The Carbon Cycle

From CGP book

Carbon is found in…

All of the earth’s systems

What are organic stores of carbon vs inorganic ones

Organic stores are living things and inorganic stores are non living things like rocks, gasses and fossil fuels

How is carbon stored in the lithosphere

Rocks and fossil fuels in the crust and upper mantle

How is carbon stored in the atmosphere

Carbon dioxide and methane

How is carbon stored in the hydrosphere

It is dissolved in rivers, lakes and oceans as CO2

How is carbon stored in the biosphere

In the tissues of living organisms and as organic matter in soil.

How is carbon stored in the cryosphere

Mostly in the soil in areas of permafrost

How much of the earth’s carbon is stored in rocks and what type are they

About 99.9% in sedimentary rocks like limestone

What percentage of the earth’s carbon is stored in fossil fuels

about 0.004%

Oceans are the ____ largest store of carbon on earth

second

How much carbon is stored in the oceans

0.04%

How is most carbon stored in the oceans

Dissolved inorganic carbon deep in the ocean

Where in the ocean is a small amount of carbon found and what is it for

Near the surface where it is exchanged with the atmosphere

How much carbon does the atmosphere contain

0.001%

How much of the earth’s carbon is stored in the biosphere

0.004%

How is carbon transferred into the soil

When living organisms die and decay

How much carbon is stored in the cryosphere

less than 0.01%

What type of system is the carbon cycle

A closed system where there are inputs and outputs of energy but the amount of carbon in the system stays the same

What is the carbon cycle

The process by which carbon is stored and transferred

What is it called when some carbon is locked away in long term stores

Sequestered carbon, like the carbon in rock and fossil fuels deep underground

If sequestered carbon is released they are effectively

inputs

What are the 7 main flows of carbon

• Photosynthesis

• Respiration

• Decomposition

• Combustion

• Ocean uptake and loss

• Weathering

• Sequestration

What is photosynthesis

Using energy from the sun, carbon dioxide and water are converted into glucose and oxygen.

How does photosynthesis transfer carbon

from the atmosphere to biomass

What kind of organisms photosynthesise and what does it enable them to do

plants and phytoplankton and it enables them to grow

How does combustion transfer carbon

from carbon stored in living, dead or decomposed biomass to the atmosphere via burning

Wildfires

How can the oceans transfer carbon (3 ways)

• When it is taken up by organisms that live in them like plankton

• CO2 directly dissolved from the atmosphere into the ocean

• Carbon transferred from the ocean to the atmosphere when carbon rich water from deep in the oceans rises to the surface and releases CO2

What does it mean for carbon to be sequestered?

It means carbon is captured and held, usually for a long time.

What is natural sequestration

the process where carbon is taken from the atmosphere and stored in solid or liquid form such as the rocks of the lithosphere and the plants of the biosphere

Carbon from the atmosphere can be sequestered in what

Sedimentary rocks and fossil fuels

How do rocks and fossil fuels form

Over millions 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 when?

We burn them in combustion

How does respiration act as a transfer of carbon

It transfers carbon from living organisms to the atmosphere when animals break down glucose for energy and release carbon dioxide and methane in the process

How does decomposition act as a transfer of carbon

it transfers carbon from dead biomass to the atmosphere and soil as humus

How does decomposition work

After death, bacteria and fungi break organisms down and CO2 and methane are released

How does chemical weathering act as a transfer of carbon

It transfers carbon from the atmosphere to the biosphere and hydrosphere

What is the main way in which weathering acts as a transfer of carbon

The main process is a form of chemical weathering called carbonation

What happens when atmospheric carbon reacts with water vapour

The atmosphere has CO₂ that combines with water vapour to produce a weak acid known as carbonic acid, this makes precipitation slightly acidic

What does acid rain do when it falls on rocks

It causes a chemical reaction which dissolves the rocks and releases minerals like calcium into the sea

What happens to the dissolved mineral molecules like calcium when they are washed into the sea

