Modelled bipolar seesaw (ECBILT-CLIO) - EPIC · 2011. 9. 28. · LPJ anomalies coupled to the HILDA...

Alfred Wegener Institutefor Polar and Marine Research

AWI

Land–atmosphere carbon exchange duringabrupt climate change

Peter KöhlerAWI,

Fortunat JoosBern, Stefan GerberBern,PEI, Reto KnuttiBern,ETH

ESF Conference OCEAN CONTROLS IN ABRUPT CLIMATE CHANGE, Obergurgl 05/2007

Climate Dynamics (2005), 25: 689-708

Data constraints on abrupt climate changes during past 60 kyr

Modelled bipolar seesaw (ECBILT-CLIO)

Terrestrial carbon storage in LPJ-DGVM

Case study for preindustrial times (1 kyr BP)

Importance of the background climate

-42-40-38-36-34

δ18 Ο

(ο/ ο

ο)

-40-38-36-34

δ18 Ο

(ο/ ο

ο)

180200220240260280

CO

2 (p

pmv)

-60000 -50000 -40000 -30000 -20000 -10000 0Age (years)

300400500600700

CH

4 (p

pbv)

A4 A3 A1A2

▲ ▲ ▲ ▲ ▲

12 81417

H6 H5 H4 H3 H2 H1YD▲ ▲

H5a▲

GISP2

BYRD

TAYLOR DOME

Data constraints onabrupt climate chan-ges in the past 60kyr

Dansgaard/Oeschger events(e.g. 17, 14, 12, 8)

Heinrich events (H1–H6)

Antarctic warming events(A1–A4)

atmospheric CO2 (±20 ppmv)

atmospheric CH4 (±200 ppbv)

Grootes and Stuiver, 1997; Johnsen etal.,1972; Indermühle et al., 1999, 2000;Blunier et al., 1998, Brook et al., 1996,2000, Blunier and Brook, 2001

Modelled bipolar seesaw (ECBILT-CLIO)

0 1000 2000Simulation time (yr)

-10

-5

0

5

Tem

pera

ture

ano

mal

y (K

)


0

5

10

15

20

NA

DW

(Sv

)

0.0

0.1

0.2

0.3

0.4

0.5Fr

eshw

ater

(Sv

) A

B

C

Scenario F❏ Scenario F∆

NATL

SO

Bipolar seesaw inECBILT-CLIOKnutti et al., 2004.

Mimicking the bipolar seesawby freshwater discharge into theNorth Atlantic (50◦– 70◦N).

Global coupled atmosphere–ocean–sea ice model

ECBILT2: T21 atmosphere(Opsteegh et al., 1998)

CLIO: OGCM + sea ice(Goose and Fichefet, 1999)

ECBILT-CLIO — Temperature

Zonally averaged ∆T over ice free land area:

North (70◦N): cooling by 7K

South (50◦S): warming by 2K.

ECBILT-CLIO — Precipitation

Zonally averaged ∆prec over ice free land area:

Drier conditions in the tropics — wetter conditions in the subtropics

-42-40-38-36-34

δ18 Ο

(ο/ ο

ο)

-40-38-36-34

δ18 Ο

(ο/ ο

ο)

180200220240260280

CO

2 (p

pmv)

-60000 -50000 -40000 -30000 -20000 -10000 0Age (years)

300400500600700

CH

4 (p

pbv)

A4 A3 A1A2

▲ ▲ ▲ ▲ ▲

12 81417

H6 H5 H4 H3 H2 H1YD▲ ▲

H5a▲

GISP2

BYRD

TAYLOR DOME







Grootes and Stuiver, 1997; Johnsen etal.,1972; Indermühle et al., 1999, 2000;Blunier et al., 1998, Brook et al., 1996,2000, Blunier and Brook, 2001

-42-40-38-36-34

δ18 Ο

(ο/ ο

ο)

-40-38-36-34

δ18 Ο

(ο/ ο

ο)

180200220240260280

CO

2 (p

pmv)

-60000 -50000 -40000 -30000 -20000 -10000 0Age (years)

