The Carbon CycleThe Carbon CycleMarine PerspectivesMarine Perspectives 1

Dynamic interactions of geochemical cycles

Oceanography (study of the oceans), and Chemical Oceanography( h i t f th b d th(chemistry of the oceans based on the distribution and dynamics of elements, isotopes, atoms and molecules) are fundamentally interdisciplinaryfundamentally interdisciplinarysciences that deal with dynamic interactions between atmosphere, lithosphere and hydrospherelithosphere and hydrosphere

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The broadest we can get: Global warming

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Spektrale Energieflußdichten für solare und terrestrische Strahlung

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Die nicht absorbierende Atmosphärep

Bilanz der reinen (N O Ar) Atmosphäre:Bilanz der reinen (N2, O2, Ar) Atmosphäre:• Etwa 6% atmosphärische Rückstreuung, etwa 10%

Reflexion an Oberfläche Land und OzeanMittl Ei t hl 288 W/ 2Mittlere Einstrahlung 288 W/m2

Schwarzkörperstrahlung gegeben durchSchwarzkörperstrahlung gegeben durch Stefan-Bolzmann-Gesetz: R = σ Ta

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σ= Stefan Bolzmann Konstante (5.67 x 10-8 J m-2 K-4 s-1)Ta = abs. Temperatur

Ta (288W/m^2) = - 6°C

Real : Tav = + 15°C5

Das solare SpektrumDas solare Spektrum

EinflußEinfluß derder AtmosphäreAtmosphäreauf dieauf dieauf die auf die EinstrahlungsbilanzEinstrahlungsbilanz, , mitmitWolkenalbedoWolkenalbedo, , WasserdampfWasserdampf COCO etc:etc:WasserdampfWasserdampf, CO, CO2 2 etc:etc:

EinfallendeEinfallende StrahlungStrahlung 342 342 W/W/ 22 tt 70%70% d hd hW/mW/m22 , etwaetwa 70% 70% durchdurchdie die AtmosphäreAtmosphäre und am und am BodenBoden absorbiertabsorbiert, i.e. 240 , i.e. 240 W/mW/m22

=> => --18 18 °°CC

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ÜberblickÜberblick

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Absorption im IR-Bereich

Absorption im IR-BereichBereichBereich

Breite Absorption durch Wasserdampf im IR-Bereich,zusätzliche Absorptionsbanden von CO2 Ozon, Methan und N2O

FCKW absorbieren stark genau in den „optischen Fenstern“ der At häAtmosphäre

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ÜberblickÜberblick

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History of the science of the greenhouse History of the science of the greenhouse y geffect

y geffect

1827 J B ti t F i i th ff t f IR• 1827: Jean Baptiste Fourier recognizes the effect of IR absorbing gases and points out the similarity to a greenhouseg

• 1860: John Tyndall measures IR absorption of CO2 and water vapor, he suggests that the cause of the ice ages might be a decrease in atmospheric COmight be a decrease in atmospheric CO2

• 1896: Svante Arrhenius calculates the effect of rising greenhouse gas concentrations on temperature; estimates 5-6 °C increase for a CO2 doubling

• 1940: G.S. Callendar does a first calculation on temperature increase due to the burning of fossil fuelstemperature increase due to the burning of fossil fuels

• 1957: Roger Revelle and Hans Suess;” .. In the build-up of carbon dioxide in the ocean, human beings are carrying out a large-scale geophysical experiment”.

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)2

(ppm

m. C

O2

Atm

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The Carbon CycleThe Carbon CycleTransfer of carbon between chemical reservoirsLiving things (biosphere)Transfer of carbon between chemical reservoirsLiving things (biosphere)Sediments (geosphere)

Organic matter/kerogenSediments (geosphere)

Organic matter/kerogeng gOil, Gas, Clathrates

Carbonate/LimestoneC CO

g gOil, Gas, Clathrates

Carbonate/LimestoneC COCaCO3

Oceans (hydrosphere)HCO ⁻

CaCO3

Oceans (hydrosphere)HCO ⁻HCO3⁻

Atmosphere (atmosphere)CO

HCO3⁻Atmosphere (atmosphere)

