Biogeochemie/GlobaleStoffkreislaufeBiogeochemistry/GlobalElementCycles

SusanTrumboreMPIfür Biogeochemie(Director)AbteilungBiogeochemischeProzesse

Email:trumbore@mpg-jena.mpg.de

Websitefortheclass:

https://www.bgc-jena.mpg.de/bgp/index.php/Site/Lectures (linktotheclasswebpage)

Webpage:https://www.bgc-jena.mpg.de/bgp/index.php/LectureSTrum/SS2016

Lesungen/Texte

• IPCC2013Reportsonclimatechange(WG1,2)• SchlesingerandBernhardt,2013,Biogeochemistry,ananalysisofglobalchange

• LeeR.Kump,J.Kasting,andCrane,TheEarthSystem,2nd edition,Prentice-Hall.

• Jacobson,M.C.,Charlson,R.J.,Rodhe,H.,andOrians,G.H.,2000,EarthSystemScience:SanDiego,CA,AcademicPress,523p.,ISBN0-12-379370-X

Biogeochemistry =Earth‘s metabolism

Organism

Biome

Region

Landscape

ECOSYSTEM

Organ

Cell

Molecule

GLOBEroleofbiotainbiogeochemicalcycles:theexchange of theelementsessentialtolife (C,N,O,H,P...)among atmosphere,biosphere,hydrosphere,lithosphere

108m

10-9m

Global C cycleCarbon takes different forms in different parts of the Earth System so transfers from one sphere to another involve change of chemical form or change of phase

Atmosphere Hydrosphere Biosphere LithosphereCarbon(C)

CO2, CH4, volatile organics

H2CO3, HCO3-

CO32-

DOC

Organic C(~CH2O)

CaCO3

Organic Cgraphite

Gas/liquid Liquid/ dissolved ion

Solid/liquid/ dissolved ion

Solid

Elements take different forms in different parts of the Earth System so transfers from one sphere to another involve change of chemical form or change of phase. What is most stable is determined by thermodynamics; what is actually there is determined by kinetics.

Atmosphere Hydrosphere Biosphere LithosphereCarbon(C)

CO2, CH4, volatile organics

H2CO3, HCO3

-

CO32- ,DOC

Organic C(~CH2O)

CaCO3

Organic Cgraphite

Nitrogen(N)

N2 N2ONH3 NOx

HNO3

NH4+ NO3

-

DON

Organic N(amino acids)

N-salts

Phosph-orous(P)

Small amounts aerosols

PO42-

Organic P (DNA)

Apatite (CaPO4)

Gas/liquid Liquid/dissolvedion

Solid/liquid/dissolvedion

Solid

H2Owatervaporliquidliquidice(cryosphere)

LANDSurface

Atmosphere

OCEAN(hydrosphere)

LITHOSPHEREWeatheringVolcanismmetamorphism

WeatheringVolcanismmetamorphism

Photosynthesis/RespirationPrecipitation/evaporationMomentum/Energy

water,saltsnutrients

Exchangesofmajorelements:C,O,N,P,S,Si,Fe,MgMostexchangesaremediatedbyBiologicalprocesses(henceBiogeochemistry)

Biogeochemistryinvolvesthebiologicalprocessesthattransferelementsbetween‘spheres’aswellastheforms

theytakeineach‘sphere’

GasexchangePrecipitation/evaporationMomentum/Energyexchange

What are global biogeochemical cycles?Describe the movement of the elements essential to life(C, N, O, H, P...) among the components of the Earth system - atmosphere, biosphere, lithosphere, land andoceans.

Relationship of these cycles to climate through greenhouse gases (CO2, methane, nitrous oxide)

Current alterations by humans with consequences for climate and sustainable land management

Whystudythem?

Source: Hansen, Clim. Change, 68, 269, 2005.

8

Manua Loa,Hawaii(NH)

SouthPole(SH)

QuestionsdrivingcontemporaryCcycleresearch

WheredoestheexcessCO2 go?

HowwillclimatechangeaffectthefateofexcessCO2?

CanwemeasureregionalCbalancewellenoughtoverifyCstorage?

CanwemanageecosystemstotakeupCandhowmuch/howfast/howexpensive?

