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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
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