They react with CO2 dissolved in the water to form calcium carbonate which is used by sea creatures to do things like make shells

Carbon flows happen over…

Different time and spatial scales

What is a spatial scale

The size or extent of the area being discussed, where something is happening and how big that where is, for example, local, regional and national are spatial scales

Examples of fast carbon flows

• photosynthesis

• Respiration

• Combustion

• Decomposition

Examples of slow carbon flows

Sequestration, it takes millions of years for carbon to be sequestered in sedimentary rocks

What are the different spatial scales carbon transfers can happen at

Plant scale

Sere scale (ecosystem scale)

Continental scale

Every carbon store can be both a…

source and a sink for carbon.

What does ‘sere’ actually mean in geography

A stage in the succession of vegetation in an ecosystem

What is succession

The natural development of an ecosystem over time, it includes the changes and evolutions of plant communities

How does the carbon cycle change across the sere scale?

Later seres (e.g. mature woodland) store more carbon in biomass and soil than early seres (e.g. grassland).

How does the water cycle change across the sere scale?

More developed seres have greater interception, infiltration, and evapotranspiration due to more vegetation.

What is a psammosere?

A type of ecological succession that develops on sand dunes, where vegetation slowly colonises over time

what are the main carbon flows/transfers at a plant scale

Respiration and photosynthesis

At a sere/ecosystem scale, what carbon transfers occur

respiration and photosynthesis as well as combustion and decomposition

At a continental scale, what carbon transfers occur

All of them, including sequestration

What are the two main ways the carbon cycle can be changed

Natural processes and human activities

What are the 2 natural processes that change the magnitude of carbon stores

Wildfires and volcanic activity

How do wildfires alter the magnitude of carbon stores (2 points)

They rapidly transfer large quantities of carbon from biomass or soil into the atmosphere as carbon dioxide and carbon monoxide

Loss of vegetation due to fires decreases photosynthesis so less carbon is removed from the atmosphere

What percentage of wood is carbon

About 50% (dry weight)

In the long term how do wildfires alter the magnitude of carbon stores

Fires can encourage the growth of new plants as they increase the fertility of soils, which then photosynthesise and take in carbon from the atmosphere

Depending on regrowth what effect can wildfires have on overall atmospheric carbon

They can have a neutral effect if there is enough regrowth

How can volcanic activity alter the magnitude of carbon stores

Carbon stored in magma is released during eruptions and the majority enters the atmosphere as CO2

How significant is volcanic activity for changes within the carbon cycle

Recent eruptions have released much less CO2 than human activities, but there is the potential for a very large eruption to disrupt the carbon cycle significantly

Since when have human impacts on the carbon cycle increased significantly

Since the Industrial Revolution in the 18th century.

Which carbon flows are humans making happen more than they would naturally?

Flows from the lithosphere and biosphere to the atmosphere

What are the main human causes of changes to the carbon cycle

• Hydrocarbon (fossil fuel) extraction and use

• Farming practices

• Deforestation

• Land use changes

How does fossil fuel extraction and use lead to changes in carbon cycle

The extraction and combustion of fossil fuels releases CO2 into the atmosphere which would have remained sequestered in the lithosphere

How do farming practices impact the carbon cycle ( main points)

• Animals release CO2 and methane when they respire and digest

• Ploughing can release CO2 held in the soil

• Growing rice in paddies releases a lot of methane because flooded rice fields have little oxygen, so microbes break down organic matter anaerobically and release methane instead of carbon dioxide.

