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Physical / Chemical Drivers of the Ocean in a High CO 2 World. Laurent Bopp IPSL / L SCE, Gif s/ Yvette , France. Introduction. Food Web / Fisheries. Climate. Atmospheric Components : CO 2 , DMS , CH4, N2O,…. Atmosphere. Biosphere Soils. Ocean. Circulation, Temperature,

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slide1

Physical / Chemical Drivers

of the Ocean

in a High CO2 World

Laurent Bopp

IPSL / LSCE, Gif s/ Yvette, France

slide2

Introduction

Food Web / Fisheries

Climate

Atmospheric Components :

CO2, DMS, CH4, N2O,…

Atmosphere

Biosphere

Soils

Ocean

Circulation,

Temperature,

Light, Dust, …

Marine Biogeochemistry

Sediment

slide3

Which aspects are

relevant to marine

biogeochemistry ?

6

Introduction

4

Temperature Change

(°C)

2

Coupled Model’s

response to increased

Atmospheric pCO2

0

9

(IS92a, IPCC 2001)

6

3

Precipitation Change

(%)

0

5

Max. Atlantic Over.

(%)

-5

-15

1850 1900 1950 2000 2050 2100

slide4

Marine

Biogeochemistry

Carbon Cycle

O2 Cycle

Nutrients Cycle

Marine Productivity

Ecosystem Structure

Introduction

Drivers of

Marine Biogeochemistry

Atmospheric pCO2

Temperature

Circulation

(Advection & Mixing)

Light Supply

Dust Deposition

Rivers Input …

slide6

Tools : Biogeochemical Models for the Global Ocean

Geochemical Models …… to ….. Simple Ecosystem Models

PO43-

Diatoms

NH4+

Si

PO43-

Phyto

PO43-

Nano-phyto

NO3-

Iron

MicroZoo

Dissolved

Zoo

D.O.M

Meso Zoo

P.O.M

Particles

Particles

Small Ones

Big Ones

Euphotic Layer (100-150m)

slide7

Outline

1. Increased Atmospheric pCO2

Atmospheric pCO2

Temperature

Circulation

(Advection & Mixing)

Light Supply

Dust Deposition

Rivers Input …

Carbon Cycle

O2 Cycle

Nutrients Cycle

Marine Productivity

Ecosystem Structure

slide8

Outline

1. Increased Atmospheric pCO2

2. Oceanic Circulation (Advection / Mixing)

Atmospheric pCO2

Temperature

Circulation

(Advection & Mixing)

Light Supply

Dust Deposition

Rivers Input …

Carbon Cycle

O2 Cycle

Nutrients Cycle

Marine Productivity

Ecosystem Structure

slide9

Outline

1. Increased Atmospheric pCO2

2. Oceanic Circulation (Advection / Mixing)

3. Atmospheric Dust Deposition

Atmospheric pCO2

Temperature

Circulation

(Advection & Mixing)

Light Supply

Dust Deposition

Rivers Input …

Carbon Cycle

O2 Cycle

Nutrients Cycle

Marine Productivity

Ecosystem Structure

slide10

Increase in DIC leads to an acidification of Ocean waters

Changes in Surface pH

All OCMIP2 Models

+0.5

40°N

+0.3

-0.3

40°S

-0.5

-0.4

-0.2

0

IS92a, IPSL model, 2099-PreIndus

(See Poster by J. Orr)

Changes in pH : Acidification

slide11

Impact of Acidification on Marine CaCO3 Production (C. Heinze, HAMOCC4)

Changes in CaCO3 Production (%), 2200 - PreIndustrial

Changes in pH & Marine Production / Ecosystem

Many studies have revealed/estimated the impact on marine ecosystems

slide12

Shoaling of Max. Mixed Layer Depth…

Consistent in 6 OAGCMs

(m)

Shoaling

80°N

+1000

IPSL

NCAR

Princeton

MPIM

Hadley

CSIRO

+100

40°N

+10

0

-10

40°S

-100

80°S

-1000

(m)

IPSL-CM2, MML, 2075-Present

Sarmiento et al. in press

Changes in Ocean Physics : Stratification

slide13

Changes in Ocean Physics : Stratification

Sarmiento et al. in press

Mechanisms of Changes

D SST

D SSS

D Mixed Layer

80°N

80°N

+1000

+100

40°N

40°N

+10

0

-10

40°S

40°S

-100

80°S

80°S

(°C)

(psu)

(m)

Changes in Winds : increase in Southern Ocean but …

slide14

Changes in Ocean Physics : Stratification

Implications for the Carbon Cycle

Implications for the Oxygen Cycle

Implications for Marine Productivity & Ecosystem

slide15

Changes in Ocean Physics & Carbon Cycle

IPCC, 2001

Climate

Change

Impact

Climate Change reduces ocean CO2 sink

(from –6% to –25% in 2050)

slide16

Re-Organisation of

the Natural C Cycle

Thermal

Circulation

-52 -117 +111

Sarmiento 96

-48 -41 +33

Matear 99

-68 -15 +33

Joos 99

(in GtC/yr, 1850-2100)

