Preliminary results from the oceanic component of the integrated earth system model of Kyousei2

1. Preliminary results from the oceanic component of the integrated earth system model of Kyousei2 Michio KAWAMIYA Chisato YOSHIKAWA Maki NOGUCHI Taroh MATSUNO Frontier Research System for Global Change, Yokohama, Japan

2. At the last steering committee meeting: • Results from a “flying leap” experiment • 5 months later… (= This talk): • Performance check • Sensitivity to surface forcing • Projection of future CO2 uptake by the ocean • Incorporation into our coupled model (MIROC) • Schedule

3. Model outline OGCM: Code: COCO3.4 (Hasumi, 2000) based on primitive equations Resolution: 1 deg. X 1. deg. 54 vertical levels (20 levels for the upper 100m) Biological model: Nitrogen based, 4-compartment model by Oschlies & Garcon (1998) modified by Oschlies (2001) Carbonate system is incorporated following the OCMIP protocol.

4. Comparative study between model-derived and reanalysis forcing fields (preparation for a global warming experiment) • Forcing fields (SST, P-E, wind stress, solar radiation) from: • OMIP data (ECMWF reanalysis) • CCSR/NIES coupled model output • Initial conditions • T, S: results from an OMIP experiment • Nitrate: World Ocean Atlas ’94 • TCO2, Alkalinity: results from an OCMIP experiment • Other biological variables: constant (0.1 mmol/m3) • Spin-up: 20 years

5. Results Surf. Chl. Nitrate Obs. Reanalysis Model-derived

6. Nutrient trap along the coast of Peru-- Reanalysis data are less realistic? -- Wind stress Surf. Nitrate W along the 15S Reanalysis Model-derived

7. Nitrate distribution in the Southern Ocean Nitrate Reanalysis Nitrate Model-derived Ekman W Reanalysis Ekman W Model-derived

8. Nitrate distribution in the Southern Ocean (2) Mixed layer depth Nitrate WOA Reanalysis Model-derived

9. Nutrient distribution in the Southern Ocean (3) P-E SSS WOA Reanalysis Model-derived

10. Air-sea exchange of CO2 Obs.(Takahashi et al.,1999) Reanalysis Model-derived

11. Summary of the difference • Nutrient trapping off Peru due to strong coastal upwelling under the OMIP forcing • Low surface nitrate in the Southern Ocean under the model-derived forcing due to shallow mixed layer • The above difference is not reflected in the air-sea CO2 exchange field because of differences in the processes governing the surface concentrations of nitrate and fCO2

12. Earlier estimates of future uptake of anthropogenic CO2 by the ocean IPCC TAR OCMIP type models: simple representation of the biological pump

13. Time evolution of atmospheric CO2 Gradual, linear increase up until 1990, then 1%/year increase

14. Air-sea exchange of CO2

15. Summary of the performance check • The experiments forced by reanalysis and model-derived data provide similar results regarding air-sea CO2 exchange. • The current and future ocean uptakes of CO2 estimate by the model are consistent with earlier results from models with simpler representation of the pelagic ecosystem. • Apparently, no bug. Go for it! • First results from a coupled carbon cycle model are expected early next year.

16. Carbon cycle model now incorporated in our coupled model (T42L20 for atmosphere, (0.5-1.4)x1.4 for ocean) Chlorophyll Nitrate

17. Project Schedule

18. Participation in C4MIP • Coupled Climate－Carbon Cycle Model Intercomparison Project (IGBP/GAIM) • Phase 1 (~2004): Emphasis on terrestrial carbon cycle models • Phase 2 (~2005): Full coupled carbon cycle models