Carbon Cycle Adapted in part from lectures by Dr. Gerardo Chin-Leo, TESC

1. Carbon CycleAdapted in part from lectures by Dr. Gerardo Chin-Leo, TESC Chautauqua UWA-6, Dr. E.J. Zita 9-11 July 2007 Fire, Air, and Water: Effects of the Sun, Atmosphere, and Oceans in Climate Change and Global Warming

2. Milankovitch Mechanism is not a complete explanation for glaciation cycles…

3. Evidence for carbon feedback contribution to long-term climate regulation

8. Interglacial Period Small Ice Caps Large Exposed Continental Mass More Nutrients to the Sea From Land Erosion High Productivity High C-Burial High CO2 Warm Temperatures Low CO2 Cool Temperatures Few Nutrients to the Sea From Land Erosion Low Productivity Low C-Burial Ice Age Large Ice Caps Small Exposed Continental Mass Feedback Loop Linking Glaciations, Atmospheric CO2 and Phytoplankton C-burial

9. Chemistry of Inorganic C in WaterCarbonate buffering and pH • CO2 + H2O <---> H2CO3- (carbonic acid) • H2CO3 <---> H+ + HCO2- (bicarbonate) • HCO3- <---> H+ + CO32+ (carbonate)

11. Atmospheric O2 and the C Cycle

12. Isotope composition of carbonate sediments reveals the net production of O2 • Photosynthesis selects C12 over C13, thus organic material is depleted (isotopically lighter) in C13 • During times of increased net O2 production, more organic C is buried, thus atmospheric and oceanic C becomes richer (isotopically heavier) in C13 • This enrichment of C13 in the environment is reflected in carbonate sediments • Assuming a constant total mass of C13 and C12, the faster the organic C is buried (more O2 accumulates) the heavier (enriched C13) the carbonates become

13. 13C Isotope Signature Scale • (Del) C13 in ‰ • (C13/ C12)sample - (C13/ C12) standard • = --------------------------------------------------- X 1000 • (C13/ C12) standard • Example: • [(0.001125 – 0.001123)/0.001123]*1000 = 1.78 • (C13/ C12) standard is the ratio in a standard sample of the fossil invertebrate Belemnitella americana (Cretaceous Peedee formation in South Carolina)

15. Evidence for the relative constancy of O2 in the atmosphere • There is evidence for the existence of forests dating back to ~360 mya. These forests need O2 to exist • There is evidence of forest fires ever since (charcoal in sediment) • Forest fires cannot occur if O2 < 13% • If O2 > 35% fires burn so fiercely that all forests would have disappeared • Consequently, O2 is believed to have remained in the range of 13-35% (current concentration is 21%)

16. 13C as an Indicator of Ancient CO2 Levels • 13C is taken by plants slower than 12C. Thus organic matter is depleted in 13C compared to CO2. • However, when CO2 concentrations are low, plants do not discriminate 13C from 12C as much as when CO2 levels are high. Thus, the 13C: 12C ratio in organic matter under low CO2 levels is higher (more 13C relative to 12C) than during times of high CO2 levels (more 13C relative to 12C) .

17. Use of 13C in Ecology • 13C is fractionated (or discriminated) by physical processes (e.g evaporation/precipitation). There is less 13C in atmospheric CO2 than in dissolved CO2 (bicarbonate) • Consequently land plants are isotopically lighter than aquatic plants • There is another fractionation of 13C based on the photosynthetic metabolism of the plant (C3, C4 or CAM). • Consequently organic matter from C3, C4 or CAM plants can be distinguished from each other based on their -13C signatures.

21. Through condensation-evaporation, water gets isotopically “lighter” as it moves to higher latitudes. Polar ice is depleted in 18O.

22. 18O indicates ancient ice volumes and temperatures • Volume: Evaporation/precipitation and formation of polar ice excludes 18O. During ice ages the concentration of 18O in the oceans increases. Benthic foraminifera fossils show the 18O:16O of ancient seawater • Paleothermometer: the formation of CaCO3 by foraminifera excludes 18O as a function of temperature. • Benthic foraminifera form shells under constant temperature thus their 18O:16O reflects the isotope composition of the water. Planktonic foraminifera experience temperature fluctuations and these are recorded as changes in their 18O:16O relative to benthic forms

23. Relationship Between 18O Content and Temperature Water 18O is derived from benthic (deep) foraminifera. Carbonate 18O is derived from planktonic foraminifera

28. From: Introduction to Marine Biogeochemistry -Libes (1992)

31. Evidence that Increasing Atmospheric CO2 is Anthropogenic • Increase consistent with onset and development of industrialization • Magnitude and rate of increase consistent with magnitude and rates of fossil fuels consumption • Suess effect: Lowering of 14C:12C in CO2 by the input of “old” carbon from fossil fuel burning (Higher 14C when lower solar magnetic activity shields Earth less from incoming cosmic rays)

32. Lower recent C14 /C12 from fossil fuel burning Little Ice Age: low solar magnetic activity throughout? Evidence of anthropogenic source for greenhouse gases

33. Solar magnetic activity and C14 production Cosmic rays excite N14→ decays to C14 Solar max: magnetic solar wind sweeps away cosmic rays → less *N14→ less C14 http://www.nuclearonline.org/newsletter/Oct05.htm

34. http://www.dsri.dk/~hsv/Noter/solsys99.html

36. Car & Driver: Global warming is natural • Earth has been getting steadily warmer since the last ice age – a few more degrees would be nice • All CO2 is the same, whether it comes from a Porsche or your lungs – anthropogenic CO2 does no extra harm • There’s 30 times as much natural CO2 as man-made • Water vapor is the dominant greenhouse gas, so why worry so much about CO2? • We can’t do anything about water vapor, so Kyoto targeting CO2 is trivial. Discuss and analyze these claims, given what we now know.

37. Inconvenient truth: accelerated GW is anthropogenic • Bad news: we can’t do anything about • Milankovitch cycles • Increasing solar luminosity • Increasing solar magnetic activity • Good news: • We CAN do something about anthropogenic emissions of greenhouse gases • Oceans and plants will absorb as much CO2 as they can.