Modelled bipolar seesaw (ECBILT-CLIO) - EPIC · 2011. 9. 28. · LPJ anomalies coupled to the HILDA...
Transcript of Modelled bipolar seesaw (ECBILT-CLIO) - EPIC · 2011. 9. 28. · LPJ anomalies coupled to the HILDA...
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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
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δ18 Ο
(ο/ ο
ο)
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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
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Modelled bipolar seesaw (ECBILT-CLIO)
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0 1000 2000Simulation time (yr)
-10
-5
0
5
Tem
pera
ture
ano
mal
y (K
)
0 1000 2000Simulation time (yr)
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)
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ECBILT-CLIO — Temperature
Zonally averaged ∆T over ice free land area:
North (70◦N): cooling by 7K
South (50◦S): warming by 2K.
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ECBILT-CLIO — Precipitation
Zonally averaged ∆prec over ice free land area:
Drier conditions in the tropics — wetter conditions in the subtropics
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δ18 Ο
(ο/ ο
ο)
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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
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-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)
Case studies for 4 time slices:
1, 13, 17, 21 kyr BP
PRE, YD, H1, LGM
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Terrestrial carbon storage in LPJ-DGVM
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Terrestrial carbon storage in LPJ-DGVM
PRE Difference LGM
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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
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Case study for preindustrial times (1 kyr BP)
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Vegetation — Tree Cover
Southward shift of the northern treeline = f(temperature)
Less trees in Sahel area (Mulitza et al.) = f(precipitation)
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Zonally averaged land carbon storage anomalies
Increase (soil respiration) & decrease (northern treeline) in C storage
Persisting anomaly 20◦S (model artefact)
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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
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But...
Evidence for CO2 fertilisation effect on vegetation growth is still poor
Körner 2006
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-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
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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)
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-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.
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Zonally averaged land carbon storage anomalies
1 kyr BP 13 kyr BP
17 kyr BP 21 kyr BP
Increase / decrease in terrestrial carbon storage
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-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)
0 1000 2000Simulation time (yr)
-75
-50
-25
0
25
50
75
0 1000 2000 3000Simulation time (yr)
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
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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)
0 1000 2000Simulation time (yr)
190
195
200
205
210
215
CO
2 (p
pmv)
0 1000 2000Simulation time (yr)
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.
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-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)
0 1000 2000Simulation time (yr)
-7,1
-7.0
-6.9
-6.8
-6.7
δ13 C
(o/ o
o)
with CO2 fert.
without CO2 fert.
0 1000 2000 3000Simulation time (yr)
-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
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-7.0
-6.8
-6.6
-6.4
-6.2
13C
[o/ o
o]
Interval I II III IV
H1 BA YD
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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)
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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.
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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
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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
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Preindustrial carbon storage LPJ-DGVM
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Glacial carbon storage LPJ-DGVM
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Difference in carbon storage LPJ-DGVM (21 – 1 kyr BP)
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-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
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-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.
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Atmospheric carbon records
LPJ anomalies coupled to the HILDA carbon cycle model
0 1000 2000 3000 4000 5000Simulation time (yr)
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
experiment background
0 1000 2000 3000 4000 5000Simulation time (yr)
-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
experiment background
Peak-to-peak-amplitudes:
∆CO2 = 13 and 21 ppmv ∆δ13C = 0.24 and 0.40 h
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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
0 1000 2000 3000 4000 5000Simulation time (yr)
-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
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-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
0 1000 2000Simulation time (yr)
-100
-50
0
50
100
Ano
mal
y (P
gC)
CO2 LGMClimate LGMLand LGM
0 1000 2000Simulation time (yr)
-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
without CO2 fertilization
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
0
50
100
Ano
mal
y (P
gC)
-100
-50
0
50
100
0 1000 2000Simulation time (yr)
-100
-50
0
50
100
Ano
mal
y (P
gC)
StandardδΤ − 50%
0 1000 2000 3000Simulation time (yr)
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)
without CO2 fertilization
∆T – 50%∆T – 25%∆T + 25%
Especially during full gla-ciation the magnitude of∆T constitutes the re-sponse