Projections of global average surface temperature and CO2

(IPCC)

The future does not look like today…...

CO2 fertilization (increase C on land)

Warming increases decomposition rate (decrease land C)

Current

Future non-analog climates in the warmest regions

HistoricalFuture

ToolstoStudyComplexBGCSystems(1)IdentifytheElementsofthesystemandhowtheyinteract

(Biogeochemicalbudget)

(2)Determinethecharacteristicresponsetimesforchemicalandphysicaltransformations(howfastdotheelementsinteract,andhowfastwillachangeaffectthesystem?howfastareinteractionscomparedtophysicalmixingconstraintsinearthreservoirs?

(3)Identifypossiblefeedbackloops/interactionswithotherbiogeochemicalcyclesorclimateconditions- willtheytendtoamplify(positivefeedback)ordamp(negativefeedback)changestothesystem?

Forverycomplexsystemswithmanyinteractingelements,weneedtoconstructcomputermodelstopredicthowthesystemwillrespondtoadisturbance

The GlobalWaterCycle – example ofaglobalbudget

• Waterevaporatesfrom the ocean tobecomevapor intheatmosphere

• Forms clouds andfallsasprecipitation

• Precipitation runsofffrom landtoreturn tothe ocean

SchemadesglobalenWasserkreislaufs.AbbildungverändertnachRaven etal.,Environment (1993),S.82.

Reservoir =theamountofthematerialofinterestinagivenform.Areservoirhasafinitecapacityandinstudyingitwedefineitsexchangeswithotherreservoirs.examples:Waterinalake,waterintheatmosphere,waterintheocean.

Howwouldyouestimatetheamountofwaterineach?

Flux =theamountofmaterialaddedto(Source)orremovedfrom(Sink)thereservoirinagivenperiodoftime.

Anexampleofafluxistheevaporationofwaterfromthesurfaceofalakeorocean(inwhichtheoceanreservoirisasourceofwaterfortheatmosphere).

• AreservoirthatisatSteadyState showsnochangeinmasswithtime

(Sourcesorfluxesin=Sinksorfluxesout)

Depth and Volume of the Oceans

Average depth 4500 m (average land height of 750 m)Greatest depth 11,035 m (greatest height on land 8850 m)Present volume 1.35 billion cubic km

~70% of Earth’s surface

S

Storage in103 km3

Fluxes in103 km3/year

Atmosphere12.9

Glaciers24.1x103

Oceans1.338x106

Rivers2.12Lakes176

Wetlands 11.5

Groundwater 23.4x103Permafrost 0.3x103

Biomass 1.12

Evapotrans-piration

71

Evaporation

Ocean505

Lake,River1

PrecipitationonLand116

Precipitationonocean

458

GroundwaterRecharge46

Soilmoisture16.5

Rivertoocean44.7

Snow toglacier2.7

GlobalWaterCycle

CalculateTTforAtmosphere,ocean,groundwater,glaciers

Rodhe’sthreekeytermsforexpressingthedynamicsofcyclingforgeochemicalreservoirs

• Turnovertime Thisisthetimeitwouldtaketoempty(orfill)thereservoir.Atsteadystatethisistheamountofmaterialinreservoirdividedbythesumofallfluxesoutorsumofallfluxesin.

• Mean(average)ResidenceTime Thisistheaveragetimespentinthereservoirbyindividualatoms- measurableastheageofatomsleavingthereservoir

• MeanAge Thisistheaveragetheaveragetimespentinthereservoirbyalltheatomscurrentlyin thereservoir(measurableastheageofatomsinthereservoir)

ForaHOMOGENEOUSreservoiratSTEADYSTATE(i.e.notchanginginamountwithtime)allthreeofthesetermsareequal.However,wemakeourbiggestmistakesindefiningsystemstobehomogeneous (i.e.allelementsinthereservoirhavethesameprobabilityofleaving)whentheyarenot.

