WCC: Carbon Cycle - Factors Driving Change in the Magnitude of Carbon Stores Over Time Flashcards
Factors driving change in the magnitude of carbon stores over time and space including flows and transfers at plant, sere and continental scales: photosynthesis, respiration, decomposition, combustion, carbon sequestration in oceans and sediments, weathering.
Chemical equation for photosynthesis
6CO2 + H2O -> 6O2 + C6H12O6
Chemical equation for respiration
C6H12O6 + 6O2 -> 6CO2 + 6H2O
Describe a lithosere
- Exposed rock is vulnerable to weathering
- Weathering releases carbon, often dissolved in water
- Lichen and mosses grow on the bare rock and a carbon exchange starts to take place
- As organic matter is added a soil develops that can support a wider range of plants
- Wildlife becomes abundant
- Climatic climax reached
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What have been the maximum and minimum amounts of carbon stored in the atmosphere throughout history? When did they occur?
Atmospheric CO2 possibly reached over 7,000 ppm in the Cambarian period around 500 million years ago. Its lowest concentration has been over the last 2 million years during the Quaternary glaciation when it sank to about 180 ppm.
Where is atmospheric carbon measured on Earth?
At the Mauna Loa Observatory on Hawaii
How has the magnitude of carbon stored in the atmosphere changed since the Industrial Revolution?
Global annual mean concentration of CO2 has increases from 280 ppm in 1958 to 400 ppm in 2015 - a percentage increase of 143% in 30 years
The present concentration of atmospheric CO2 is higher than is has been for how many years?
At least 800,000 years, buts it’s likely the highest that its been in the past 20 million years.
What sources is the recent rise in atmospheric CO2 being attributed to?
Anthropogenic sources, mainly burning fossil fuels and deforestation
What is the name of the graph showing changing concentration of atmospheric CO2?
the Keeling curve
As well as readings from MLO, name another method of measuring atmospheric CO2 over time. How does it work?
Studying the CO2 in trapped ice cores from Antarctica and Greenland can give a proxy measure of the CO2 in the atmosphere at the time is was laid down, allowing the change over time to be seen
When did the daily average of atmospheric CO2 at MLO first exceed 400 ppm?
May 2013
At what rate is atmospheric CO2 currently rising?
2 ppm/year
How is the rate of increase of atmospheric CO2 changing?
It is accelerating
Describe how the magnitude of soil carbon stores can change over time.
Carbon can remain in soils for hundreds of years, however deforestation, land use change and soil erosion can release the stored carbon very rapidly
How is carbon uptake from vegetation changing over space?
Carbon uptake is increasing in the middle and high latitudes of the northern hemisphere, but decreasing in the tropics and southern hemisphere
What is a major reason why less carbon is being absorbed in the tropics and southern hemispere?
Drought
What is photosynthesis?
The process whereby organisms use light energy from the sun to combine CO2 from the atmosphere with water to form carbohydrates which store energy.
Word equation for photosynthesis
Carbon dioxide + water + sunlight -> glucose + oxygen
Which organisms photosynthesise?
Terrestrial plants
Phytoplankton
Photosynthetic algae
Bacteria
What is respiration?
A chemical process that occurs in cells where oxygen from the atmosphere is used to convert glucose into energy to be used in an organism’s life functions
What are the by-products of respiration?
Carbon dioxide and water
Which organisms respire?
All organisms - animals, plants, photosynthetic algae and bacteria
Is there a balance between photosynthesis and respiration? How does this impact the carbon cycle?
No as not all organic matter is used in respiration. This means over time photosynthesis removes more CO2 from the atmosphere than respiration releases.
Word equation for respiration
Oxygen + glucose -> energy + water + carbon dioxide
What is decomposition?
Physical, chemical and biological mechanisms transforming organic matter into increasingly stable forms
What are the biological mechanisms resulting in decomposition of organisms?
Feeding and digestion aided by the catalytic effect of enzymes
Why is decomposition important in the carbon cycle?
It ensures carbon can be continually recycled into the soil and made available for life
What carries out the decomposition process?
Decomposers
What do decomposers do?
Break down the cells and tissues in dead organisms into large biomolecules and then break those down into smaller molecules and individual atoms
Give 3 examples of decomposers.
Earthworms
Fungi
Bacteria
Where is the carbon from decomposed material transferred to?
The atmosphere and soil
What is combustion?
The burning of organic material is the presence of oxygen to give off CO2, water and energy
If an organic material which contains elements as well as carbon, hydrogen and oxygen is combusted, what will form and why?
