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Carbon cycle + Energy security - Coggle Diagram
Carbon cycle + Energy security
carbon cycle -
describes the movement of carbon through earth atmosphere, biosphere, pedosphere, hydrosphere + lithosphere
involves dynamic balance between different carbon stores (reservoirs) + fluxes (flows) that connect them
operates at multiple spatial + temporal scales, from local to global, and daily to geological timescales
Major carbon stores
Lithosphere:
in sedimentary rocks, fossil fuels
solid, liquid, gas
largest store, formed over millions of year
includes both organic + inorganic carbon
Hydrosphere:
in oceans, rivers, lakes
dissolved CO2, carbonates
oceans absorb CO2 through diffusion.
oceanic carbon mainly exists as hydrogen carbonate ions
Pedosphere:
in soils, peat bogs
organic matter, humus
soils store carbon from decayed plant/animal matter
peat can be up to 60% carbon
Biosphere:
forests, plants, animals
organic matter
fast moving store
forests act as carbon sinks via photosynthesis
tropical forests = high carbon biomass
Atmosphere: - air -
Forms of carbon
solid form - coal, biomass, calcium carbonate
liquid form - crude oil, organic acids in soil
gas form - CO2, methane (CH4) in atmosphere
Fluxes of carbon
Photosynthesis:
plant absorb CO2 and convert it to glucose, removes atmospheric carbon
daily to seasonal
Respiration:
organisms release CO2 back into the atmosphere from breaking down food
continuos
Decomposition:
microbes break down dead organisms, releasing carbon to soil + atmosphere
week to decades
Combustion:
burning of biomass or fossil fuels releases CO2 rapidly
instantaneous
Ocean:
atmosphere exchange: - CO2 is constantly exchanged between ocean surface and atmosphere, affected by temp
short-term
Volcanic outgassing:
carbon from earths mantle is released into atmosphere via volcanic eruptions
geological - millions of years
Chemical weathering:
CO2 dissolves in rainwater, forms carbonic acid that weathers silicate rocks, locking carbon
thousands to millions of years
Sedimentation:
marine organisms use carbon to form shells, when they die, carbon is buried in ocean sediments
geological
Fossil fuel formation:
over millions of years, dead organisms become coals, oil, or gas under pressure
Human impact on carbon cycle
have accelerated fluxes, esp:
combustion of fossil fuels - adds 9-10 Pg/year of carbon to the atmosphere
deforestation - reduces photosynthetic uptake, increases CO2
land use change - urbanisation + agriculture alter carbon storage in soils + vegetation
have contributed to climate change, ocean acidification, + feedback loops in global system
Important terms + concepts
carbon sequestration: the long term storage of carbon in oceans, vegetation, soils, and rocks
carbon sink - a natural store that absorbs more carbon than it emits (e.g. forests, oceans)
carbon source - a store that emits more carbon than it absorbs (e.g. fossil fuel burning sites)
Net Primary Productivity: the amount of carbon uptake after subtracting plant respiration from photosynthesis
biological pump - the process by which oceans move carbon from the surface to the deep ocean
carbon budget - balance between carbon emissions and absorption on earth, critical for climate targets
Feedback mechanisms
Positive feedback: warmer climate -> melts permafrost -> releases methane -> more warming
Negative feedback: higher CO2-> boosts plant growth -> more CO2 absorbed -> stabilises atmosphere
Key stats
atmospheric CO2 concentration - 420ppm
oceans absorb around 25-30% of anthropogenic CO2 emissions annually
the Amazon stores 17% of the world's terrestrial carbon