Lesson 7- What is the carbon cycle and where is carbon stored? Flashcards
Different types of carbon
- Carbon dioxide(CO₂)is a gas found inoceans, soils and the atmosphere andas a waste product in respiration(animal and human)
- Methane(CH₄)is a greenhouse gasfound in rocks, oceans, permafrost,soils, etc.
- Hydrocarbons(fossil fuels)found insedimentary rocks in gas, liquid, or solidform
- Calcium carbonate commonsubstance found in limestone rock,shells, eggs, etc.
- Carbon biomoleculesare
organicmolecules including carbohydrates, fats,proteins etc., and form 50% of the totaldry mass of living things
What is the carbon cycle?
- The Earth’s carbon pools include the atmosphere, soils, oceans, and crust, each storing significant amounts of carbon.
- Fluxes, such as photosynthesis, respiration, decomposition, and combustion, move carbon between these pools.
- Through photosynthesis, carbon from the atmosphere is used by plants to grow, which later returns to the atmosphere via respiration, decomposition, or combustion.
- This continuous cycle maintains the crucial balance of carbon in ecosystems.
What are the two types of carbon cycles?
- Local carbon cycle and Global carbon cycle
-Slow carbon cycle and fast carbon cycle
Types of carbon cycle- Local carbon cycle
- The carbon cycle on a local scale is in a specific area.
- For example within a rainforest the carbon cycle is an open system because carbon can enter and leave the system.
-This can be through deforestation or burning transferring carbon out of the system into the atmosphere.
Types of carbon cycle- Global carbon cycle
- The global carbon system can be subdivided into systems operating on land, oceans and atmosphere.
- On a global scale the carbon cycle is a closed system because only energy from the sun can cross into the cycle.
- No new carbon enters or leaves
Types of carbon cycle- Slow carbon cycle
- Long-term or slowcarbon cycle: The movement of carbon between the atmospheric, oceanic and lithospheric stores
- The atmosphere, oceans and land are linked together transferring carbon in a giant slow-moving systemwhich takes between100 and 200 million yearsfor carbon to flow through it
Types of carbon cycle- Fast carbon cycle
- Short-term or fastcarbon cycle: The movement of carbon from living things to the atmosphere and oceans
- The short-term orfast cycle through the biosphere moves up to a thousand times more carbonin a shorter space of time
How is carbon distributed globally?
- The main stores of carbon are located in, and transferred between the biosphere (plants), lithosphere (rocks), pedosphere (soils), cryosphere (ice), atmosphere (air) and hydrosphere (water).
What is a sink and a source?
- Sink = taking in more carbon than giving out.
- Source = giving out more carbon than taking in
Over time some sources can turn into sinks and some sinks can turn into sources.
Stores of carbon
- Biosphere- plants animals
- Lithosphere- ground
- Pedosphere- soil
- Cryosphere- ice
- Atmosphere-air
- Hydrosphere-water
Stores of carbon-Biosphere
- 0.0012% of all carbon
-Residence Time of 18 years
Stores of carbon- Lithosphere
- 99.98% of all carbon
-Sedimentary rocks like limestone (Calcium carbonate)
-Residence time of 240-300 million years
Stores of carbon- Pedosphere
- 0.0031% of all carbon
- Stores 300 billion tonnes of carbon as organic matter Peat soils containing the most
-Residence time of days to 1000’s of years
Stores of carbon- Cryosphere
-0.0018% of all carbon
- Permafrost of tundra contains plant material
-Residence time of 1000s of years
Stores of carbon- Atmosphere
- 0.0015% of all carbon
- Mainly as Carbon Dioxide and Methane (CO4)
-Residence time of 6 years
Stores of carbon- Hydrosphere
- 0.0076% of all carbon
- 90% of oceanic carbon is dissolved as bicarbonate with carbonate ions and dissolved C02
-Residence time of 25 years for surface of ocean but deep ocean carbon can be 1250 years
How are the stores of carbon changing over time?
1) Global distribution of vegetation and ecosystems
2) Global distribution of land masses
3)Seasonal changes in plants
4) Human caused seasonal changes
Stores of carbon changing-Global distribution of vegetation and ecosystems
- Changes the amount of stored carbon - the Arctic and the Sahara Desert have virtually no plant storage, whereas the Amazon rainforest has all-year-round storage, Equally, tropical trees will store more carbon than a small bramble (change over space).
Stores of carbon changing- Global distribution of land masses
- Carbon uptake is higher in the middle/high latitudes of the northern hemisphere but less in the southern hemisphere (less land mass) (change over space).
