Water And Carbon: The Carbon Cycle Flashcards
(43 cards)
What is the fast carbon cycle?
The rapid exchange of carbon between the Earth’s atmosphere, living organisms, and the ocean, primarily driven by biological processes like photosynthesis and respiration
What is the slow carbon cycle?
It involves the long-term movement of carbon between the atmosphere, lithosphere (Earth’s crust), and oceans, primarily through processes like rock weathering and the formation of sedimentary rocks
How much carbon is stored in the lithosphere?
- Over 99.9% of the carbon on Earth is stored in sedimentary rocks such as limestone
- About 0.004% of the carbon on Earth is stored in fossil fuels, such as coal and oil, in the lithosphere
- Marine sediments and sedimentary rocks contain up to 100 million GtC
- Soil organic matter contains between 1500 - 1600 GtC
- Fossil fuel deposits of coal, oil and gas contain approx. 4100 GtC
- Peat, which is dead but decayed organic matter found in boggy area, contains approx. 250 GtC
How much carbon is stored in the atmosphere?
- Carbon is stored as carbon dioxide and in smaller quantities as methane (CH4) in the atmosphere.
- The atmosphere contains about 0.001% of the Earth’s carbon.
- Estimated store of 720-800 GtC (about 0.04% of the atmosphere)
- Measured in the Mauna Loa observatory (MLO) on Hawaii since 1958
How much carbon is stored in the hydrosphere?
- Carbon dioxide is dissolved in rovers, lakes and oceans.
- The oceans are the second largest carbon store on earth, containing approximately 0.04% of the Earth’s carbon. The majority of carbon here is found deep in the ocean in the form of dissolved inorganic carbon.
- A small amount is found at the ocean surface where it is exchanged with the atmosphere.
- Surface layer (euphotic zone)—> where sunlight penetrates so that photosynthesis can take place contains approx. 900 GtC
- Intermediate (twilight) zone —> and the deep layer of water contain approx. 37100 GtC
- Living organic matter —> approx. 30 GtC and dissolved organic matter 700 GtC
This gives a total for oceanic carbon of between 37000 GtC to 40000 GtC
What is the biological carbon pump?
- Phytoplankton Photosynthesis:
Tiny marine plants (phytoplankton) use photosynthesis to absorb carbon dioxide from the surface waters, converting it into organic matter. - Sinking of Organic Matter:
As phytoplankton and other marine organisms die, their remains (and fecal matter) sink to deeper waters. - Deep Ocean Storage:
A portion of this sinking carbon is sequestered in the deep ocean for centuries to millennia, effectively removing it from the atmosphere.
What is the carbonate pump?
- Shell-Building Organisms:
Many organisms, like corals and plankton, use carbon to create calcium carbonate shells. - Seafloor Burial:
When these organisms die, their shells sink to the ocean floor, where they accumulate and eventually become sedimentary rock, like limestone, further sequestering carbon. - Long-Term Storage:
This carbonate-based sediment can remain buried for millions of years, effectively storing carbon for the long term.
What are the other factors, aside from carbon pumps, that contribute to oceanic storage of carbon?
- Ocean Solubility: The ocean’s surface water dissolves carbon dioxide from the atmosphere.
- Thermohaline Circulation: The ocean’s deep circulation (thermohaline circulation) also plays a role in distributing carbon and nutrients throughout the ocean.
- Mixing and Advection: Physical mixing of water and the movement of suspended organic matter can also contribute to the transfer of carbon to the deep ocean.
How much carbon is stored in the biosphere?
- Carbon is stored in the tissues of living organisms. It is transferred to the soil when a & living organisms die and decay.
- The biosphere contains approximately 0.004% of the Earth’s total carbon.
- In tropical forests approx. 50% of the carbon is stored in the biomass
- Living vegetation —> at the global level, 19% of the carbon in the Earth’s biosphere is stored in plants
- Biomass —> varies from between 35-65% of the dryweight is carbon
- Plant litter —> leaf tissues account for about 70% of litter in forests. Plant litter includes leaves, cones, needles, twigs and bark
How much carbon is stored in the cryosphere?
- The cryosphere contains less than 0.01% of the Earth’s carbon.
- Most of the carbon in the cryosphere is in the soil in areas of permafrost where decomposing plants and animals have frozen into the ground.
What is the carbon cycle?
The process by which carbon is stored and transferred. The carbon cycle is a closed system - there are inputs and outputs of energy, the amount of carbon in the system remains the same. However, some carbon is locked away in long-term stores, e.g. rock and fossil fuels deep underground. If these are released by e.g. burning fossil fuels, they are effectively inputs.
What is the role of photosynthesis in the fast carbon cycle?
- Photosynthesis transfers carbon stored in the atmosphere to biomass.
- Plants and phytoplankton use energy from the Sun to change carbon dioxide and water into glucose and oxygen. This enables plants to grow.
- Carbon is passed through the food chain and released through respiration and decomposition.
What is the role of respiration in the fast carbon cycle?
- Respiration transfers carbon from living organisms to the atmosphere.
- Plants and animals break down glucose for energy, releasing carbon dioxide and methane in the process.
What is the role of combustion in the fast carbon cycle?
Combustion transfers carbon stored in living, dead or decomposed biomass to the atmosphere by burning. Wildfires cause carbon flow.
What is the role of decomposition in the fast carbon cycle?
- Decomposition transfers carbon from dead biomass to the atmosphere and the soil.
- After death, bacteria and fungi break organisms down, CO2 and methane are released. Some carbon is transferred to the soil in the form of humus.
What is ocean uptake and loss?
- CO2 is directly dissolved from the atmosphere into the ocean. It is also transferred to the oceans when it is taken up by organisms that live in them, e.g. plankton.
- Carbon is also transferred from the ocean to the atmosphere when carbon-rich water from the deep in the oceans rises to the surface and releases CO2.
What is chemical weathering?
Chemical weathering transfers carbon from the atmosphere to the hydrosphere and biosphere.
Atmospheric carbon reacts with water vapour to form acid rain falls onto rocks, a chemical reaction occurs which dissolves the rocks. The molecules resulting from this reaction may be washed into the sea. Here, they react with CO2 dissolved in the water to form calcium carbonate, which is used by sea creatures, e.g. to make shells.
What is sequestration?
- Carbon from the atmosphere can be sequestrated in sedimentary rocks or as fossil fuels. Rocks and fossil fuels from over million of years when dead animal and plant material in the ocean falls to the floor and is compacted.
- Carbon in fossil fuels is sequestered until we burn them.
What are the four fast carbon stores?
Photosynthesis, respiration, combustion and decomposition
What is the slow carbon store?
Sequestration
What is an example of a positive feedback cycle in the water cycle?
Temperatures rise → Evaporation increases → amount of water vapour in atmosphere increases → greenhouse effect increases → etc
What is an example of a negative feedback cycle in the water cycle?
Temperatures rise → Evaporation increases → Amount of water vapour in atmosphere increases, causing more clouds to form → Increased cloud cover reflects more of Sun’s energy back into space → Temperatures fall.
What is an example of a positive feedback cycle in the carbon cycle?
Temperatures rise → Plant respiration rate increases → Amount of CO2 in atmosphere increases → greenhouse effect increases → etc.
What is an example of a negative feedback cycle in the carbon cycle?
CO2 in atmosphere increases → Extra CO2 causes plants to increase growth → plants remove and store more CO2 from atmosphere → Amount of CO2 in atmosphere reduces.
