Water and Carbon Cycles: Systems Framework

Question 1

Define what a system is

Answer 1

A set of interrelated components working together towards some kind of process

Question 2

What is an open system?

Answer 2

Matter and energy can enter and leave the system

Question 3

What is a closed system?

Answer 3

Matter cannot leave the system, it can only cycle between stores, energy can enter and leave the system

Question 4

What is dynamic equilibrium?

Answer 4

When there is disruption to one of the elements, so the other elements will change in order to return to a state of equilibrium, causing feedback loops

Disruptions:
Physical disruptions – storms or drought
Human disruptions – deforestation, urbanisation, water abstraction
Sudden disruptions may result in sudden change e.g. flooding

Question 5

What is positive feedback?

Answer 5

The effects of an action are amplified or multiplied by subsequent secondary effects

Question 6

What is negative feedback?

Answer 6

The effects of an action are nullified or reduced by subsequent secondary effects

Question 7

What are elements?

Answer 7

A constituent part of the system

Question 8

What is an attribute?

Answer 8

Characteristics of an element

Question 9

What is a relationship?

Answer 9

the way in which the elements of a system interact

Question 10

What are the inputs in the water cycle?

Answer 10

precipitation

matter and energy being added to the system

Question 11

What are the outputs in the water cycle?

Answer 11

river discharge

matter or energy leaving the system

Question 12

What are the stores in the water cycle?

Answer 12

ocean, groundwater, clouds

where matter or energy builds up

Question 13

What are the flows in the water cycle?

Answer 13

channel flows

matter or energy moving from one store to another

Question 14

What are the boundaries of the water cycle?

Answer 14

watershed

limits of the system

Question 15

What is an example of a positive feedback loop?

Answer 15

Global temp rise -> warms oceans -> increased oceanic temperatures -> warm water is less able to dissolve gases -> dissolved CO2 is released by warmer oceans -> more CO2 back into atmosphere -> global temp rises

Question 16

What is an example of a negative feedback loop?

Answer 16

burning fossil fuels increased atmospheric CO2 -> global temp increases -> more plant growth -> increased CO2 uptake by biosphere -> reduces atmospheric CO2 slowing rate of global temp increase

Question 17

What is a threshold?

Answer 17

A point in a condition or process that, once passed, triggers some kind of change

Question 18

Describe the varying sizes of global water stores

Answer 18

• oceanic stores is the largest, 1.4 sextillion litres of water which is 97% of all the water in the hydrosphere
• cryospheric store second largest (e.g. Ross Ice shelf or Greenland Ice sheets), 26 million km^3, contains 69% of freshwater (3% of all water is freshwater)
• terrestrial water next, rivers take up 1 million squared km, largest being the Amazon River
• biosphere second to last largest store, less than >1% of all freshwater, all living parts on the Earth
• atmosphere is the smallest store, clouds, rain, vapour, ice crystals, a store 10 million% smaller than ocean

Question 19

Explain the sizes of the global water stores

Answer 19

• Large stores have the longest residency times as the scale of processes is small relative to their size and they return the same amount (e.g. hydrosphere and evaporation/precipitation)
• small stores have shorter residence times because the scale of the flows acting upon them are large relative to their size (e.g. atmosphere and evaporation/precipitation)

Question 20

Describe the flows between water stores

Answer 20

1. Evaporation, increases amount of water stored in the atmosphere, liquid water changes state into a gas
2. Condensation, vapour changes to liquid water, decreases water stored in the atmosphere
3. Cryospheric Processes, including accumulation and ablation, changes amount of water stored in cryosphere

Question 21

What process are changing the size of the global water stores?

Answer 21

transpiration and respiration
plant uptake
percolation
groundwater flow
precipitation/condensation
evaporation

Question 22

What does the magnitude of each water store depend on?

Answer 22

The amount of water flowing between them

Question 23

What factors control the size of flows between water stores?

Answer 23

1. evaporation = solar energy, supply of water, humidity of the air and temperature of air
2. condensation = amount of water in atmosphere, solar radiation and condensation nuclei
3. cryospheric processes = global climate

Question 24

What is the size of the largest water store?

Answer 24

Largest store is in the ocean with 1.3 million 1000km^3

Question 25

What is the size of the intermediate water stores?

Answer 25

Freshwater stores have intermediate sizes

- atmospheric water 2.7 (1000km^3) to cryosphere 26350 (1000km^3)

Question 26

What is the size of the smallest water store?

Answer 26

The smallest store is the atmosphere, over 10 million% smaller than the ocean store

Question 27

What is the largest flow of water stores?

Answer 27

Ocean evaporation and precipitation 413 1000km^3/year

Question 28

Q: Explain the role of cryospheric change in the water cycle [4 marks]

Answer 28

• Cryospheric change has a regulatory role in sea levels
• The cryosphere is a major store of water
• In a period of cooling (glacial period) the cryosphere will grow in size
• In a period of warming the cryosphere will add water to the cycle. As the water cycle restarts more of the ice melts and returns water to the sea

Question 29

What is a natural cause of variation in the water cycle?

Answer 29

Storm events transfer significant amounts of water from the atmosphere store to the hydrosphere and lithosphere stores.

Question 30

Outline an example of positive feedback feedback in the water cycle? [4 marks]

Answer 30

• a system where the effects of an action are increased or
  amplified by its subsequent knock-on effects
• Higher temperatures increase the melting of snow and ice
  leading to a reduction of surface albedo so more sunlight
  absorbed by land and sea. Temperatures increase further,
  which leads to further melting.

Question 31

Explain the concept of dynamic equilibrium in relation to the water cycle. [4 marks]

Answer 31

• Dynamic equilibrium refers to the tendency towards a natural
  state of balance within the hydrological cycle
• The cycle is a closed system as no water enters or leaves the system; it is simply recycled around the system
• The dynamic equilibrium is easily upset by extreme events such as storms or droughts
• Such events and processes cause sudden changes in the state of the system and disrupt or interfere with dynamic equilibrium as is the case with flooding