1c. The carbon and water cycles have distinctive processes and pathways that operate within them Flashcards
1
Q
What is the water balance?
A
A method for understanding the flows of water cycling through a system
2
Q
Equation for the water balance?
A
Precipitation = evaporation + streamflow +/- storage
P = E + Q +/- S
3
Q
What are the main flows in the water cycle?
A
Evaporation
Transpiration
Condensation (+ cloud formation)
Precipitation
Interception
Ablation
Run-off
Infiltration
Percolation
Throughflow
Groundwater flow
4
Q
What is evaporation?
A
- Process of water changing from a liquid to a water vapour
- Energy itself does not heat the water, but transfers into latent heat (the heat required to cause a change in state, without change of temperature), this is then released when condensation occurs
5
Q
What is transpiration?
A
- Transfer of water vapour from vegetation to the atmosphere
- Occurs mostly via stomata
- 10% of atmospheric water originates from transpiration
6
Q
What is condensation?
A
- Involves water vapour returning to a liquid state
- When water vapour reaches dew-point (temperature when the air becomes saturated) water droplets and clouds appear
7
Q
What are the three main types of cloud?
A
- Cumuliform clouds
- Stratiform clouds
- Cirrus clouds
8
Q
What are cumuliform clouds?
A
- Have flat bases and considerable vertical development
- Most often form through convection
9
Q
What are stratiform clouds?
A
- Layer-type clouds
- Most often form through advection
10
Q
What are cirrus clouds?
A
- Wispy clouds that do not produce precipitation
- Form at a high altitude and consist of tiny ice crystals
11
Q
What are the types of cloud formation (and rainfall)?
A
Convectional
Relief
Frontal
Advection (not a type of rainfall)
12
Q
What is convectional formation?
A
- Air is warmed by contact with the ground or sea surface, subsequently rises through the atmosphere
- As the air rises and pressure falls the air cools via adiabatic expansion, forming clouds
13
Q
What is relief formation?
A
Air masses rise as they cross a mountain barrier or as turbulence forces their ascent
14
Q
What is frontal formation?
A
- Warm and cool air meet
- Warm air forced upwards, then cools to form clouds
15
Q
What is advectional formation?
A
Air masses move horizontally across a relatively cooler surface
16
Q
What is environmental lapse rate (ELR)?
A
- Vertical temperature profile of the lower atmosphere at any given time
- On average temperature falls by 6.5 degrees celsius for every kilometre of height gained
17
Q
What is dry adiabatic lapse rate (DALR)?
A
- Rate at which a parcel of dry air (less than 100% humidity so that condensation is not taking place) cools
- Cooling, caused by adiabatic expansion, is approximately 10 degrees celsius per kilometre
18
Q
What is saturated adiabatic lapse rate (SALR)?
A
- Rate at which a saturated parcel of air (one in which condensation is occuring) cools as it rises through the atmosphere
- Since condensation releases latent heat, the SALR, at around 7 degrees celsius per kilometre, is lower than the DALR
19
Q
What is adiabatic expansion and why does it occur?
A
- What happens to a parcel of air as it rises, as air pressure decreases, volume increases and temperature decreases
- As air rises, it decreases in temperature and expands
- Same amount of air has a larger volume due to less air pressure and less compression, which leads to expansion
- When air expands, less interactions between the molecules, therefore temperature falls
20
Q
What is absolute atmospheric instability?
A
- When graphed, dry adiabatic lapse rate is to the right of environmental lapse rate (DALR is higher than ELR), means that the parcel of air is warmer than the surroundings
- This then causes the parcel of air to rise, then cool at a rate of 10 degrees celsius per kilometre
- This air continues to rise until it reaches the dew point, where the air becomes saturated
- This then causes the air to begin to cool at 7 degrees celsius per kilometre as latent heat is released due to condensation
- This continues until the temperature of the parcel of air is the same temperature, or cooler, than the surroundings
21
Q
What is absolute atmospheric stability?
A
- When graphed, environmental lapse rate is to the right of the dry adiabatic lapse rate (ELR is higher than DALR), means that the air is cooler than its surroundings, therefore does not rise unless obstacle present to force it to do so
- If obstacle forces the air to rise, the air will return to the ground if dew point has not been reached once the obstacle has been cleared
- Clouds could form if dew point is reached (and obstacle is still present), but if temperature of parcel of air is lower than surroundings still, it will sink
- As soon as the obstacle has been passed, the air will sink back down
22
Q
What is conditional atmospheric instability?
A
- When graphed, environmental lapse rate is to the right of the dry adiabatic lapse rate (ELR is higher than DALR), means that the air is cooler than its surroundings, therefore does not rise unless obstacle present to force it to do so
- If obstacle forces the air to rise, the air will return to the ground if dew point has not been reached once the obstacle has been cleared
- If the obstacle is still present and dew point has been reached, clouds may form due to the lowered lapse rate (7 compared to 10), parcel of air could become warmer than surroundings
- If the parcel of air becomes warmer than its surroundings, it will then rise freely which results in atmospheric instability
- Atmosphere is stable until the parcel of air becomes warmer than its surroundings
23
Q
What is precipitation?
A
- Any form of water that falls from the atmosphere to the land or oceans
- Duration of rainfall affects the speed of transfer through the drainage basin
- Long periods of rainfall leads to soil becoming saturated, subsequent increase in surface runoff
- Short periods of rainfall usually absorbed by soil and vegetation
24
Q
What is interception?
A
- Temporary storage of water on the surface of plants and buildings before it reaches the surface
25
What is ablation?
