Dynamic equilibrium

Define dynamic equilibrium

A system displaying unrepeated average state through time.

When undisturbed, why are most systems in a state of dynamic equilibrium?

They have continuous and fluctuating inputs, throughputs, outputs allowing it to find a balance

Define negative feedback loops

An automatic response to change in a system that restores equilibrium

Give an example of negative feedback

• Heavy rainfall will increase the amount of water stored in aquifers.

• This in turn will raise the water table increasing flow in springs until the water table reverts to normal levels

Define Positive feedback loops

An automatic response to change in a system that generates further change

Give an example of positive feedback loop

• If there was a rise in deforestation, there is a rise of CO2 in the atmosphere which leads to higher temps

• That means more greenhouse gases which traps heat enhancing global warming

• Leads to higher temps

How can rising temperatures impact the water cycle? (Positive feedback)

• Global scale: with warmer temps, evaporation increases and the atmosphere holds more vapour.

• This results in more cloud cover and precipitation. Thus this leads to more photosynthesis and thus evapotranspiration.

How can more atmospheric vapour impact the water cycle? (negative feedback)

More vapour creates greater cloud cover which reflects more solar radiation back into space leading to slower temperatures.

How does the water cycle respond to change in the long term?

The system response to above average precipitations by increasing river flow and evaporation and excess water recharges aquifers, increasing water storage in permeable rocks.

What occurs when there are droughts?

The system adjusts itself to lower precipitation by reducing run-off and evapotranspiration. Meanwhile, as the water table falls, springs and seepage dry up, helping to conserve groundwater stores.

How does the water cycle respond on the small scale?

• During droughts, shallow routed trees like silver birch becomes stressed; water is lost in transpiration is not replaced by a similar uptake of water from the soil.

• The tree responds, reducing transpiration losses by shedding some or all of its leaves.

• This negative feedback loop restores the alter balance and tree survival

What state is the global carbon cycle in?

Disequilibrium due to human activities

What is carbon fertilisation?

Negative feedback could neutralise rising levels of atmospheric CO2 by stimulating photosynthesis.

What is the impact of carbon fertilisation?

Excess CO2 is extracted from the atmosphere and stored in the biosphere. Eventually much of this CO2 is stored in soil and ocean sediments, allowing the system to return to a steady state.

What is increased NPP through carbon fertilisation dependent on?

The availability of light, soil nutrients, nitrogen and water

How can global warming impact the carbon cycle Arctic tundra? (Positive feedback)

• Global warming is occurring fastest

• Less snow coverage

• More sunlight absorbed due to less albedo

• More warming and melting of the active layer

• 1600 GT of CCO2 slowly release from the active layer adding to the greenhouse effect and global warming