The carbon cycle

what is the carbon cycle

the route carbon follows around the earth

a complex process which carbon goes through as it is transformed from organic carbon (living organisms) to inorganic carbon and back again

what is a carbon sink

as reservoiur which absorbs more carbon than it releases

eg the atmosphere, vegetation, soils, oceans and geological stores

what is a carbon source

releases more carbon than it absorbs

Where is carbon stored (from the largest to smallest store)

Lithosphere
Hydrosphere

Pedosphere (soils)

Cryosphere

Atmosphere

Biosphere

What are the transfers within the carbon cycle

photosynthesis- transfers carbon to be stored in the biomass and then passed through the food chain

combustion- carbon stored in living, dead, or decomposed biomass is released into the atmosphere by burning

ocean uptake and loss- the ocean absorbs carbon as well as sea creatures absorbing it, it is transferred back to the atmosphere when deep carbon rich water rises and releases CO2

sequestration- carbon from atmosphere is captured and held in rocks or as fossil fuels, forming due to the compaction of dead matter in the oceans

respiration- transfer from living organisms into the atmosphere

decomposition- carbon from dead biomass into the atmosphere and soil as decomposers break them down

weathering- transfers carbon from the atmosphere into hydrosphere and biosphere as carbonic acid creates acid rain which dissolves rocks to enter the ocean

How long does the slow/long term carbon cycle take

100-200 million years

What are the stages of the long term carbon cycle

the atmosphere contains carbon dioxide which combines with water to form carbonic acid, making rain water slightly acidic

This causes chemical weathering converting silicates to carbonates

The carbonates enter the ocean and are used by sea creatures to form shells. The ocean also absorbs carbon directly from the atmosphere

Sea creatures die and sink to the ocean floor where they become compacted forming sedimentary rocks, with the carbon being stored as fossil fuels

The sea floor moves towards destructive plate boundaries where the carbon stored in the rock is released back to the atmosphere through volcanic eruptions

how much more carbon is moved by the short term carbon cycle

100 to 1000 times more

what are the stages of the short term carbon cycle

carbon dioxide is absorbed by photosynthesis from plants and microscopic life in the sea

plants and animals that eat them break down carbohydrates, releasing carbon dioxide through respiration and methane through digestion

when plants and animals die, bacteria, fungi, and other decomposers break them down, releasing CO2 and methane back into the atmosphere

some of the carbon is released into the soil in the form of hummus

combustion such as wildfires or deliberate burning of fuel also releases carbon into the atmosphere

How can humans impact the carbon cycle

Burning fossil fuels
Deforestation (slash and burn)

Peat bog drainage

Farming and agriculture

Consuming plants and animals

What is organic carbon

Biological carbon which is living eg found in plants and all life forms

What is inorganic carbon

geological carbon found in sedimentary rocks, diamond, graphite, coal, oil, and gas

how can forest fires cause changes

CO2 returns to the atmosphere as trees are burnt
Nutrients are returned to the soil and new saplings can grow

New vegetation absorbs much of the CO2 released creating a negative feedback loop
BUT larger and more frequent fires caused by humans threatens this balance

How can volcanic activity influence the carbon cycle

Magma is made up of 4 parts including CO2

When volcanoes erupt this is released into the atmosphere, and even when not erupting CO2 can be released

BUT

volcanoes have produced less than 1% of the CO2 produced by human activity

Sulfur dioxide has a cooling effect

what are natural causes of changes in the carbon cycle

the earth naturally changes climate as a result of orbital cycles which cause periods of cooling (glacials) and warming (interglacials)

Milankovitch cycles are changes in orbit cycles which affect the incoming solar radiation and so impact global temps by having an eliptical vs circular orbit

how can the oceans create a positive feedback loop

large amounts of freshwater melted from ice disrupts the natural ocean circulation and causes a ‘see-sawing’ of heat between the hemispheres

As the southern ocean is warmed the solubility of CO2 in the water increases and so oceans release more CO2 into the atmosphere

this causes further warming due to the enhanced greenhouse effect, leading to a positive feedback loop

what are human factors driving change in the carbon cycle

cement manufacture
Farming
Livestock farming
Land use change- deforestation
Combustion of fossil fuels

How does cement manufacture impact the carbon cycle

Contributes CO2 to the atmopshere

calcium carbonate is heated, producing lime and CO2 contributing 2-5% of global carbon emissions

for every 1000Kg of cement 900Kg of CO2 is released

How does farming impact the carbon cycle

soil is ploughed and layers are inverted mixing in air and increasing microbial activity and decomposition

Machinery such as tractors release Carbon
Biological processes in rice paddies generate methane making up 10% of all agricultural carbon emissions

Rice is the primary food source for 50% of the world
Livestock farming (See next card)

How does livestock farming impact the carbon cycle

livestock eg cattle ruminate (enteric fermentation) which produces methane as a biproduct

cattle in the US emit around 5.5 million tonnes of methane a year 20% of total methane emissions

methane is 23 times more powerful in trapping heat

how has land use change/ deforestation had an impact on the carbon cycle

13 million hectares of forest cut down each year

slash and burn releases CO2 and less trees means less photosynthesis

secondary impacts include soils drying out and less carbon being stored in the ground

how has land use change (urbanisation) impacted the carbon cycle

over half the world population is urban- expected to reach 60% by 2030

replacing open land with concrete and tarmac- huge impact on short term carbon cycle as stores are replaced or covered

urban areas are 2% of the surface but 97% of all human CO2 emission s

what are the types of carbon sequestration

into the geological store (can be used with carbon capture technology)
into biological matter

into deep oceans

How does combustion of fossil fuels impact the carbon cycle

IPCC 90% of human caused carbon release comes from the combustion of coal, oil, and natural gas

41% from electricity generation

22% from transport
carbon has remained locked in deposits for up to 11 million years and when burnt the stored carbon is released as CO2 as well as water vapour

what have the impacts of the changing carbon cycle been on the ocean

1. oceans absorb 30% of CO2 leading to acidification

since 1750 the pH has dropped by 0.1 leading to coral bleaching- 60% of coral reefs lost by 2030

2. melting sea ice and reduced reflection amplifies warming due to reduced albedo effect

Sea ice provides a habitat for algae- loss impacts food chain

3. Sea level rise- increased melting of land ice means net gain of water