booklet 6- 3.1.1.3- the carbon cycle

Question 1

what physical factors impact stores and transfers in the carbon cycle?

Answer 1

• natural climate change (ice ages, el Nino + nina, milankovitch cycles, continental drift + weathering, permafrost melting)
• wildfires
• volcanic acivity

Question 2

explain natural climate change factors -ice ages, el Nino + Nina, Milankovitch cycles

Answer 2

ice ages- last one= 25,000 years ago
- colder temps= more ocean absorption of CO2= less in atmosphere
- warmer temps= melting ice, carbon released, more respiration, decomposition, ocean outgassing
- El Nino- short term warming phase= reduce CO2 absorption from oceans (La nina= opposite)
- milankovitch cycles- long term
–> earths orbit changes in 3 cycles which affects solar radiation= leads to glaciations (ice ages) + interglacial warming
(procession (wobbling of earths axis= changing time of seasons + range of temps.), eccentricity, obliquity (more tilt= warmer summers, cooler winters (vice versa))

Question 3

explain natural climate change factors - continental drift + weathering, permafrost melting

Answer 3

• continental drift + weathering
  –> long term tectonic movements affect ocean currents etc= alter carbon storage
  –> high mountains= more chemical weathering= more CO2 from atmosphere absorbed through carbonic acid reactions
  –> continents move= ocean currents shift= influence global carbon cycle + climate change
• permafrost melting
  –> short term
  –> cold periods = carbon locked in permafrost + ocean methane hydrates
  –> temps rise= permafrost melts= releases CO2 + methane= warming (positive feedback)–> occurs at arctic

Question 4

explain the factor wild fires

Answer 4

• short term
• burning= transfers carbon from biosphere to atmosphere as CO2 –> can turn areas from being carbon sinks to a carbon source
  BUT burning can encourage growth of plants long-term so wildfires are only a short term fluctuation in the carbon cycle.
• rising temps= increase wild fires= contributes to greenhouse gases into atmosphere –> more common in summer where lower levels of precipitation
  –> real world example= Los Angeles 2025 (January), 25 deaths, 12,000 structures destroyed, 180,000 buildings evacuated, $275 bn worth of damage, 40,588 acres burned

Question 5

explain the factor volcanic activity

Answer 5

‘long term changes’
- carbon stored in rocks for millions of years and released mainly as CO2 to atmosphere through volcanic eruptions = warming
- SO2 from volcanoes can lead to temporary cooling by reflecting sunlight
—> Mount Pinatubo released 42 mill tonnes of CO2 and SO2
- weathering of volcanic rocks = removed CO2 from atmosphere via chemical reactions = long term cooling
- 130-380 mill tonnes of CO2 = released annually through volcanic activity vs 30 bn tonnes released by human activities (so is relatively low)

Question 6

what are the human/anthropogenic factors that impact stores and transfers in the carbon cycle?

Answer 6

• hydrocarbon fuel extraction and burning
• farming practices
• deforestation
• urbanisation

Question 7

explain hydrocarbon fuel extraction and burning

Answer 7

• extraction —> carbon diffuses from atmosphere = phytoplanktons etc use carbonate ions for shells —> when they die = they sink and compress to oil, coal and gas over a long period of time
  —> ppl extract them for energy and heat BUT rate of extraction = increased carbon stores in atmosphere and decreased in the lithosphere —> extraction is now 3x faster since 1970s —> extraction damages environment and biodiversity = less vegetation to photosynthesise CO2 from atmosphere
• burning —> releases CO2, methane, water vapour= greenhouse gases that trap heat in earths atmosphere
  hydrocarbon = fossil fuels —> they lock carbon in lithosphere for long periods of time
• increase CO2 in atmosphere when burnt= climate change —> increased significantly following industrial revolution —> before in 1750 CO2 in atmosphere was 280 ppm vs 420 ppm in 2023
• long term carbon stores
• human burning fossil fuels (normally rapid and large scale and disturbs natural carbon cycle) = release carbon that was locked away for millions of years = release CO2 —> 90% carbon release comes from this
• more developed countries = release more CO2

