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What are the 2 major recurrent questions?

Falkowski et al., (2000) Science The global carbon cycle: A test of our knowledge of Earth as a system. What are the 2 major recurrent questions? Can we distinguish between anthropogenic and natural biogeochemical cycles?

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What are the 2 major recurrent questions?

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  1. Falkowski et al., (2000) ScienceThe global carbon cycle: A test of our knowledge of Earth as a system • What are the 2 major recurrent questions? • Can we distinguish between anthropogenic and natural biogeochemical cycles? • What is the sensitivity of Earth’s climate to changes in atmospheric CO2? • What does ice core data tell us?

  2. What does ice core data tell us? • CO2 oscillated in 100K year cycles between 180 and 280 ppm • On millennial time scales – CO2highly correlated with Temp changes • *Although temps may change abruptly without a discernable change in CO2– the opposite is not true • i.e. If CO2changes >> Temp will to • How are CO2records inferred? • Ice cores and fossilized shells use the ratio of isotopic oxygen-16 (light) and 18 (heavy) • Less heavy oxygen in ice cores means temperatures were colder

  3. Terminology DIC Solubility pump Biological pump Sink vs. Source • Dissolved inorganic carbon, related to pH levels. CO2 is soluble in water, reacting to created ionic and non-ionic species (e.g. carbonate CO32-) • Physical-Chemical transport of carbon from the ocean’s surface to deep water. Driven by sea temperature (colder>>more soluble) and THC. • Biological transport of carbon from surface to deep ocean waters. Organic or PIC (CaCO3) from calcifying species Dissolved inorganic carbon, related to pH levels. CO2 is soluble in water, reacting to created ionic and non-ionic species (e.g. carbonate CO32-) • (coccolithophores)

  4. The active carbon reservoirs and their strengths. • Atmospheric CO2 exchanges rapidly with oceans and terrestrial ecosystems • The remarkable consistency of the upper and lower limits of the glacial-interglacial atmospheric CO2 concentrations, and the apparent fine control over periods of many thousands of years around those limits, suggest strong feedbacks that constrain the sink strengths in both oceans and terrestrial ecosystems. • The rates of absorption and emission of CO2 from the oceans and terrestrial ecosystems are asymmetrical. • Because of this asymmetry – average CO2 atmospheric concentrations of the past was only 220ppm, not 280 (pre-industrial value often cited). • How is atmospheric CO2regulated? • Total DIC in the oceans is 50x that of the atmosphere • Land than atmosphere? 3x • Millennial time scales oceans determine atm. CO2 concentrations, not vice-versa • Why is ocean uptake finite? • CO2dissolves in water > forming a weak acid • Reacts with carbonate anions CO32- and H20 to form bicarbonate (HCO3-) ** Requires additional cations from slow weathering of rocks

  5. The higher concentration of DIC in the ocean interior (below 300m) is a result of two processes: • The Solubility Pump • Efficacy depends on the THC • The Biological PumpCO2 concentrations, and the apparent fine control over periods of many thousands of years around those limits, suggest strong feedbacks that constrain the sink strengths in both oceans and terrestrial ecosystems.

  6. The trade winds normally pile up warm surface water in the western Pacific while upwelling colder water in the east from below the surface along the equator and off the west coast of South America. During El Niño, the trade winds weaken along the equator as atmospheric pressure rises in the western Pacific and falls in the eastern Pacific. Anomalous warming in the central and eastern Pacific ensues as warm water in the western Pacific migrates eastward and upwelling is reduced

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