- Loss of water stored as ice or snow through melting, run-off, evaporation, sublimation, calving of icebergs or removal of loose snow by wind
26
What is infiltration?
- Process where by gravity and capillary action draw water into the soil in lateral movement
27
What is percolation?
- Downward vertical movement of water within a soil
- Rate depends on the size of the pores through which water travels
28
What is run-off?
- All the water which enters a river and flows out of the drainage basin
- Overland flow, through flow, and groundwater flow all contribute to this
29
What is throughflow?
- Transference of water from the soil storage zone to the channel, much slower rate than overland flow
30
What is groundwater flow?
- When the rock or soil is saturated, the water is transferred slowly through rock and into the bed of the river
31
What is overland flow?
When the rainfall is too intense and falls more quickly than it can be infiltrated into the soil, a thin layer of water forms on the surface and it begins to move downslope under gravity
32
What is saturated overland flow?
- When there is too much rainfall and the soil capacity is reached, a thin layer of water forms on the surface and it begins to move downslope under gravity
33
What are the main fluxes in the carbon cycle?
Precipitation
Photosynthesis
Weathering
Respiration
Decomposition
Combustion
Sequestration
Sediments
34
What is precipitation (carbon cycle)?
- Atmospheric CO2 dissolves in rainwater to form weak carbonic acid
- Rising concentrations of CO2 in the atmosphere due to anthropogenic emissions have increased the acidity of rainfall
- This has contributed to increased acidity of ocean surface waters with potentially harmful effects on marine life
35
What is photosynthesis?
- Using the sun's energy, CO2 from the atmosphere and water, green plants and marine phytoplankton convert light energy to chemical energy (glucose) ad release oxygen
- Flux of carbon from the atmosphere to land plants and phytoplankton via photosynthesis averages around 120 gigatonnes per year
- CO2 absorbed from the atmosphere
36
What is weathering?
- Weathering is the in situ breakdown of rocks at
or near the Earth’s surface by chemical, physical and biological processes
- Estimated that chemical weathering transfers 0.3 billion tonnes of carbon to the atmosphere and oceans every year
- Carbonation releases carbon from limestones to streams, rivers, oceans and the atmosphere
- Physical weathering by freeze-thaw breaks rocks down into smaller particles but involves no chemical changes, it increases the surface area exposed to chemical attack
- Biological weathering processes such as chelation also contribute to rock breakdown
37
What is respiration?
- Process in which carbohydrates fixed in photosynthesis are converted to CO2 and water
- Glucose + oxygen -> carbon dioxide + water + energy
- Absorbs oxygen and emits CO2
38
What is decomposition?
- Decomposer organisms such as bacteria ad fungi break down dead organic matter, extracting energy and releasing CO2 to the atmosphere and mineral nutrients to the soil
- Rates of decomposition depend on climatic conditions, fastest rates occur in warm humid environments, slowest rates occur in cold or dry conditions
39
What is combustion?
- Occurs when organic material reacts or burns in the presence of oxygen
- Combustion process releases CO2 as well as other gases, such as sulphur dioxide and nitrogen oxides
- Combustion is a natural process, wildfires caused by lightning strikes are essential to the health of some ecosystems (eg. coniferous forests of the Rocky Mountains)
- Combustion shifts log jam, freeing carbon and nutrients previously inaccessible to forest trees, opens up the forest canopy, creating new habitats and increasing biodiversity
- Also results from human activities (eg. deliberate firing of forest and grassland in order to clear land for cultivation or improve the quality of grazing
- Combustion of fossil fuels transfers nearly 10 gigatons of CO2 per year from the geological store to the atmosphere, oceans and biosphere
40
What are the two types of carbon sequestration in the oceans?
Physical (inorganic) pump
Biological (organic) pump
41
Describe the physical (inorganic) pump
- Involves the mixing of surface and deep ocean waters by vertical currents, creating a more even distribution of carbon, both geographically and vertically, in the oceans
- Initially, CO2 enters the oceans from the atmosphere via diffusion
- Surface ocean currents then transport the water and its dissolved CO2 polewards where it cools, becomes more dense and sinks
- This downwelling only occurs in a handful of places (eg. the North Atlantic between Greenland and Iceland)
- Downwelling carries dissolved carbon to the ocean depths where individual carbon molecules may remain for centuries
- Eventually, deep ocean currents transport the carbon to areas of upwelling
- There cold, carbon-rich water rises to the surface and CO2 diffuses back into the atmosphere
42
Describe the biological (organic) pump
- Carbon exchanged between the oceans and atmosphere through the actions of marine organisms
- Globally, nearly half of all carbon fixation by photosynthesis takes place in the oceans, around 50 GT of carbon is drawn from the atmosphere by the biological pump every year
- Phytoplankton, floating near the ocean surface combines sunlight, water and dissolved CO2 to produce organic material
- Whether consumed by animals in the marine food chain, or through natural death, carbon locked in the phytoplankton either accumulates in sediments on the ocean floor or is decomposed and released into the ocean as CO2
- Other marine organisms such as tiny coccolithophores, molluscs and crustaceans extract carbonate and calcium ions from seawater to manufacture plates, shells and skeletons of calcium carbonate
- Most of this carbon-rich material eventually ends up in ocean sediments and is ultimately lithified to form chalk and limestone
43
What is sedimentation / shell formation?
- CO2 diffuses from the atmosphere into the oceans where marine organisms make their shells and skeletons by fixing dissolved carbon together with calcium to form calcium carbonate
- On death, these remains sink to the ocean floor, there they accumulate and over millions of years, heat and pressure convert them to carbon rich, sedimentary rocks
- Typical residence times for carbon held in rocks
is around 150 million years