300400500600700

CH

4 (p

pbv)

A4 A3 A1A2

▲ ▲ ▲ ▲ ▲

12 81417

H6 H5 H4 H3 H2 H1YD▲ ▲

H5a▲

GISP2

BYRD

TAYLOR DOME







Case studies for 4 time slices:

1, 13, 17, 21 kyr BP

PRE, YD, H1, LGM


PRE Difference LGM

Vegetation versus soil carbon

Vegetation Soil

Rule of thumb:

Tropics: more than 2/3 of carbon in the vegetation

Boreal areas: more than 2/3 of carbon in the soil

Case study for preindustrial times (1 kyr BP)

Vegetation — Tree Cover

Southward shift of the northern treeline = f(temperature)

Less trees in Sahel area (Mulitza et al.) = f(precipitation)

Zonally averaged land carbon storage anomalies

Increase (soil respiration) & decrease (northern treeline) in C storage

Persisting anomaly 20◦S (model artefact)

0 1000 2000 3000 4000 5000Simulation time (yr)

-80

-60

-40

-20

0

20

40

60

Car

bon

stor

age

anom

aly

(PgC

)

F❏

with CO2 ff

F❏

without CO2 ff

ECBILT-ctrl

1 kyr BP

experiment background

flux recover

1

2

3Land carbon anomaly

1. CO2 fertilization (NPP =

f(CO2)) is dampening the

amplitude by factor of two

2. Final offset (20–30 PgC)

due to single PFT reorga-

nisation (precipitation) in a

few grid cells in the tropics

3. Peak-to-peak-amplitude:

∆C(terrestrial) = 70 and

120 PgC

But...

Evidence for CO2 fertilisation effect on vegetation growth is still poor

Körner 2006

-80

-60

-40

-20

0

20

40

60

80

Ano

mal

y (P

gC)

0 1000 2000 3000Simulation time (yr)

-80

-60

-40

-20

0

20

40

60

80

totalsoil+littervegetation

1 kyr BP1

23

4

Soil versus vegetation

1. Soil respiration is reduced

during cold times

⇒ carbon gain

2. Treeline shifts to South

⇒ carbon loss

3. Warming at the end of the

experiment leads to increased

soil respiration

⇒ carbon loss

4. Treeline back North /

delayed recovery

⇒ carbon gain

Importance of the background climate

Atmospheric CO2 concentration (ice cores)

Land ice sheet extent / sea level (ICE–4G)

Global temperature / precipitation fields (HadSM3 model output)

-20000 -15000 -10000 -5000 0Time (yr BP)

-80-60-40-20

020406080

100120

Car

bon

stor

age

anom

aly

(PgC

)

200021002200230024002500

26002700280029003000

Ter

rest

rial

car

bon

(PgC

)

freshwater release exp.

background without

Impact ofclimate changeduringTermination I

Size and direction of carbon

storage anomaly depends on

background climate, mainly

background temperature.

Zonally averaged land carbon storage anomalies

1 kyr BP 13 kyr BP

17 kyr BP 21 kyr BP

Increase / decrease in terrestrial carbon storage

-75

-50

-25

0

25

50

75

Ano

mal

y (P

gC)

-75

-50

-25

0

25

50

75

totalsoil+littervegetation

-75

-50

-25

0

25

50

75

Ano

mal

y (P

gC)

-75

-50

-25

0

25

50

75

Ano

mal

y (P

gC)


-75

-50

-25

0

25

50

75


0 1000 2000 3000-75

-50

-25

0

25

50

75

Ano

mal

y (P

gC)

1 kyr BP 13 kyr BP

21 kyr BP17 kyr BP

Impact ofclimate changefordifferent times

without CO2 fertilization

13 kyr BP: YoungerDryas cold event

17 kyr BP: Heinrich eventduring partly glaciation

21 kyr BP: Heinrich eventduring full glaciation

275

280

285

290

295

300

CO

2 (p

pmv)

without CO2 fert.

with CO2 fert.

