280 likes | 526 Vues
Geoscience Systems: Modeling oxygen and carbon dioxide over the past 600 million years. Robert A. Berner Yale University December 20, 2010. Short Term Carbon Cycle. Marine photosynthesis. Ocean C. Atmosphere C. Gas exchange. Terrestrial Respiration. Terrestrial
E N D
Geoscience Systems: Modeling oxygen and carbon dioxide over the past 600 million years Robert A. Berner Yale University December 20, 2010
Short Term Carbon Cycle Marine photosynthesis Ocean C Atmosphere C Gas exchange Terrestrial Respiration Terrestrial Photosynthesis Degassing River transport Litter fall Root decay Calcification Soil C Biota C Marine respiration
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-
Long Term Carbon Cycle Rock Organic C Rock Carbonate C Organic C Burial Carbonate C Burial Carbonate C Weathering Organic C Weathering Ocean Atmosphere Biota Soils C Volcanic,Metamorphic, Diagenetic, Degassing Volcanic, Metamorphic, Diagenetic Degassing
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 1814-1852 Founder of long term C and S cycles
Mountain Building & Erosion CO2 System = Negative response Solar Radiation Weathering Ca-Mg Silicates Ca-Mg carbonate burial +/- Continental drift A B Climate (T + pptn) +/- CO2 Land Plants Weathering Org C Organic C sed. Burial Long Term Volc/Met/Diag Degassing Long Term
Surficial System C Mass Balance Fwc + Fmc + Fwg + Fmg = Fbc + Fbg dcFwc + dcFmc + dgFwg + dgFmg = dbcFbc + dbgFbg w = weathering; m= metamorphism: b= burial c = carbonate : g = organic matter d = measure of 13C/12C
Controls on Atmospheric O2 Organic Matter Burial and Weathering CO2 + H2O CH2O + O2 Sedimentary Pyrite Formation and Weathering 2Fe2O3 + 16 Ca++ + 16HCO3- + 8SO4-- 15O2 + 4FeS2 + 16 CaCO3 + 8H2O
Isotope Mass Balance Rock Carbonate C Rock Organic C Org C Burial (+O2) CaCO3 Burial Weathering Weathering ( - O2) Oceanic Carbon and Sulfur Volc/met gas oxidation (-O2) Volc/met gas Weathering ( - O2) Weathering Rock Sulfate S Rock Sulfide S Sulfide Burial (+O2) CaSO4 Burial
CaSO4 dissolution SO4
Isotope Feedback for Atmospheric O2 Sulfur Isotope Fractionation aS Carbon Isotope fractionation aC O2 Organic C burial Pyrite S burial Fborg Fbpyr = K/a
Rapid Recycling and O2 Burial of Organic C Pyrite S Weathering of Organic C Pyrite S Uplift Sea level drop O2
Geological Forcing and Oxygen Continental Relief and Erosion Volc-Met- Diagen Degassing Weathering Phosphorus Weathering FeS2 Weathering Organic C FeS2 Burial O2 Organic C sed. Burial
Modern dragonfly
Plants, Fires and Oxygen Feedbacks Fires Erosion Charcoal O2 Land Plants Organic C sed. Burial
P Tr
Permo-Triassic Extinction feedbacks h Plant-derived Organic burial CO2 In air i a O2 in air g b Volcanism Land plants Ocean Temp. j f O2 In sea H2S In air c Ocean stratification & anoxicity k e d Sulfate reduction
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