Surface Carbon Cycle Flashcards
How much carbon is in the world’s soils?
1500PgC
What are the major fluxes of surface carbon?
Atmosphere-ocean and atmosphere- biosphere fluxes
Natural and anthropogenic fluxes
Name some examples of major fluxes for surface carbon cycle
Photosynthesis
Plant respiration
Microbial decomposition
Ocean-atmosphere exchange
Fossil fuel combustion and land cover change
What is the difference between fast and slow carbon?
Fast carbon:
Includes carbon on land in vegetation, soils, peat, freshwater, atmosphere, ocean and surface ocean sediments
Large exchange fluxes and relatively fast residence times (>1 - 1000 years)
Slow carbon:
Huge carbon stores in rocks and sediments
Residence times are >10,000 years
How much carbon does photosynthesis remove from the atmosphere and then store?
120GtC/year
Stores around 600PgC
What type of feedback loop is the CO2 fertilisation effect?
Negative feedback loop
How much carbon does plant respiration release into the atmosphere?
60GtC/year
Around half of the CO2 returned to the atmosphere in the terrestrial portion of the carbon cycle
What is net primary productivity in plants?
Net carbon gained by plants
Balance between carbon gained by photosynthesis and lost by respiration
What is soil respiration?
Dead organic matter is decomposed and CO2 is released into the atmosphere
60GtC/year
What is runoff?
Small fraction of carbon is transported away by water running over the soil surface, eventually reaching oceans
~0.6GtC/year
How much carbon does the ocean store?
38,000 PgC
Mainly in the form of inorganic carbon
What is the solubility pump?
Atmosphere has a higher concentration of CO2 than the ocean
CO2 flows from atmosphere into the ocean
CO2 in the water undergoes dissolution and chemical reactions
Depends strongly on temperature (CO2 is more soluble in colder water)
HCO3- the most dominant form of inorganic carbon in sea water
What is the biological pump?
Controlled by CO2, nutrients and pH
Surface waters are depleted in alkalinity and dissolved CO2 because of the pump
The pump exports carbon (organic and inorganic) from the surface waters to the deep oceans
What are the two ways the ocean absorb CO2?
Solubility pump
Biological pump
How much carbon do oceans take up and release?
Take up around 92GtC/year and release 90GtC/year