Question 8

explain farming practices

Answer 8

• release carbon indirectly through burning fossil fuels to run machinery and fertilisers based on fossil fuel —> BUT started using organic fertilisers rather than nitrogen
• direct release of carbon through ploughing (ploughing and overgrazing = disrupts soil carbon and releases CO2 BUT started using rotational grazing in Mexico). And harvesting = disturbing soil and slash and burn techniques for livestock (livestock release/produce methane e.g. 20% USA methane emission is from cattle)
• growing cover crops = root structures stabilise soil and soil carbon
• agroforestry = increases soil carbon sequestration
• rice paddies = release methane due to water logged conditions = which promote anaerobic decomposition
• drawing peatland to make farmland = releases methane

Question 9

explain deforestation

Answer 9

• generates 20% of global CO2 emissions
• in disturbed forestry = carbon neutral (any decomp and slow release of CO2= compensated for growth of new vegetation)
• burning wood to clear woodland = releases CO2 to atmosphere
• woodland to cattle farming land etc= reduce system ability to absorb CO2 = it becomes a source not a sink
• deforestation = occurs in tropical areas for building, mining , commercial crops (palm oil etc) , energy, road building, population growth
• timber= valuable source that comes from wood and can build furniture etc
• carbon = stored in soil and in tree
• CO2= transferred from atmosphere to biosphere during photosynthesis and respiration
• Amazon rainforest , South America (20% in Brazil—> extracts gold and copper) —> 20% deforested —> 80% got cattle ranching
  —> building of Trans Amazonian highway= allows for further exploitation
  —> dam built for hydroelectric power

Question 10

explain urbanisation

Answer 10

• stores such as trees are removed. Parks, infrastructure, housing, concrete pavements replace it
• 2% earths land = urban but is responsible for 97% of human CO2 emissions
• more fossil fuels got industry development, transport etc
• waste and landfill decompose and release methane
• heat island effect as concrete absorbs more heat = temps rise and more CO2 emissions to atmosphere
• BUT recently = more sustainable urbanisation (renewable energy sources and increased green practices and spaces)
  e.g. London ULEZ, congestion charge, promoting electric vehicles, 40% electricity from renewable sources , aims for net-zeros carbon emissions by 2030

Question 11

what is a carbon source?

Answer 11

any process, area or ecosystem tht releases more CO2 to the atmosphere than it absorbs

Question 12

what is a carbon sink?

Answer 12

natural/artificial system that absorbs and stores more CO2 from the atmosphere than it releases

Question 13

what is the spearman’s rank test?

Answer 13

• measures strength and direction of relationship between 2 variables
  —> value between +1 (perfect positive correlation)and -1 (perfect negative correlation)—> if 0 then there’s no correlation at allct

Question 14

what are natural carbon sources ?

Answer 14

found on land + sea, include organic and non-organic processes that release CO2 and provide input into atmospheric carbon cycle . Carbon moves from one store to another and fluxes

Question 15

what are examples of natural carbon sources?

Answer 15

ocean-atmosphere exchange
volcanic activity
decomposing vegetation
wildfires
animal respiration
soil respiration
hydrothermal vents

Question 16

explain each natural carbon source

Answer 16

ocean-atmosphere exchange
- oceans outgasing = largest source of CO2 to atmosphere
- oceans absorb CO2 from atmosphere + release it

volcanic activity
- surface and submarine volcanoes release lots of CO2 and carbon compounds

decomposing vegetation
- plants and biomass decompose and release CO2

wildfires
- release CO2 as burn vegetation

animal respiration

soil respiration
- micro organisms in soil break down organic matter and release CO2

hydrothermal vents
- undersea vents release CO2 from earths interior

Question 17

what are examples of natural carbon sinks?

Answer 17

tropical rainforest and vegetation
grasslands
tundra
soil
ocean-atmosphere feedback

Question 18

explain each natural carbon sink

Answer 18

tropical rainforests and vegetation
- one of main terrestrial carbon sinks
- photosynthesis= absorb CO2 from atmosphere and store it in biomass

grasslands
- store carbon in roots and surrounding soil

tundra
- slow growing ecology , plants extract CO2 from atmosphere during growth
- bogs= cold, acid, anaerobic = plants decompose slowly
- carbon= stored in peat

soil
- plants release surplus carbon through roots into soil carbon (humus)
- animal faeces , dead vegetation etc = decompose if condition too acidic

ocean - atmosphere feedback
- high latitudes = oceans absorb CO2 from atmosphere where it dissolves in water
- absorb 30% of all human CO2 emissions
- self regulating feedback cycles operating in the exchange over years
- atmospheric CO2= ocean absorption = increased biological activity —> lots stored in deeper ocean
—> this may drop temps = terrestrial plant growth reduces= diminish sourcing of CO2 from atmosphere

Question 19

what is the carbon budget?

