 10³ Period (kyr)

10^-1

2 5

10⁰

2 5

10¹

2 5

10²

2

Spectralpower(-)

40-kyr world (1.2-1.8 Myr BP)

B

18O

10¹ 2 5 10² 2 5 10³ Period (kyr)

10^-1

2 5

10⁰

2 5

10¹

2 5

10²

2

Spectralpower(-)

MPT (0.6-1.2 Myr BP)

18O

10¹ 2 5 10² 2 5 10³ Period (kyr)

10^-1

2 5

10⁰

2 5

10¹

2 5

10²

2

Spectralpower(-)

100-kyr world (0-0.6 Myr BP)

C

18O

Benthic δ¹⁸O stack LR04 (Lisiecki and Raymo, 2005)

(4)

Paleo Reconstructions — Carbon Cycle

5 4 3

LR0418 O(o /oo)

A

^MIS¹³⁵⁷⁹¹¹¹³¹⁵¹⁷¹⁹²¹²³²⁵²⁷²⁹³¹³³³⁵³⁷³⁹⁴¹⁴³⁴⁵⁴⁷⁴⁹⁵¹⁵³⁵⁵⁵⁷⁵⁹⁶¹⁶³⁶⁵

180 200 220 240 260 280 300

CO 2(ppmv) 100-kyr

MPT 40-kyr

B

180 ppmv 280 ppmv

Vostok, EPICA Dome C

Petit et al., 1999

Siegenthaler et al., 2005 Luthi et al., 2008

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) -1.0

-0.8 -0.6 -0.4 -0.2 0.0 0.2

13 C(o /oo)

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) -1.0

-0.8 -0.6 -0.4 -0.2 0.0 0.2

13 C(o /oo)

C

(5)

Paleo Reconstructions — Carbon Cycle

5 4 3

LR0418 O(o /oo)

A

^MIS¹³⁵⁷⁹¹¹¹³¹⁵¹⁷¹⁹²¹²³²⁵²⁷²⁹³¹³³³⁵³⁷³⁹⁴¹⁴³⁴⁵⁴⁷⁴⁹⁵¹⁵³⁵⁵⁵⁷⁵⁹⁶¹⁶³⁶⁵

180 200 220 240 260 280 300

CO 2(ppmv) 100-kyr

MPT 40-kyr

B

180 ppmv 280 ppmv

CO₂ = f(pH) = f(¹¹B)

(Honisch & Hemming, 2005, unpublished data)

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) -1.0

-0.8 -0.6 -0.4 -0.2 0.0 0.2

13 C(o /oo)

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) -1.0

-0.8 -0.6 -0.4 -0.2 0.0 0.2

13 C(o /oo)

C

(6)

Paleo Reconstructions — Carbon Cycle

5 4 3

LR0418 O(o /oo)

A

^MIS¹³⁵⁷⁹¹¹¹³¹⁵¹⁷¹⁹²¹²³²⁵²⁷²⁹³¹³³³⁵³⁷³⁹⁴¹⁴³⁴⁵⁴⁷⁴⁹⁵¹⁵³⁵⁵⁵⁷⁵⁹⁶¹⁶³⁶⁵

180 200 220 240 260 280 300

CO 2(ppmv) 100-kyr

MPT 40-kyr

B

180 ppmv 280 ppmv

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) -1.0

-0.8 -0.6 -0.4 -0.2 0.0 0.2

13 C(o /oo)

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) -1.0

-0.8 -0.6 -0.4 -0.2 0.0 0.2

13 C(o /oo)

C

ÔDP846(3ô^{S, 91}ôW); ODP677 (1ôS, 83ôW)

(Raymo et al., 1997, 2004)

(7)

Paleo Reconstructions — Carbon Cycle

10¹ ² ⁵ 10² ² ⁵ 10³ Period (kyr)

10^-1

2 5

10⁰

2 5

10¹

2 5

10²

2

Spectralpower(-)

40-kyr world (1.2-1.8 Myr BP)

E

13C

10¹ ² ⁵ 10² ² ⁵ 10³ Period (kyr)

10^-1

2 5

10⁰

2 5

10¹

2 5

10²

2

Spectralpower(-)

MPT (0.6-1.2 Myr BP)