COCO2CO213

Looking at carbon cyclesLooking at carbon cyclesLooking at carbon cyclesLooking at carbon cycles

• Atmospheric increase from pre-industrial 280 ppm in 1800 to 380 ppm todayThi i l 50 60 % f th t ti b d• This is only 50-60 % of the expectation based on release figures from fossil fuel burning and cement production (244 +/- 20 x 1015 g from 1800 to 1994)production (244 +/- 20 x 10 g from 1800 to 1994)

• About 116 +/- 19 x 1015 g taken up by the ocean from 1850 to 1994 (Sabine et al., 2004)( )

• So what is the role of the ocean and how does its b t k?carbon system work?

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15

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The fast exchanging carbon reservoirs

7502000

After Siegenthaler andand Sarmiento, 1993.

Entire deep ocean: 39.500 17

Getting conceptual: a box model viewGetting conceptual: a box model view

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The Carbon Cycle - ReservoirsThe Carbon Cycle - Reservoirs

Reservoirs in 1015 gAt h 760

Reservoirs in 1015 gAt h 760Atmosphere 760Ocean 38,400 (as DIC)Land biota 600

Atmosphere 760Ocean 38,400 (as DIC)Land biota 600Land biota 600Marine biota 3Soil organic matter 1 600

Land biota 600Marine biota 3Soil organic matter 1 600Soil organic matter 1,600

Sedimentary rocks 78,000,000

Soil organic matter 1,600

Sedimentary rocks 78,000,000Sedimentary rocks 78,000,000Fossil fuels 5,000Gas hydrate deposits 3,000

Sedimentary rocks 78,000,000Fossil fuels 5,000Gas hydrate deposits 3,000 y p ,y p ,

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The Geological Carbon CycleThe Geological Carbon CycleThe Geological Carbon CycleThe Geological Carbon CycleCycling of carbon between rocks andCycling of carbon between rocks andCycling of carbon between rocks and minerals, seawater, and the atmosphere.Cycling of carbon between rocks and minerals, seawater, and the atmosphere.

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The Geological Carbon CycleThe Geological Carbon Cycle

0 22 0.20.4

0.120.22

Fluxes in 1015 gC/yrg y21

Chemical WeatheringChemical Weathering

Dissolution of carbonateDissolution of carbonateCO2 + H2O <=> H2CO3 <=> H+ + HCO3¯CaCO3 + H+ + HCO3¯ <=> Ca2+ + 2HCO3¯CO2 + H2O <=> H2CO3 <=> H+ + HCO3¯CaCO3 + H+ + HCO3¯ <=> Ca2+ + 2HCO3¯CaCO3 H HCO3 Ca 2HCO3CaCO3 H HCO3 Ca 2HCO3

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Carbon Cycle - FeedbacksCarbon Cycle - Feedbacks

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Long-term TrendsLong-term Trends

Atmospheric CO2 controlled by rates of th i l t t t i li /

Atmospheric CO2 controlled by rates of th i l t t t i li /weathering, plate tectonic cycling/

seafloor spreadingweathering, plate tectonic cycling/ seafloor spreadingWeathering rate based on total land area => mountain building!Weathering rate based on total land area => mountain building!gUltimately, the geochemical carbon cycle regulates the long term

gUltimately, the geochemical carbon cycle regulates the long termcycle regulates the long term atmospheric concentration of CO2

cycle regulates the long term atmospheric concentration of CO2

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Long term TrendsLong term TrendsLong-term TrendsLong-term Trends

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So Back to the millenium timescaleSo Back to the millenium timescaleSo … Back to the millenium timescaleSo … Back to the millenium timescale

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Controls on the carbonate systemControls on the carbonate systemControls on the carbonate systemControls on the carbonate systemThe shortest description of the carbonate system EVER:The shortest description of the carbonate system EVER:

CO2gas + H2O = H2CO3 = H+ + HCO3-

Attention : pCO2(T) ~ pCO2(To) x (1+ 0.0423 (T-To))

HCO - = H+ + CO 2-

CO2gas + H2O = H2CO3 = H+ + HCO3-

Attention : pCO2(T) ~ pCO2(To) x (1+ 0.0423 (T-To))