230

235

240

245

250

255

CO

2 (p

pmv)


190

195

200

205

210

215

CO

2 (p

pmv)


175

180

185

190

195

200

CO

2 (p

pmv)

1 kyr BP 13 kyr BP

21 kyr BP17 kyr BP

Impacts onatmosphericCO2

LGM amplitude:

∼7–12 ppmv

To be consistent with theice core record the mari-ne carbon cycle needs tocontribute about the samemagnitude.

-7.0

-6.9

-6.8

-6.7

-6.6

δ13 C

(o /

oo)

-7.0

-6.9

-6.8

-6.7

-6,6

δ13 C

(o /

oo)


-7,1

-7.0

-6.9

-6.8

-6.7

δ13 C

(o/ o

o)

with CO2 fert.

without CO2 fert.


-7.1

-7.0

-6.9

-6.8

-6.7

δ13 C

(o /

oo)

1 kyr BP 13 kyr BP

21 kyr BP17 kyr BP

Impacts onatmosphericδ13C

LGM amplitude:

∼–0.2 to –0.3h

Ice core recordnot clear on δ13C:

H1 & YD:– 0.2 to –0.4h excursion

but both events occurduring the last glacial/interglacial transition

-7.0

-6.8

-6.6

-6.4

-6.2

13C

[o/ o

o]

Interval I II III IV

H1 BA YD

180200220240260280

pCO

2[p

pmv]

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

0

100

200

300

400

50014

C[o

/ oo]

Data constraints on δ13C

Taylor Dome (Smith et al., 1999)

EPICA Dome C (Monnin et al., 2001)

INTCAL98 (Stuiver et al., 1998)Cariaco basin (Hughen et al., 2004)

Conclusions

• Abrupt climate changes caused by the bipolar seesaw lead to opposing

trends in terrestrial carbon storage: a southward shift of the northern

treeline (carbon loss) and a reduction in soil respiration in mid latitudes

(carbon gain).

• The overall net effect on carbon storage depends on the global balance

of losses and gains and is highly sensitive to the applied background

climatology.

• Be careful about the magnitude because of the unknowns in the CO2fertilisation feedback.

• The increase of 20 ppmv in atmospheric CO2 during the Antarctic

warming events A1–A4 might by ∼50% caused terrestrial carbon re-

lease.

• OUTLOOK Impact of same ECBILT-CLIO scenarios on CH4 cycle

in LPJ-DGVM: see poster by Jed Kaplan and Joe Melton.

LPJ-DGVMSitch et al., 2003 GCB.

Drivers:– monthly mean temperature,precipitation and insolation fields– CO2– terrestrial ice free land area

Spatial resolution: 3.75◦× 2.5◦

Plant functional types (PFT)—————————————————Tropical broadleaved evergreen treeTropical broadleaved raingreen treeTemperate needle-leaved evergreen treeTemperate broadleaved evergreen treeTemperate broadleaved summergreen treeBoreal needle-leaved evergreen treeBoreal summergreen treeC3 grassC4 grass

180

200

220

240

260

280

300

CO

2 (p

pmv)

180

200

220

240

260

280

300

-10

-5

0

5

10

15

20

∆Are

a (

1012

m2 )

-12

-10

-8

-6

-4

-2

0

∆T (

K)

20 15 10 5Time (kyr BP)

-12

-10

-8

-6

-4

-2

0

global land

30oS-30

oN

30oN-90

oN

20 15 10 5 0Time (kyr BP)

-175

-150

-125

-100

-75

-50

-25

0

∆pre

c (m

m y

r-1 )

A B

C D

ice retreat

net change

sea level

Background forcing ofLPJ-DGVMsame as in Joos et al., 2004 GBC.

