3.1.1.3- Carbon Cycle

Geo: Water and Carbon Cycle- Physical Paper

what is the carbon cycle

process of the continuous movement and storage of carbon between different spheres in order for life to be present on Earth

what type of system is the carbon cycle

closed system

importance of the carbon cycle

• needed for photosynthesis in plants; what the rest of life on Earth gets its energy from

• energy sources for industrial development and technology

main stores of the carbon cycle

• lithosphere (rocks and soil)

• hydrosphere (oceans)

• cryosphere (snow and ice)

• biosphere (plants and animals)

what is a carbon sink

a store of carbon that absorbs more than it releases

what is a carbon source

something that releases more carbon than it stores

what is a transfer and what are the transfers of the carbon cycle

• transfer= processes involved in transferring carbon between stores

• combustion

• photosynthesis

• decomposition

• respiration

• burial and compaction

• carbon sequestration

• weathering

why is the distribution of carbon stores across the world varied

• climate and temperature= warmer and more humid areas e.g. rainforests will have more biodiversity, which contains carbon, therefore meaning more carbon stores compared to the arctic where there are few trees and little wildlife

• oceans vs land= a lot more carbon is found in the oceans compared to on land; however there is a lot more below the soils

what comprises the most of the carbon store on Earth

marine sediments and sedimentary rocks in the lithosphere; 99.9% of the total carbon store

two types of carbon cycle

short carbon cycle and long carbon cycle

time period of the short carbon cycle and what transfers take place in it

• within a lifespan; days to years

• photosynthesis

• respiration

• decomposition (depending on the temperature and the O2 supply)

• combustion

how are trees involved in the carbon cycle

• carbon enters the three from the leaves and roots (atmospheric and lithospheric carbon)

• store carbon in their leaves and trunks; wood 50% carbon

• use carbon in photosynthesis to produce glucose

• when they die they decompose; releases the carbon stored in trees back into the environment

• also during winter when deciduous trees shed their leaves; decompose on the forest floor and brings the carbon and nutrients back into the soil

• combustion; when trees are burned this releases the carbon stored inside them back into the environment

• part of the SHORT carbon cycle

what is the terrestrial carbon cycle

the exchange of carbon between land ecosystems (soil, vegetation, microbes etc) and the atmosphere

• photosynthesis

• respiration

• decomposition

what is vegetation succession

process of change in a species that make up an ecological community over time

what is primacy in vegetation succession

surfaces where no vegetation has been before e.g. glacial retreat exposing rock, lava flows, sand dunes etc

what are the two stages of vegetation succession and their alternate names

• primary succession; priseres

• secondary succession; subseres

what is priseres

occurs on any surface that has no previous vegetation eg. bare rock

what is subseres with examples

occurs on surfaces that have already been covered by vegetation (colonised) but have since been modified or destroyed

e.g. fire following lightning strikes, landslides or human activities like deforestation

stages of vegetation succession

• starts with a pioneer community/species (colony)

• takes the form of a ground layer of hardy plants, lichens and mosses as they are able to grow without soil

• these plants then form the soil layer that will allow more complex plants to grow

• the dead plant remains are then decomposed by microorganisms into humus

• this then begins to form a soil and more plants are then able to grow

• each seral stage shows an increase in the height and number of species of plants; growth of biomass and biodiversity

• then climax community is the most advanced stage; largest number of trees and species etc

how is the carbon cycle necessary for vegetation succession

• the carbon in the rocks is what is needed to form the soil layer below so that more complex plants can grow

• decomposition of dead plant matter is also necessary to provide the carbon and nutrients required in the soil

where is soil the best and why is it important in the carbon cycle

• top layer of soil is the richest; most minerals and nutrients for plants and is a different colour to the soil below

• important component of the carbon cycle as it can absorb and store carbon over moderate time periods

• helps to establish life through vegetation succession

what causes vegetation succession

weathering

what is weathering

• the breakdown of rock

• can be biological, chemical or freeze thaw (mechanical)

how does weathering relate to vegetation succession

• chemical weathering of limestone; water reacts with calcium carbonate in the limestone to create carbonic acid

• when rainwater doesn’t evaporate quickly, it stays on the rock surface and reacts with it

• limestone made up of old calcium deposits from dead sea creatures compacted over millions of years

• this releases the minerals inside the limestone and makes indentations, cracks, breaks and ridges etc where plants are able to grow

• vegetation is then able to grow in these cracks and is able to live off of these released minerals

positives and negatives of different height plants for each other

• taller plants will always dominate smaller ones by blocking out the sunlight to the ones further down

• but taller plants also allow smaller plants underneath to grow by providing shelter from harsh elements like rain and wind

how long does the long carbon cycle last

100-200m years; very long time scales

long carbon cycle transfers

• burial and compaction

• carbon sequestration

• weathering (can be short or long term)

• fossil fuel creation

long term carbon cycle in the hydrosphere

• limestone weathering; causes the carbon to be released and flow into oceans via surface runoff; this eventually ends up in oceans

• enters the ocean and carbon enters the shells and skeletons of ocean organisms

• these die and the shells/skeletons fall to the bottom of the ocean, where they collect and pressure compacts them into layers at the bottom of the sea

• over millions of years they form fossil fuels due to the pressure above them from the water and more layers which then causes carbon sequestration

