climate feedback on the marine carbon cycle in carboocean earth system models j. segschneider 1, e....
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Climate feedback on the marine carbon cycle in CarboOcean Earth System Models
J. Segschneider1, E. Maier-Reimer1
L. Bopp2, J. Orr2
1Max-Planck-Institute for Meteorology, Hamburg, Germany2Institut Pierre-Simon Laplace, Gif-sur-Yvette, France
EU FP6 IP 511176 (GOCE)
Background:
Main goal of core theme 5 within CarboOcean: Provide coupled climate carbon cycle simulations
to
• provide predictions of oceanic carbon sources and sinks
• identify and possibly quantify the feedback processes between climate and the oceanic carbon cycle
Atmospheric pCO2 rises because of anthropogenic emissions
Atmospheric temperature rises and hence circulation is changed
Ocean state (temperature and circulation) are influenced by atmospheric conditions, internal dynamics may amplify perturbations
Physical conditions impact on marine carbon cycle and hence oceanic CO2 uptake, which impacts on atmospheric pCO2
Controlling mechanisms for climate feedback on marine CO2 cycle
Possible marine feedback mechanisms
physical pump: - higher SST/reduced solubility - reduced deep water formation/transport to abyss + less ice cover/increased gas exchange at high latitudes ? wind/gas exchange
biological pump: - weakening MOC, less nutrients at surface, less export
alkalinity pump: - acidifcation/less calcification + less silicate/more calcification
Sign indicates impact on oceanic CO2 uptake
Instrument
Earth System Models CM4, COSMOS1 comprising
- Atmosphere dynamics and chemistry LSCE: LMDZ-4, MPIM: ECHAM5
- Ocean dynamics and biogeochemistry LSCE: ORCA/PISCES, MPIM: MPIOM/HAMOCC5.1
- Land biosphere LSCE: ORCHIDEE, MPIM: JSBACH
To be added: NCAR CSM1.4 (some results, as used by Bern group)
BCM (Bergen climate model)
Forcing protocol (same as C4MIP):
historical 20C3M CO2 emissions 1860 -1999 (418GtC)
future SRES A2 CO2 emissions 2000-2100 (1770GtC)
two experiments: one with climate feedback
one without climate feedback
Quantifying sensitivity: New results from CarboOcean
ocean ocean
•IPSL •MPI•C4MIP
IPSL-CM2C IPSL-CM4 MPIM NCAR
o (PgC / °C) -30 -16 -22 -17
Quantifying climate impact
Mechanisms for climate impact:
• Increasing Sea Surface Temperature decreases CO2 solubility• Decreased mixing with sub-surface and deep- waters prevents the penetration of anthropogenic carbon into deep ocean• Decrease in biological production reduces the amount of carbon transported to depth.
Identifying mechanisms for climate impact
NCAR
IPSL CM2 IPSL CM4 MPIM NCAR
SST [oC]
Export [PgC/yr]
Identifying mechanisms:
NCAR
IPSL CM2 IPSL CM4 MPIM NCAR
SST [oC]
Identifying mechanisms:
NCAR
IPSL CM2 IPSL CM4 MPIM NCAR
mixed layer depth [m]
IPSL CM2 IPSL CM4 MPIM MOC [Sv]
NCAR
SST [oC]
Identifying mechanisms:
NCAR
IPSL CM2 IPSL CM4 MPIM NCAR
IPSL CM2 IPSL CM4 MPIM
mixed layer depth [m]
MOC [Sv]
Identifying mechanisms:
0
0.5
1
1.5
2
2.5
3
-40 -30 -20 -10 0
Gamma (PgC/°C)
SS
T (°
C) IPSL-CM2C
IPSL-CM4
MPI
NCAR
-2
-1.5
-1
-0.5
0
-40 -30 -20 -10 0
Gamma (PgC/°C)
Exp
ort
(Pg
C/y
r)
IPSL-CM2C
IPSL-CM4
MPI
NCAR
Identifying/Quantifying climate impact:
SST
Export
-10
-8
-6
-4
-2
0
-40 -30 -20 -10 0
Gamma (PgC/°C)
TH
C (S
v) IPSL-CM2C
IPSL-CM4
MPI
-60
-50
-40
-30
-20
-10
0
-40 -30 -20 -10 0
Gamma (PgC/°C)
Mix
ed L
ayer
Dep
th (m
)
IPSL-CM2C
IPSL-CM4
MPI
NCAR
Identifying/Quantifying climate impact:
MOC
MLD
Regionalisation
Regionalisation
Identifying mechanisms:
- 10%
opex90
- 13%
Identifying mechanisms:
caex90
+ 20%
Identifying mechanisms:
Conclusions -identifying mechanisms-
CO2 induced warming and weaker MOC weaken physical pump
Decrease in export production weakens biological pump
Increase in calcite export strengthens alkalinity counter pump
All this points to weakening potential for oceanic uptake
Conclusions -quantifying feedback-
CarboOcean models range from -16 to -30 GtC/K
indication for linear relationship with :
nearest for MLD
less clear for export (if CM4 omitted),
inverse if anything for MOC (?)
scattered for SST
MPIIPSLSabine et al. 2004
Anthropogenic DIC
MPI-OM grid