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geography > carbon cycle: key topic one > Flashcards

carbon cycle: key topic one Flashcards

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1
Q

Where is carbon found?

A

everywhere: oceans, rocks, soils, the atmosphere and in all forms of life

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2
Q

What is the carbon cycle?

A

the cycle by which carbon moves from one Earth sphere (atmosphere, hydrosphere, lithosphere and biosphere) to another

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3
Q

What type of system is the carbon cycle?

A

a closed system, but made up of interlinked subsystems which are open and have inputs and outputs

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4
Q

What are the two main components of the carbon cycle?

A

stores and fluxes/flows

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5
Q

What is a carbon store?

A

function as sources (adding carbon to the atmosphere) and sinks (removing carbon from the atmosphere)

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6
Q

What is a carbon flux/flow?

A

movements of carbon from one store to another; provide the motion in the carbon cycle

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7
Q

What are the four main stores of carbon?

A

atmosphere, hydrosphere, lithosphere, biosphere

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8
Q

How is carbon stored in the atmosphere?

A

as carbon dioxide and carbon compounds, such as methane

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9
Q

How is carbon stored in the hydrosphere?

A

as dissolved carbon dioxide

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10
Q

How is carbon stored in the lithosphere?

A

as carbonate in limestones, chalk and fossil fuels, as pure carbon in graphite and diamonds

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11
Q

How is carbon stored in the biosphere?

A

as carbon atoms in living and dead organisms

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12
Q

How do carbon stores vary?

A

in size, capacity and locations

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13
Q

How are carbon fluxes between the carbon stores of the carbon cycle measured?

A

in either petagrams or gigatonnes of carbon per year

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14
Q

What are the two major fluxes?

A
  • between the oceans and the atmosphere
  • between the land and atmosphere
  • both via the biological processes of photosynthesis and respiration
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15
Q

How do carbon fluxes vary?

A

in terms of flow and on different timescales

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16
Q

What is most of the worlds carbon and where does it form from?

A

geological in rocks
- resulting from the formation of sedimentary carbonate rocks (limestone) in oceans and biologically derived carbon in shale, coal and other rocks

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17
Q

How much carbon is in the lithosphere?

A

over 100 million Pg of carbon

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18
Q

Where is most lithospheric carbon concentrated?

A

in the sedimentary rocks of the crust

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19
Q

How do sedimentary rocks form?

A

1) sediment is deposited in layers in a low-energy environment (lake, seabed)
2) further layers are deposited and sediment undergoes diagenesis
3) lower layers become compressed and chemical reactions cement particles together

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20
Q

What is diagenesis?

A

the physical and chemical changes that occur during the conversion of sediment to sedimentary rock

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21
Q

What is lithification?

A

the conversion of loose, unconsolidated sediment into solid rock

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22
Q

What is limestone composed of and how much is carbon by weight?

A

calcium carbonate and 40% carbon by weight

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23
Q

How much lithospheric carbon is found in limestone?

A

80%

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24
Q

How is limestone formed?

A
  • after small marine animals die, their shells and skeletons build up on the ocean floor.
  • over time, the layers of fragments press down on each other, squeeze out the water, and recrystallise into solid rock
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25
Q

How does carbon re enter the atmosphere?

A
  • the burning of fossil fuels
  • erosion of limestone
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26
Q

How does chemical weathering release carbon into the atmosphere?

A
  • carbon dioxide in the atmosphere reacts with moisture to form weak carbonic acid
  • when this falls as rain, it reacts with some of the surface minerals and slowly dissolves them
  • the decomposition of rock minerals in their original position by agents such as water, oxygen, carbon dioxide and organic acids
27
Q

How do volcanic eruptions and earthquakes release carbon into the atmosphere?

A
  • pockets of carbon dioxide exist in the Earth’s crust
  • volcanic eruptions and earthquakes can release these gas pockets
  • this is called outgassing
28
Q

What is outgassing?

A

the release of gas, previously dissolved, trapped, frozen or absorbed in some material (e.g. rock).

29
Q

Where does outgassing mostly occur?

A

mainly along mid-ocean ridges, subduction zones and at magma hotspot

30
Q

What are the three types of oceanic carbon pump?

A
  • biological pump
  • physical pump
  • carbonate pump
31
Q

What is an oceanic carbon pump?

A

circulates and stores carbon

32
Q

What does the biological pump do?

A

1) moves carbon dioxide from the ocean surface to marine plants called phytoplankton through photosynthesis
2) converts carbon dioxide into food for zooplantic and their predators

33
Q

What happens to the carbon dioxide in the biological pump?

A
  • most of the carbon dioxide taken up by phytoplankton is recycled near the surface
  • about 30% sinks into deeper waters before being converted back into carbon dioxide by marine bacteria
34
Q

What do physical pumps do?

A

move carbon compounds to different parts of the ocean in downwelling and upwelling currents

35
Q

What is the full process of the physical pump?

A

1) downwelling occurs in parts of the ocean where cold, denser water sinks
2) these currents bring dissolved carbon dioxide down to the deep ocean
3) it then moves in slow-moving deep ocean currents, staying there for hundreds of years
4) eventually, these deep ocean currents (part of the thermohaline circulation) return to the surface by upwelling
5) the cold deep ocean water warms as it rises towards the ocean surface and some of the dissolved carbon dioxide is released back into the atmosphere

36
Q

What does the carbonate pump do?