13C

10¹ ² ⁵ 10² ² ⁵ 10³ Period (kyr)

10^-1

2 5

10⁰

2 5

10¹

2 5

10²

2

Spectralpower(-)

100-kyr world (0-0.6 Myr BP)

F

13C

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) -1.0

-0.8 -0.6 -0.4 -0.2 0.0 0.2

13 C(o /oo)

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) -1.0

-0.8 -0.6 -0.4 -0.2 0.0 0.2

13 C(o /oo)

C

(Raymo et al., 1997, 2004)

100-kyr MPT

40-kyr

(8)

Variation in Glacial/Interglacial Amplitudes

5 4 3

LR0418 O(o /oo)

A

^MIS¹³⁵⁷⁹¹¹¹³¹⁵¹⁷¹⁹²¹²³²⁵²⁷²⁹³¹³³³⁵³⁷³⁹⁴¹⁴³⁴⁵⁴⁷⁴⁹⁵¹⁵³⁵⁵⁵⁷⁵⁹⁶¹⁶³⁶⁵

180 200 220 240 260 280 300

CO 2(ppmv) 100-kyr

MPT 40-kyr

B

180 ppmv 280 ppmv

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) -1.0

-0.8 -0.6 -0.4 -0.2 0.0 0.2

13 C(o /oo)

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) -1.0

-0.8 -0.6 -0.4 -0.2 0.0 0.2

13 C(o /oo)

C

ÔDP846(3ô^{S, 91}ôW); ODP677 (1ôS, 83ôW)

(Raymo et al., 1997, 2004)

(9)

Variation in Glacial/Interglacial Amplitudes

40K MPT 100K

0 -0.5 -1 -1.5

-2

G/IG(18 O)(o / oo)

LR04 climate

0.0 0.2 0.4 0.6 0.8 1.0 1.2

fratio(-)

40K MPT 100K

0 20 40 60 80 100 120

G/IG(CO 2)(ppmv)

ice core CO₂

0.0 0.2 0.4 0.6 0.8 1.0 1.2

fratio(-)

40K MPT 100K

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

G/IG(13 C)(o /oo)

deep Pacific

0.0 0.2 0.4 0.6 0.8 1.0 1.2

fratio(-)

right y-axis: f_ratio = ^∆_∆^40k,MPT

100k

reduced G/IG amplitude in 40k:

climate (LR04): ∼ 50% of 100k carbon (CO₂): ???

carbon (δ¹³C): ∼ 70% of 100k

(10)

Outline

The data The model

The EPICA Time Window

The Southern Ocean Decoupling Hypothesis Other Theories

Take-home messages

(11)

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

(12)

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, submitted), K¨ohler & Fischer (2006)

(13)

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

DIC + ALK −> CO2, HCO3, CO3, pH

K¨ohler et al. (2005, submitted), K¨ohler & Fischer (2006)

(14)

Outline

The data The model

The EPICA Time Window

The Southern Ocean Decoupling Hypothesis Other Theories

Take-home messages

(15)

EPICA drilling sites:

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

(16)

The EPICA Time Window

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

(17)

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

(18)

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?

(19)

Time-dependent processes:

Which How (T I) What (ppmv) ?

Physics (without ocean circulation)

1 Temperature +(3–5) K +30 !

2 Sea level / salinity +125 m –15 !

3 Gas exchange / sea ice –50% –15 ?

Ocean circulation

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

5 Southern Ocean ventilation +20 Sv +35 o

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 ?

Sum +75

Sum (without sea ice) +90

Vostok (incl. Holocene rise) +103

(20)

000000 000000 000000 000000 000000 000000 000000 000000

111111 111111 111111 111111 111111 111111 111111 111111

00000 00000 00000 00000 00000 00000 00000 00000

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 mediate

inter−

surface

deep

water carbon

-7.0 -6.8 -6.6 -6.4 -6.2

13 CO2[o /oo]

TD ¹³CO₂ Interval I II III IV

200 220 240 260 280

pCO2[ppmv] EDC pCO₂

Termination I

-450 -440 -430 -420 -410 -400 -390 -380

D[o /oo]

EDC D

0 10 20 30 40 50

2+ nss-Ca[ppb] 60

EDC nss-Ca²⁺

400 500 600 700

CH4[ppbv]

