The Carbon Cycle Flashcards
(21 cards)
What is the carbon cycle?
Biogeochemical cycle where carbon is stored and moved between spheres through flows and fluxes. It’s a closed system. Stores add carbon to the atmosphere and sinks remove it.
What are the major stores of the carbon cycle?
Oceans, atmosphere, biosphere, lithosphere.
Describe the geological carbon cycle.
The ‘slow’ cycle. Centred on the huge carbon store in rocks and sediments with reservoir turnover rates of at least 100000 years. Organic matter that is buried in deep sediments, protected from decay, takes millions of years to turn into fossil fuels. Carbon is exchanged with the fast component through volcanic emissions of CO2, chemical weathering, erosion and sediment formation on the sea floor.
Describe the processes within the geological carbon cycle.
Weathering - breakdown of rocks.
Lithification - process in which sediments compact under pressure and become solid rock.
Dissolution/diffusion - CO2 is absorbed/dissolved by oceans.
Volcanic outgassing - CO2 is released during volcanic eruptions.
Describe the biological cycle.
Movement of carbon through the process of photosynthesis and cellular respiration, also the consumption of living matter by other organisms. It holds 1000x more carbon than the geological cycle.
What is carbon sequestration?
The removal and storage of carbon from the atmosphere in sinks.
It occurs through photosynthesis and is held in oceans/forests/soils.
It’s crucial as it prevents too much carbon being in the atmosphere and helps regulate the planetary temperature balance.
How much carbon is being added by humans?
8 PgC yr-1 into the atmosphere and the earth takes 4 PgC yr-1.
What is the reservoir turnover time?
How long carbon spends in a store (rock has long turnover).
Describe the processes within the terrestrial cycle.
Limestone bedrock - shell building organisms forming layers and turned into rock.
Coal - biologically derived from decayed organisms.
Shale - biologically derived from organisms embedded in mud.
Coral - organisms cemented together over time to form limestone structures.
What happens to carbon in water?
Carbon sinks in cold water and then moves around the planet, it comes out again when it meets warms water.
Describe terrestrial sequestration.
Plants capture CO2 from the atmosphere and the store it as carbon in the stems and roots of plants as well as in the soil. The plants retain and use the carbon to live and grow.
Terrestrial carbon is found in plants/animals/soil and microorganisms. This is the quick cycle.
Primary consumers (bugs/herbivores) feed on producers and return carbon through respiration too. Other organisms eat dead plants/animals/waste and are biological decomposers. When plants/animals die, remains fall to the ground and carbon is transferred to soil. Carbon is stored in soil as organic matter and respired by plants/animals/bacteria/fungi.
Describe the biological ocean pump.
-Phytoplankton float on the ocean’s surface for sunlight for photosynthesis. Carbon is absorbed by them for food, carbon is then passed up the food chain by consumers which release CO2 back into the ocean and atmosphere. Around 0.1% reaches the sea floor after the dead phytoplankton sink where they decompose/turn into sediment. Phytoplankton sequester over 2 billion metric tonnes of carbon a year in the deep ocean.
Describe the carbonate ocean pump.
-Relies on inorganic carbon sedimentation. Marine organisms use calcium carbonate to make hard outer shells and inner skeletons like some plankton species.
-When organisms die and sink, many shells dissolve before reaching the sea floor sediments. This carbon becomes part of the deep ocean currents. Shells that dont dissolve build up slowly on the sea floor forming limestone sediments like cliffs.
Describe the thermohaline ocean pump.
-Based on the oceanic circulation of water including upwelling/downwelling and the thermohaline current.
-The colder the water, the more potential CO2 has of being absorbed. Warm waters release CO2 into the atmosphere.
-As major currents like the North Atlantic Drift, move waters from the tropics to the poles, the water cools and can absorb more atmospheric CO2. High latitude and Arctic zones with deep oceans have cooler water, which sinks due to its higher density, taking CO2 accumulated at the surface downwards.
How much more carbon do the oceans hold than the atmosphere?
50x more carbon.
Describe the process of chemical weathering.
1- In the atmosphere, carbon reacts with CO2 and carbonic acid forms. Once it reaches the surface as rain, it reacts with some surface minerals, dissolving them.
2- These dissolved ions are carried by rivers to oceans which combine with bicarbonate ions and precipitate as minerals.
3- Deposition and burial turns the calcite sediment into limestone.
4- Subduction of the sea floor under continental margins by tectonic spreading.
5- Some of this carbon rises to the surface, then degassed to the atmosphere.
Describe the process of chemical weathering.
1- In the atmosphere, carbon reacts with CO2 and carbonic acid forms. Once it reaches the surface as rain, it reacts with some surface minerals, dissolving them.
2- These dissolved ions are carried by rivers to oceans which combine with bicarbonate ions and precipitate as minerals.
3- Deposition and burial turns the calcite sediment into limestone.
4- Subduction of the sea floor under continental margins by tectonic spreading.
How is carbon released into the atmosphere through volcanic eruptions?
There are small amounts of CO2 in the Earth’s crust. Disturbance by volcanic eruptions/earthquake activity may allow pulses/more diffuse fluxes into the atmosphere.
What impact has climate change had on the ecosystems and habitats?
-Coral reefs dying, in 2000, 10% of coral reefs were dead.
-Less food in the rainforests, more forest fires, more rainforest droughts, extinction of species.
Describe the positive feedback loop in the tundra biome.
Methane emissions-> increased greenhouse emissions->increased warming of tundra which releases methane->back to start.
Describe the nutrient cycle.
The warm, forest floor conditions and the insects break down dead leaves/plants. This provides nutrients that are easily absorbed by roots. Due to the abundance of forest vegetation they are used up quickly. However if the protective canopy is taken away, soil becomes infertile as nutrients are leached out of the soil, top soil is easily washed away.
