1.1 - Carbon Cycle

Question 1

What is the fast carbon cycle?

Answer 1

Consists of multiple processes:
- absorption of CO₂ from atmosphere and ocean by plants and phytoplankton.
- respiration by other organisms releasing CO₂ into atmosphere
- emission of carbon compounds by organisms after digesting carbon rich material
- decomposition of animals releasing carbon
- combustion releasing carbon compounds
- atmosphere-ocean exchange of CO₂ between both
- net direction is usually from atmosphere to ocean but can change

Question 2

What is the slow carbon cycle?

Answer 2

• transfer of CO₂ from atmosphere and land to oceans
  
  • acid rain dissolves carbon rich rock, calcium ions flow into ocean via rivers, react with carbonate ions in water to form calcium carbonate
  • deposited on ocean floor
  • atmospheric carbon diffuses into ocean in atmosphere-ocean exchange of CO₂
• phytoplankton sequester CO₂ during lifetimes, are then consumed
  
  • resulting excrement + dead phytoplankton fall onto seabed, converted into sedimentary rock over time
    
    • at collision tectonic boundaries, sediment is uplifted, exposed to weathering, may then return back to ocean
    • at subduction zones, carbon rich sediment is ejected in form of gases eg. CO₂ + CH₄
      
      • carbonic acid may be created or absorption of CO₂ into ocean

Question 3

What is the largest carbon store?

Answer 3

• Sedimentary rock store (8.3 million PgC)

Question 4

What are the fluxes into the atmosphere store?

Answer 4

• Freshwater outgassing
• Volcanic eruptions (smallest, 1*10⁵ kg/yr)
• Land use change
• Fossil fuel use and cement production
• Ocean to atmosphere
• Respiration and fire (largest, 1.18*10⁸ kg/yr)

Question 5

What are the fluxes out of the atmosphere store?

Answer 5

• Rock weathering (smallest 4*10⁵ kg/yr)
• Photosynthesis (largest 1.23*10⁷ kg/yr)
• Atmosphere to ocean

Question 6

What is lake outgassing?

Answer 6

• underground volcanic chimneys emit CO₂
  
  • dissolved into water in crater lake of volcano
  • gas infused water stays at the bottom of lake (due to density)
• Earthquakes trigger landslides
  
  • debris enters volcano crater
  • lake is unsettled
  • water from bottom of lake reaches surface
    
    • dissolved gasses released
    • since gases are denser than air, flow down side of volcano into valleys

Question 7

How long does one cycle of the slow carbon cycle take?

Answer 7

• 100 - 200 million years

Question 8

What is the size of the sedimentary rock store?

Answer 8

• 83 million PgC

Question 9

What is the size of the atmospheric carbon store?

Answer 9

• 589 PgC

Question 10

What is the size of the terrestrial carbon store?

Answer 10

• 550 PgC

Question 11

What is the size of the respiration and fire flux?

Answer 11

• 118.7PgC/yr

Question 12

What is the size of the fossil fuel store?

Answer 12

• 1471 PgC

Question 13

What is the size of the permafrost store?

Answer 13

• 1700 PgC

Question 14

What is the size of the atmosphere to ocean flux?

Answer 14

• 80 PgC/yr

Question 15

What is the size of the ocean to atmosphere flux?

Answer 15

• 78.4 PgC/yr

Question 16

What is the size of the rock weathering flux?

Answer 16

• 0.4 PgC/yr