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Physical / Chemical Drivers
of the Ocean
in a High CO2 World
Laurent Bopp
IPSL / LSCE, Gif s/ Yvette, France
Sediment
Marine Biogeochemistry
Atmospheric Components :
CO2, DMS, CH4, N2O,…
Circulation, Temperature, Light, Dust, …
Ocean
Atmosphere
Biosphere Soils
Climate
IntroductionFood Web / Fisheries
Introduction
1850 1900 1950 2000 20502100
Tem
pera
ture
Change
(°C
)Pre
cipit
ati
on C
hang
e (
%)
Max.
Atl
anti
c O
ver.
(%
)
0
2
4
6
0
3
6
9
-15
-5
5
Coupled Model’sresponse to increasedAtmospheric pCO2
(IS92a, IPCC 2001)
Which aspects arerelevant to marinebiogeochemistry ?
Introduction
Drivers of Marine Biogeochemistry
Atmospheric pCO2
Temperature
Circulation(Advection & Mixing)
Light Supply
Dust Deposition
Rivers Input …
Marine Biogeochemistry
Carbon Cycle
O2 Cycle
Nutrients Cycle
Marine Productivity
Ecosystem Structure
Tools : Ocean-Atmosphere General Circulation Models
IPSL Coupled Model
PO43-
Particles
Euphotic Layer (100-150m)
PO43- Phyto
Zoo
Particles
Dissolved
PO43-
Diatoms
MicroZoo
P.O.M
D.O.M
Si
IronNano-phyto
Meso Zoo
NO3-
NH4+
Small Ones Big Ones
Tools : Biogeochemical Models for the Global Ocean
Geochemical Models …… to ….. Simple Ecosystem Models
Outline
Atmospheric pCO2
Temperature
Circulation(Advection & Mixing)
Light Supply
Dust Deposition
Rivers Input …
Carbon Cycle
O2 Cycle
Nutrients Cycle
Marine Productivity
Ecosystem Structure
1. Increased Atmospheric pCO2
Outline
Atmospheric pCO2
Temperature
Circulation(Advection & Mixing)
Light Supply
Dust Deposition
Rivers Input …
Carbon Cycle
O2 Cycle
Nutrients Cycle
Marine Productivity
Ecosystem Structure
1. Increased Atmospheric pCO2
2. Oceanic Circulation (Advection / Mixing)
Outline
Atmospheric pCO2
Temperature
Circulation(Advection & Mixing)
Light Supply
Dust Deposition
Rivers Input …
Carbon Cycle
O2 Cycle
Nutrients Cycle
Marine Productivity
Ecosystem Structure
1. Increased Atmospheric pCO2
2. Oceanic Circulation (Advection / Mixing)
3. Atmospheric Dust Deposition
Changes in pH : Acidification
Increase in DIC leads to an acidification of Ocean waters
Changes in Surface pH
IS92a, IPSL model, 2099-PreIndus
+0.5
+0.3
-0.3
-0.5
(See Poster by J. Orr)
All OCMIP2 Models
0-0.2-0.4
0°
40°N
40°S
Changes in pH & Marine Production / Ecosystem
Many studies have revealed/estimated the impact on marine ecosystems
Changes in CaCO3 Production (%), 2200 - PreIndustrial
Impact of Acidification on Marine CaCO3 Production (C. Heinze, HAMOCC4)
Changes in Ocean Physics : Stratification
-1000
+1000
+100
+10
0
-10
-100
IPSL-CM2, MML, 2075-Present
Shoaling of Max. Mixed Layer Depth…
(m)
(m)
Shoaling
80°S
40°S
0°
40°N
80°N
Sarmiento et al. in press
Consistent in 6 OAGCMs
IPSLNCARPrincetonMPIMHadleyCSIRO
Changes in Ocean Physics : Stratification
+1000
+100
+10
0
-10
-100
(m)
80°S
40°S
0°
40°N
80°N
Sarmiento et al. in pressMechanisms of Changes
(psu)(°C)
Mixed LayerSSSSST
80°S
40°S
0°
40°N
80°N
Changes in Winds : increase in Southern Ocean but …
Changes in Ocean Physics : Stratification
Implications for the Carbon Cycle
Implications for the Oxygen Cycle
Implications for Marine Productivity & Ecosystem
Changes in Ocean Physics & Carbon Cycle
IPCC, 2001
Climate Change reduces ocean CO2 sink(from –6% to –25% in 2050)
Climate ChangeImpact
Changes in Ocean Physics & Carbon Cycle
Mechanisms
Thermal Circulation
Re-Organisation of the Natural C Cycle
Sarmiento 96
Matear 99
Joos 99
(in GtC/yr, 1850-2100)
-52 -117 +111
-48 -41 +33
-68 -15 +33
Climatic Effect on CO2 sink at 4xCO2
gC m-2 yr-1
Decrease sink
Increase sink
Stratification prevents anthropogenic CO2 penetration
(HAMOCC3-OPA-LMD)
Changes in Ocean Physics & Carbon Cycle
Main Effect :
Changes in Ocean Physics & Oxygen Cycle
