1. Carbon dioxide, ocean acidification, and coral reefs
NorCal SETAC
8 May 2008
Carbon dioxide, ocean acidification, and coral reefs
Ken Caldeira Carnegie Institution Department of Global Ecology
Stanford, CA USA
Thanks: Long Cao, Mike Wickett

2. Ocean carbonate chemistry

3. Ca HCO3-, CO32-, and CaCO3 in H2O H2O HCO3- CO32- CaCO3 (solid) H C O

4. Ca Addition of CO2 CO2 H2O HCO3- CO32- CaCO3 (solid) C O H C O C O H O4

5. Ca CO2 + H2O  H2CO3 HCO3- CO32- H2CO3 CaCO3 (solid) H C O H C O C O C5

6. Ca H2CO3  H+ + HCO3- H+ HCO3- CO32- HCO3- CaCO3 (solid) C O H C O C O6

7. Ca H2CO3  H+ + HCO3- HCO3- CO32- HCO3- H+ CaCO3 (solid) C O H C O C O7

8. Ca H+ + CO32-  HCO3- HCO3- CO32- HCO3- H+ CaCO3 (solid) C O H C O C O8

9. Ca H+ + CO32-  HCO3- HCO3- CO32- HCO3- H+ CaCO3 (solid) C O H C O C O9

10. Ca H+ + CO32-  HCO3- HCO3- CO32- HCO3- H+ CaCO3 (solid) C O H C O C O10

11. Ca H+ + CO32-  HCO3- HCO3- HCO3- HCO3- CaCO3 (solid) C O H C O C O H11

12. Ca CaCO3  Ca2+ + CO32- HCO3- HCO3- HCO3- CO32- Ca2+ (dissolved) C O H12

13. Ca CaCO3  Ca2+ + CO32- HCO3- HCO3- HCO3- CO32- Ca2+ (dissolved) C O H13

14. Ca CaCO3  Ca2+ + CO32- HCO3- HCO3- HCO3- CO32- Ca2+ (dissolved) C O H14

15. Ca CaCO3  Ca2+ + CO32- HCO3- HCO3- HCO3- CO32- Ca2+ (dissolved) C O H15

16. Marine organisms with calcium carbonate shells or skeletons
Coccolithophorids
Pteropod
Foraminifera
Open ocean
Coral
Encrusting red algae
Deep sea coral
Sea floor
Courtesy Chris Langdon

17. Sensitivity of coral calcification to saturation state (compilation of 12 species)
Courtesy Chris Langdon

18. Calcification exceeds bioerosion
Sensitivity of coral calcification to saturation state (compilation of 12 species)
Calcification exceeds bioerosion
Courtesy Chris Langdon

19. Fossil fuel CO2 emissions, ocean chemistry, and corals

20. IPCC “no policy” scenarios
550 ppm around mid-century
Around 750 ppm at end of century
IPCC, 2001

21. Trajectory of Global Fossil Fuel Emissions
50-year constant growth rates
to 2050
B %,
A1B %,
A %
A1FI %
2006
2005
Current emissions are tracking above the most intense fossil fuel scenario established by the IPCC SRES (2000), A1FI- A1 Fossil Fuel intensive; and moving away from stabilization scenarios of 450 ppm and 650 ppm.
Observed %
Raupach et al. 2007, PNAS

22. Deteriorating chemical condition for coral reefs
aaa
Deteriorating chemical condition for coral reefs 1 2 3 4
Ωaragonite 5
Optimal for coral reefs
Corrosive to coral reefs 22

23. CO2 stabilization even at “low” levels means losing the high-saturation waters where warm-water corals are most commonly found.

24. Marine organisms with calcium carbonate shells or skeletons
Coccolithophorids
Pteropod
Foraminifera
Open ocean
Coral
Encrusting red algae
Deep sea coral
Sea floor
Courtesy Chris Langdon

25. Small amounts of CO2 damage sea urchins
SEA URCHIN GROWTH
Sea Bream larva
What might CO2 do to fish larvae?
Natural air = 380 ppm
Smaller bodies (not just thinner shells) Effects worse when combined with warming
Natural air ppm CO2
Shirayama and Thornton 2005

27. Amounts include total fossil-fuel plus net land biosphere emissions to the atmosphere
Caldeira and Wickett (2005)

28. Predicted future CO2 concentration exceed those inferred for past 25 million years
Even if most fossil-fuel carbon is never released to the atmosphere, we will produce geologically unusual conditions
Paleo-CO2 [lines]
(Pagani et al., 1999; Pearson and Palmer, 2000)
Year 2300 atmospheric CO2 predictions for scenarios involving fossil-fuel plus net biomass release over several centuries [colors] (Caldeira and Wickett, 2005)

29. Anthropogenic CO2 emissions exceed natural emissions by a factor of about 100

30. 65 Ma

31. What happened at the K/T boundary?
Asteroid or comet impact into CaSO4-rich platform at Chicxulub
CO2 releases
~50 PgC impact metamorphism
Land biomass burning
Reduced organic C pump in ocean
SO2 releases (Sigurdsson et al, 1991)
x 1015 mol SO2
NASA

32. Mel Pollinger

33. Time scale for recovery after mass extinction
(< 2 million years)

34. …growth with ever increasing environmental risk
The choice is ours …
…growth with ever increasing environmental risk
. . . or develop approaches that allow growth and development while diminishing environmental risk 34

35. Jobs, energy security, education, & economic growth Development of an advanced clean energy system
Courtesy Gene Berry, LLNL 35

36. 36

37. CO2 released to the atmosphere becomes carbonic acid in the oceans
Carbonic acid is corrosive to shells and skeletons of marine organisms, threatens extinctions
It will take tens of thousands of years for ocean chemistry to return to normal
The only practical way to prevent ocean acidification is to greatly reduce CO2 emissions soon