5.1b

• how much of the hydrosphere is freshwater?

  less than 3% --> most is saline water in the oceans
• distribution of water?

  oceans = 96.9%

  cryosphere = 1.9%

  groundwater = 1.1%

  surface water = 0.01%

  atmosphere = 0.01%

  biosphere = 0.001%
• cryosphere?

  areas of the earth where water is stored as snow or ice
• surface water?

  water stored in rivers and lakes
• biosphere?

  water stored as soil moisture
• blue water?

  water stored in rivers, streams, lakes and groundwater in liquid form (visible)
• green water?

  water stored in soil and vegetation (invisible)
• the amount of water present in each store varies over a range of scales from local to global. the size and importance of each store depends on the amount of water flowing between them
• which store stores water for the longest?

  groundwater
• fluxes?

  the rate of flow between the stores
• over longer time scales, some stores grow while others shrink e.g. since the last Ice Age, rising temperatures in the polar regions caused glaciers to melt, therefore reducing the size of the cryosphere. at the same time, other stores e.g. the ocean received meltwater and therefore grew
• why do annual fluxes between atmosphere, ocean and land vary?

  • evaporation
  • condensation
  • precipitation
  • cryospheric processes
• evaporation?

  • occurs when liquid water changes state into a gas, becoming water vapour - normally gains energy from solar radiation --> increases the amount of water stored in the atmosphere
  • the scale of evaporation varies by location and season. if there is a lot of solar radiation, a large supply of water and warm, dry air, the amount of evaporation will be high
  • if there isn't much solar radiation, little available liquid water and cool air that is already nearly saturated, evaporation will be low
• condensation?

  • when water vapour changes state to become a liquid - it loses energy to the surroundings --> air containing water vapour cools to its dew point e.g. when temperatures fall at night due to heat being lost to space
  • water droplets can stay in the atmosphere of flow into other subsystems e.g. when it condenses, it can form dew on leaves and other surfaces - this decreases the amount of water stored in the atmosphere
  • the scale of condensation flow depends on the amount of water vapour in the atmosphere and the temperature
• what is the dew point?

  the temperature at which water will change state from a gas to a solid
• precipitation?

  • the main flow of water from the atmosphere to the ground
  • clouds form when warm air cools, causing the water vapour to condense into water droplets which gather as clouds. when droplets are big enough, they fall as precipitation
  • precipitation and cloud formation varies seasonally e.g. in UK, more precipitation in winter than summer or by location e.g. more precipitation in the tropics than at the poles
• cryospheric processes?

  • accumulation (build up of snow or ice) and ablation (melting of snow or ice) change the amount of water stores in the cryosphere --> varies with temperature
  • during periods of cold, e.g. ice age, inputs into the cryosphere are greater than the outputs (more accumulation than ablation) opposite with warm temps
  • climate change is causing more rapid rates of ablation and so reduces the amount of water in the cryosphere