1. Recycling of the elements

2. Importance of Carbon All life is based on carbon
CO2 important greenhouse gas
Regulates ocean acidity
Transfer to sedimentary rocks keeps atmosphere oxygen-rich

3. GLOBAL CARBON CYCLE Terrestrial and marine processes
Biologic and non-biologic
Tens of years to millions of years

4. TERRESTRIAL ORGANIC CARBON CYCLE

5. TIME SCALES Years to decades Millions In atmosphere Photosynthesis
Decomposition
Millions
Burial and lithification in marine sediments

6. SHORT TIME SCALES CO2 removed from atmosphere via photosynthesis
Returned via respiration & decomposition
Methane released from soils
Some terrestrial organic carbon buried in sedimentary basins or brought to sea
Decomposition in ocean releases carbon
Some organic matter is buried in marine sediments

7. LONGER TIME SCALES Organic matter lithified (mostly shales)
If organic matter high enough, fossil fuels may form
Tectonic uplift exposes rocks to weathering, organic matter oxidizes, CO2 produced and reenters the atmosphere

8. RESERVOIR DYNAMICS
HOW DOES THIS SYSTEM OF RESERVOIRS RESPOND TO PERTURBATIONS?

9. SYSTEMS APPROACH Atmosphere is a reservoir of carbon
Reservoirs are temporary repositories
Size changes in response to inflow/outflow
If atmospheric concentration remains the same (that is - inflow=outflow) system is at steady state

10. SYSTEMS APPROACH
System not at steady state – anthropogenic disturbances have caused a steady rise in CO2
For steady state to be achieved, couplings that link reservoir size to inflow/outflow must exist
A negative feedback loop exists – CO2 fertilization
As CO2 increases, photosynthesis increases, which causes CO2 to decrease

11. CO2 FERTILIZAITON
TERRESTRIAL BIOTA TEND TO STABILIZE ATMOSPHERIC CO2 LEVELS

12. SHORT-TERM TERRESTRIAL ORGANIC CARBON CYCLE

13. SHORT-TERM MARINE ORGANIC CARBON CYCLE
Producers – phytoplankton
Top 100 meters – sufficient light for photosynthesis
Gas exchange with atmosphere
Consumers – zooplankton
Organic matter settles to bottom
Only 1% makes it to the bottom
Decomposers recycle nutrients
0.1% of organic matter that settles ends up in the sediment
Decomposition releases CO2 & nutrients (needed at surface)

14. THE MARINE BIOLOGICAL PUMP

15. RESULT – BIOLOGIC PUMP & THERMOHALINE CIRCULATION
DO concentrations minimum due to aerobic decomposers
DO increases with depth due to thermohaline circulation
Surface waters depleted of C & nutrients due to photosynthesis and sinking
Decomposers release nutrients, but use up oxygen

16. LONG-TERM ORGANIC CARBON CYCLE
Geologic processes the important controls on atmospheric CO2 on longer time scales

17. CARBON LEAKS & OXYGEN REPLENISHMENT
Buried organic carbon is a leak from the short-term organic carbon cycle
Maintains atmospheric O2
For every carbon atom that enters the sedimentary rock reservoir, one oxygen molecule is left behind

18. INORGANIC CARBON CYCLE

19. REMOVAL OF CO2
The net effect of CaCO3 weathering on land and CaCO3 precipitation in the ocean is zero
Combining silicate weathering on land and carbonate precipitation in the sea leads to a net conversion of atmospheric CO2 to solid CaCO3
Net outflow of CO2 from the atmosphere
A reduction in atmospheric CO2 creates a concentration gradient and CO2 will diffuse from the oceans to the atmosphere
There must be a return flux of CO2 to offset this outflow
There is …

20. THE CARBONATE-SILICATE GEOCHEMICAL CYCLE
Plate tectonics provides return flux of CO2 via metamorphic and volcanic CO2 inputs to the atmosphere

21. SHAL WE BECOME MARS?
Without this balance between inflow and outflow of CO2, it would be quickly depleted and Earth would soon freeze
But, how is this balance maintained?

22. LONG-TERM FEEDBACKS IN THE CARBONATE-SILICATE CYCLE
THE FEEDBACK TENDS TO STABILIZE EARTH’S CLIMATE AGAINST PERTURBATIONS

23. THE PHOSPHORUS CYCLE

24. THE PHOSPHORUS FEEDBACK LOOP

25. THE NITROGEN CYCLE