Lesson 7- What is the carbon cycle and where is carbon stored?

Question 1

Different types of carbon

Answer 1

• 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

Question 2

What is the carbon cycle?

Answer 2

• 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.

Question 3

What are the two types of carbon cycles?

Answer 3

• Local carbon cycle and Global carbon cycle

-Slow carbon cycle and fast carbon cycle

Question 4

Types of carbon cycle- Local carbon cycle

Answer 4

• 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.

Question 5

Types of carbon cycle- Global carbon cycle

Answer 5

• 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. See diagram below.

Question 6

Types of carbon cycle- Slow carbon cycle

Answer 6

• 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 agiant slow-moving systemwhich takes between100 and 200 million yearsfor carbon to flow through it

Question 7

Types of carbon cycle- Fast carbon cycle

Answer 7

• Short-term or fastcarbon cycle: The movement of carbon from living things to the atmosphere and oceans
• The short-term orfast cyclethrough thebiospheremoves up to athousand times more carbonin ashorterspace oftime

Question 8

How is carbon distributed globally?

Answer 8

• 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).

Question 9

What is a sink and a source?

Answer 9

• 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.

Question 10

Stores of carbon

Answer 10

• Biosphere- plants animals
  -Lithosphere- ground
• Pedosphere- soil
• Cryosphere- ice
• Atmosphere-air
• Hydrosphere-water

Question 11

Stores of carbon-Biosphere

Answer 11

• 0.0012% of all carbon
  -Residence Time of 18 years

Question 12

Stores of carbon- Lithosphere

Answer 12

• 99.98% of all carbon
  -Sedimentary rocks like limestone (Calcium carbonate)
  -Residence time of 240-300 million years

Question 13

Stores of carbon- Pedosphere

Answer 13

• 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

Question 14

Stores of carbon- Cryosphere

Answer 14

-0.0018% of all carbon
- Permafrost of tundra contains plant material
-Residence time of 1000s of years

Question 15

Stores of carbon- Atmosphere

Answer 15

• 0.0015% of all carbon
• Mainly as Carbon Dioxide and Methane (CO4)
  -Residence time of 6 years

Question 16

Stores of carbon- Hydrosphere

Answer 16

• 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

Question 17

How are the stores of carbon changing over time?

Answer 17

1) Global distribution of vegetation and ecosystems
2) Global distribution of land masses
3)Seasonal changes in plants
4) Human caused seasonal changes

Question 18

Stores of carbon changing-Global distribution of vegetation and ecosystems

Answer 18

• 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).

Question 19

Stores of carbon changing- Global distribution of land masses

Answer 19

• 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).

Question 20

Stores of carbon- Seasonal Changes in plants

Answer 20

• 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).

Question 21

Stores of carbon- Human caused seasonal changes

Answer 21

• 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).

Question 22

How does carbon move from one store to another?

Answer 22

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

Question 23

What is a sere?

Answer 23

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

Question 24

Types of sere

Answer 24

• 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

Question 25

Climatic Climax Community

Answer 25

• 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

Question 26

Global scale transfer within oceans: known as halosere transfer

Answer 26

• 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)

Question 27

What is the mechanism for global ocean currents?

Answer 27

• 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

Question 28

How does carbon downwell to deep ocean stores?

Answer 28

• 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

Question 29

How does carbon upwell in the ocean?

Answer 29

• 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!).

Question 30

What is the biological pump?

Answer 30

• 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.

Question 31

Biological pump in more depth

Answer 31

• 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)

Question 32

How does the biological pump actually work?

Answer 32

• 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

Question 33

The solubility cycle/carbonate pump:

Answer 33

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