Geoscience Systems: Modeling oxygen and carbon dioxide over the

past 600 million years

Robert A. BernerYale UniversityDecember 20, 2010

AtmosphereC

OceanC

SoilC

BiotaC

Gas exchange

TerrestrialPhotosynthesis

TerrestrialRespiration

Litter fallRoot decayCalcification

Degassing River transport

Marine respiration

Marine photosynthesis

Short Term Carbon Cycle

Carbon Masses

FORM 1018 moles C

Sedimentary rock CaCO3 3000

Sedimentary rock CaMg(CO3)2 2000 Sedimentary organic carbon 1250 Oceanic HCO3

- + CO3-- 2.8

Soil organic carbon 0.3 Life 0.04 Atmospheric CO2 0.056

Long Term Carbon Cycle Over millions of years

HCO3-

RockCarbonate

C

Rock Organic

C

OceanAtmosphere

BiotaSoils

C

Carbonate C Burial

Organic C Burial

Volcanic, Metamorphic,Diagenetic Degassing

Organic CWeathering

Volcanic,Metamorphic,Diagenetic, Degassing

Long Term Carbon Cycle

Carbonate CWeathering

Weathering plus Sedimentation

CaSiO3 + 2 CO2 + H2O ---> Ca++ + 2HCO3- + SiO2

Ca++ + 2HCO3- ---> CaCO3 + CO2 + H2O

Overall Silicate Reaction

CO2 + CaSiO3 ---> CaCO3 + SiO2

CO2 Reactions Weathering and sedimentation

CO2 + (Ca,Mg)SiO3 --- Ca,Mg)CO3 + SiO2

Metamorphism/volcanism/diagenesis

(Ca.Mg)CO3 + SiO2 ---> CO2 + (Ca,Mg)SiO3

Organic matter burial

CO2 + H2O ---> CH2O + O2

Organic matter weathering & metamorphism/volcanism/diagenesis

CH2O + O2 ---> CO2 + H2O

Jacques Ebelmen 1814-1852Founder of long term C and S cycles

WEATHERING OF SILICATES ON THE CONTINENTS

TECTONICS

1. Mountain uplift—(increased erosive stripping: orographic rainfall)2. Continental drift (latitude change)

BIOLOGICAL EVOLUTION

1. Rise of vascular land plants2. Rise of angiosperms

SOLAR RADIATION (GLOBAL CLIMATE)

CARBON DIOXIDE (FEEDBACK)

1. Greenhouse effect2. Plant growth fertilization

MountainBuilding &

Erosion

Climate(T + pptn)

WeatheringCa-Mg

Silicates

Volc/Met/DiagDegassing

WeatheringOrg C

CO2LandPlants

OrganicC sed.Burial

Solar Radiation

Long Term

Long Term

Ca-Mgcarbonate

burial

+/-

AB

Continentaldrift

+/-

CO2 System= Negative response

Surficial System C Mass Balance

Fwc + Fmc + Fwg + Fmg = Fbc + Fbg

cFwc + cFmc + gFwg + gFmg = bcFbc + bgFbg

w = weathering; m= metamorphism: b= burialc = carbonate : g = organic matter

= measure of 13C/12C

METHOD OF CO2 CALCULATION

Fwsi = Fbc - Fwc = fB(T,CO2) f

R(t) f

E(t) fAD(t)0.65 Fwsi(0)

fB(T,CO2) = (Fbc - Fwc) / f

R(t) f

E(t) fAD(t)0.65 Fwsi(0)

--------------------------------------------------------------------------------------------

fB(T,CO2) = f(T)f(Bio)

f(T) = exp {ACT [T(t) - T(0)]} x {1 + RUN [T(t) – T(0)]}0.65

T(t) –T(0) = ln RCO2 – Ws(t/570) + GEOG(t)

f(Bio) = (RCO2)0.5 for pre-vascular plant weathering

f(Bio) = [2RCO2/(1 + RCO2)]FERT for weathering affected by plants

Sedimentary Pyrite Formation and Weathering

2Fe2O3 + 16 Ca++ + 16HCO3- + 8SO4

--

15O2 + 4FeS2 + 16 CaCO3 + 8H2O

Organic Matter Burial and Weathering

CO2 + H2O CH2O + O2

Controls on Atmospheric O2

Rock Organic

C

RockCarbonate

C

RockSulfide

S

RockSulfate

S

OceanicCarbon

and Sulfur

SulfideBurial (+O2)

CaSO4

Burial

Org CBurial(+O2)

CaCO3

Burial

Weathering

Weathering

Weathering ( - O2)

Weathering ( - O2)

Volc/met gas oxidation (-O2) Volc/met gas

Isotope Mass Balance

SO4

CaSO4

dissolution

O2

CarbonIsotope

fractionationC

SulfurIsotope

FractionationS

Pyrite Sburial

Organic Cburial

Isotope Feedback for Atmospheric O2

Fborg

Fbpyr

= K/

O2

Burial ofOrganic CPyrite S

Weathering ofOrganic CPyrite S

Uplift

Sea level drop

Rapid Recycling and O2

0

5

10

15

20

25

30

35

40

O2 %

-600 -500 -400 -300 -200 -100 0

Time Ma

Phanerozoic Oxygen

WeatheringOrganic

C

OrganicC sed.Burial

O2

Weathering Phosphorus

Geological Forcing and Oxygen

Volc-Met-Diagen

Degassing

ContinentalRelief and

Erosion

WeatheringFeS2

FeS2

Burial

0

5

10

15

20

25

30

35

40

O2 %

-600 -500 -400 -300 -200 -100 0

Time Ma

Animal Gigantism

Moderndragonfly

LandPlants

OrganicC sed.Burial

O2

Plants, Fires and Oxygen Feedbacks

Charcoal

Fires

Erosion

0

5

10

15

20

25

30

35

40

O2 %

-600 -500 -400 -300 -200 -100 0

Time Ma

P Tr

Sulfatereduction

H2SIn air

Land plants

Plant-derivedOrganicburial

O2

in air

O2

In sea

CO2

In air

Oceanstratification & anoxicity

OceanTemp.

Volcanism

a

b

c

de

f

g

i

j

k

hPermo-Triassic Extinction feedbacks

EFFECTS OF RISE AND SPREAD OF LARGE LAND PLANTS

1. Atmospheric CO2 removal by increased silicate weathering

2. Additional CO2 removal by increased burial of organic matter

3. Extra O2 added to atmosphere by increased organic burial

4. CO2 drop induced global cooling via the greenhouse effect

5. Elevated O2 induced animal gigantism

Oxford University Press, 2004