• also releases carbon from the movement of tectonic plate boundaries that release through eruptions of volcanoes

what is carbon sequestration

where carbon is taken from the atmosphere and stored in liquid or solid form

key info about respiration as a transfer of carbon

• short term

• in cells of plants and animals

• CO2 + water → glucose + O2

• gives CO2 back to the atmosphere; biosphere to atmosphere transfer

• glucose energy used for growth and repair, movement, temperature etc

key info about decomposition as a transfer of carbon

• short term

• breakdown of dead organisms matter by decomposers like bacteria, fungi etc

• through decomposition carbon from the bodies returned to the atmosphere as CO2

• some organic material passed into soil where it may be stored for 100s of years

• how plants get more carbon

• decomposer

key info about burial and compaction as a transfer of carbon

• long term

• organic matter buried by sediments and becomes compacted

• over millions of years, these organic sediments containing carbon may form hydrocarbons/fossil fuels

• coral and shelled organisms take up CO2 from the water and convert into calcium carbonate to build their shells

• when dead, shells accumulate on sea bed; some dissolve and rest compact to form limestone

• stores carbon for millions of years

key facts about photosynthesis as a transfer of carbon

• short term

• water + CO2 → glucose + O2

• uses light energy from the sun to do this; occurs in chlorophyll

• releases O2 into the air and removes CO2 from the atmosphere into the biomass of the plants

• some glucose used in respiration and the rest converted into starch

• needs to happen for plants to be able to live

key facts about combustion as a transfer of carbon

• short term

• when organic matter in the presence of O2, it is converted into energy, CO2 and water

• because living things contain carbon so release when burned

key facts about carbon sequestration as a transfer of carbon

• long and short term

• Transfer of carbon from atmosphere to plants, soils, rock and oceans; natural and human 

• Carbon capture and storage (CCS) captures up to 90% of CO2 emissions from fossil fuels 

• Also smaller scale e.g. changing farming practices  

• Also occurs by the compaction of carbon shells at the bottom of the ocean floor  

key facts about weathering as a transfer of carbon

• long or short term

• decay of rocks

• where CO2 absorbed by rainwater to form carbon acid falls on limestone which slowly breaks down the limestone rock, allowing carbon to be absorbed into the water and is then transferred into the water cycle through surface runoff

• can also return to the atmosphere as CO2

two types of period that impacts temperatures on Earth

• glacial period; ice ages and Earth cooler

• interglacial period; where Earth a lot warmer, warm period

natural causes of climate change

• solar output variation

• orbital changes; Milankovitch cycles

• volcanic activity

how does solar output variation cause natural climate change

• some years have more sunspots and some have less, making Earth hotter or colder

• when more of the suns energy is reaching Earth, different areas will have hotter temperatures as a result of this, therefore changing the climate

when does sunspot data show there was a small increase and by how much

• increase between late 1800s and mid-1900s

• at most up to 0.1C-1C of warming

• no significant net change in suns solar output from 1970s-present

how do orbital changes cause natural climate change

• natural shape of the orbit changes ever 10,000 years due to gravity changes with Mars

• this orbital eccentricity causes slight variations in the amount of suns radiation that warms up the Earth

• interglacial= circular orbit; higher and steadier temperatures, meaning more living things, warmer Earth and therefore more CO2

• glacial= more dramatic temperature changes; cooler, less living things, less nutrient cycling so CO2 not rising

why is there a large surge in CO2 released after a glacial period

• higher temperatures so oceans warming and land surface thaws

• also weathering of rocks that are uncovered by melting glaciers

• more living organisms

how does volcanic activity cause natural climate change

• CO2 released by volcanic eruptions enters the atmosphere, increasing the atmospheric greenhouse gas levels and so can cause the temperature to rise

• also releases sulfur dioxide, which is converted into sulfuric acid

• this then forms droplets which reflect radiation from the sun back into space (albedo), lowering the temperature

significance of each natural climate change

• solar output variation= less significant; only in certain areas and not all the time

• Milankovitch cycles= most significant; felt globally and has a large impact on CO2 levels and temperatures

• volcanic activity= sulfuric acid and CO2 released cancel each other out and little change is felt

  • produce less than 1% of CO2 released currently by human activity

when was the Little Ice Age and what happened in it

• 1350-1900

• 0.1-1.0C cooler than the present

• Arctic sea was further south than today

• polar bears carried by ice to Iceland

• farm production declined due to cool temperatures

• rivers and lakes froze much more frequently and thicker than they do today

impacts of deforestation

• loss of habitats for animals; leads to the movement of animals away from these areas or their population decline

• decline in total biomass as trees make up large majority of this

• stored carbon inside of them is released back into the atmosphere; contributes to greenhouse gases in the atmosphere and therefore climate change and global warming

• less interception as the leaves of the tree do not catch the rainfall; means soil degradation, flood risk and overall hydrology of these regions

human causes of climate change

• fossil fuel combustion

• farming (especially of cattle)

• deforestation

• mining

• transport

• energy

• rice paddies

• CFCs

• urbanisation

• industrialisation and manufacturing; disposal

• waste accumulation; produces lots of methane

• aviation

• fracking for shale gas

• construction

• drying out of peatlands

• flaring

what is flaring

where pipes that extract oil (not very deep underground) have excess gas, so they have to burn this excess as there is an explosion risk

three modern reasons for drops in CO2 emissions; when and why caused this

• dissolution of the USSR (1991)= deindustrialisation and different economic systems and new countries with less infrastructure and economic support

• global financial crisis (2008)= less funding and money to put into construction, industry etc

• covid-19 pandemic (2020)= people travelling less because of lockdown, less aviation etc