Summary Positive and Negative Feedbacks

Water Cycle - Positive Feedbacks

Positive feedback - Where the effects of an action are amplified or multiplied by subsequent
knock-on or secondary effects - pushing the balance further away from equilibrium

Examples:

 The cycle of increasing water vapour (which acts as a greenhouse gas) in the
atmosphere causing increased warming, which in turn causes the atmosphere to
hold more water vapour - as temperatures warm, more water vapour evaporates
from the surface into the atmosphere,

 Ice reflects the sun’s rays. As this ice melts, less light is reflected. Its instead
absorbed by the ocean raising the temperature and increasing the rate of melting ice
further. Ice albedo feedback (the less ice there is, the more its melting)


 Ice caps melt, contributing to sea-level rise. This then increases glacier carving,
increasing the rate they are melting. (Ice caps melt, sea level rises, the higher sea can
erode a greater proportion of the ice cap)

 Humans remove water from fossil aquifers, which a large percentage is then
evaporated, speeding up evaporation and rainfall. 70% of the water in the desert
evaporates from irrigation

 Ice acts as insulation if the ice breaks the heat from the ocean can escape causing
more melting to occur