biogeochemical cycles - carbon cycle

carbon cycle

• carbon is fundamental building block of life 
• carbon in the atmosphere: is in the form co2, arrived naturlly on earth from volcanoes, is fourth most abundant gas, 

where is carbon found? 

• organic sotres = living things 
• inorganic stores = lithopshere, atmosphere 
• frozen stores/sinks = cryosphere 
• water stores/sinks = hydrosphere 

carbon behaviour: 

• fast carbon - transferes quickly between sources e.g. respiration, photosynthesis, decomposition, combustion 
• slow carbon - sequestration - takes millions of years for carbon to be sequestered in sedimentary rocks 

carbon cycle is a closed system: 

• are inputs + outputs of energy but the amount of carbon in the system remains the same
• some carbon is locked away - sequstered in long term stores e.g. fossil fuels + rocks 
• if released e.g. through burning fossil fuels they are input back into the cycle 

3 main processes in the carbon cycle; 

• carbon in the atmosphere as carbon dioxide from repsiration + combustion 
• carbon dioxide is absorbed by producers to make glucose in photosynthesis 
• animals feed on plants passing carbon compounds along the food chain, most carbon consumed is exhaled as co2 that was formed during aerobic respiration, plants + animals die 
• decomposers break down the dead organic matter + return the carbon in thier bodies to the amtosphere as co2 by respiration, when decomposition is blocked may form fossil fuels that later extracted for combustion/energy 

carbon cycle is process by which carbon is stored + transfered 

carbon stores change in size overtime as of carbon flows between stores: photosynthesis, respiration, decomposition, combustion, ocean uptake + loss, weathering, sequestration 

are natural processes at play altering the magnitude of carbon stores - natural events e.g. wildfires have impact 

wildfires: 

• large quantities of carbon are transfered from biomass/soil to the atmosphere 
• loss of vegetation decreased photosynthesis = less carbon uptake 
• fires can encorage growth of new plants 
• fires can have neutral effect on atmospheric carbon 

volcanoes: 

• carbon is stored within the earth magma is released during volcanic eruptions - released as co2 
• huge + long term eruptions can have effect on concentrations as are transboundry 

how do humans imapct the carbon cycle? 

fossil fuel extraction + use 

deforestation 

farming practices 

land use changes 

the carbon cycle affects: oceans, land, atmosphere + climate 

= global warming 

= climate change 

factors affecting amount of carbon in atmosphere: 

what is the carbon budget? 

a carbon budget is the cumulative amount of carbon dioxide emissions permitted over a period of time to keep within a certain temp threshold 

atmosphere: inputs - volcanic eruptions, burning fossil fuels, respiration, ocean loss, outputs - photosynthesis, sequestration, decomposition, ocean uptake 

the balance of the inputs + outputs of a subsystem determines whether it acts as a: 

• carbon source - the outputs of carbon outweigh the inputs so it releases more carbon than it absorbs e.g. burning fossil fuels 
• carbon sink - the inputs of carbon outweigh the outputs so it absorbs more carbon than is released e.g. rainforest photosynthesis 

feedbacks within the water + carbon cycles: 

• the…