The Carbon Cycle Flashcards
Carbon
Carbon is an element and is extremely important. It can be found in both organic and inorganic stores
Carbon in each of the Earths subsystems
Lithosphere - over 99% of carbon is stored in sedimentary rocks like limestone
Atmosphere - carbon is stored as CO2 and methane - contains around 0.001 % of earths carbon
Hydrosphere- CO2 is dissolved in rivers, lakes and oceans. Oceans are the second largest carbon store on earth containing approx 0.04%
Biosphere - Carbon is stored in the tissues of living organisms it is transferred to the soil when they die and decay - approx 0.004%
Cryosphere - Contains less than 0.01% of Earths carbon and most here is trapped in permafrost where decomposed animals and plants have been frozen in the ground
Carbon is transferred between different stores
The carbon cycle is the process by which carbon is stored and transferred. It is a closed system as energy is input and output but the amount of carbon on earth stays the same. Stores can include the atmosphere, vegetation, soils, fossil fuels, earths crust, oceans and sediments
Carbon flows/ transfers
Photosynthesis - transfers carbon from the atmosphere store to biomass from solar energy to enable plant growth. Carbon is passed through food chain and released via respiration/ decomposition
Ocean uptake and loss - CO2 is directly dissolved from the atmosphere into the ocean and is also transferred to the oceans when taken up by organisms living in them such as plankton. Carbon may move from ocean to atmosphere when carbon rich water from deep in the oceans rises to surface and releases CO2.
Sequestration- Carbon from the atmosphere can be captured and held in sedimentary rocks or as fossil fuels. Carbon in fossil fuels is sequestrated until we burn them - combustion. - increases carbon to atmosphere
Weathering - chemical weathering transfers carbon from the atmosphere to the hydrosphere and biosphere. Atmospheric carbon reacts with water vapour to form acid rain and when this acid falls on to rocks they dissolve. Molecules from this may wash into sea and react with CO2 to form calcium carbonate
Decomposition- transfers carbon from dead biomass to the atmosphere and soil. After death bacteria and fungi break organisms down . CO2 and methane are released
Carbon flows happen over different time and spatial scales
Fast carbon flows quickly transfer carbon between sources. It only takes a matter of minutes/hours/days. Eg photosynthesis, respiration, combustion and decomposition
Slow carbon flows slowly transfer carbon between sources eg sequestration which takes millions of years.
The carbon flows also depend on spatial scale. Plant scale - respiration and photosynthesis. Ecosystem scale - combustion and decomposition. Continental scale - sequestration
Natural processes that can change the carbon cycle
Wildfires - rapidly transfer large quantities of carbon from biomass to the atmosphere. Loss of vegetation decreases photosynthesis so less carbon removed from atmosphere. Although in longer term, fires can encourage growth of new plants which take in carbon from the atmosphere for photosynthesis
Volcanic activity- Carbon stored within the Earth in magma is released during volcanic eruptions. The majority enters the atmosphere as CO2. Recent eruptions have released less CO2 than human activities however there is the potential for a very large eruption to significantly disrupt the carbon cycle
Human activities changing the carbon cycle
Hydrocarbon extraction and use - extracting and burning fossil fuels releases CO2 into atmosphere
Deforestation - forests may be cleared for agriculture, logging or developments. Clearance reduces the size of the carbon store and if the forest is burned there is a rapid flow of carbon from the biosphere to atmosphere
Farming practices - Agricultural activities release carbon to atmosphere such as animals release CO2 and methane when they respire and digest food. Ploughing can release CO2 stored in soil in the lithosphere and growing rice in rice paddies releases a lot of methane.
Land use changes - natural to urban is a major source of carbon. Vegetation is removed to make room for buildings and concrete production accounts for around 8% of emissions
The carbon budget
Difference between inputs of carbon in a subsystem and outputs of carbon from it. The balance of inputs and outputs determines whether it acts as a carbon source or carbon sink.
The carbon cycle affects the atmosphere and climate
The carbon cycle affects the amount of gases containing carbon in the atmosphere. These are greenhouse gases - they trap some of the suns energy keeping heat in and the Earth warm. As concentrations of GHGs increase in the atmosphere temperatures are expected to rise . This is global warming. Other aspects of climate are also expected to rise such as more intense storms
The carbon cycle affects the land
The carbon cycle allows plants to grow as it is needed for photosynthesis. Without decomposition nutrients would never be recycled. Changes in the carbon cycle can reduce the amount of carbon stored in the land eg warmer temperatures from global warming causes permafrost melting so previously stored carbon is released to atmosphere. Increase in temp could also cause an increase in frequency of wildfires
The carbon cycle affects the oceans
As part of the carbon cycle carbon dioxide is dissolved directly into the oceans from the atmosphere. CO2 in oceans is used by organisms such as phytoplankton and seaweed, photosynthesis and marine organisms to form calcium carbonate shells. Increase levels of CO2 in the atmosphere can increase the acidity of the oceans because the oceans initially absorb more CO2. This can have adverse effects on marine life.
Global warming also affects oceans as organisms sensitive to temperatures like phytoplankton may be unable to survive at higher temps so their numbers decrease and less CO2 will be used for photosynthesis and less carbon is removed from atmosphere. Warmer water is also less able to absorb CO2 so potential CO2 to be dissolved in the sea decreases
