Physical / Chemical Drivers of the Ocean in a High CO 2 World

Transcription

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

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

3 Introduction Coupled Model s response to increased Atmospheric pco 2 (IS92a, IPCC 2001) Temperature Change ( C) Precipitation Change (%) Which aspects are relevant to marine biogeochemistry? Max. Atlantic Over. (%)

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

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

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

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

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

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

10 Changes in ph : Acidification Increase in DIC leads to an acidification of Ocean waters Changes in Surface ph All OCMIP2 Models N S IS92a, IPSL model, 2099-PreIndus (See Poster by J. Orr)

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

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

13 Changes in Ocean Physics : Stratification Mechanisms of Changes SST SSS Mixed Layer Sarmiento et al. in press 80 N N 40 N N S S S ( C) (psu) (m) 80 S 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 Impact Climate Change reduces ocean CO 2 sink (from 6% to 25% in 2050)

16 Changes in Ocean Physics & Carbon Cycle Mechanisms Thermal Circulation Re-Organisation of the Natural C Cycle Sarmiento 96 Matear 99 Joos (in GtC/yr, )

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

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, 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) 0 m Temperature & Currents SEC 300 m 0 m Changes in T & U ( ) 300 m South Equatorial Current : shallower and weaker No more warm & oxygenated water to the sub-surface

21 Changes in Ocean Physics & Marine Productivity Different approaches may be used Empirical Models based on Observational constraints (see Poster by P. Schultz) Mechanistic Models of Marine Biology

22 Changes in Ocean Physics & Marine Productivity Simulation NPZD-IPSL, gc m -2 an -1 Zonal Mean ( ) -30 % +30 % - 30 gc m -2 an -1 Decreases globally (-5/10%) BUT increases at high latitudes (+20/30%) Similar response with different bio & dynamical models

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

24 Changes in Ocean Physics & Marine Productivity 80 N Less Nutrient But Longer Growing Season 80 N 40 N 40 N IPSL NCAR Princeton MPIM Hadley CSIRO S 40 S 80 S (m) (days) 80 S Sarmiento et al. in press

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

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) 5 1 (mg/m3) Sensitivity Exp: Dust deposition x2 or /2 (20 (see yr) talk by O. Chl Aumont) (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,

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30 Oceanic Carbon Cycle : Coupling climate and carbon Climate (OPA-LMD) Climatic effect : - pco2 : + 70 ppm (20 %) - Temperature : ~15-20 % pco 2 Emissions Observations Coupled simulation Uncoupled simulation Carbon models (HAMOCC3,SLAVE) pco 2 (ppm)

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

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 ( )