4.1 Water systems

• Solar radiation and gravity

• Heat for evaporation, gravity for drainage

• System with stores and flows

• Stores: boxes; flows: arrows

• Oceans (96.5%), glaciers/ice caps (1.7%), groundwater (1.7%)

• Surface freshwater (0.02%), atmosphere (0.001%), organisms (0.0001%)

• Transpiration, sublimation, evaporation, condensation, advection, precipitation

• Melting, freezing, run-off, infiltration, percolation, streamflow, groundwater flow

• Agriculture, deforestation, urbanization alter flows and stores

• Reduced evapotranspiration, increased run-off → flash floods

• Flow diagrams of inputs and outputs

• Calculate sustainable harvesting rates

• Polarity, cohesion, adhesion, solvent properties

• Transparency, high specific heat capacity

• Density variations with temperature

• Gas solubility variations

• Absorb atmospheric CO₂ and sequester it

• Moderates atmospheric CO₂ increases

• Saturation point may be reached

• Short-term: dissolved CO₂ → ocean acidification

• Long-term: biomass accumulates on seabed → fossil fuels

• Cold water below, warmer above

• Density differences restrict mixing → stratification

• Water densest at 4°C → freezing from surface down

• Occurs in deeper lakes, coastal areas, seas, ocean

• Thermocline: transition layer between warm surface and cold deep water

• Differences in dissolved oxygen and mineral nutrients

• Global warming and salinity changes

• Most pronounced in upper 200m

• Bring cold, nutrient-rich waters to surface

• Mass vertical movement from depths

• Seasonal cycles in stratified lakes and ENSO

• Driven by temperature and salinity differences

• Ocean conveyor belt distributes heat globally

• Affects climate