6 - the global carbon cycle ✅ Flashcards
1
Q
what processes transfer carbon between land, oceans and the atmosphere (9)
A
- photosynthesis
- respiration
- decomposition
- eruptions
- weathering and erosion
- natural burning
- burning fossil fuels
- diffusion
- carbon sequestration
2
Q
what is the difference between the geosphere and biosphere carbon cycle
A
GEOSPHERE - operates at a very long, slow time scale from thousands to millions of years
BIOSPHERE - operates at much faster rate, seconds to hundreds of years
3
Q
what is the importance of carbon and water (2)
A
- cycling of carbon and water are central to supporting life on earth
- just like the water cycle, conceptualised as a system with key stores and pathways at a global scale
4
Q
what are the key stores in the carbon cycle (6)
A
- oceans
- ocean sediments
- soils
- bedrock
- vegetation
- the atmosphere
5
Q
what are carbon stores
A
carbon stores are places where carbon can be found in the earth system
6
Q
how does the carbon cycle act as a system (2)
A
- the earths carbon reservoirs naturally act as both adding and as sinks removing carbon from the atmosphere
- if all sources are equal to all sinks the carbon cycle is said to be in BALANCE and there is no change in the size of pools over time
7
Q
what are carbon movements
A
FLUXES are movements of carbon between different reservoirs (processes)
- each flux is a chemical reaction or a physical process
- each flux will take carbon out of one store and put it in another eg photosynthesis
8
Q
how have humans impacted the carbon cycle (2)
A
- land use change and depletion of fossil fuels are two largest impacts
- 90% of anthropogenic carbon is from combustion of fossil fuels
9
Q
what is carbon sequestration (2)
A
- the natural capture and storage of CO2 from the atmosphere by physical/biological processes eg photosynthesis
- in recent times humans have tried to develop artificial carbon sequestration
10
Q
how does fossil fuel combustion work (3)
A
- hydrocarbon combustion takes place rapidly in the presence of oxygen and releases CO2
- industrial societies burn coal, oil and gas transferring large amounts of stored CO2 into the atmosphere
- some is stored in the oceans
11
Q
what is the effect of fossil fuel combustion (2)
A
- around 85% of global energy consumption comes from fossil fuels despite renewable energy efforts
- traditional societies burn biomass to provide heat and cooking, releasing CO2
12
Q
what is photosynthesis (3)
A
- process by which carbohydrate molecules are produced from CO2 and H2O using energy from light
- as they photosynthesise plants ‘fix’ gaseous CO2 from the atmosphere into solid form in living tissues in plants
- oxygen released as by product into atmosphere
13
Q
what is the equation for photosynthesis
A
6CO2 + 6H2O —> C6H12O6 + 6O2
14
Q
how can photosynthesis effectiveness be measured (3)
A
- its more active in some parts of the world than others
- the net primary productivity (NPP) of an ecosystem is a measure of the rate at which new organic matter is produced by photosynthesis per unit area per unit time
- 3 highest rates of NPP are in shallow, warm-water estuaries, marshes and tropical rainforests
15
Q
what is respiration (3)
A
- CO2 released back into atmosphere by living organisms by respiration
- plants create energy by breaking down stored glucose (sugars). CO2 is byproduct
- respiration is reversal of photosynthesis process
16
Q
respiration equation
A
C6H12O6 + 6O2 —> 6CO2 + 6H2O
17
Q
what is the relationship between photosynthesis and respiration (3)
A
- 2 processes not in balance
- some organic matter produced by photosynthesis buried in sedimentary rocks or stored underground as fossil fuels
- over geological time more carbon is removed from atmosphere by photosynthesis than returned by respiration
18
Q
what is decomposition (2) and how is it broken down
A
- when living organisms die, their cells break down due to physical processes (wind and water), chemical processes (leaching and oxidation) and biological processes (feeding and digestion)
- bacteria and fungi break down cells and tissues, releasing carbon dioxide into atmosphere
19
Q
how do rates of decomposition change (3)
A
- rates vary greatly
- in Arctic Tundra, plant and animal remains may still be visible for years
- in warm, humid conditions dead plants and animals may decompose within a matter of days
20
Q
what enables plants to carry out photosynthesis
A
CHLOROPHYLL which is in chloroplasts containing the green pigment
it absorbs light energy from the Sun
21
Q
what things do plants need to make food by photosynthesis (7)
A
water
oxygen
nitrogen
carbon dioxide
fertiliser
chlorophyll
sunlight
22
Q
what does the physical (inorganic) pump do (4):
how is it transferred
where is it dissolved
what process transports it
relation to ocean
A
- CO2 transfers between atmosphere and ocean by diffusion
- CO2 dissolved in surface of ocean can be transferred to deep ocean where cold dense waters sink
- downwelling carries carbon molecules to great depths where it remains for centuries
- level of CO2 diffusion determines acidity of ocean
