The Global Carbon Cycle

Question 1

What is the carbon cycle?

Answer 1

A closed system, where the only inputs and outputs are between stores. The amount of carbon is fixed so the mass balance does not change. It is also a biochemical cycle in which carbon moves between the lithosphere, oceans and atmosphere.

Question 2

What are carbon stores known as?

Answer 2

Reservoirs.

Question 3

What is a carbon flow known as?

Answer 3

Flux.

Question 4

What is the time carbon is held in a store?

Answer 4

Residence time.

Question 5

What is the largest reservoir and what is the average residence time?

Answer 5

The lithosphere - 99.9% of global carbon with a 150 million year residence time on average.

Question 6

What is the second largest reservoir and what is the average residence time?

Answer 6

Oceans - 0.064% of global carbon with a 1250 year residence time maximum.

Question 7

Which is the faster flux and which is the slower flux?

Answer 7

Land-atmosphere is a fast flux and land-ocean is a slow flux.

Question 8

How is fossil fuel combustion a flux?

Answer 8

Burning oil, coal and gas releases carbon dioxide into the atmosphere.

Question 9

What is carbon sequestration?

Answer 9

Carbon dioxide being removed from the atmosphere and being held in solid or liquid form.

Question 10

What is carbon photosynthesis?

Answer 10

Plants use light, water and carbon dioxide to produce glucose and oxygen.

Question 11

What is respiration?

Answer 11

Living organisms produce energy through glucose and oxygen reacting together, resulting in carbon dioxide being released.

Question 12

What is decomposition?

Answer 12

When organic matter dies it breaks down by physical and chemical decomposition, and biological rotting, which releases carbon dioxide into the atmosphere.

Question 13

Why is the amount of carbon dioxide returned by respiration and decomposition less than the amount sequestered?

Answer 13

Some carbon becomes part of the sedimentary rock and fossil fuel pools.

Question 14

How does climate have an impact on photosynthesis, respiration and decomposition rates?

Answer 14

Higher temperature, up to the optimum level, means the organisms have a higher metabolic rate and therefore carry out all these processes faster.

Question 15

What are the main land-atmosphere fluxes?

Answer 15

Fossil fuel combustion, photosynthesis and sequestration, respiration and decomposition.

Question 16

What are the main atmosphere-ocean fluxes?

Answer 16

Absorption by biota and diffusion into and out of oceans.

Question 17

How does absorption by biota work to fix carbon in the oceans?

Answer 17

Phytoplankton absorbs carbon dioxide by photosynthesis, which passes through the marine food chain when the phytoplankton is eaten. Some carbon ends up in sediments when dead organisms settle on the seabed.

Question 18

How does diffusion into and out of oceans work to fix carbon in the oceans?

Answer 18

Where the ocean is in contact with the atmosphere, carbon is absorbed by the water. Cold water sinking transfers the carbon to the deep ocean. Water moving to the surface and warming loses carbon dioxide to the atmosphere.

Question 19

How does weathering work to fix carbon into the oceans?

Answer 19

Particles of rock are carried to the oceans and deposited. The chemical weathering process of carbonation dissolves the calcium carbonate in rocks, changing minerals containing lime into soluble biocarbonates. There, it is used to create shells, which form deposits when the organisms de, creating a carbon pool.

Question 20

How does river transport and indirect movement by the water cycle work to fix carbon into the oceans?

Answer 20

Channel for, through flow and groundwater flow move dissolved calcium carbonate to the oceans.

Question 21

How does carbon sequestration work to fix carbon into the oceans?

Answer 21

Deposited sediments build up over time, forming new carbon pools of sedimentary rocks.