Block 6 (The Global Carbon Cycle)

Question 1

Define the carbon cycle

Answer 1

A biochemical cycle, in which carbon moves between the lithosphere, oceans, atmosphere

Question 2

What type of system is the global carbon cycle?

Answer 2

Closed (no matter in or out, but energy can move in or out)

Question 3

What components is the global carbon cycle made up of?

Answer 3

• Fluxes (inputs + outputs)

- Stores/reservoirs

Question 4

Carbon flows through abiotic + biotic things. What sphere is the abiotic things?

Answer 4

Geosphere - e.g. rock

Question 5

At what time scale does carbon move through the geosphere?

Answer 5

Long time scale (slow)

Question 6

At what time scale does carbon move through the biosphere?

Answer 6

Biosphere (e.g. plants)

Question 7

Define carbon stores/reservoirs

Answer 7

Places in the Earth’s system where carbon can be found

Question 8

Carbon flows through abiotic + biotic things. What sphere is the biotic things?

Answer 8

Biosphere

Question 9

What are the 5 global carbon stores?

Answer 9

• Lithosphere + sedimentary rock
• Oceans
• Fossil fuels
• Biosphere
• Atmosphere

Question 10

What is the percentage of global carbon stored + average residence time in the lithosphere store?

Answer 10

• 99.9%

- 150 mill yrs

Question 11

What is the percentage of global carbon stored + average residence time in the ocean store?

Answer 11

• 0.064%

- 25 mill -> 1250 mill

Question 12

What is the percentage of global carbon stored + average residence time in the fossil fuel store?

Answer 12

• 0.007%

- 150 mill yrs

Question 13

What is the percentage of global carbon stored + average residence time in the biosphere store?

Answer 13

• 0.003%

- 18 yrs

Question 14

What is the percentage of global carbon stored + average residence time in the atmosphere store?

Answer 14

• 0.001%

- 6 yrs

Question 15

Define residence time?

Answer 15

Time carbon is held in a store

Question 16

Define mass balance

Answer 16

The theory that the total amount/mass of global carbon doesn’t change (it just shifts between stores)

Question 17

What is the mass balance of the global carbon is fixed?

Answer 17

Approx 1.85 bill bill tonnes

Question 18

Define fluxes/flows

Answer 18

Movements/transfers of carbon between stores

Question 19

Define inputs

Answer 19

The flux movement of carbon into a store

Question 20

Define outputs

Answer 20

The flux movement of carbon out of a store

Question 21

Define processes

Answer 21

Physical mechanisms that drive the inputs/outputs from stores (e.g. photosynthesis)

Question 22

Give 3 ways that the carbon cycle is relevant for humans?

Answer 22

• Carbon is ubiquitous (everywhere)
• Carbon is a building block (for humans + living beings)
• Carbon has become an important factor in anthropogenic climate change

Question 23

What did The Paris Agreement + COP-26 agree on carbon emissions?

Answer 23

• Must be lowered

- Global temps should stay within 1.5C increase of pre-industrial levels

Question 24

What type of carbon is stored in biotic things?

Answer 24

Organic carbon

Question 25

What type of carbon is stored in abiotic things?

Answer 25

Inorganic carbon

Question 26

What are the 3 types of carbon pathways we must know?

Answer 26

- Between land + atmosphere (at a local, short term scale) - Between ocean + atmosphere - Between land + oceans

Question 27

Which of the three carbon pathways is the ‘fast’ pathway? Why?

Answer 27

Between land and atmosphere | Carbon has relatively short residence times in land + atmosphere stores

Question 28

What are the processes involved in the land-atmosphere carbon pathway?

