4.1

Question 1

% of the earth covered by water and % of water that is fresh

Answer 1

• 70% of earth covered by water
• 97% is seawater
• 2.6% is freshwater

Question 2

the life of a water molecule

Answer 2

• water on earth = constantly cycled
• size of storages in cycle = long time for water molecule to flow from one storage to another
• water can be both renewable and a non-renewable resource –> e.g. atmosphere and rivers are renewable, oceans and ice-caps are non-renewable

Question 3

transfers (flows) of water

Answer 3

• ocean surface currents –> driven by winds and tides
• ocean conveyer belt –> large scale circulation of oceans
• surface runoff - flow of water along surface after heavy rain
• infiltration - soaking of water in porous soils

Question 4

ocean circulation and climate

Answer 4

• water = high heat capacity –> can absorb lots of heat energy from equatorial regions + transport it towards the poles
• has effect of evening out world’s climate –> tropics cooler, southern/northen latitudes warmer
• e.g: heat transported by gulf stream maintains western europe’s mild climate

Question 5

water transfer and transformations

Answer 5

TRANSFORMATIONS
- evaporation - liquid water → water vapor (gas)
- condensation - water vapor → liquid water (cloud formation)
- evapotranspiration - evaporation of water from plant’s stomata during photosynthesis (transportation and evaporation combined)
- sublimation - ice → water vapor
- freezing/melting
TRANSFERS
- precipitation
- infiltration
- stream flow
- advection –> clouds transported by wind

Question 6

what powers the global hydrological cycle

Answer 6

• powered by solar radiation –> drives endothermic transformations of water
• differential heating of atmosphere creates differences in air pressure, leading to winds
• tropics: evaporation / thermal expansion power ocean currents

Question 7

human impacts on the hydrological cycle

Answer 7

• agriculture: water flowing through agriculture land can pick up fertilizers, animal waste, and pesticides –> leads to pollution and spread of diseases
• urbanization: concrete prevents water from reaching aquifers - causing surface run-off (collecting waste) which leads to pollution of ecosystems
• deforestation: vegetation protects soil from impact of raindrop –> reducing soil erosion + impends movement of water allowing time for infiltration

Question 8

flash flooding

Answer 8

• climate change increases probability of heavy precipitation
• land clearance for agriculture –> water absorbed less effectively (e.g. wetland draining)
• deforestation increases rate of runoff –> tree leaves intercept falling precipitation + moist floors allow rapid infiltration

Question 9

the ocean conveyor belt

Answer 9

• driven by differences in water density driven by temperature (colder = more dense) and salinity (high salinity = high density)
• cold air at the poles cools the water –> becomes denser and sinks –> water that freezes & evap leaves behind salt that raises density –> the cold water warms at the equator = less dense and rises to surface
• water transfers heat to its environment and it absorbs from it
• global warming: melting glaciers in Poles increase warm water input –> could prevent formation of water density gradient leading to collapse of conveyor belt & positive feedback