AQA A Level Geography - Carbon Cycle

Major compounds with carbon

Carbon dioxide

Methane

Hydrocarbons

Calcium carbonate

Carbon biomolecules

Fluxes

A movement of carbon between the stores

Long-term/slow carbon cycle

The movement of carbon between atmospheric, oceanic, and lithospheric stores

Short-term/fast carbon cycle

The movement of carbon from living things to the atmosphere and oceans

Time taken for the long carbon cycle

Carbon takes between 100 million and 200 million years to flow through it

Time taken for the short carbon cycle

Moves up to 1000x carbon than the long carbon cycle in a shorter time period

Percent of carbon in the biosphere

0.0012%

Forms of carbon in the biosphere

Living plants and animals including marine/aquatic life

Residence time of carbon in the biosphere

18 years

Percent of carbon in the lithosphere

99.983%

Forms of carbon in the lithosphere

Sedimentary rocks containing carbon (e.g limestone)

Hydrocarbons (fossil fuels)

Marine sediments from marine skeletons

Residence time of carbon in the lithosphere

240-300 million years

Pedosphere

The soil mantle of the earth

Percent of carbon in the pedosphere

0.0031%

Forms of carbon in the pedosphere

Organic matter in the soil, soil organisms, and the remains of dead plants and animals

Residence time of carbon in the pedosphere

Days to 1000s of years

Percent of carbon in the cryosphere

0.0018%

Forms of carbon in the cryosphere

Plant material in the permafrost

Residence time of carbon in the cryosphere

1000s of years

In ice cores, millions of years

Percent of carbon in the atmosphere

0.0015%

Forms of carbon in the atmosphere

Carbon Dioxide (CO2) and Methane (CH4)

Residence time of carbon in the atmosphere

6 years

Percent of carbon in the hydrosphere

0.0076%

Forms of carbon in the hydrosphere

90% dissolved bicarbonate with carbonate ions and dissolved CO2

Residence time of carbon in the hydrosphere

Surface - 25 years

Deep - 1250 years

GtC

Gigatonnes

1 GtC

1 billion tonnes

Hydrocarbons

The largest forms of carbon stored on Earth

PHOTOSYNTHESIS - transfers in the local carbon cycle

Carbon sequestration when living organisms convert CO2 from the atmosphere and water into oxygen and glucose.

Occurs when chlorophyll react with CO2 creating carbohydrate glucose.

Happens at daytime.

RESPIRATION - transfers in the local carbon cycle

Plants and animals convert oxygen and glucose into energy, producing water and CO2.

Happens during the night

Net carbon dioxide absorbers

Plants - they absorb more CO2 than they emit

DECOMPOSITION - transfers in the local carbon cycle

Living organisms die and are broken down by decomposers (detritivores and bacteria). They respire and return CO2 to the atmosphere. Organic matter is also returned to the soil adding carbon to the pedosphere.

Happens more when conditions are right - warm, damp, humid

DIFFUSION - transfers in the local carbon cycle

The oceans absorb CO2 from the atmosphere, increasing ocean acidity. This can harm aquatic life - coral bleaching.

THERMOHALINE CIRCULATION - continental transfer in the carbon cycle

Thermohaline circulation is the global movement of ocean water driven by temperature differences, that ac to store and transport carbon:

1. Warm water from the tropics is carried to colder polar regions due to oceanic surface currents

2. The water cools, and as a result is able to absorb more CO2 from the atmosphere (as gas solubility increases as temperature decreases)

3. As it is colder it is therefore denser and so sinks

4. When it return to the surface it warms, and so releases some CO2 to the atmosphere

5. This makes the ocean act as a carbon pump, giving the ocean a lot more CO2 than it would have if the surface water was not being constantly replenished

WEATHERING/EROSION - transfers in the local carbon cycle

CO2 in air mixes with rainwater creating carbonic acid, which erodes rocks by carbonation weathering.

BURIAL AND COMPACTION - transfers in the local carbon cycle

Shelled marine organisms die and their shell fragments fall and become compacted, forming limestone. Organic matter and decaying marine organisms also compact over time and this forms fossil fuel deposits.

NATURAL CARBON SEQUESTRATION - transfers in the local carbon cycle

Plants sequesters carbon during photosynthesis and stores carbon in its mass.

ARTIFICIAL CARBON SEQUESTRATION - transfers in the local carbon cycle

Carbon Engineering (name of company): Company that sequesters carbon directly from the atmosphere, and converts it into fuel, with is first commercial factor currently under construction in Texas. Initially, it aims to capture 500,000 tonnes annually, with plans to scale up to the full 1 million tonnes capacity.

