1. Ralph Keeling Scripps Institution of Oceanography Global oceanic and land carbon sinks from the Scripps flask sampling networks

2. Ocean CO 2 uptake: H 2 O + CO 2 + CO 3 = ↔ 2HCO 3 - Land photosynthesis & respiration Fossil-fuel burning B F O ΔCO 2 = F – O – B Atmospheric CO 2 budget

3. Ocean CO 2 uptake: H 2 O + CO 2 + CO 3 = ↔ 2HCO 3 - Land photosynthesis & respiration: CO 2 + H 2 O ↔ O 2 + H 2 O Fossil-fuel burning: CH y + (1+y/4)O 2 → CO 2 + (y/2)H 2 O B F O ΔCO 2 = F – O – B ΔO2 = -1.4F + 1.1B Atmospheric CO 2 and O 2 budgets

4. Ocean CO 2 uptake: H 2 O + CO 2 + CO 3 = ↔ 2HCO 3 - Land photosynthesis & respiration: CO 2 + H 2 O ↔ O 2 + H 2 O Fossil-fuel burning: CH y + (1+y/4)O 2 → CO 2 + (y/2)H 2 O B F O Atmospheric CO 2 and O 2 budgets Z ΔCO 2 = F – O – B ΔO2 = -1.4F + 1.1B + Z

6. Time OutgasOceanLand Period Corr. SinkSink Manning (2001) 1990-2000 0.10 1.68±0.51.44±0.7 & IPCC(2001) Keeling & 1990-2000 0.28 1.86 ± 0.61.26±0.8 Garcia (2002) Manning & 1993-2003 0.482.24 ± 0.610.51±0.74 Keeling (2005, submitted) Units: Pg C yr -1 Recent O 2 based Carbon budgets

7. Time OutgasOceanLand Period Corr. SinkSink Manning (2001) 1990-2000 0.10 1.68±0.51.44±0.7 & IPCC(2001) Keeling & 1990-2000 0.28 1.86 ± 0.61.26±0.8 Garcia (2002) Manning & 1993-2003 0.482.24 ± 0.610.51±0.74 Keeling (2005, submitted) Units: Pg C yr -1 Recent O 2 based Carbon budgets Increase in estimated ocean sink results from (1) Upwards revision of outgassing correction, as indicated. (2) Observed O 2 loss rate higher over 2000-2003 period.

8. Interannual variations in CO 2 O 2 /N 2 and 13 C/ 12 C Correlations between CO 2, δ 13 C, and O 2 imply land dominance of variability on El Nino time scales

9. Discussion: Dominance of land to interannual variability also supported by atmospheric inversions. This is now beyond dispute. Nevertheless, the smaller oceanic contribution to variability remains poorly resolved. All available approaches have problems: CO 2 Inversions: can’t distinguish well between coastal oceans and land fluxes. 13 C/ 12 C: complicated by possible variations in isotopic fractionation factor with land biota changes. O 2 : complicated by interannual variations in air-sea O 2 exchange.

10. Discussion, continued: Measurements of O 2 nevertheless may prove helpful, by providing a test of ocean models that predict CO 2 variability. The test is realizable via the tracer APO = O 2 + 1.1 CO 2 ΔCO 2 = F – O – B ΔO2 = -1.4F + 1.1B + Z ΔO 2 +1.1 ΔCO 2 = -0.3F -1.1O + Z Interannual variability in APO should reflect interannual variability in the combined air-sea CO 2 and O 2 flux, since interannual variability in fossil-fuel burning (F) is small. Z = Air-sea O 2 flux

11. Observed versus Modeled variations in APO Summary of findings: Relatively good model-to-model agreement. Observations show ~ ~2x more variability. If models underestimate APO variability, do they also underestimate CO 2 variability? Needs more work to resolve.

12. Acknowledgements Charles D Keeling Andrew Manning Roberta Hamme Bill Paplawsky Galen McKinley Mick Follows Corinne LeQuere Christian Roedenbeck Laurent Bopp

13. Ocean biogeochem. Models MPI Jena model Authors: Buitenhuis, LeQuere, Rodgers Physics: OPA-ORCA Bio model: Dynamic Green Ocean type Forcing: daily NCEP Resolution: 0.5 ° x2 ° tropics and poles 2 ° x2 ° sub-tropics Gas exchange: Liss and Merlivat IPSL model Authors: Bopp, Rodgers Physics: OPA-ORCA Bio model: Dynamic Green Ocean type Forcing: daily NCEP, mixed boundary conditions Resolution:0.5°x2° tropics and poles 2°x2° sub-tropics Gas exchange: Wanninkhov (1992) MIT model Authors: McKinley, Follows, Marshall Physics: MITgcm-ECCO Biogeo: phosphate & light based export Forcing: 12 hr NCEP Resolution: 1°x1° extra-tropics 0.3°x1° tropics Gas exchange: Wanninkhov (1992)

14. Global APO changes