HCO - = H+ + CO 2-HCO3 = H + CO3pH-dependent carbonate speciation

CO2 + H2O = C(H2O) + O2

HCO3 = H + CO3pH-dependent carbonate speciation

CO2 + H2O = C(H2O) + O2CO2 + H2O C(H2O) + O2Organic matter formation and decomposition

Ca2+ + 2 HCO3- = CaCO3 + CO2aq

CO2 + H2O C(H2O) + O2Organic matter formation and decomposition

Ca2+ + 2 HCO3- = CaCO3 + CO2aq3 3 2aq

Carbonate formation

Carbonate – formation means more acid and depletion of CO32-

3 3 2aqCarbonate formation

Carbonate – formation means more acid and depletion of CO32-p 3

Organic matter formation means less acid and increase of CO32-

Remineralization of organic matter means more acid and depletion of CO32-

p 3Organic matter formation means less acid and increase of CO3

2-

Remineralization of organic matter means more acid and depletion of CO32-

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Air-Sea ExchangeAir-Sea ExchangeAir Sea ExchangeAir Sea Exchange

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decreasingdecreasing

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i0ºC

63 mmol/kg CO2(aq)

24ºC29 mmol/kg CO2(aq)

warming

At equilibrium with At 24°C, should only be qatmosphere 29 mmol/kg CO2(aq)

Supersaturated by 34 mmol/kgSupersaturated by 34 mmol/kg

W i i th l th t h ff t d thi tWarming is the only process that has affected this water mass.For a closed system, warming alone will lead to supersaturation.Cooling will have the opposite effect.Cooling will have the opposite effect.

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Gas ExchangeGas Exchange

Flux outFluxes are equal at equilibrium.

At disequilibrium, net transport occurs to alleviate the imbalance.

Flux in

Processes that cause imbalance:prod ction/cons mption of a gas in aterproduction/consumption of a gas in water,production/consumption of a gas in atmosphere,temperature changes…temperature changes…

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Gas Exchange Fick’s 1st Law of DiffusionGas Exchange Fick s 1st Law of Diffusion

F = -D(dC/dz)

F = flux (mass/area time)D = molec. diffusion coeff. (area/time)dC/dz = con’c gradientdC/dz = con c gradient

dC/dz = (Cg - Cl)/z

Stagnant Boundary Layer Model

F (D/ )(C C )F = -(D/z)(Cg-Cl)

F = flux (mass/area time)D = molec. diffusion coeff. (area/time)z = thickness of filmCl = con’c of gas in mixed layerCg = con’c of gas in water at top of filmKH*pair =

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Di l d tit t (C N P Si ) t d i t

biogeochemical cycles

Dissolved constituents (C, N, P, Si …) are converted into particulate constituents along the way.

Coccolithophorids

Photosynthesis (forward) Respiration (reverse)

Satellite Image - ReflectanceCoccolithophorids

OHCOCaCOHCOCa

OOCHHCO

22332

2222

2

0

++↔+

+↔+−+

Photosynthesis (forward) – Respiration (reverse)

OHCOCaCOHCOCa 22332 ++↔+

Precipitation (forward) – Dissolution (reverse) 33

Ocean circulationOcean circulationOcean circulationOcean circulation

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Through the ‘particle conspiracy’ horizontal and vertical

biogeochemical cycles

Through the particle conspiracy , horizontal and vertical segregation of dissolved chemicals occurs.(see http://www.agu.org/eos_elec/97025e-table.gif)

Surface OceanSurface Ocean

Deep Ocean

The Great Particle ‘Conspiracy’

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The outcome of the conveyer beltThe outcome of the conveyer belt

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Carbonate saturationCarbonate saturationCarbonate saturationCarbonate saturationUnit for the saturation state ofUnit for the saturation state ofsaturation state of seawater vor calcitesaturation state of seawater vor calcite

With:With:With:With:

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Ocean circulation

Ocean circulationcirculationcirculation

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The biological and the physical pump The biological and the physical pump

Chisholm ( 2000) Nature, 407: 685-68742

Processes conceptualized in the context of biogeochemical cyclesbiogeochemical cycles

Connectivity of air – sea – land through tectonics, erosion/weathering, sedimentation

Burial of these two materials in sediments has different effects on the partial pressure of CO2 in the atmosphere! Why? 43

ASE fluxesASE fluxes

Global annual mean CO2-fluxes as a result of an integratedGlobal annual mean CO2 fluxes as a result of an integratedcompilation (from Takahashi et al., DSR II, 2002).