Carbon Capture and Storage (CCS)

CO2 is captured and transported via pipelines to depleted gas fields and saline aquifers

Advantages of CCS

1. Can be fitted to existing coal power stations

2. Captures 90% of CO2 produced

3. Demand for CO2, transport systems already exist

4. Potential to capture half the world's CO2 emission

Disadvantages of CCS (Carbon capture and storage)

1. Very expensive

2. Increases energy demand for power stations

3. No space in existing power stations

4. Economically viable, used to push oil out of ground, further fossil fuel usage

Sere

Stage of vegetation succession

Vegetation succession

When a plant community develops and becomes more complex over time

Lithosere

Bare rock

Halosere

Salty environment

Psammosere

Sand coastal environment

Hydrosere

Freshwater environment

Carbon source

A store which emits more carbon than it stores

e.g damaged tropical rainforest

Carbon sink

A store which takes in more carbon than it emits

e.g healthy tropical rainforest

Global distribution of carbon

Unevenly distributed

Plant storage focused in tropics/northern hemisphere

Example of a changing carbon store

Trees

Carbon stocks in Brazil and Indonesia

Decrease of around 5 GtC of carbon in the last 25 years

Global pattern of forests

Forests are declining in the tropical areas in the southern hemisphere

Forests are growing in the northern hemisphere

How have Carbon stocks (amount of carbon stored in its ecosystems) in Russia, USA, China changed since the 1990s?

Increases of 0.3, 2.9, 2.3 GtC respectively

Reason for forest growth in Europe and Asia

Conversions of agricultural land and plantations to new forests (eg Afforestation of 148,000 hectares of mangrove in Bangledesh to decrease tidal flooding and cyclones

Change in rate of forest loss

9.5 million hectares per year in 1990s

5.5 million hectares per year in 2010-15

Brazil and carbon storage

Brazil has the most carbon stored on land, and also the most extensive deforested area.

China and forests

Has the largest amount of afforested area

Net Primary Productivity (NPP)

The amount of carbon absorbed by forests

NPP of the Amazon?

Positive all year round - around 13.75 GtC/year, national geographic stating this to be 25% of all terrestrial NPP (as opposed to aquatic NPP)

NPP of deciduous forests

Negative in winter but on average positive all year

WILDFIRES - natural impacts and changes in carbon cycle

Transfers carbon from biosphere to atmosphere by releasing through burning. Extreme wildfires can turn carbon sinks into carbon sources.

Example of wildfire releasing carbon cycle

2019 tundra wildfires in Siberia, Alaska, Canada, and Greenland

2019 Tundra Wildfires

A large area of tundra in Siberia, Alaska, Canada and Greenland experienced wildfires and it contributed to a significant amount of greenhouse gases into the atmosphere.

VOLCANIC ACTIVITY - natural impacts and changes in carbon cycle

Carbon stored within the earth releases during volcanic eruptions as CO2 gas. Not much CO2 is contributed to the overall cycle.

Example of volcanic activity releasing carbon

1815 Mount Tambora eruption

1815 Mt Tambora, Indonesia

Produced sulphur dioxide gas, blocked radiation from the sun, lowered global temps by 0.4-0.7°C the next year.

This reduced photosynthesis, affecting the carbon cycle.

NATURAL CLIMATE CHANGE - natural impacts and changes in carbon cycle

Higher temperatures are associated with higher concentrations of CO2.

An increase in CO2 enhances global warming.

A change in temperature affects the levels of CO2 in atmosphere as melted permafrost releases methane.

COLD CONDITIONS - natural impacts and changes in carbon cycle

Affect weathering - cold water holds more CO2, but colder temperatures mean more freeze thaw, so more chemicals weathering.

Respiration and photosynthesis are reduced.

Decomposition is reduced.

Less sediment transported - more water stored in cryosphere.

Frozen soil stops transfer of carbon.

WARM CONDITIONS - natural impacts and changes in carbon cycle

Increase rate of deposition, increased rate of carbon transfer to soil.

Melting of permafrost, releasing carbon and methane.

This further enhances greenhouse effect.

Causes of the enhanced greenhouse gas effect

Deforestation, farming practices, urbanisation, fertilisers

DEFORESTATION (land use change) - human impacts and changes in carbon cycle

Generates 20% of global CO2 emissions

Burning of wood for heating or 'slash and burn' immediately releases CO2 into the atmosphere.

