global carbon cycle Flashcards
what does the global carbon cycle consist of and how is it connected?
number of stores and sinks connected by flows of carbon
what are the principle stores?
atmosphere
the oceans
carbonate rocks
fossil fuels
plants and soils
what is the biggest store?
carbonate rocks
how much carbon is stored in carbonate rocks?
60 to 100 trillion tonnes
what are the 2 strands to the carbon cycle?
fast carbon cycle
slow carbon cycle
what is the slow carbon cycle?
the movement of carbon between the atmosphere, lithosphere and the oceans.
how does the carbon move in the slow carbon cycle?
CO2 diffuses from the atmosphere to the oceans, where marine organisms make their shells and skeletons. when they die, the remains of these organisms sink to the ocean floor. They accumulate over millions of years and convert to carbon rich sedimentary rock due to heat and pressure. Then, sometimes they are subducted at plate boundaries, and are vented to the atmosphere in volcanic eruptions. Other rocks are exposed to the surface, and attacked by chemical weathering processes such as carbonation, forming an acid, which gets into streams, rivers, and oceans.
how much carbon moves in the slow carbon cycle?
10-100 million tonnes/year
what is the typical residence time for carbon held in sedimentary rocks?
150 million years
how much carbon is released by the volcanic eruptions?
200 million tonnes
how much quicker are transfers in the fast carbon cycle than the slow?
10-100x
what are the main stores in the fast carbon cycle?
atmosphere
oceans
living organisms
soils
what are the 2 key components to the fast carbon cycle?
plants
microscopic physoplankton
how much carbon goes through the fast carbon cycle/ year?
1 billion to 100 billion tonnes / year
how do plants remove carbon from the atmosphere?
they absorb CO2 from the atmosphere and combine it with water to make carbohydrates } photosynthesis
(fundamental to the food chain)
what are 3 processes that result in the release of CO2 to the atmosphere?
respiration
decomposition
fires
describe how carbon moves between the oceans and the atmosphere
atmospheric CO2 dissolves in the ocean surface waters, while oceans ventilate CO2 back to the atmosphere.
how long does the exchange take between the atmosphere and the ocean?
carbon molecules are stored for 350 years by natural sequestration.
what else is a very carbon dense area, where carbon is stored?
peat bogs
What are the 6 processes involved in carbon exchange?
Precipitation
Photosynthesis
Weathering
Respiration
Decomposition
Combustion
Explain how precipitation works in the carbon cycle
Atmospheric C02 dissolves in rainwater to form weak carbonic acid. This is natural process
However, rising concs of CO2 in the atmosphere due to anthropogenic emissions, have increased the acidity of the rainfall, meaning increased acidity of ocean surface water + harmful effects on marine life
Explain how photosynthesis works in the carbon cycle
The flux of carbon from atmosphere - land plants - phytoplankton via photosynthesis is around 120 GT / year
Plants release CO2 to atmosphere during respiration which occurs while they use energy created by photosynthesis
What is the photosynthesis word equation?
Carbon dioxide + water = glucose + oxygen
What is the photosynthesis chemical equation?
6CO2 + 6H2O → C6H12O6 + 6O2
Explain how weathering works in the carbon cycle?
Most weathering involves rainwater which contains dissolved CO2, from soils and atmosphere. As rainwater is a weak carbonic acid, it dissolves limestone and chalk through carbonation which releases carbon to rivers oceans and atmosphere
Biological weathering such as chelation contribute to rock breakdown - rainwater and dead decaying organic material attack rock mineral
How much carbon does weathering transfer to the atmosphere and oceans / year?
0.3 billion tonnes / year
Explain respiration’s effect on the carbon cycle
Emits carbon
Explain effect of decomposition on the carbon cycle
Decomposed organisms eg fungi + bacteria break down dead organic matter, realising carbon to the atmosphere and nutrients to the soil
Rates depend on climatic condition
Explain effect of combustion on carbon cycle
Organic material burns in the presence of carbon
Acts as natural fuel in wildfires…
Also results from human activities
Releases carbon to atmosphere
What is downwelling?
When surface ocean currents transport water and dissolved CO2 polewards, where or cold, becomes more dense and sinks
What is downwelling known as?
Physical/ inorganic pump
What is upwelling?
Deep ocean currents transport carbon to areas of upwelling
There, cold, carbon rich water rises to the ocean surface and CO2 diffuses back into the atmosphere
What is the biological/ organic pump?
Carbon exchanged between oceans and atmosphere through actions of marine organisms
Where does downwelling occur?
Cold areas
Iceland, greenlands, North Atlantic
Where does upwelling occur?
Warmer areas
Equator