Reservoir(e.g.waterinatmosphere)

LandEvaporation Land

PrecipitationOceanPrecipitation

OceanEvaporation

ChangeinReservoirsizewithtime=Inputs– Outputs

IfInputs=Outputs,reservoirisatSTEADYSTATE

Timetoemptythereservoir=Amountinreservoir/Rateoftotaloutput(i.e.ifinputsstopped,howlongtoemptythereservoir)

Measuringstocksandfluxesattheglobalscaleisamajorchallenge

• Howwouldyouestimate:– AmountofCinlivingbiomass(landandocean)– MolesofO2 intheatmosphere

• Fluxes:– Rateofglobalphotosynthesis(molesCfixedperyear)

– RateofCO2exchangewiththesurfaceocean

Characteristictimesforexchange(fromRodheChapter inEarthSystemScience)– oftenmoreimportantthanchemical reactionrates

Thisiswhywewillstudyeachofthespheresfirst,tounderstandwhatdeterminestheseexchangetimes

Surface Mixed layer

Deep Ocean (interbasin transport 100- 1000 yrs)

years

hours

Planetary Boundary Layer hours

monthTroposphere

Interhemispheric transport 1 year

Stratosphere

Land slow transfers (water)

years

CompositionofLandPlants

Wheredocomponentsofplantscomefrom?

Linksbetweenearth’sclimateandbiogeochemistry

• Greenhousegases• Directradiativeeffects(albedo,aerosol,cloud)

• Effectsonthewatercycle• Impactsofatmosphericchemistry,climate,nutrientavailabilityonbiology

Two types of feedback loops influence future CO2 trajectories in models

Climate-carbon feedbackMostly assumed positive

Negative concentration – carbon feedback

(Elevated CO2 increases photosynthesisand rates ocean carbon uptake)

CO2

Carbon uptake

Air temp

+

-

-

CO2

Carbon uptake

-+ +-

CMIP3/C4MIP emulation with MAGICC6 is 811–1170ppm. As discussed above, the lower range of theCMIP5 ESMs is due to one single model, MRI-ESM1,which already severely underestimates the present-dayatmospheric CO2 concentration. Not including this modelwould mean that the lower end of the MAGICC6 range issignificantly lower than the lower end of theCMIP5ESMs.The warming ranges simulated by the CMIP5 ESMs

and by the CMIP3/C4MIP model emulations are quitesimilar (Figs. 2b and 2d). The first set of models displaysa full range of 2.58–5.68C, while the latter set has a 90%probability range of 2.98–5.98C.

5. Twenty-first-century land and ocean carbon cycle

To further understand the difference in simulatedatmospheric CO2 over the twenty-first century, weanalyzed the carbon budget simulated by the models, asalready done for the historical period. In the E-drivenruns, the ESMs simulate the atmospheric CO2 concen-tration as the residual of the prescribed anthropogenic

emissions minus the sum of the land and ocean carbonuptakes—these latter two fluxes being interactivelycomputed by the land and ocean biogeochemical com-ponents of the ESMs. Figure 4 shows the cumulativeland and ocean carbon uptakes simulated by the CMIP5ESMs. Any difference in simulated atmospheric CO2

comes from differences in the land or ocean uptakes.The models show a large range of future carbon up-

take, both for the land and for the ocean (Figs. 4a and4b). However, for the ocean, 10 out of the 11 modelshave a cumulative oceanic uptake ranging between 412and 649PgC by 2100, the exception being INM-CM4.0with an oceanic uptake of 861PgC. As discussed in thehistorical section, the reasons for this large simulateduptake are unknown. The simulated land carbon fluxesshow a much larger range, from a cumulative source of165PgC to a cumulative sink of 758PgC. Eight modelssimulate that the land acts as a carbon sink over the fullperiod. Land is simulated to be a carbon source by twomodels, CESM1-BGC and NorESM1-ME, both sharingthe same land carbon cycle model, and byMIROC-ESM.

FIG. 4. Range of (a) cumulative global air to ocean carbon flux (PgC), (b) cumulative global air to land carbon flux(PgC) from the 11ESMsE-driven simulations, (c) the annual global air to ocean carbon flux, and (d) annual global airto land carbon flux. Color code for model types is as in Fig. 1.

15 JANUARY 2014 FR I EDL I NGSTE IN ET AL . 521

Friedlingstein et al. 2014

CMIP5

C Uptake

C Loss

PredictionsoffutureLandCbalancearehighlyuncertain,wejustdonotknowenough

Large losses of C in tropics

Offsets a big portion of emissions