Answer 28

1) Fossil fuel combustion 2) Carbon sequestration + photosynthesis 3) Respiration 4) Decomposition

Question 29

Outline the fossil fuel combustion process in the land-atmosphere carbon pathway

Answer 29

- Burning coal, oil, natural gas releases CO2 into atmosphere - Land -> Atmosphere - (Provides 85% of global energy consumption)

Question 30

Outline the carbon sequestration + photosynthesis process in the land-atmosphere carbon pathway

Answer 30

- Sequestration = CO2 removed from atmosphere + stored as liquid or solid. - Photosynthesis = natural sequestration done by green plants. CO2 removed from atmosphere,combined with water, leaves glucose + O2. - Atmosphere -> Land - Photosynthesis formula: 6C02 + 6H20 -> C6H1206 + 602 - (Opposite of respiration - happens slightly faster)

Question 31

Outline the respiration process in the land-atmosphere carbon pathway

Answer 31

- Living organisms release CO2 when they react glucose + oxygen together to release energy - Land -> Atmosphere - Respiration formula: C6H12O6 + 6O2 -> 6CO2 + 6H20 - (Opposite of photosynthesis - happens slightly slower)

Question 32

Outline the decomposition process in the land-atmosphere carbon pathway

Answer 32

- When organic matter dies it is broken down, releasing CO2 - Land -> Atmosphere - Physical breakdown processes: wind + water - Chemical breakdown processes: leaching + oxidation - Biological breakdown processes: bacteria/fungi feed and digest

Question 33

When is the rate of the decomposition process fastest?

Answer 33

In warm, oxygenated conditions

Question 34

What is Net Primary Productivity (NPP)?

Answer 34

Rate new organic matter is produced by photosynthesis (per unit area, per unit time)

Question 35

Where is NPP highest?

Answer 35

Warm water estuaries, marshes, rainforests

Question 36

What are the processes involved in the ocean-atmosphere carbon pathway?

Answer 36

- Physical (inorganic) carbon cycle pump | - Biological (organic) carbon cycle pump

Question 37

Outline the process of the physical (inorganic) pump in the ocean-atmosphere carbon pathway

Answer 37

DOWNWELLING (Atmosphere -> Ocean) - CO2 diffuses from atmosphere to water surface - Dissolved CO2 moves into deep water as cold water (dense) sinks UPWELLING (Ocean -> Atmosphere) - CO2 in deep water can move up to surface as warm water (less dense) rises - CO2 in surface water diffuses into atmosphere

Question 38

Outline the process of the biological (organic) pump in the ocean-atmosphere carbon pathway

Answer 38

- Atmosphere -> Ocean - CO2 from atmosphere absorbed by phytoplankton in photosynthesis - Phytoplankton eaten by other marine organisms, who gain carbon - These marine organisms are eaten by others, carbon passes through marine food web - Some carbon falls to sea floor as they die + is squashed into sediment

Question 39

Which of the 3 carbon pathways is ‘slow’? Why?

Answer 39

Land-Ocean | Happens in a long sequence that takes a long time

Question 40

What is the sequence of the land-ocean carbon pathway?

Answer 40

1) Weathering 2) Transport to oceans 3) Marine shells 4) Lithification

Question 41

Outline the sequence of the land-ocean carbon pathway

Answer 41

1) Weathering - Rocks broken down in situ - Carbon is left in the form of soluble bicarbonates - Most commonly this is by carbonation 2) Transport to oceans - Dissolved bicarbonates move to oceans - Transported by: channel flow, through flow, groundwater flow 3) Marine shells - In oceans, dissolved bicarbonates are used by marine organisms to make shells 4) Lithification - Marine organisms die - Carbon-rich shells are lithified (turned into rock) - An oceanic sediment layer/‘carbon pool’ is formed - Eventually, some carbon is returned to atmosphere by tectonic movements (CO2 released from subducting melting rock)

Question 42

What is carbonation? What is its significance in carbon pathways?

Answer 42

- Type of chemical weathering - Rainwater combines with dissolved CO2 to create a weak carbonic acid that changes rock containing limes -> bicarbonates - Most common weathering process in first stage of the land-ocean carbon pathway