Answer 19

amount of carbon stored and transferred within carbon cycle on global/local scale

Question 20

what does the carbon budget have an impact on?

Answer 20

land
atmosphere
oceans

Question 21

explain how the carbon budget has an impact on land?

Answer 21

• soul made from organic matter (dead plants etc broken down by decomposition and stored in soil) and cycles through carbon system
  —> also brings important nutrients in further vegetation growth
• carbon in grass provides food for signals
• carbon provides energy in form of fossil fuels (hydrocarbons formed from organic remain of sea creatures etc) and wood
• carbon = valuable resources in charcoal, diamond , graphite etc

Question 22

carbon budget and impact on land more key points

Answer 22

• seasons and vegetation cause fluctuations in CO2 absorption rate (more in summer)
• long term carbon cycle involves a bio geochemical interaction
  —> slow carbon cycles = tectonic activity , acid rain falling and chemical weathering ; carbonation, calcium bicarbonate breaking down ions and creatures in sea
• CO2 taken up by plants increased since 1960s —> they take up 25% of emissions
  —> due to changing land use e.h. intensive farming grows crops /replacing farm land with trees
• positive feedback effect (more CO2 in atmosphere = more plant growth )
• increased temps = longer growing season BUT also has negative effects

Question 23

explain carbon budget and its impact on atmosphere

Answer 23

• ocean- atmosphere exchange —> ocean out gassing , oceans absorb and release CO 2 to and from atmosphere
• volcanic activity- release CO2 and carbon compounds
• tundra= cold so plants decompose at slower rate = carbon stored in peat —> hot plants grow, take in CO2 slowly but if too hot permafrost melts releasing methane and CO2
  —> Northern turners regions = worlds largest and large carbon sink
• soil is one of largest carbon sinks —> plants release surplus carbon through roots to soil carbon (humus) —> animal faeces, dead material = slowly decompose and store in carbon
• most CO2= stays in atmosphere for thousands of years
• enhanced greenhouse effects = too much radiative forcing= warming etc —> not all infrared energy is reflected back —> natural greenhouse effect also occurs
  —> before radiative forcing didn’t occur occur but it’s now increasing due to greenhouse gas emissions etc
  —> although need some greenhouse gases to stop earth from being frozen
• wildfires = cation quickly released to atmosphere
• deforestation= big impact on carbon in atmosphere

Question 24

explain the carbon budget and its impact on oceans

Answer 24

• cooler water= absorb more CO2 , warmer /saturated concentration waters release more
• phytoplankton (zooplankton consumer there and release CO2 in digestion) absorbs CO2 in ocean via photosynthesis and is good for other marine organisms = carbon passes along food chains
• carbon pump transfer carbon from surface waters to deeper ocean as faecal matter and sink dead organic structures = carbon rich marine deposits on ocean floor —> marine ecosystems shell materials = calcium bicarbonate’s—> converted into CaCO3 = further accumulation of carbon compounds on sea floor as they die
• dissolving CO2 in ocean creates carbonic acid —> makes oceans more acidic, less alkaline = dissolves calcium carbonate rocks. it also reacts with carbonate ions and forms bicarbonate BUT coral reefs need carbonate ions to form shells so there shells are becoming fragile

Question 25

carbon budget and its impact on oceans more points (examples of feedback loops)

Answer 25

- positive feedback (global warming)- warmer oceans = less phytoplankton as they need cool, nutrient rich water= more carbon in atmosphere and oceans less effective carbon sinks - positive feedback (melting sea ice)- less reflective ice replaced with warm water (warm water= algae blooms= blocks water = phytoplankton can’t absorb sunlight and photosynthesise) = ocean absorb more sunlight = amplifies warming = more melting - positive feedback (ocean salinity)- deep North Atlantic —> high temps and precipitation = melting Greenland ice sheet= more freshwater reaching oceans = slow down large scale ocean circulation= effected climate in NW Europe * sea levels rises 3.5mm/year since 1990s —> due to higher temps, less winters, thermal expansion (accounted for 50% of sea level rise in past centuries)