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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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