Stores of carbon- Seasonal Changes in plants
- There is a seasonal change in the amount of carbon in the terrestrial (land) biosphere because plants grow and decay differently during the summer compared to the winter (change over time).
Stores of carbon- Human caused seasonal changes
- CO2 emissions change with the seasons we use more fossil fuels in winter in the northern hemisphere than in the summer, equally in winter there are less plants to absorb CO2 (change over time).
How does carbon move from one store to another?
1) Photosynthesis by the tree which removes CO2 directly from the atmosphere
2) Respiration by the tree and microbes in the soil, returns carbon to the atmosphere as CO2
3) Decomposition of leaf litter or death of the tree, also returns carbon to the atmosphere or soil
4) Combustion due to wildfires releasing large amounts of stored carbon in the tree
What is a sere?
A ‘sere’ is a stage in the succession of vegetation in an ecosystem
- When environmental equilibrium or balance is reached further succession stops the final stage of a sere is reached
Types of sere
- A lithosere is vegetation succession that occurs on bare rock
- A hydrosere occurs in freshwater e.g. a pond
- A halosere occurs in salt-rich conditions e.g. salt marshes
- A psammosere occurs in sandy areas e.g. sand dunes
Climatic Climax Community
- The end nature of the vegetation found is mostly due to the climatic conditions and is known as the ‘climatic climax community’
- In the UK, the usual climatic climax community for a lithosere is a deciduous wood
- The carbon cycle at a ‘sere’ scale is much more complex involving numerous different stores, and many transfers which all vary over space and time
Global scale transfer within oceans: known as halosere transfer
- Oceans are a carbon store (usually a sink and take in more carbon than they give out by 0.6 Gtc / year) but are also a transfer.
- This is important as carbon can be transferred from the oceans to the atmosphere and the other way round.
- Carbon dioxide (CO2) is absorbed by the ocean’s surface through diffusion
- Dissolved CO2 is then taken from the surface down to the intermediate and deep ocean stores through downwelling currents (96 GtC per year)
What is the mechanism for global ocean currents?
- Thermoline circulation
- Density of sea water is determined through temperature and saltiness. The difference from one location to another in density drives the ocean currents.
- Cold water absorbs more CO2, therefore, as the equatorial waters move toward the poles, more CO2 is absorbed
How does carbon downwell to deep ocean stores?
- Occurs because as salinity increases the water gets denser, therefore, the water sinks (downwelling) taking CO2 from the ocean’s surface to the deep ocean stores.
- Downwelling is good as it locks away carbon for a while in the deep ocean.
- Allowing more diffusion to occur at the surface and helping to regulate the carbon stored in the atmosphere
How does carbon upwell in the ocean?
- Upwelling of carbon to the surface stores occurs because as salinity decreases the water becomes less dense and rises (upwells) to the surface oceans (105.6 GtC per year)
- Upwelling means that carbon that was stored in the deep ocean is moved to the surface where it can go back into the atmosphere (not too great!).
What is the biological pump?
- This is where living things in the oceans transfer carbon from the atmosphere and then also from the surface ocean store to the deep ocean store.
Biological pump in more depth
- The biological cycle sequesters carbon in the ocean through photosynthesis by phytoplankton and other marine animals which converts CO2 into organic matter (10GtC per year)
- This acts as a biological pump transporting carbon from the oceans’ surface to the intermediate and deep ocean stores (10 GtC per year)
How does the biological pump work when the phytoplankton die?
- As the biological organisms die, their dead cells, shells and other parts sink into the mid and deep water – this is then the stored carbon which can even form sedimentary rocks such as limestone.
- Also, the decay of these organisms releases carbon dioxide into the intermediate and deep water stores
- Oceans regulate the composition of the atmosphere by moving carbon from the ocean’s surface (where it may vent back into the atmosphere) and storing it in the mid and deep ocean store, along with the dissolved carbon store, which regulates the carbon cycle
The solubility cycle/carbonate pump:
1)Oceans absorb CO2 through diffusion.
2) When CO2 mixes with H2O (water) it forms a weak carbonic acid.
3) This reacts with hydrogen in the water to form carbonates which are stored in the upper ocean.
4)Some organisms use these carbonates to make their shells or skeletons
5) When these organisms die some material sinks to the ocean floor and forms the sea bed sediment store (1750 GtC)
6)Over time, through chemical and physical processes, the carbon is transformed into rocks such as limestone
