1. The use of δ 18 O in atmospheric CO 2 Matthias Cuntz Research School of Biological Sciences (RSBS), ANU, Canberra, Australia Philippe Ciais, Georg Hoffmann, Philippe Peylin, Jérôme Ogée Laboratoire des Sciences du Climat et de l’Environnement (LSCE), Gif-sur-Yvette, France Roger J. Francey, Colin E. Allison Division of Atmospheric Research (DAR), CSIRO, Melbourne, Australia Pieter P. Tans, James W. C. White Climate Monitoring and Diagnostic Laboratory (CMDL), NOAA, Boulder, Colorado and Institute of Arctic and Alpine Research (INSTAAR) and Department of Geological Sciences, University of Colorado, Boulder, Colorado Wolfgang Knorr Max Planck Institute of Biogeochemistry (MPI-BGC), Jena, Germany Ingeborg Levin Institute of Environmental Physics (IUP), University of Heidelberg, Germany Graham D. Farquhar, Lucas A. Cernusak Research School of Biological Sciences (RSBS), ANU, Canberra, Australia

2. The idea

3. The idea: deconvolution x = O 2 /N 2  Ocean/Biosphere x = 13 CO 2  Ocean/Biosphere x = 14 CO 2  Fossil Fuel x = CO 17 O  Stratosphere-Troposphere Exchange x = CO 18 O  Gross Biosphere Fluxes x = 18 O 2, 17 O 2  Gross Biosphere Fluxes on Paleo Time Scales (Dole Effect)

4. CO 2 equilibrates isotopically with H 2 O in 18 O Equilibration: COO + H 2 18 O CO 18 O + H 2 O soil/leaf- water air α kin CO 18 O: α eq R w H 2 18 O: R w CO 18 O: α kin α eq R w diffusive zone

5. Example: Respiration isoflux soil atmosphere εsεs δaδa δsδs δ s : δ 18 O of CO 2 equilibrated with soil water ε s : kinetic fractionation of diffusion out of soil soil depth ca. 15 cm

6. 18 O vs. 13 C

7. Double deconvolution

8. The measurements

9. CO 2 and δ 18 O SSC at Alert, Canada (ppm) (‰ VPDB-CO 2 ) CO 2 δ 18 O -3 -2.5 -2 -1.5 -0.5 0 19921992.519931993.51994

10. CO 2 and δ 18 O stations worldwide

11. CO 2, δ 13 C, δ 18 O diurnal cycles, Tver forest, Russia Langendörfer et al. (2002)

12. The global picture

13. CO 2 F diff +  300 F fos 6 F ao  102 F oa 100 Surface water 0 ‰ VSMOW F retro-diff = F assimilation + 200 = -100 F bur 3 Leaf water +7 ‰ VSMOW F respiration 100 Soil water  9 ‰ VSMOW Evapotranspiration Evaporation Distillation  13 ‰ VSMOW  18 ‰ VSMOW Rain Tropopause F assimilation -100  5 ‰ VSMOW  10 ‰ VSMOW, H 2 O, δ 18 O-H 2 O cycles cycle cycles

14. CO 2, H 2 O, δ 18 O-H 2 O, δ 18 O-CO 2 cycles F diff +  300 F fos 6 F ao  102 F oa 100 Surface water 0 ‰ VSMOW F retro-diff = F assimilation + 200 = -100 F bur 3 Leaf water +7 ‰ VSMOW Atm. O 2  17 ‰ VPDB-CO 2 F respiration 100 Soil water  9 ‰ VSMOW Evapotranspiration Evaporation Distillation  13 ‰ VSMOW  18 ‰ VSMOW Rain  5 ‰ VSMOW Rain  10 ‰ VSMOW F invasion ±20 (  140) Troposph. δ 18 O-CO 2 +0.5 ‰ VPDB-CO 2 Tropopause Stratosph. δ 18 O-CO 2 +2.5 ‰ VPDB-CO 2 F ste ±100 (+200) (-30)(-80) (  1540) (2220) (1540)(  680) (-116)(-58)

15. CIAISO SiB2 CO 2 GISS δ 18 O-H 2 O other CO 2 sources δ 18 O-CO 2 TM2 – Atmosphere: Isotopic comp. of precip. & vapour CO 2 fluxes CO 2 fluxes Veg. & soil param. CO 18 O fluxes CO 2 fluxes CO 2 δ 18 O-CO 2 CO 2 fluxes Ciais et al. (1997a,b), Peylin et al. (1999)

16. δ 18 O-CO 2 SSC CIAISO Alert Cape Grim Peylin et al. (1999) Point Barrow Mauna Loa

17. ECHAM4 Meteo., cloud, etc. Isotopic comp. of precip., soil and vapour BETHY Atmosphere CO 2 fluxes other CO 2 sources Leaf Soil OFRAC Others Transport Fractionation physics CO 2 fluxes CO 2 fluxes Meteo., soil, etc. param. Veg. & soil param. CO 18 O fluxes δ 18 O-CO 2 CO 2 fluxes WFRAC H 2 18 O CO 2 fluxes δ 18 O-H 2 O MECBETH : δ 18 O-H 2 O CO 2 δ 18 O-CO 2 Cuntz et al. (2003a,b)

18. δ 18 O-CO 2 SSC MECBETH Alert Kumukahi Seychelles American Samoa Cape Grim South Pole Cuntz et al. (2003b)

19. δ 18 O-CO 2 SSC MECBETH

20. Why?  CO 2 net fluxes  CO 2 gross fluxes  Inner-stomatal CO 2 concentration  Isotopes in precipitation at high northern latitudes? }  Isotopes in soil water ? Relative influence of respiration and assimilation  Soil water isotope gradient (Riley et al. 2002)  Night-time leaf gas exchange (Cernusak et al. 2004)  Nocturnal leaf water values (Ogee et al. 2003, Cernusak et al. 2002) Cuntz et al. (2003a,b)

21. ECHAM5 Meteo., soil, cloud, etc. Atmosphere CO 2 fluxes other CO 2 sources Transport Fractionation physics CO 2 fluxes CO 18 O fluxes δ 18 O-CO 2 WFRAC H 2 18 O δ 18 O-H 2 O Future MECBETH : δ 18 O-H 2 OCO 2 δ 18 O-CO 2 OFRAC BETHY LPJ CO 2 fluxes δ 18 O-H 2 O Rain Vapour [CO 2 ] CO 2 fluxes [CO 2 ] Land surface parameters

22. CCM Meteo., soil, cloud, etc. Atmosphere CO 2 fluxes other CO 2 sources Transport Fractionation physics CO 2 fluxes CO 18 O fluxes δ 18 O-CO 2 CCMISO H 2 18 O δ 18 O-H 2 O Future CCM-ISO-LSM : δ 18 O-H 2 OCO 2 δ 18 O-CO 2 ISOLSM LSM CO 2 fluxes δ 18 O-H 2 O Rain Vapour [CO 2 ] CO 2 fluxes [CO 2 ] Land surface parameters

23. Summary Idea: use δ 18 O-CO 2 to separate assimilation from respiration  must know Δ’s, i.e. water isotopes in biosphere Built global model of δ 18 O in atmospheric CO 2 : MECBETH δ 18 O-CO 2 not yet fully resolved, i.e. big error on Δ’s  soil water description  night-time δ 18 O-CO 2 exchange  know leaf/soil water  know Δ’s  separate assimilation from respiration  better biosphere parameterisations  better source/sink determination, one day!

24. FIN