1. Physical / Chemical Drivers of the Ocean in a High CO 2 World Laurent Bopp IPSL / LSCE, Gif s/ Yvette, France

2. Sediment Marine Biogeochemistry Atmospheric Components : CO 2, DMS, CH4, N2O,… Circulation, Temperature, Light, Dust, … Ocean Atmosphere Biosphere Soils Climate Introduction Food Web / Fisheries

3. Introduction 185019001950200020502100 Temperature Change (°C) Precipitation Change (%) Max. Atlantic Over. (%) 0 2 4 6 0 3 6 9 -15 -5 5 Coupled Models response to increased Atmospheric pCO 2 (IS92a, IPCC 2001) Which aspects are relevant to marine biogeochemistry ?

4. Introduction Drivers of Marine Biogeochemistry Atmospheric pCO 2 Temperature Circulation (Advection & Mixing) Light Supply Dust Deposition Rivers Input … Marine Biogeochemistry Carbon Cycle O 2 Cycle Nutrients Cycle Marine Productivity Ecosystem Structure

5. Tools : Ocean-Atmosphere General Circulation Models IPSL Coupled Model

6. PO 4 3- Particles Euphotic Layer (100-150m) PO 4 3- Phyto Zoo Particles Dissolved PO 4 3- Diatoms MicroZoo P.O.M D.O.M Si Iron Nano-phyto Meso Zoo NO 3 - NH 4 + Small OnesBig Ones Tools : Biogeochemical Models for the Global Ocean Geochemical Models…… to ….. Simple Ecosystem Models

7. Outline Atmospheric pCO 2 Temperature Circulation (Advection & Mixing) Light Supply Dust Deposition Rivers Input … Carbon Cycle O 2 Cycle Nutrients Cycle Marine Productivity Ecosystem Structure 1. Increased Atmospheric pCO 2

8. Outline Atmospheric pCO 2 Temperature Circulation (Advection & Mixing) Light Supply Dust Deposition Rivers Input … Carbon Cycle O 2 Cycle Nutrients Cycle Marine Productivity Ecosystem Structure 1. Increased Atmospheric pCO 2 2. Oceanic Circulation (Advection / Mixing)

9. Outline Atmospheric pCO 2 Temperature Circulation (Advection & Mixing) Light Supply Dust Deposition Rivers Input … Carbon Cycle O 2 Cycle Nutrients Cycle Marine Productivity Ecosystem Structure 1. Increased Atmospheric pCO 2 2. Oceanic Circulation (Advection / Mixing) 3. Atmospheric Dust Deposition

10. 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

11. Changes in pH & Marine Production / Ecosystem Many studies have revealed/estimated the impact on marine ecosystems Changes in CaCO 3 Production (%), 2200 - PreIndustrial Impact of Acidification on Marine CaCO3 Production (C. Heinze, HAMOCC4)

12. Changes in Ocean Physics : Stratification -1000 +1000 +100 +10 0 -10 -100 IPSL-CM2, MML, 2075-Present Shoaling of Max. Mixed Layer Depth… (m) Shoaling 80°S 40°S 0° 40°N 80°N Sarmiento et al. in press Consistent in 6 OAGCMs IPSL NCAR Princeton MPIM Hadley CSIRO

13. 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 press Mechanisms of Changes (psu)(°C) Mixed Layer SSS SST 80°S 40°S 0° 40°N 80°N Changes in Winds : increase in Southern Ocean but …

14. Changes in Ocean Physics : Stratification Implications for the Carbon Cycle Implications for the Oxygen Cycle Implications for Marine Productivity & Ecosystem

15. Changes in Ocean Physics & Carbon Cycle IPCC, 2001 Climate Change reduces ocean CO 2 sink (from –6% to –25% in 2050) Climate Change Impact

16. Changes in Ocean Physics & Carbon Cycle Mechanisms ThermalCirculation 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

17. Climatic Effect on CO 2 sink at 4xCO 2 gC m -2 yr -1 Decrease sink Increase sink Stratification prevents anthropogenic CO 2 penetration (HAMOCC3-OPA-LMD) Changes in Ocean Physics & Carbon Cycle Main Effect :

18. Changes in Ocean Physics & Oxygen Cycle Recent data have shown O 2 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,…) Depth Zonal Mean, Global Ocean, Changes in O2, 2100 - Present The main driver is stratification (reduced ventilation & mixing)

19. Changes in Ocean Physics & Oxygen Cycle Focus on the Equatorial Pacific Dissolved O 2 at 100 m ( mol/l) Anoxic / Suboxic Zone increases by 30 % in 2100

20. 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

21. 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…

22. 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

23. Ocean Stratification increases Surface nutrient -5 to –10 % Oligotrophic Gyres Area increases Opposition high/low latitudes (NPZD-IPSL) Growing Season lenghtens > +10 days 1xCO 2 2xCO 2 -1xCO 2 Changes in Ocean Physics & Marine Productivity

24. (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 IPSL NCAR Princeton MPIM Hadley CSIRO

25. Changes in Ocean Physics & Marine Ecosystem Boyd and Doney (2002) Increase in N 2 fixation with Global Warming +1 +0.02 -0.02 -0.2 +0.2 Bopp (2001) Decrease in diatoms relative abundance

26. 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 CO 2 Fertilization Climate Change Transport

27. 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)

28. Conclusions In a high CO 2 world, the ocean will be… More acidic More stratified More 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, …

30. Oceanic Carbon Cycle : Oceanic Carbon Cycle : Coupling climate and carbon 186020002100 Coupled simulation Observations pCO 2 (ppm) Climate (OPA-LMD) Carbon models (HAMOCC3,SLAVE) pCO 2 Emissions Climatic effect : - pCO2 : + 70 ppm (20 %) - Temperature : ~15-20 % Uncoupled simulation

31. Comparison to Cox et al. 2000 IPSL : 700 ppm 770 ppm Geochemical Flux (gC m -2 an -1 ) of anthropic CO 2 at 700 ppm Hadley IPSL (OPA-LMD-HAMOCC3) Differences : - Terrestrial Biosphere - Oceanic Sink Southern Ocean Hadley : 700 ppm 950 ppm Climatic Effect Ocean Carbon Cycle : Coupling carbon and climate

32. Diatoms Abundance with Global Warming (using the PISCES model) Diatoms replaced by NanoPhyto at mid/high Latitudes Mechanisms : Stratification Nutrient Supply Silica and Iron Limitation Diatoms/ NanoPhyto Changes in Diatoms Abundance (2090-1990) +1 +0.02 -0.02 -0.2 +0.2