GISP2 EDC CH₄

-42-41 -40-39 -37-38-36-35 -34

18 O[o /oo]

GISP2 ¹⁸O

-120 -100 -80 -60 -40 -20 0

sealevel[m]

sea level

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

0 5 10 15 20

Flux[106 m3 /s]

SO mixing NADW

H1 YD

-7.0 -6.8 -6.6 -6.4 -6.2

13 C[o /oo]

Interval I II III IV

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]

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

0 100

200 300 400 500

14 C[o /oo]

14

C

Assumptions on changes in

- Fe fertilization in SO - Ocean circulation

(NADW, SO mixing) - Climate ( T,

sealevel, sea ice) - CaCO₃ chemistry - terrestrial biosphere

Forcing ⇒ Model ⇒ Results

K¨ohler et al. (2005) Global Biogeochemical Cycles

(21)

The EPICA Time Window

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

(22)

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

(23)

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

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

(24)

Outline

The data The model

The EPICA Time Window

The Southern Ocean Decoupling Hypothesis Other Theories

Take-home messages

(25)

Beyond EPICA — Forcings

OLD EPICA 740kyr

K¨ohler & Fischer (2006)

5 10 15

SST(oC)

5 4 3 2

18O(o/oo)

0 -1 -2

18O(o/oo)

-15 -10 -5 0

T(K)

1.0 0.5 0.0

18O(o/oo)

-100 -50 0

sealevel(m)

-450 -420 -390 -360

D(o/oo) 1 5 7 9 11 13 15 17

700 600 500 400 300 200 100 0

Time (kyr BP) 500

400 300 200 100 0

Feflux(gm-2yr-1)

⇒

000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000

111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111

000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000 000000000000

111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 111111111111 0000000

0000000 0000000 0000000 0000000 0000000 0000000 0000000 0000000 0000000 0000000 0000000

1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111

0000000 0000000 0000000 0000000 0000000 0000000 0000000 0000000 0000000 0000000 0000000 0000000

1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111 1111111

⇒

_CO₂_, _δ¹³_C

740 kyr 2 Myr

NEW MPT 2 Myr

this study

LR04-based

5 10 15

SST(oC)

5 4 3 2

18O(o/oo)

0 -1 -2

18O(o/oo)

-15 -10 -5 0

T(K)

1.0 0.5 0.0

18O(o/oo)

-100 -50 0

sealevel(m)

-450 -420 -390 -360

D(o/oo) 1 5 7 9 11 13 15 17

700 600 500 400 300 200 100 0

Time (kyr BP) 500

400 300 200 100 0

Feflux(gm-2yr-1)

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) 5

4 3

LR0418O(o/oo) A ^MIS¹³⁵⁷⁹¹¹¹³¹⁵¹⁷¹⁹²¹²³²⁵²⁷²⁹³¹³³³⁵³⁷³⁹⁴¹⁴³⁴⁵⁴⁷⁴⁹⁵¹⁵³⁵⁵⁵⁷⁵⁹⁶¹⁶³⁶⁵

100-kyr MPT

40-kyr

⇒

5 4 3

18(o/oo) ^LR04 A

-100 -50 0

sealevel(m)

S_NHICE S_LR04, r²= 93%

Bintanja 1 Myr

B

-15 -10 -5 0 5

T(K) ^S_NHICE

S_LR04 r²= 78%

Bintanja 1 Myr

C

1.0 0.5 0.0

18O(o/oo) S_NHICE

S_LR04, r²= 90%

Bintanja 1 Myr

D

40 35 30 25 20 15

Area(1012m2) S_NHICE S_LR04

E

-5 0 5 10

Siweath(1012mol/yr) S_REGOLITH

S_LR04

F

0 -1 -2 18O(o/oo)

correl. to LR04, r²= 42%, not taken ODP677

G

-440 -400 -360

D(o/oo) S_LR04, r²= 73%

EPICA Dome C

H

2.0 1.5 1.0 0.5 0.0

Time (Myr BP) 0

200 -2-1Feflux(gmyr) 400

S_IRON S_LR04, r²= 53%

EPICA Dome C

I

EDC period pre-EDC period