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Proposed Glacial Control Through Carbon Cycling
Quaternary - Recent (complex multi-story ecosystems) < 1.6 x 106 years INSOLATION. | C3 Photosynthesis Predominates Increased sensitivity to (broad leaf, migrates to high latitude [<50 deg.] orbital forcing and high rainfall in 20-25oC band) |----> Increased --> Global ----------> Glacial retreat |Biodiversity bands| <----| | CO2 warming | |re-activated | | | CH4 Continued gas-hydrate Atmospheric CO2 | . release (warmth, readily modified | . perma-frost flooding) by biosphere Fossil carbon . | | CH4 increases | | oxidation <-------| Warm & wet | Atmospheric CO2 | | | . | | |> 300 ppmv [present = 380 ppmv]| | | . Reduced forest biomass, "High" CO2 accommodated ecosystems develop, | Gas- . surface coal peat & forest fires Increased biomass, peat & gas-hydrate accumulation | hydrates . | | | release . Cool & dry, low CO2 systems Photosynthetic | | . | re-emerge after draw-down of CO2 Short period | . | ecosystem re-definition | 40,000 - 100,000 yrs | . | | | | . Glacial <------- Reduced <----------| effective | . advance Atmospheric | Carbon photosynthetic | Glacial . | CO2 | sequestering draw-down | excavation . | | |maximum sea-level| | | fossil carbon | increased increased | change 120 m | | | Sea- nutrient input oceanic | |<------------------ level -----> from exposed ----> productivity <-----| lowers land
Atmospheric CO2 170 ppmv (50% of present level)
C4 Photosynthesis Predominates (many grasses can operate under low CO2 regimes but may also have higher optimal temperatures for growth and lower water demand - tropical grasslands)
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