23
Q
what does the biological (organic) pump do (3), its relation to food chain and where is CO2 transferred
A
- ocean phytoplankton (biota) absorb CO2 through photosynthesis
- they form the bottom layer of food chain and carbon passes along as creatures consume one another
- organic carbon may be transferred to the deep ocean when dead organisms sink
24
Q
what is the relationship between carbon and the ocean (2)
(cycles)
A
- both fast cycle (photosynthesis) and slow cycle (downwelling) processes are involved in the flow of carbon into and out of ocean storage
- scientific research is taking place into how humans are destroying the delicate balance in oceans
25
what is the slow carbon cycle and two processes involved
cycling of carbon between bedrock stores on the land and oceans through weathering
erosion and deposition is at a continental scale and long time scale
26
what is the effect of chemical weathering (2)
(water and carbonate rocks)
- involves rainwater containing dissolved CO2 producing weak carbonic acid (H2CO3)
- carbonation affects carbonate rocks like chalk and limestone as the calcium carbonate reacts with carbonic acid to become calcium bicarbonate which is soluble
27
how much carbon is transferred by chemical weathering and how is calcium bicarbonate transferred
- globally 0.3bn tonnes of carbon are transferred from rocks to atmosphere and ocean each year by chemical weathering
- calcium bicarbonate is transported by overland flow, throughflow and groundwater flow
28
what is exemplification of weathering (3)
- large amounts of carbon have been removed in solution from limestone areas of the UK eg Llandudno cliffs
- carbonation weathering affects the surfaces of exposed rock eg Malham Cove
- in chalk regions groundwater transfers calcium bicarbonate in solution into rivers eg South Downs
29
how does oceanic carbonate work (4)
- carbonate is used by marine organisms to create shells
- when they die, shells deposited as carbonate rich sediments on ocean floor
- eventually turned into rock (lithified) which can store carbon for millions of years
- estimated that this layer may store 100m Giga tonnes of carbon
30
how is land and ocean carbon stored (2)
SYNOPTIC LINK**
- some carbon returned to atmosphere by volcanism as subduction occurs at plate boundaries
- huge volumes of carbon constantly on move in tectonic processes, but at very slow rate of geological movement (cm/year)
31
where is one of the biggest carbon stores in the world (4) and link to water cycle
- Himalayas
- formed of oceanic sediments rich in calcium carbonate (evidence of Tethys Sea in tectonics)
- weathering releasing carbon which is being eroded and transported back to oceans
- monsoon rainfall increases this process (link to water cycle)
32
in which speed of cycle is carbon permanently sequested
SLOW carbon cycle permanently sequesters carbon in form of carbonates into rock or subducted into mantle
less than 1 gigaton/yr of carbon
33
how much carbon do we emit every year and where does this go (4)
- we add 9 BILLION tons of carbon every year
- about 22% of that gets diffused into the ocean
- about 35% gets absorbed on land by plants and with some amount added by chemical weathering
- leaves 1/2 of our total carbon emissions which remain long term in the atmosphere
34
how is carbon released from biosphere into atmosphere (3)
CO2 comes from aerobic respiration of organic carbon into carbon dioxide
and CH4 (methane) comes from anaerobic respiration (without oxygen)
after respiration they are typically emitted into atmosphere
35
how much carbon does the ocean hold and in what forms
around 36,000 billion tons (gigatons) of carbon
mostly in form of bicarbonate ion and remainder being carbonate (CO3)
36
what process happens with CO2 in the ocean and how is thermohaline circulation affected
at surface of oceans, seawater becomes cooler and more carbonic acid is formed as CO2 becomes more water soluble
this is coupled to thermohaline circulation which transports denser surface water into deeper layers around globe
37
how is carbonic acid formed
formed when CO2 is dissolved in water (eg rain)
consumption of carbonic acid will induce more CO2 to be taken out of the atmosphere
38
what is the effect of carbonic acid and what factor impacts it
will dissolve silicate rocks consuming the carbonic acid and removing CO2 from the atmosphere
acts as a negative feedback response, higher temp = more CO2 enriched rain and more weathering
39
what is the chemical reaction equation for carbonic acid
CO2 + H2O —> H2CO3
carbon dioxide + water —> carbonic acid
40
what is the theory of the himalayas in the role of CO2 and what has been happening recently
chemical weathering of silicate rocks takes CO2 out of the atmosphere
more recently, CO2 removal rates are less and the dominant carbon sink effect of the Himalaya is erosional removal of biologic carbon and burial at sea and O18/O16 shows cooling climate during this time period
41
what has been expected of the Himalayas
- chemical weathering was expected to remove all CO2 from atmosphere and it hasnt