A variety of pollutant molecules such as sulphur dioxides and nitrogen oxides will form as the other elements will ultimately combine with oxygen
What is carbon sequestration?
The transfer of carbon from the atmosphere to plants, soils, rock formations and oceans
Name 8 transfers driving change in the magnitude of carbon stores.
Photosynthesis Respiration Decomposition Combustion Burial and compaction Carbon sequestration Weathering Oceanic carbon pumps
What is burial and compaction?
Where organic matter is buried by sediments and becomes compacted
What can the burial and compaction of organic matter form over time?
Hydrocarbons such as coal and oil
Give an example to illustrate how burial and compaction can transfer carbon from one store to another
Corals and shelled organisms take up CO2 from the water and convert it into calcium carbonate to build their shells. When they die the shells accumulate on the seabed. Some of the carbonate dissolves, releasing CO2. The rest becomes compacted to form limestone, storing carbon for millions of years.
What is weathering?
The breakdown or decay of rocks in situ
How does weathering act as a transfer in the carbon cycle?
When CO2 is absorbed by rainwater it forms carbonic acid. This slowly dissolves carbonate rocks with the carbon being held in solution. Dissolved carbon moves through runoff to the oceans.
Which soil carbon stores are affected by weathering?
Soil
Peat
Sedimentary rocks
Where does carbon transferred through weathering end up and how does it get there?
The oceans through runoff
What is the oceanic carbon pump?
Where carbon in the surface waters of the ocean sinks to the bottom, transferring carbon from the upper layers to the lower layers of the ocean
What is a greenhouse gas?
Any gaseous compound in the atmosphere that is capable of absorbing infrared radiation, thereby trapping and holding heat in the atmosphere.
What is the most important transfer of CO2 in the oceans?
Vertical deep mixing
What is vertical deep mixing?
The transfer of surface water into the deep ocean and back again.
Explain how the oceanic carbon pump acts as a transfer in the carbon cycle.
It carries carbon from the upper layers of the ocean and the atmosphere to the lower layers of the ocean and the lithosphere
Describe the correlation between water temperatures and the amount of CO2 that can be dissolved
Negative - colder waters can hold more dissolved CO2
Explain the process of vertical deep mixing.
Warm water in oceanic surface currents is carried from the warm tropics to the cold polar regions. It cools, allowing it to store more dissolved CO2 and making it dense enough to sink below the surface layer. Upwelling can bring the cold water back to the surface where it will warm up and release some of its CO2 to the atmosphere.
What is a sere?
A vegetation succession that relates to a specific environment
What is a vegetation succession?
The development and associated changes in a plant community through time
What is a seral stage?
A stage in a vegetation succession
Name 4 seres
Lithosere
Hydrosere
Halosere
Psammosere
What is a lithosere?
Vegetation succession on bare rock
What is a hydrosere?
Vegetation succession in water e.g a freshwater pond
What is a halosere?
Vegetation succession in saline conditions e.g coastal salt marsh
What is a psammosere?
Vegetation succession in coastal sand e.g sand dunes
What happens to the carbon stored in permafrost if it melts?
Is it converted into CO2, CH4, and dissolved organic carbon and transferred to the atmosphere and hydrosphere
What are the 2 primary types of carbon sequestration?
Geologic sequestration
Terrestrial or biologic sequestration
What is geological carbon sequestration?
Where CO2 is captured at its source and then injected in liquid form into underground stores
Give 4 underground stores that can be used for geological sequestration.
Depleted oil and gas reservoirs
Uneconomic coal seams
Deep salt formations
Deep ocean
Why is the ocean capable of absorbing more carbon than terrestrial systems?
It’s bigger
What is terrestrial or biological carbon sequestration?
The use of plants to capture CO2 from the atmosphere and then to store is as carbon in stems, roots and soil
Give 3 disadvantages with terrestrial carbon sequestration.
- A forest planted to capture carbon might lose carbon back to the atmosphere in the event of a fire or disease
- Land-based sequestration plantations are slow growing and require active monitoring and magaement
- The carbon within the systems is never permanently removed from the atmosphere
What is the aim of terrestrial carbon sequestration?
To develop a set of land management practices that maximises the amount of carbon stored in the soil and plant material in the long term
Explain the main advantage of oceanic carbon sequestration.
The sequestered carbon is sunk within weeks or months of being captured, but once in the deep ocean it is in a circulation system measured in thousands of years.
What is soil respiration?
The respiration of bacteria in the soil during decomposition, releasing CO2 into the atmosphere
