1. Mass balance
1.1. There is a fixed volume of water globally
2. Earth's subsystem
2.1. Cryosphere
2.1.1. All frozen water
2.2. Lithosphere
2.2.1. Outermost part of Earth's layers
2.3. Hydrosphere
2.3.1. All water on Earth
2.4. Biosphere
2.4.1. Water within all living things
2.5. Atmosphere
2.5.1. Gaseous water
2.6. All subsystem stores can change with time and space
3. Changes to stores can vary with time and space
3.1. Cryosphere changes
3.1.1. Ice ablation
3.1.1.1. Melting of ice
3.1.2. Ice accumulation
3.1.2.1. Build up of snow and ice
3.2. Seasonal variation
3.2.1. Level of ice accumulation and ablation will vary by seasons e.g. summer vs winter
3.3. Millennial variation
3.3.1. Evidence of changes to cryosphere storage e.g. hothouse Earth (about 65-35 million years ago) and Snowball Earth (750-650 million years ago)
3.3.2. Milankovitch Cycles will affect cryosphere storage
3.3.2.1. Eccentricity
3.3.2.1.1. 1. Every 100,000 years, Earth’s orbit changes from spherical to elliptical, changing solar input.
3.3.2.2. Tilt
3.3.2.2.1. 2. The Earth’s axis is currently tilted at 23.5°, but this changes over 41,000-year cycle between 22° and 24.5°, also affecting solar input.
3.3.2.3. Precession
3.3.2.3.1. 3. The Earth’s axis wobbles, changing over 22,000 years, bringing further climate change.
3.4. Locational variation
3.4.1. Changes in climates will determine the storage of water within the system e.g. Tropical Rainforests will have more storage in the biosphere compared to desert environments
4. System
4.1. Global water cycle
4.1.1. Closed system as water cannot be lost or gained
4.2. Drainage basin system
4.2.1. Open system as water can be lost or gained e.g. if rainfall falls on the watershed
5. Systems have components
5.1. Inputs
5.1.1. Water entering the system
5.1.2. e.g. Precipitation is the only input
5.2. Flows
5.2.1. Movements of water between stores
5.2.2. e.g. Throughflow, overland flow, stem flow
5.3. Stores
5.3.1. Wherever the water is held
5.3.2. e.g. Oceans (largest store of water - 97%)
5.4. Outputs
5.4.1. Water leaving the system
5.4.2. e.g. Evaporation
6. Exam Question
6.1. Explain why the Milankovitch cycles change the size of cryosphere storages on earth (6)
6.1.1. One way Milankovitch cycles can affect cryosphere storage is Eccentricity. This is the orbit shifting from spherical to elliptical. This changes the cryosphere storages as during the elliptical orbit, the proximity of Earth to the Sun decreases, leading to greater solar intensity, and the rise in temperature will result in the melting of ice caps. Tilt is when the axis changes from between 22 degrees and 24.5 degrees. This encourages warmer winters and colder summers. When faced towards the Sun, solar intensity increases and cryosphere storage decreases (ice ablation) and vice versa for tilting away. Precession is when the earth’s axis wobble. The shifts cause the solar radiation to be distributed differently. Lower solar intensity leads to ice accumulation.