carbon cycle

Question 1

chemical weathering processes

Answer 1

1. Water reacts with atmospheric CO2 in the atmosphere, forming carbonic acid. Once this water reaches the surface as rain, it is weakly acidic and reacts with surface minerals, slowly dissolving them into their component ions.
2. calcium ions transport by rivers from land to oceans. they combine with bicarbonate ions to form calcium carbonate and precipitate out as minerals like calcite.
3. Deposition and burial turns calcite sediment into limestone.
4. Subduction of sea floor under continental margins by tectonic spreading.
5. some of this carbon rises to surface within heated magma, then is ‘degassed’ as CO2 and returned to atmosphere.

Question 2

volcanic outgassing

Answer 2

-pockets of CO2 are in earths crust.
-disruptions by eruptions or earthquake activity may allow pulses into the atmosphere.
-it occurs at active or passive volcanic zones (plate boundaries), places with no current volcanic activity, direct emissions from fractures in Earth’s crust.
-volcanoes currently emit 0.15-0.36 Gt CO2 annually

Question 3

thermohaline circulation (biological process)

Answer 3

the global system of surface and deep water ocean currents is driven by temperature and salinity differences between areas of oceans. main current begins in polar oceans where water gets cold.
sea ice forms, surrounding sea gets saltier, increases in density and sinks. current is recharged as it passes by extra cold, salty water.
two branches warm and rise as they travel northward, then loopback southward and westward.
the now warmed surface waters continue circulating around the globe, eventually return to the North Atlantic, coolant the cycle begins again.

Question 4

oceanic sequestration (biological process)

Answer 4

93% of CO2 is stored in undersea algae, plants and coral with the remainder in a dissolved form. increased oceanic acidification reduces the capacity for extra CO2 storage.

Question 5

primary producers

Answer 5

plants- take carbon out of the atmosphere through photosynthesis and release CO2 back into the atmosphere through respiration.

Question 6

consumers

Answer 6

consumer animals eat plants and carbon from the plant becomes part of its fats and proteins.
micro-organisms feed on waste material from animals which makes carbon part of these micro-organisms.

Question 7

decomposition

Answer 7

plant and animal deaths cause tissues such as leaves decay faster than more resistant structures (wood). fastest in tropical climates due to high temps, rainfall and oxygen levels. slow in cold, dry conditions with oxygen shortages.

Question 8

diurnal carbon fluxes

Answer 8

during the day, fluxes are positive, from the atmosphere to the ecosystem, at night the flux is negative, with loss from the ecosystem to the atmosphere.

Question 9

seasonal carbon fluxes

Answer 9

in the northern hemisphere winter, when few land plants are growing and many are decaying, atmospheric CO2 concentration increases. spring plants grow and concentrations drop.

Question 10

biological pump

Answer 10

• Organisms in the ocean absorb co2 from atmosphere
• Passed along chain by the consumer fish. transferring CO2 to water and atmosphere.
• Phytoplankton float near surface for sunlight to photosynthesise.
  Only 0.1% reaches sea floor after deadbphytoplankton sink where they decompose or turn into sediment.

Question 11

carbonate pump

Answer 11

Oceans absorb carbon from atmosphere
Shells & organisms take this in - Either sink to. botrom where it builds
UP, or is released back into ocean.
* Dissolved COz with water makes carbonic acid. These then form carbonate ions which shell-building organisms use.
“ Example → White Cliffs Dover: limestone from calcium carbonate sediments.

Question 12

physical pump

Answer 12

• Main process is thermohaline circulation alongside upwelling and downwelling
• Oceanic circulation
• Colder water = more COz absorption
  *COr conc. higher deep ocean than at surface
• Tropical wares release CO2, cold absorb CO2

Question 13

climate: capacity to store organic carbon

Answer 13

dictates plant growth and microbial and detritivore activity. rapid decomposition occurs at higher temps or under waterlogged conditions. High rainfall also allows for an increased potential carbon storage than the same soil type in lower rainfall places.

Question 14

soil type: capacity to store organic carbon

Answer 14

clay rich soils have higher carbon content than sandy soils

Question 15

management and use of soils: capacity to store organic carbon

Answer 15

soils globally have lost 40-90 billion tonnes of carbon since 1850. this loss of carbon is due to land-use change.

Question 16

enhanced greenhouse effect

Answer 16

Earth receives solar radiation and most is reflected off the surface, back into the atmosphere. In the enhanced effect, the role of greenhouse gases creates a layer known as the ozone layer. When solar radiation reaches the earth, it reflects off the earth’s surface and some goes into the atmosphere, whilst the rest becomes trapped in the atmosphere due to the ozone layer.