Recent data have shown O2 decreases in most regions of the ocean in the past 40 years (Emerson et al. 2001, Ono et al. 2001, Wanatabe et al. 2001, Matear et al. 2000, …)
Models suggest an amplification of this decrease in the coming decades(Bopp et al. 2002, Plattner et al. 2002, Matear et al. 2000,…)
Dep
th
Zonal Mean, Global Ocean, Changes in O2, 2100 - Present
The main driver is stratification (reduced ventilation & mixing)
Changes in Ocean Physics & Oxygen Cycle
Focus on the Equatorial Pacific
Dissolved O2 at 100 m(mol/l)
Anoxic / Suboxic Zone increases by 30 % in 2100
Changes in Ocean Physics & Oxygen Cycle
Mechanisms of Changes (3°S, Equatorial Pacific)
Temperature & Currents
Changes in T & U(2090-1990)
0 m
300 m
0 m
300 m
SEC
South Equatorial Current : shallower and weaker
No more warm & oxygenated water to the sub-surface
Changes in Ocean Physics & Marine Productivity
Mechanistic Models of Marine Biology
Empirical Models based on Observational constraints
(see Poster by P. Schultz)
Different approaches may be used…
• Similar response with different bio & dynamical models
Zonal Mean(2100-1990)
-30 % +30 %
• Decreases globally (-5/10%) BUT increases at high latitudes (+20/30%)
Simulation NPZD-IPSL, 2100-1990 30 gC m-2 an -1
- 30 gC m-2 an -1
Changes in Ocean Physics & Marine Productivity
Ocean Stratification increasesSurface nutrient -5 to –10 %
Oligotrophic GyresArea increases
Opposition high/low latitudes
(NPZD-IPSL)
Growing Season lenghtens
> +10 days
1xCO2 2xCO2-1xCO2
Changes in Ocean Physics & Marine Productivity
Changes in Ocean Physics & Marine Productivity
(m)
80°S
40°S
0°
40°N
80°N
Sarmiento et al. in press
80°S
40°S
0°
40°N
80°N
(days)
Less Nutrient … But Longer Growing Season IPSLNCARPrincetonMPIMHadleyCSIRO
Changes in Ocean Physics & Marine Ecosystem
Boyd and Doney (2002)
Increase in N2 fixationwith Global Warming
-1
+1
+0.02
-0.02
-0.2
+0.2
Bopp (2001)
Decrease in diatoms relative abundance
Changes in Dust Deposition
Recent papers suggest a high sensitivity of atmospheric dust loading to climate change
Mahowald and Luo (2003) : dust loading changes-20 / -60 %
Tegen et al. (2004) : dust loading changes +10 / -25 %
Mechanisms of changes
Sources of Dust Land Use CO2 Fertilization Climate Change
Transport
Changes in Dust Deposition & Marine Productivity Dust Deposition ……… and annual-mean Chlorophyll (M. Werner & I. Tegen) (PISCES model, O. Aumont)
(mg/m3)
5
0
1
(see talk by O. Aumont)
-0.5
+0.5
+0.1
-0.1
-0.5
+0.5
+0.1
-0.1
Sensitivity Exp: Dust deposition x2 or /2 (20 yr) Chl (mg/m3)
Conclusions
In a high CO2 world, the ocean will be…
More acidicMore stratifiedMore oligotrophic, but better light conditions Less oxygenated
But large uncertainties remain… in particular concerning …
Ocean Physics (Mixing ? Southern Ocean Circulation ?) Dust Deposition Changes Impact on Ecosystem Structure
Many Thanks to …
O. Aumont, J. Orr & OCMIP, C. Heinze, J. Sarmiento, I. Tegen, M. Werner, …
Oceanic Carbon Cycle : Oceanic Carbon Cycle : Coupling climate and carbon
1860 2000 2100
Coupled simulation
Observations
pCO2 (ppm)
Climate (OPA-LMD)
Carbon models(HAMOCC3,SLAVE)
pCO2
Emissions
Climatic effect : - pCO2 : + 70 ppm (20 %) - Temperature : ~15-20 %
Uncoupled simulation
Comparison to Cox et al. 2000
IPSL : 700 ppm 770 ppm
Geochemical Flux (gC m-2 an-1) of anthropic CO2
at 700 ppm Hadley
IPSL (OPA-LMD-HAMOCC3)
Differences :
- Terrestrial Biosphere
- Oceanic SinkSouthern Ocean
Hadley : 700 ppm 950 ppm
Climatic Effect
Ocean Carbon Cycle : Ocean Carbon Cycle : Coupling carbon and climateCoupling carbon and climate
Diatoms Abundance with Global Warming (using the PISCES model)
Diatoms replaced by NanoPhytoat mid/high Latitudes
Mechanisms :
Stratification
Nutrient Supply
Silica and Iron Limitation
Diatoms/ NanoPhyto
Changes in Diatoms Abundance (2090-1990)
-1
+1
+0.02
-0.02
-0.2
+0.2