Converting woodland to grassland reduced ability to absorb CO2.

Where is deforestation concentrated?

Around tropical areas - this is due to building, mining, ranching, and commercial agriculture (soya, palm oil)

FARMING PRACTICES (land use change) - human impacts and changes in carbon cycle

Burning fossil fuels to run machinery.

Ploughing disturbs soil and releases carbon (no till farming)

Slash and burn (26% of Amazon deforested by 2022, 15% of GHG emissions linked to deforestation)

Livestock produces methane (up to 20% of GHG emissions)

Nitrous oxide in farming practices

It is produced by soil microbes that develop in rice fields

The impact is equivalent to 1200 coal power plants.

However, 50% of the world's population relies on rice as a primary food source.

However China have tired to begin shifiting to wheat, increase its production by 40Mt (million metric tonnes) from 1990-2022

Ploughing

Turning over the soil with a plough to prepare for planting

URBANISATION (land use change) - human impacts and changes to carbon cycle

Removal of trees for space for housing and concrete roads

Emissions from transport, industry, and land development

Percent of urban area on Earth

2%

Percent of anthropogenic CO2 emissions from urban land

97%

Percent of anthropogenic CO2 emissions from cement industry

7.5%

Relevance of cement industry in the carbon cycle

Cement and concrete are key building materials

The chemical conversion of limestone to lime creates CO2

The amount of CO2 released depends on types of material used in production (e.g firing of limestone, burning of fossil fuels)

EXTRACTING HYDROCARBONS (fuel extraction/burning) - human impacts and changes to carbon cycle

Carbon is locked up within the lithosphere over a long time.

Extraction of hydrocarbons produce energy and heat - the rate of extraction has increased, moving lithospheric stores to the atmosphere.

Extraction processes are destroying the environment and biodiversity, reducing vegetation, reducing photosynthesis.

Formation of hydrocarbons

1. Carbon diffuses from the atmosphere, allowing phytoplankton and animal life to use the ions for shells/skeletons

2. The phytoplankton and animals die and sink to the ocean floor

3. Over a very long time, they are compressed into oil, coal, and gas.

Hydrocarbon extraction rate (rate at which hydrocarbons, eg oil, gas, coal) are removed from the earth in 1970

6 billion tonnes

Hydrocarbon extraction rate now

15 billion tonnes

Hydrocarbon

Compounds composed of only carbon and hydrogen (oil and natural gas)

BURNING HYDROCARBONS (fuel extraction/burning) - human impacts and changes to carbon cycle

CO2, methane and water vapour are released, they act as greenhouse gases and trap heat within the Earth's atmosphere. This is an increase in greenhouse gases.

1960-2022 rise in global concentrations of CO2

320 ppm to just over 418 ppm

Percent of CO2 emissions coming from burning fossil fuels and industry

90%

Countries dominating CO2 emissions

China and the USA

Carbon Budget

Amount of carbon stored and transferred within the carbon cycle on a global or local scale - it includes carbon emissions by various processes against natural/human sequestration

Calculating the carbon budget

Carbon footprint calculator

Carbon footprint calculator

Total amount of greenhouse gases produced to support human activities, measured in Gtc/yr

Atmospheric impacts of the carbon cycle

- CO2 in atmosphere warms earth

- Increased emissions enhance greenhouse effect

- Wildfires and deliberate burning release carbon quickly into the atmosphere

- Deforestation disturbs carbon cycle

Land impacts of the carbon cycle

- Soil made from organic matter and cycled through carbon system

- Carbon in grass provides food for animals

- Carbon provides energy in fossil fuel/wood form

- Carbon is a valuable resource in diamonds, graphite, charcoal

Ocean impacts of the carbon cycle

- Forms carbonic acid and hydrogen irons that dissolve the Calcium carbonate used to build marine shells and skeletons

-eutrophication (over-enrichment of water with nutrients), leads to extensive growth of algae and aquatic plants which block of sunlight for photosynthesis, which destroys biodiverity

Enhanced greenhouse gas effect

Global warming is currently being caused because of abnormally high levels of greenhouse gases being anthropogenically produced.

Radiative forcing

The difference between incoming solar radiation absorbed by the Earth and the energy radiated back out into space.

Pattern of radiative forcing, and what is it?

Increased in recent years, the balance between incoming solar radiation and outgoing IR radiation within the Earth's atmosphere

Milankovitch Cycles

Changes in the shape earth's orbit and tilt that cause glacial periods and interglacial periods