Water and carbon cycles as natural systems

Question 1

Define positive feedback.

Answer 1

A cyclical sequence of events that increases change, positive feedback loops exaggerate the outputs of a system, driving it in 1 direction, promoting environmental instability.

e.g.
drainage basin: rising sea levels can destabilise ice shelves, increasing the rate of calving - leads to an increase in melting, causing sea levels to rise further

woodland carbon cycle: increased temperatures cause melting of permafrost, where trapped greenhouse gases are released - enhancing the greenhouse effect, raising temperatures further.

Question 2

Define negative feedback.

Answer 2

Cyclical sequence of events that neutralises the effects of a system, regaining stability.

e.g.
drainage basin: increased surface temperatures lead to an increase in evaporation from the oceans, leading to more cloud cover - clouds reflect radiation from the sun resulting in high albedo.

woodland carbon cycle:
increased atmospheric co2 leads to increased temperatures, promoting photosynthesis rates - in turn this removes more co2 from the air, counteracting the rise in temperatures.

Question 3

Define dynamic equilibrium.

Answer 3

Represents a state of balance within a constantly changing system.

e.g.
Remote area where there has been no significant natural or human impacts, or one that has had time to adjust to change.

Question 4

Define closed system.

Answer 4

Transfers of energy both into and beyond the system boundary.

e.g. The carbon cycle

Question 5

Define open system.

Answer 5

Matter and energy can be transferred from the system across the boundary into the surrounding environment.

e.g. Drainage basin

Question 6

Define isolated system

Answer 6

No interactions with anything outside the system boundary, no inputs or outputs.

Question 7

Define input.

Answer 7

An input into the system from the outside.

e.g.
drainage basin: precipitation
woodland carbon cycle: precipitation with dissolved co2

Question 8

Define output.

Answer 8

An output from the system to the outside.

e.g.
drainage basin: runoff
woodland carbon cycle: dissolved carbon within runoff

Question 9

Define energy.

Answer 9

Power or driving force.

e.g.
drainage basin: latent heat associated with changes in the state of water
woodland carbon cycle: production of glucose through the process of photosynthesis

Question 10

Define stores.

Answer 10

The included elements or parts of a system.

e.g.
drainage basin: trees,puddles,soil
woodland carbon cycle: trees, soil, rocks

Question 11

Define flows/transfers.

Answer 11

Links between the components.

e.g.
drainage basin: infiltration, groundwater flow, evaporation
woodland carbon cycle: burning, absorption