Carbon Cycle1. IntroductionContinuous Carbon CyclingMauna Loa Observatory & C.D. KeelingHigh-precision Atm CO2: at MLO since 1958Atm CO2 Observations in lower troposphereGlobal Distribution of CO2Globally averaged CO2UnitsAtm CO2 increase ~50% FF emissionConservation of Carbon in AtmFossil Fuel EmissionAtm CO2 Signature of Fossil Fuel Emission: N-S gradientTerrestrial Carbon CycleDeforestationNDVI-seasonalImpact on Atmospheric CO2Atmospheric CO2 Signature of Ecosystem C Exchange: Seasonal CycleOcean C from the Atm’s Perspective:Marine ProductivityOceanC : Mainly Dissolved Inorganic Carbon (DIC)Air-Sea Fluxes of CO2Atm CO2 Signature of Air-sea Flux: ToughSUMMARYCarbon Cycle1. IntroductionInez FungUC BerkeleyMSRI-NCAR Summer Graduate Workshop on Carbon Data AssimilationMSRI July 17-28 2006Continuous Carbon Cycling• Fluxes PgC/yr• Inventory PgC• Turnover time= Inventory/FluxMauna Loa Observatory & C.D. Keeling• 180 ppmv Last Glacial Maximum• 280 ppmv in the preindustrial (~1800AD)• 380 ppmv in 2005High-precision AtmCO2: at MLO since 1958Atm CO2 Observations in lower troposphereWLEF, Park Falls, WisconsinMauna Loa, Hawaii• In situ: tower, continuous • Flask: 2m, twice weekly• >400m Tall Tower: 11, 30, 76, 122, 244 and 396 m; ContinuousGlobal Distribution of CO2• secular trend• N-S gradient• Seasonal cycle• Interannual variationsGlobally averaged CO2Units33CairCair14 2218mb6C( kgC / m ) ( kgAir / m ) ( MWt / MWt )MWt 12gm / mole; MWt 29gm / moleArea dxdydz 5 10 ( m )100PMassAtm dxdydz ( kgAir / m ) Area ~ 5 10 kgAirg12MassC( 300 ppmv )X(moleC / moleAir )MassAtm ( 300 x10 ) ( )29~60ρρ−=× ×====×== ××=× ×∫∫121PgC 0.5 p010 kg 6pmv( mi00PgC 600GtCxed _entireAtm )→×= =Atm CO2 increase ~50% FF emission0123456781980 1985 1990 1995 2000Fossil Fuel emissionAtm increaseLand and OceanPgC/yrConservation of Carbon in AtmNNNAtm _transport mixingz0SourcesSinChem PkrodsSC()tC P=+∂++∂ℑ =oa bbao aa(F FLandUs )eS)F (F FF − −=+ + +bao baa ao(F FCCC(F F'C ))() − + −=+ℑ=Fossil Fuel Emission>95% emission in Northern HemisphereAtm CO2 Signature of Fossil Fuel Emission: N-S gradientTerrestrial Carbon Cycle• Growth, mortality, decay•GPP: Gross Primary Productivity (climate, CO2, soil H2O, resource limitation)•Ra:Autotrophic respiration (T, live mass,…)•Rh: Heterotrophic respiration: Decay (T, soil H2O,..)• NPP=GPP-Ra120 PgC/yr 60 601200 PgC800 PgCGPPRa RhTough to estimate • deforested area• Carbon inventory before deforestation• Fate of removed carbon• Fate of litter and soil carbonTough to discriminate atm CO2signatureDeforestationVeg Type(x,y) Æ annual mean NPP(x,y)NDVI-seasonalAugust 2000February 2001Satellite Greenness index: NDVIÆ Seasonality of NPPSeasonality of Rh not well-definedNet flux not well-defined at every locationImpact on Atmospheric CO2PhotosynthesisRespiration0.000.200.400.600.801.0 01.2 012345678910111213141516171819202122232425Jan DecFrom AtmTo AtmCO2Flux• Seasonal asynchrony between photosynthesis and decompositionÆ net fluxes of CO2to and from atmÆ seasonal cycle of CO2in atm• Annual imbalance Æ carbon source/sinkAtmospheric CO2Signature of Ecosystem C Exchange: Seasonal CycleMauna Loa, HawaiiPt. Barrow, Alaska6.5 ppmv 16 ppmvSource: NOAA/CMDL• Amplitude of atmospheric CO2seasonal cycle increases poleward: telecoping of growing season and greater asynchroneity bet’ fluxes• Growing season net flux ~15-20% of annual NPPOcean C from the Atm’s Perspective: DIC = CO2*+ HCO3-+ CO3=1-2 % 80-90%CO2DIC, NO3depthatmremineralizationphotosyn100 Pg C/yrNNoa aoGasExchRate( m / s )so lub ility( T )molatm _ ssfc _ocne/fm3cCCO2* pCOFk)2F(β−= × − ×  Is possible when upwelling brings:•Nutrients from below to euphotic zone•Cold waterSmall Flux, small inventory of organic CBut alters DIC(z)Marine ProductivityOceanC : Mainly Dissolved Inorganic Carbon (DIC)Biology and DIC:•Depletion near sfc•Enrichment at DepthLatitude Æ NDepthAtlantic PacificConveyor Belt Transport of DIC:•Southward in Atlantic•Northward in PacificOcn currents ~ cm/sTime scale ~ 103yrAir-Sea Fluxes of CO2NNocn oa aosfc_ocn atm_sfcGasExchRate( m / s )so lub ility( T )moleC / m3FFFk ( CO2* pCO2 )∆β=−=×−×  Atm CO2 Signature of Air-sea Flux: Tough• Ocean circulation redistributes C in ocean• Expect elevated CO2 at equator, lower CO2 at high latitudes• Difficult to separate from FF and other signatures0.8 ppmv0-0.8080N80SAtlantic transectPacific transectModeled atm CO2SUMMARYNNz0SourcesSinksAtm _transport mixingboa ao aabSS(C )(FLandUse ( F FC))tFF F+=ℑ− −∂+=∂=+ + +FF: mainly NH, relatively aseasonalLandUse: mainly source tropics, sink in mid-latitudesOcean: outgassing in equatorial oceans, absorption at mid-hi latitudes (in summer. Not sure about winter)Vegetation and soils: annual mean fluxes~0 locally, fluxes have large diurnal (~100 ppmv) and seasonal ranges (~30