A

these form sediments from dead organisms that fall to the ocean floor, especially the hard outer shells and skeletons of fish, crustaceans and corals, all rich in calcium carbonate

37
Q

What is the thermohaline circulation?

A

the global system of surface and deep ocean currents driven by temperature and salinity differences between different parts of the ocean

38
Q

How do plants sequester carbon out of the atmosphere?

A

during photosynthesis, carbon then enters the food chains and nutrients cycles of terrestrial ecosystems

39
Q

How do animals play a role in sequestering carbon?

A
  • they consume plant matter, the carbon sequestered in the plant becomes part of their fat and protein
  • respiration returns some of the carbon back to the atmosphere
40
Q

What happens in the carbon cycle after animals sequester carbon?

A
  • waste from animals is eaten by micro-organisms (bacteria and fungi) and detritus feeders (e.g. beetles)
  • carbon becomes a part of these creatures and when plants and animals die their remains fall to the ground and carbon is released back into the soil
41
Q

What does diurnally mean for carbon fluxes within ecosystems?

A
  • during the day, fluxes are positive - from the atmosphere into the ecosystem
  • the reverse applies at night when respiration occurs but not photosynthesis
42
Q

What does seasonally mean for carbon fluxes within ecosystems?

A
  • during winter, carbon dioxide concentrations increase because of the low levels of plant growth
  • however, as soon as spring arrives and plants grow, these concentrations begin to decrease until the onset of autumn
43
Q

How is biological carbon stored in soils?

A

the form of dead organic matter

44
Q

How much carbon do soils store?

A

between 20% and 30% global carbon

45
Q

What does the amount of carbon stored in the soil depend on?

A

climate, vegetation cover, soil type, land use

46
Q

Why does the climate affect the amount of carbon in the soil?

A

dictates the rates of plant growth and decomposition; both increase with temperature and rainfall

47
Q

Why does the vegetation cover affect the amount of carbon in the soil?

A

this affects the supply of dead organic matter, being heaviest in tropical rainforests and least in tundra

48
Q

Why does the soil type affect the amount of carbon in the soil?

A

clay protects carbon from decomposition, so clay-rich soils have a higher carbon content

49
Q

Why does the land use affect the amount of carbon in the soil?

A

cultivation and other forms of soil disturbance increase the rate of carbon loss

50
Q

What is the greenhouse effect?

A

the warming of the atmosphere as gases such as CO2, CH4 and water vapour absorb heat energy radiated from the Earth

51
Q

How is the Earth’s climate driven by incoming short-wave solar radiation?

A
  • only 31% is reflected back into space by clouds, GHGs and by the land surface
  • 69% is absorbed at the Earth’s surface, especially by the oceans
  • much of this radiation absorbed at the surface is re-radiated as long wave radiation
  • large amounts of this long-wave radiation are, however, prevented from returning into space by clouds and GHGs
  • the trapped long-wave radiation is then re-radiated back to the Earth’s surface
52
Q

How does photosynthesis play a role in the carbon cycle?

A

photosynthesis by terrestrial and oceanic organisms plays an essential role in keeping carbon dioxide levels relatively constant and thereby helping to regulate the Earth’s mean temperature

53
Q

How does the amount of photosynthesis vary?

A

varies spatially, particularly with net primary productivity (NPP)

54
Q

What is net primary productivity?

A

the amount of organic matter that is available for humans and other animals to harvest or consume

55
Q

How does net primary productivity vary?

A
  • highest in the warm and wet parts of the world, particularly in the tropical rainforests and in shallow ocean waters
  • least in the tundra and boreal forests
56
Q

What does soil health depend on?

A

the amount of organic carbon stored in the soil

57
Q

What is the storage amount of carbon determined on in soil?

A

determined by the balance between the soil’s inputs (plant and animals remains, nutrients) and its outputs (decomposition, erosion and uptake by plant and animal growth)

58
Q

What does a healthy soil have?

A

a large surface reservoir of available nutrients which, in their turn, condition the productivity of ecosystems

59
Q

What does carbon do in soil organic matter?

A

helps to give soil its moisture-retention capacity, its structure and fertility

60
Q

What is the number one threat to the global carbon cycle?

A

fossil fuel combustion

61
Q

What does additional carbon dioxide in the atmosphere cause for the climate?

A
  • a rise in the mean global temperature
  • more precipitation and evaporation
  • sudden shifts in weather patterns
  • more extreme weather events, such as floods, storm surges and droughts
  • the nature of climate change is varying from region to region (some areas are becoming warmer and drier and others wetter)
62
Q

What does additional carbon dioxide in the atmosphere cause for ecosystems?

A
  • sea level: this is rising because of melting ice sheets and glaciers; many major coastal cities around the world are under threat from flooding by the sea
  • ecosystems: a decline in the goods and services they provide; a decline in biodiversity; changes in the distributions of species; marine organisms threatened by lower oxygen levels and ocean acidification; the bleaching of corals etc.
63
Q

What does additional carbon dioxide in the atmosphere cause for hydrological cycle?

A

increased temperatures and evaporation rates cause more moisture to circulate around the cycle

geography (6 decks)

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