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Environmental changes > The Carbon Cycle > Flashcards

The Carbon Cycle Flashcards

1
Q

Why is knoledge about the carbon cukle important?

A
  • It is essetial to understand climate change.
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2
Q

Rough approximation of carbon reservoirs:

A
  • Land 2000 - 4000 (?) [Pg]
  • Ocean 40 000
    ( - Rock (magma) 1 200 000
  • Fossil fuels 5000 - 10 000
  • Atm. ca 840 today (?) annual increase 6 Pg
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3
Q

Approximate Carbon fluxes (to and from atm):

A
  • Land 120 +-
  • Ocean 80 +-
  • Rocks 0.4 +-
  • Fossil fuels 10 + !
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4
Q

CO2 concentration in atmosphere

A
  • 410 ppm
  • current increase of 2 ppm/year
  • Has stayed quite steady bellow 400 ppm for millions of years before.
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5
Q

Flux from volcanic activity and weathering:

A
  • 0.1 +- Pg C/year
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6
Q

What is the net effect from volcanic feedback and what is the response time?

A
  • negative feedback to temperature

- tau_cycle = 100 000 of years

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7
Q

Ocean warming net effect:

A
  • positive feedback to temperature.
    The ocean take up atmosphereic heat, but the warmer it gets the less CO2 goes there from the atmosphere.
    (The higher the revelle-factor gets)
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8
Q

Qualitative effect from ocean carbon pumps:

A
  • Carbon is slowely transported to the deep ocean
    (one pump pumps it down and the other pumps it up, via photosytheses and shellbuilding respectively. Some dead biota sinks.)
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9
Q

What is the sauration state for the pumps?

A

(dissolves, omega<1

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10
Q

Why is Ocean carbon reservoir so complex?

A
  • Many parts of the ocean carbon mechanisms are well understod, like most chemical reactions and temperature influence on CO2 solubility.
  • The ocean circulation are vary complex and less understod.
  • The ocean is stabilizing the carbon system by absorbing CO2, but we dont fulle understand what will happen in the future.
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11
Q

Most stable forms of C on Earth:

A

Oxidized

  • CO2
  • CO3(2-)
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12
Q

How is CO2 broken down?

A
  • Most of the CO2 is not broken down at all, only transported around the different reservoirs
  • Photosynthesis stores solar energy by reducing CO2 to organic carbon (Uses exergy from sun to create chemical disequilibria. Essential for life on Earth.)
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13
Q

What other carbon reservoir has most impact on the atmospheric carbon reservoir?

A
  • The Ocean is the largest carbon reservoir and greatly influences atmospheric CO2 levels on 10- 10 000 of years, through many different mechanisms.
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14
Q

Why is it easy to create CO2 and hard to create CH4?

A
  • CH2O is organic C and has oxidation state 0
  • C in CO2 has oxidation state (+4)
  • C in CH4 has oxidation state (-4) and contains stored energy that may be relised by oxidation. Energy demanding to create.
  • Higher oxidation numbers are thermodynamically more stable. (Closer to chemical equilibrium)
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15
Q

Explain:

  • GPP Gross Primary Production
  • NPP Net Primary production
  • NEP Net Ecosystem Production
A
  • Total energy assimilated in photosynthesis
  • Total energy in plant mass production
  • Total energy in accumulating (mainly dead) organic matter
    (Energy for CO2 land fluxes)
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16
Q

How is cellulose broken down?

A
  • Only microbes posses the enzyme cellulase needed for breaking down celulose into its suger components.
    (- These microbes also exists in cows.)
17
Q

3 different forms of living carbon:

A
  • Carbohydrates (cellulose)
  • Proteins
  • Lipids
18
Q

Largest vegitation carbon reservoir?

A
  • Peatland (torvmark)
19
Q

When you have all the rain you need for forestation, what is the main factor that determines forest or no forest?

A

Fires

20
Q

What determines plant carbon densities?

A
  • Temperature
  • Sunlight
  • Water
  • Nutrients
  • Atmospheric CO2 levels
    ( and even if trees grow more quickly, they might not become larger)
21
Q

What is the risks og climate change and desforestation?

A
  • Forest areas might become permanent grasslands. Binds much less carbon than forests.
22
Q

Why is there stil reduced carbon in peatland soils and permafrost soils?

A
  • Peatland: Low oxegyn concentration

- Permafrost: Low temperature

23
Q

How can reduced soil carbon exist?

A
  • Soil carbon is degradable by microbes and enzymes.

- It is the lack of accesability of soil C for the microbes and enzymes that stabilizes soil C over long time.

24
Q

Why does peatlands store carbon?

A
  • Plant litter production outpaces decay
  • slow O2 diffusion in water, slow decay
  • The stored carbon is protected as long as the peat remains waterlogged (wetland).
25
Q

What is the most reduced and energy rich form of carbon?

A

CH4 - Methane

26
Q

How is Methane contributing to climate change?

A
  • GHG
  • 100 times stronger than CO2 /kg
  • Residence time in atm. ca 10 years
  • 2’nd most contributing to Global Warming, after CO2
27
Q

How is CH4 produced?

A
  • oxygen-free conditions, by anarobic bacteria and fungi
  • Inside Earth by high pressure and temp.
  • Incomplete oxidation in combustion
    (- does only occur when low concentration of other electon acceptors, SO4(2-), NO3(1-). Seawater has high SO4(2-) )
28
Q

Why is CH4 produced by ruminants (cows)?

A
  • They have an organ called rumen that hosts the fermentative and methanogenetic microbes, who can break down cellulose, and therefore cows can manage by just eating grass.
29
Q

How much of land carbon do we find in dead organic matter in soils, including peatland and permafrost?

A

80%

30
Q

Where are more than 80% of the living land carbon?

A

In forests

31
Q

How many domestic ruminants do we have in the world today?

A

3.9 billions ( humans = 7.6 billions )

32
Q

The ocean CO2 uptake cycle, chemical formulas:

A
  • CO2(gas) CO2(aqueous) 1 year
  • CO2+H2O+CO3(2-) 2(HCO3(1-)) 10-1000 years
  • CaCO3+CO2+H2O Ca(2+)+2(HCO3(1-)) 1000-10 000 years
33
Q

Examples of a few feedbacks for for land C cycle to atmospheric CO2:

A
  • Photosyntesis (-)
  • Temp (mostly +)
  • Rainfall
  • More grassland
  • Respiration
    etc
34
Q

Time before significant permafrost loss:

A
  • 100-1000 years

- slow feedback

35
Q

Main underlying drivers of C emissions:

A
  • food
  • housing
  • travel (fastest increase)
36
Q

Main sorces for CO2 emissions?

A
  • Fossil energy use is the main cause of CO2 emissions.

- Land has been a large net sourse (acumulated though time) from deforestation to food production.

37
Q

How much higer are CO2 and CH4 concentratiosn now looking back a million years.

A
  • CO2 about 30% higher

- CH4 about 300% (3 times) higher

38
Q

How much of the CO2 emissions has and will the ocean absorb?

A
  • The ocean has absorbed about 30% of teh emissions since 1750, and will most likely absorb about 50% in the long run.
  • Most of the mechanisms of ocean uptake are known with medium or high confidence.
39
Q

How will the land c cykle respond to future CO2 emissions?

A
  • The plats will probably be a net sink.
  • The soil will probably be a net source.
  • The over all responce (feedback) is very uncertain.

Environmental changes (9 decks)

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