Changes in Ocean Physics & Carbon Cycle

Mechanisms

slide17

Changes in Ocean Physics & Carbon Cycle

Climatic Effect on CO2 sink at 4xCO2

(HAMOCC3-OPA-LMD)

gC m-2yr-1

Decrease sink

Increase sink

Main Effect :

Stratification prevents

anthropogenic CO2 penetration

slide18

Models suggest an amplification of this decrease in the

coming decades

(Bopp et al. 2002, Plattner et al. 2002, Matear et al. 2000,…)

Zonal Mean,

Global Ocean,

Changes in O2,

2100 - Present

Depth

The main driver is stratification

(reduced ventilation & mixing)

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, …)

slide19

Changes in Ocean Physics & Oxygen Cycle

Focus on

the Equatorial Pacific

Dissolved O2 at 100 m

(mmol/l)

Anoxic / Suboxic Zone increases by 30 % in 2100

slide20

Changes in Ocean Physics & Oxygen Cycle

Mechanisms of Changes (3°S, Equatorial Pacific)

0 m

SEC

Temperature & Currents

300 m

0 m

Changes in T & U

(2090-1990)

300 m

South Equatorial Current : shallower and weaker

No more warm & oxygenated water to the sub-surface

slide21

Different approaches may be used…

Empirical Models based on Observational constraints

(see Poster by P. Schultz)

Mechanistic Models of Marine Biology

Changes in Ocean Physics & Marine Productivity

slide22

Zonal Mean

(2100-1990)

-30 %

+30 %

• Similar response with different bio & dynamical models

Changes in Ocean Physics & Marine Productivity

30 gC m-2 an -1

Simulation NPZD-IPSL, 2100-1990

- 30 gC m-2 an -1

• Decreases globally (-5/10%) BUT increases at high latitudes (+20/30%)

slide23

Growing Season lenghtens

> +10 days

Opposition high/low latitudes

Changes in Ocean Physics & Marine Productivity

(NPZD-IPSL)

Ocean Stratification increases

Surface nutrient

 -5 to –10 %

Oligotrophic Gyres

Area increases

1xCO2

2xCO2-1xCO2

slide24

Changes in Ocean Physics & Marine Productivity

Less Nutrient … But Longer Growing Season

IPSL

NCAR

Princeton

MPIM

Hadley

CSIRO

80°N

80°N

40°N

40°N

40°S

40°S

80°S

80°S

(m)

(days)

Sarmiento et al. in press

slide25

Increase in N2 fixation

with Global Warming

Boyd and Doney (2002)

+1

+0.2

Decrease in diatoms

relative abundance

+0.02

-0.02

-0.2

Bopp (2001)

-1

Changes in Ocean Physics & Marine Ecosystem

slide26

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

slide27

Sensitivity Exp: Dust deposition x2 or /2 (20 yr) D Chl (mg/m3)

+0.5

+0.5

+0.1

+0.1

-0.1

-0.1

-0.5

-0.5

Changes in Dust Deposition & Marine Productivity

Dust Deposition ……… and annual-mean Chlorophyll

(M. Werner & I. Tegen)(PISCES model, O. Aumont)

5

1

(mg/m3)

0

(see talk by O. Aumont)

slide28

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, …

Conclusions

In a high CO2 world, the ocean will be…

More acidic

More stratified

More oligotrophic, but better light conditions

Less oxygenated

slide30

Climatic effect :

- pCO2 : + 70 ppm (20 %)

- Temperature : ~15-20 %

Observations

Coupled simulation

Uncoupled simulation

1860

2000

2100

pCO2 (ppm)

Oceanic Carbon Cycle : Coupling climate and carbon

Climate (OPA-LMD)

Emissions

pCO2

Carbon models

(HAMOCC3,SLAVE)

slide31

Geochemical Flux (gC m-2 an-1)

of anthropic CO2

at 700 ppm

Hadley

  • Differences :

IPSL (OPA-LMD-HAMOCC3)

- Terrestrial Biosphere

- Oceanic Sink

Southern Ocean

Ocean Carbon Cycle : Coupling carbon and climate

  • Comparison to Cox et al. 2000

IPSL : 700 ppm 770 ppm

Hadley : 700 ppm 950 ppm

Climatic Effect

slide32

Mechanisms :

Stratification 

Nutrient Supply 

Silica and Iron Limitation 

Diatoms/ NanoPhyto 

Diatoms Abundance with Global Warming(using the PISCES model)

Diatoms replaced by NanoPhyto

at mid/high Latitudes

+1

+0.2

+0.02

-0.02

-0.2

-1

Changes in Diatoms Abundance (2090-1990)