carbon cycle 2.1.6a - pathways and processes

Question 1

what are the three timescales of the carbon cycle

Answer 1

1. (seconds/minutes) Shortest timescale
2. (10-500 years) Longer timescale
3. (million years)Longest timescale

Question 2

give an example of the shortest timescale of (seconds/minutes) in the carbon cycle

Answer 2

an example of the shortest timescale in the carbon cycle- is when plants take carbon out of the atmosphere through carbon sequestration via photosynthesis, then release it back out to the atmosphere through respiration

Question 3

give an example of the longer timescale of 10-500 years in the carbon cycle

Answer 3

an example of the longer timescale in the carbon cycle - when carbon is stored in dead plant material which is incorporated within the soil, so stays locked in their for years until broken down by soil microbes

Question 4

give an example of the longest timescale of millions of years in the carbon cycle

Answer 4

an example of when carbon is locked in for millions of years which is the longest timescale- occurs wehn organic matter is buried in deep sediments and over time transfers into deposits of coal, oil, natural gas and fossil fuels.
only when we burn these substances, is it released into the atmosphere

Question 5

what is the name of the curve graph which shows the accumulation of carbon dioxide in the atmosphere

Answer 5

The Keeling Curve

Question 6

why is their a variation of amounts of co2 in the atmosphere

Answer 6

due to:
- photosynthesis variation in seasons
- human activity (use more energy in winter)
- Forest fires more combustion in the summer

Question 7

How many Gct of carbon is found in plant stores

Answer 7

560 Gct

Question 7

What is an example of carbon fixation

Answer 7

carbon sequestration in trees can store large amounts of carbon due too the wood being big and dense,
this leads to carbon fixation because the carbon exists in the organic forms (in a tree)

Question 8

Name the three types of sequestration

Answer 8

1. Terrestrial sequestration (trees)
2. Geological sequestration
3. Ocean sequestration

Question 9

Terrestrial sequestration
what is it

Answer 9

terrestrial sequestration is a large amount of carbon being stored in Soils and Vegetation
( 560 Gct of carbon is stored in plants, importance to woody stems of trees)

Question 10

geological sequestration
what is it

Answer 10

geological sequestration is the natural pores in geologic (rock) formations, so the carbon is locked in long term within the rocks

serve as a reservoir for long-term storage or the build up/ compression of dead biological matter on the ocean floor to become sedimentary layers via fertilisation

Question 11

ocean sequestration
what is it

Answer 11

the carbon store though direct absorption or fertilisation

Question 12

what are the contributing factors of terrestrial sequestration

Answer 12

• photosynthesis
• respiration
• leaf litter
  -decomposition
  -soil

Question 13

within terrestrial sequestration
what is the role of ‘leaf litter’

Answer 13

leaf litter is dead plant material
All litter begins to decompose, which makes this a carbon flux ( a flow of carbon) in order to enrich the soil

Question 14

within terrestrial sequestration
what is the role of ‘decomposition’

Answer 14

when living organisms die, decomposers e.g. worms and fungi, feed on the dead organic matter and break it down into
-co2
-nutrients
-water

This is soil respiration
- it releases carbon to surrounding soil and atmosphere

Question 15

within terrestrial sequestration
what is the role of ‘soil’

Answer 15

carbon exists in soil, in the form of= soil organic carbon (SOC)
this is the main component of soil organic matter (SOC)
soc is formed from the decay of organic materials (plants, animals, soil microbes, plant roots)

Question 16

what is the total amount of carbon in the worlds ‘‘soil”

Answer 16

1500 Gtc- which is more than atmosphere store and vegetation store combined

Question 16

why is the ‘humus layer’ important

Answer 16

it is a carbon sink
- its organic matter that if left undistrubed can store soil carbon for a long time period

Question 17

how does co2 enter the ocean

Answer 17

molecules of co2 enter the ocean by diffusing into the sea surface water, and dissolve through the process diffusion

Question 18

name the four variables that contribute to the amount of co2 that diffuses and then dissolves into the ocean

Answer 18

1. strong wind mixing with ocean circulation- enhances mixing of surface water and deep waters which helps dissolve the co2
2. concentration of co2 in atmosphere- allows more to be diffused into oceans
3. temperature of the water- colder waters absorb more co2
4. ocean alkalinity and pH- more alkaline the more absorption of co2

Question 19

what happens when the co2 is dissolved into the ocean?

Answer 19

the co2 enters the Ocean Carbon Cycle
through different mechanisms

Question 20

name the 3 mechanisms of the ocean carbon cycle that co2 can enter

Answer 20

1. physical carbon pump
2. biological carbon pump
3. carbonate pump

Question 21

Summarise with key terms what the Physical Carbon Pump is, in terms of it being an ocean carbon pathway

Answer 21

-The Thermohaline System is the physical pump in oceans which allows co2 to be constantly exchanged between the ocean and atmosphere.
-The co2 is diffused into the cold surface waters in polar regions because co2 is absorbed more in cold temperatures
- The dissolved co2 is transported to the deep ocean via down-welling currents due the water being cold and dense so it sinks, and often remains in the deep ocean for centuries
-Then often near coastlines, up-welling occurs, when the water warms and rises to the surface, releasing some co2 back into the atmosphere, but most co2 is sequestered and stored in the deep ocean.

Question 22

Summarise with key terms what the Biological Carbon Pump is, in terms of it being an ocean carbon pathway

Answer 22

• The biological carbon pump is the organic sequestration of co2 fromt he atmosphere to the ocean by Phytoplankton. They absorb co2 at the surface through photosynthesis
  -Phytoplankton are the base of the marine food web, so when they are consumed or die, the carbon is passed on through marine life, or their rich-biomass sinks down to the deep ocean and is stored in sediments

Question 23

Summarise with key terms what the Carbonate Pump is, in terms of it being an ocean carbon pathway

Answer 23

• The Carbonate Cycle involves the transfer of carbon, through the formation of calcium carbonate by marine organisms. For example, coral and shellfish utilize the dissolved co2 and use it to create calcium carbonate structures
• When they die, the calcium carbonate shells accumulate in the sea bed contributing to sediment formation such as limestone e.g. white cliffs of dover