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)2

(ppm

m. C

O2

Atm

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Die anthropogene Störung des Kohlenstoffkreislaufs

Atmosphere590800 (590) 1.7

1.9550

12060

590

74 74

610800 (590)

91.9 90

1.75.4

550(610)

6060

345

74 74

900

(74) (74)

1 500 918 (900)3

1134

101

1.560 900

90

1.500(1.560)

3000-4000

918 (900)

91.8

TerrestrischeBiosphäre

101

37 10037 200 (37 100)

FossilFuels

(90)

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BiosphäreOzean37.10037.200 (37.100)

600 800Die anthropogene Störung des Kohlenstoffkreislaufs

ATMOSPHERE39000

6002070

80039140

TR

IAL

ER

E „Physical Pump“?

ER

RE

ST

IOS

PH

E

„Biological Pump“

T B

OC47 OCEAN

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σθ = 26 surface is near the surfacenear the surface, shallower in the Atlantic WHY

σθ = 27.3 is approximately at 900approximately at 900 m water depth (intermediate water masses)

Fig. 4. Maps of anthropogenic CO2 on the (A) 26 0 and (B) 27 3 potential density surfaces BoldFig. 4. Maps of anthropogenic CO2 on the (A) 26.0 and (B) 27.3 potential density surfaces. Boldlines at the edge of the colored region indicate areas where the density surface outcrops. Thehighest values are generally observed closest to the outcrop and decrease toward the equator. (Sabine et al., 2004)

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CARBOOCEAN CARBOOCEAN –– Marine inventory of anthropogenic COMarine inventory of anthropogenic CO22

Invasion of anthropogenic CO2 into the oceans (source:Sabine et al., Science, 2004) 50

Fig. 1. Column inventory of anthropogenic CO2 in the ocean (mol / m2). High inventories are associated with deep water formation in the North Atlantic and intermediate and modeare associated with deep water formation in the North Atlantic and intermediate and mode water formation between 30° and 50°S. Total inventory of shaded regions is 106 +/-17 Pg C (from Sabine et al, 2004). 51

FeedbacksFeedbackspCO2 - Tsurface - CO2 solubility f(T)pCO2 - Tsurface - Ocean circulationpCO2 - Tsurface - CO2 solubility f(T)pCO2 - Tsurface - Ocean circulation2 surfacepCO2 => weathering (slow)Some more sophisticated controls …

2 surfacepCO2 => weathering (slow)Some more sophisticated controls …Some more sophisticated controls …Some more sophisticated controls …

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Advanced studies: Effect of changing atmospheric pCO2 on the rain rate

Advanced studies: Effect of changing atmospheric pCO2 on the rain rateatmospheric pCO2 on the rain rate

Riebesell et al., Nature 407, 364-367, 2000atmospheric pCO2 on the rain rate

Riebesell et al., Nature 407, 364-367, 2000

• Atmospheric (and thus surface ocean) pCO2 is expected toAtmospheric (and thus surface ocean) pCO2 is expected to increase by a factor of 3 with respect to preindustrial levels by the end of the 21th century

• Rising pCO2-levels in the surface ocean are already known to affect coral reef calcification (actually T rather than pCO )affect coral reef calcification (actually, T rather than pCO2).

• Ocean carbonate system however more controlled by calcifying phytoplankton (80% of calcification, most dominant coccolithophores)

• Test of effect by exposing widespread coccolithophores to various pCO2 levels and observe impact on calcification

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Advanced studies: Effect of changing atmospheric pCO2 on the rain rate

Advanced studies: Effect of changing atmospheric pCO2 on the rain rateatmospheric pCO2 on the rain rate

Riebesell et al., Nature 407, 364-367, 2000atmospheric pCO2 on the rain rate

Riebesell et al., Nature 407, 364-367, 2000

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The Carbon CycleThe Carbon CycleMarine PerspectivesMarine Perspectives 55