The use ofδ18O in atmospheric CO2

Matthias CuntzResearch School of Biological Sciences (RSBS), ANU, Canberra, Australia

Philippe Ciais, Georg Hoffmann, Philippe Peylin, Jérôme OgéeLaboratoire des Sciences du Climat et de l’Environnement (LSCE), Gif-sur-Yvette, France

Roger J. Francey, Colin E. AllisonDivision of Atmospheric Research (DAR), CSIRO, Melbourne, Australia

Pieter P. Tans, James W. C. WhiteClimate 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 KnorrMax Planck Institute of Biogeochemistry (MPI-BGC), Jena, Germany

Ingeborg LevinInstitute of Environmental Physics (IUP), University of Heidelberg, Germany

Graham D. Farquhar, Lucas A. CernusakResearch School of Biological Sciences (RSBS), ANU, Canberra, Australia

The idea

The idea: deconvolution

x = O2/N2 Ocean/Biosphere x = 13C O2 Ocean/Biospherex = 14C O2 Fossil Fuelx = CO17O Stratosphere-Troposphere Exchangex = CO18O Gross Biosphere Fluxesx = 18O2,17O2 Gross Biosphere Fluxes on Paleo

Time Scales (Dole Effect)

i

i2 (t)F

dt

COd

i

ii (t)F(t)Δdt

dx

CO2 equilibrates isotopically with H2O in 18O

Equilibration: COO + H218O CO18O + H2O

eqα

soil/leaf-water

airαkin

CO18O: αeqRw

H218O: Rw

CO18O: αkin αeqRw

diffusivezone

Example: Respiration isoflux

soil

atmosphereεs

δa

δs

RassRR FδεδFΔ

δs: δ18O of CO2

equilibratedwith soil water

εs: kineticfractionation of diffusion out of soil

soildepth

ca.15 cm

18O vs. 13C

Global Values 18‰

13‰

18FGtC‰/yr

13FGtC‰/yr

Respiration R -16 -18 -1600 -1800

Assimilation A 19 18 1900 1800

Ocean O 1 2 100 200

Burning processes B -18 -18 -180 -180

minorBΔOΔAΔRΔdt

δdBOAR

a

Double deconvolution

AΔRΔdt

dδ2)

ARdt

dC1)

ARa

a

Adt

dCR,

ΔΔdt

dCΔ

dt

dδ

A a

AR

aR

a

Themeasurements

CO2 and δ18O SSC at Alert, Canada

340

345

350

355

360

365

370

1992 1992.5 1993 1993.5 1994

(p

pm

) (

‰ V

PD

B-C

O2)

CO2

δ18O

-3

-2.5

-2

-1.5

-1

-0.5

0

1992 1992.5 1993 1993.5 1994

CO2 and δ18O stations worldwide

CO2, δ13C, δ18O diurnal cycles, Tver forest, RussiaLangendörfer et al. (2002)

The globalpicture

CO2

Fdiff +300

Ffos6

Fao102

Foa100

Surface water0 ‰ VSMOW

Fretro-diff = Fassimilation+ 200 = -100

Fbur3

Leaf water+7 ‰ VSMOW

Frespiration100

Soil water9 ‰ VSMOW

Evapotranspiration

Evaporation

Distillation 13 ‰VSMOW

18 ‰VSMOW

RainRain

Tropopause

Fassimilation-100

5 ‰ VSMOW10 ‰ VSMOW

, H2O, δ18O-H2O cyclescycle cycles

CO2, H2O, δ18O-H2O, δ18O-CO2 cycles

Fdiff +300

Ffos6

Fao102

Foa100

Surface water0 ‰ VSMOW

Fretro-diff = Fassimilation+ 200 = -100

Fbur3

Leaf water+7 ‰ VSMOW

Atm. O2

17 ‰ VPDB-CO2

Frespiration100

Soil water9 ‰ VSMOW

Evapotranspiration

Evaporation

Distillation 13 ‰VSMOW

18 ‰VSMOW

Rain5 ‰ VSMOW

Rain10 ‰ VSMOW

Finvasion±20 (140)

Troposph. δ18O-CO2 +0.5 ‰ VPDB-CO2

Tropopause

Stratosph. δ18O-CO2 +2.5 ‰ VPDB-CO2

Fste ±100 (+200)

(-30) (-80)

(1540)

(2220) (1540)(680)

(-116)(-58)

CIAISO

SiB2CO2

GISS δ18O-H2O

other CO2

sources

δ18O-CO2

TM2 – Atmosphere:

Isotopic comp.of precip. & vapour

CO2

fluxes

CO2

fluxesVeg. & soilparam.

CO18Ofluxes

CO2

fluxes

CO2δ18O-CO2

CO2

fluxes

Ciais et al. (1997a,b), Peylin et al. (1999)

δ18O-CO2 SSC CIAISO

Alert

Cape Grim

Peylin et al.(1999)

Point Barrow

Mauna Loa

ECHAM4

Meteo., cloud, etc.

Isotopic comp.

of precip., soil and vapour

BETHY

Atmosphere

CO2

fluxes

other CO2

sources

Leaf

Soil

OFRAC Others

Transport

Fractionationphysics

CO2

fluxes

CO2

fluxes

Meteo., soil, etc. param.

Veg. & soilparam.

CO18Ofluxes

δ18O-CO2

CO2

fluxes

WFRAC

H218O

CO2

fluxes

δ18O-H2O

MECBETH

: δ18O-H2O CO2δ18O-CO2

Cuntz et al. (2003a,b)

δ18O-CO2 SSC MECBETH

Alert

Kumukahi

Seychelles

American Samoa

Cape Grim

South Pole

Cuntz et al. (2003b)

Cuntz et al. (2003b)δ18O-CO2 SSC MECBETH

Why?

CO2 net fluxes CO2 gross fluxesInner-stomatal CO2 concentrationIsotopes 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)

ECHAM5

Meteo., soil, cloud, etc.

Atmosphere

CO2

fluxes

other CO2

sources

Transport

Fractionationphysics

CO2

fluxesCO18Ofluxes

δ18O-CO2

WFRAC

H218O δ18O-H2O

Future MECBETH

: δ18O-H2O CO2 δ18O-CO2

OFRAC

BETHYLPJ

CO2

fluxes

δ18O-H2ORainVapour

[CO2]

CO2

fluxes

[CO2]

Land surface parameters

CCM

Meteo., soil, cloud, etc.

Atmosphere

CO2

fluxes

other CO2

sources

Transport

Fractionationphysics

CO2

fluxesCO18Ofluxes

δ18O-CO2

CCMISO

H218O δ18O-H2O

Future CCM-ISO-LSM

: δ18O-H2O CO2 δ18O-CO2

ISOLSM

LSMCO2

fluxes

δ18O-H2ORainVapour

[CO2]

CO2

fluxes

[CO2]

Land surface parameters

Summary

• Idea: use δ18O-CO2 to separate assimilation from respiration

must know Δ’s, i.e. water isotopes in biosphere

• Built global model of δ18O in atmospheric CO2: MECBETH

• δ18O-CO2 not yet fully resolved, i.e. big error on Δ’s

soil water description night-time δ18O-CO2 exchange

know leaf/soil water know Δ’s separate assimilationfrom respiration better biosphere parameterisations better source/sink determination

, one day!

FIN