Present day mean climatology(Leemans and Cramer 1991) withfollowing pertubations:

A: CO2 (EPICA Dome C, Monninet al., 2001) GISP2 age scale

B: land area from Peltier 1994

C,D: ∆T and ∆prec fromHadley Centre Unified Model

Preindustrial carbon storage LPJ-DGVM

Glacial carbon storage LPJ-DGVM

Difference in carbon storage LPJ-DGVM (21 – 1 kyr BP)

-60 -40 -20 0 20 40 60 80Latitude

-0,4

-0,3

-0,2

-0,1

0

0,1

0,2

Ano

mal

y in

rel

ativ

e fo

liar

proj

ectiv

e co

ver

tropical trees

temperate trees

grasses

boreal trees1 kyr BP

Impact of climatechange on vegetation

Grasses replace boreal trees northof 50◦N

Boreal trees replace temperatetrees in mid high latitudes

Small reduction in tropical treecover

-20000 -15000 -10000 -5000 0Time (yr BP)

-80-60-40-20

020406080

100120

Car

bon

stor

age

anom

aly

(PgC

)

200021002200230024002500

26002700280029003000

Ter

rest

rial

car

bon

(PgC

)

freshwater release exp.

background without

Impact ofclimate changeduringTermination I

Background terrestrial carbon:

ice retreat: + 610 PgCsea level rise: – 190 PgCCO2 fertilization: + 650 PgCclimate change: – 250 PgCtotal: + 820 PgC

Size and direction of carbonstorage anomaly depends onbackground climate.

Atmospheric carbon records

LPJ anomalies coupled to the HILDA carbon cycle model


270

275

280

285

290

295

300

atm

osph

eric

CO

2 (p

pmv)

F❏

with CO2 ff

F❏

without CO2 ff.

ECBILT-ctrl

1 kyr BP



-7.1

-7.0

-6.9

-6.8

-6.7

-6.6

atm

osph

eric

δ13

C (

o /oo

)

F❏

with CO2 ff

F❏

without CO2 ff

ECBILT-ctrl

1 kyr BP


Peak-to-peak-amplitudes:

∆CO2 = 13 and 21 ppmv ∆δ13C = 0.24 and 0.40 h

Sensitivity studies

0 1000 2000 3000 4000Simulation time (yr)

-80

-60

-40

-20

0

20

40

60

Car

bon

stor

age

anom

aly

(PgC

)

F❏

F∆ECBILT-ctrl


-80

-60

-40

-20

0

20

40

60

Car

bon

stor

age

anom

aly

(PgC

)

F❏

F❏δP-only

F❏δT-only

ECBILT-ctrl

1 kyr BP 1 kyr BP

BA

experiment background backgroundexperiment

Shape of freshwater discharge Temperature vs. Precipitation

-100

-50

0

50

100

-100

-50

0

50

100

Ano

mal

y (P

gC)

-100

-50

0

50

100

Ano

mal

y (P

gC)

-100

-50

0

50

100


-100

-50

0

50

100

Ano

mal

y (P

gC)

CO2 LGMClimate LGMLand LGM


-100

-50

0

50

100

Ano

mal

y (P

gC)

StandardCO2 PREClimate PRELand PRE

1 kyr BP 13 kyr BP

21 kyr BP17 kyr BP

Sensitivityanalysisonboundaryconditions


vary CO2vary climatevary land area

LPJ is most sensitive toclimate variations

-100

-50

0

50

100

-100

-50

0

50

100

Ano

mal

y (P

gC)

-100

-50

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Ano

mal

y (P

gC)

-100

-50

0

50

100


-100

-50

0

50

100

Ano

mal

y (P

gC)

StandardδΤ − 50%


0 1000 2000 3000

-100

-50

0

50

100

Ano

mal

y (P

gC)

δΤ − 25%δΤ + 25%

1 kyr BP 13 kyr BP

21 kyr BP17 kyr BP

Sensitivityanalysison themagnitudeof thetemperatureanomaly (∆T)


∆T – 50%∆T – 25%∆T + 25%

Especially during full gla-ciation the magnitude of∆T constitutes the re-sponse

Modelled bipolar seesaw (ECBILT-CLIO) - EPIC · 2011. 9. 28. · LPJ anomalies coupled to the HILDA...

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Transcript of Modelled bipolar seesaw (ECBILT-CLIO) - EPIC · 2011. 9. 28. · LPJ anomalies coupled to the HILDA...