The Carbon Cycle within the Oceans

1. The Carbon Cycle within the Oceans Allyn Clarke With much help from Ken Denman, Glen Harrison and others

2. Global Carbon Reservoirs and Fluxes (Sarmiento and Gruber, 2006, Sabine et al, 2004) Pre-Industrial

4. Global Carbon Reservoirs and Fluxes (Sarmiento and Gruber, 2006, Sabine et al, 2004)

5. Is the ocean uptake changing? • Improved estimates of ocean uptake of CO2 suggest little change in the ocean carbon sink of 2.2 ± 0.5 GtC yr–1 between the 1990s and the first five years of the 21st century. • Models indicate that the fraction of fossil fuel and cement emissions of CO2 taken up by the ocean will decline if atmospheric CO2 continues to increase.

6. Solubility Pump

7. Annual Total Air-Sea CO2 Flux, 1995 - 4° x 5° estimates of monthly sea to air CO2 flux - 940,000 pCO2 observations, after Takahashi et al., 2002- 41 years of NCEP/NCAR monthly average winds plotted by Jim Christian, CCCMA/IOS

8. Anthropogenic CO2 in the Ocean • ~48% of all fossil fuel emissions have ended up in the ocean, ~ 1/3 of its potential storage Total118  19 PgC Sabine et al. (2004) Science 305: 367-371.

9. Biogeochemical studies in the Labrador Sea - observations and modelling

10. AR7W potential temperature (0–50 m) and SST

11. AR7W total inorganic carbonCentral Labrador Sea (100–500 m) OSD/BIO

12. Labrador Shelf and Slope Phytoplankton Small cells are increasing Medium cells are not changing Large cells are decreasing

13. --- 1000ppm --- Coupled - Uncoupled --- 200 ppm --- --- 300ppm --- 2100 1850 1850 2100 Coupled Climate-Carbon Cycle Models Sequester Less Carbon A Positive Feedback to Climate Change C4MIP Results:Friedlingstein et al. SRES: A2

14. Simulated Land + Ocean CO2 Uptake (PgC/yr) Land Uptake is Highly Uncertain 12 12 Land Ocean 0 0 -6 2100 2100 1850 1850

15. Canadian Model of Ocean Carbon (CMOC-1)Includes: Ocean Biological Pump + Calcifiers + N2 fixers:[Zahariev, Denman and Christian] Developed (i) in 1-D MLM:Denman and Peña, 1999, 2002 (ii) in regional 3-D OGCM: Haigh, Denman & Hsieh, 2001

16. Annual mean ΔpCO2 (referenced to 1995) [Takahashi et al, 2002] Canadian Model of Ocean Carbon (CMOC-1) Air-Sea CO2 Fluxes (mols-C m-2 yr-1) Zahariev,Christian,Denman CCCma/IOS

17. (a) (b) (c) (d) 20 µm Four 'PFTs': Plankton Functional Types The PARADIGM Group, Oceanography, March 2006

18. CO2 in the Ocean & the 'Biotic' Pumps Removes C and–ve charge- so increases pCO2 Atmosphere >90% DIC = CO2 + HCO3_ + CO3= 'Carbonate Pump' Ca2+ + 2HCO3_ CaCO3 +H2O + CO2 Photosynthesis: 'Organic Pump' 'Calcite' nCO2 + 2nH2O  nCH2O + nO2 + nH2O 'POC' + 'DOC'

19. Iron Fertilization Studies • Joint Canada / Japan – University / Government experiment at OWS Papa – July 2002 under Canadian SOLAS program • Major findings published in Deep-Sea Research, Part II, Volume 53, issues 20-22, 2006 • 22 scientific papers • Result was similar to that of the other iron fertilization experiments. See a response in the productivity but very little observable increase in carbon sequestration.

20. SeaWiFS image 16 July 2000 SeaWiFS image 25 April 1998 Carbonate (CaCO3) Pump -Coccolithophorid Emiliania huxleyi Image courtesy of Southampton Oceanography Centre, UK SEM image

21. Impact of CO2 uptake on the ocean • Ocean CO2-uptake has lowered the average ocean pH (increased acidity) by approximately 0.1 since 1750. • Consequences for marine ecosystems may include reduced calcification by shell-forming organisms, and in the longer-term, the dissolution of carbonate sediments.

22. Adding CO2 Increases Ocean Acidity K1 K2 CO2 + H2O  HCO3- + H+  CO32- + 2H+ This decrease in pHalso increases surface ocean pCO2, which opposes invasion of atmospheric CO2 into the ocean:  a positive feedback

23. ? Surface pH is Decreasing [prepared by Arne Körtzinger (IFM,Kiel) for the IMBER Science Plan on the basis of WOCE data: Schlitzer, 2000] http://ioc.unesco.org/iocweb/co2panel/Publications.htm

24. Phytoplankton Grown Under Different CO2 Concentrations ~300 ppm ~780 –850 ppm Riebesell et al. 2000. Nature, 407, 364-367.

25. Summary • The oceans are a significant sink for carbon • Canadian observations and ocean modellers have contributed greatly to our ability to model the ocean carbon cycle. • Models project a diminishing relative contribution of the ocean sink • Iron fertilization is unlikely to be a useful mitigation technique • Ocean acidification has potential for serious impacts on marine ecosystems

26. Thank You

27. Oceanic Acidity is Not Uniform: Saturation Depth Patterns Corals Coccolithophorids Feely et al. 2004. Science, 305: 362-366.

28. Weight % of CaCO3 in Sediments From: Archer, D.E., 1996. Global Biogeochemical Cycles, 10(1), 159-174.

29. Present Pre- industrial S N Saturation Layer in N. Pacific is shrinking Feely et al. 2004. Science, 305: 362-366.

30. Impacts from wetlands and hydro reservoirs • Observed increases in atmospheric methane concentration, compared with preindustrial estimates, are directly linked to human activity, including agriculture, energy production, waste management, and biomass burning. • Constraints from methylchloroform observations show that there have been no significant trends in OH radical concentrations, and hence in methane removal rates, over the past few decades (see Chapter 2). • The recent slow down in the growth rate of atmospheric methane since about 1993 is thus likely attributed to the atmosphere approaching an equilibrium during a period of near constant total emissions. • However, future methane emissions from wetlands are likely to increase in a warmer and wetter climate, and to decrease in a warmer and drier climate.

32. AR7W silicate and nitrate(60–200 m) ERD/BIO

33. AR7W chlorophyll and bacteria (0–100 m) & total organic carbon (water column) ERD/BIO

34. AR7W zooplankton biomass(0–100 m) ERD/BIO