How has the growing global population affected carbon emissions from farming

Food production has risen to meet demand so emissions from farming practices have increased, mechanisation of farming also has exacerbated this

How does deforestation impact the carbon cycle

Clearance reduces the size of carbon stores and if the forest is cleared by slash and burn practices, there is a rapid flow of carbon from the biosphere to the atmosphere

How does land use change change the carbon cycle

Change of land use from natural/agricultural to urban is a major source of carbon in 2 ways

• Vegetation removal for buildings reduced carbon storage in the biosphere

• Concrete production releases lots of CO2

What is the carbon budget

The difference between the inputs of carbon into a subsystem and the outputs of carbon from it

Example of inputs and outputs of carbon in the atmosphere

Inputs of carbon come from volcanic eruptions, combustion of fossil fuels and respiration

Outputs occur through photosynthesis, sequestration, decomposition and chemical weathering

The balance of inputs and outputs of a subsystem determines what

Whether it is a carbon source or carbon sink

What is a carbon source

The outputs of carbon outweigh the inputs, meaning it releases more than it absorbs

What is a carbon sink

the inputs of carbon outweigh the outputs, meaning it absorbs more than it releases

What are the 3 things that are most effected when there is a change to the carbon cycle

• atmosphere and climate

• land

• oceans

How is CO2 used in the oceans

by organisms like phytoplankton and seaweed to photosynthesise and other creatures to form calcium carbonate shells and skeletons

How do increased levels of atmospheric CO2 affect the ocean

It can increase the acidity of oceans as they initially absorb more of it which can harm marine life

An example of global warming affecting the oceans

Organisms that are sensitive to temperature like phytoplankton may be unable to survive at higher temperatures so their numbers decrease and they take up less CO2 through photosynthesis so less carbon removed from the atmosphere

What is the issue with warmer water in the carbon cycle

It is less able to absorb CO2 so as temperatures rise, the amount of CO2 dissolved in the sea decreases which can exacerbate atmospheric CO2 levels and contribute to further warming.

How might changes in the carbon cycle reduce the amount of carbon stored in the land (2 points)

warmer temperatures caused by global warming are making the permafrost melt which releases the carbon that they stored into the atmosphere

Warmer temperatures can increase incidence of wildfires

What are greenhouse gasses

Gases in the atmosphere that trap heat, such as carbon dioxide, methane, and water vapour, contributing to the greenhouse effect and global warming.

What is global warming

as concentrations of greenhouse gasses in the atmosphere increase, temperatures will rise due to the enhanced greenhouse effect

How is water and carbon fundamental to life

All living things contain carbon and all living things need water to survive

what is the global carbon budget

1 trillion tonnes

How much of the carbon budget have we already burned through

approximately 52%

What is the natural greenhouse effect

where the suns rays travel into the earth’s atmosphere as visible radiation and reflect off of the earth’s surface as infrared radiation. The layer of gasses surrounding the earth trap in the heat which is reflected and this is what keeps earth warm

What is the enhanced greenhouse effect

the additional warming due to there being a higher amount of greenhouse gasses in the atmosphere which further trap the infrared radiation emitted from the earth’s surface

natural causes of greenhouse gas emission

volcanic activity, fluctuations in solar output

5 consequences of enhanced greenhouse effect

• thermal expansion of water molecules and melting of ice causing sea level rise and flooding

• ocean acidification due to gasses dissolving in sea

• melting ice caps

• More extreme weather

human causes of greenhouse gas emission (4)

• burning of fossil fuels releases co2

• deforestation destroys carbon stores and means less can be absorbed

• decomposing waste in landfill releases methane

• agriculture releases nitrogen oxides

CO2 taken up by plants has increased since when

1960, possibly due to green revolution

what percentage of emissions are removed by vegetation

25%

how has increasing agricultural intensity altered the carbon cycle

more crops from less land increases CO2 take up

what is ‘carbon fertilisation’

The process whereby more CO2 available in the atmosphere results in more photosynthesis and more plant growth

If 10% of permafrost were to melt how much would global temperatures increase by

approximately 0.7 to 1.0 degrees Celsius by 2100

how much of the CO2 released into the atmosphere has been taken up by the oceans

about 30%

Since 1750 how has the ocean’s pH changed

a 30% decrease in alkalinity, leading to ocean acidification.

dissolving carbon into the ocean creates what

carbonic acid

what does carbonic acid in the ocean react wit

carbonate ions in the water to form bicarbonate