Processes Driving Change In The Magnitude Of Water Cycle Stores Over Time And Space Flashcards
Summary of what changes the size of stores in the global water cycle? (No examples)
Transfers/Flows which are processes, which determine how much water is inputted or outputted into the system. This may due to natural or anthropogenic (human) factors
What are the main global transfer processes which change the magnitude of water cycle stores?
- Precipitation
- Evaporation
- Condensation
- Sublimation
- Interception
- Overland Flow
- Infiltration
- Throughflow
- Percolation
- Groundwater Flow
(Also, climate change)
Define Precipitation
Transfer of water from the Atmosphere to the ground. It can take the form of snow, rain, hail, dew
Define Evaporation
Transfer of water from liquid state to gaseous state (water vapour). The vast majority occurs from the oceans to the Atmosphere
Define Condensation
Transfer of water from a gaseous state to a liquid state, for example, the formation of clouds
Define Sublimation
Transfer of water from a solid state (ice) to a gaseous state (water vapour)
Define Interception
Water intercepted and stored on leaves of plants
Define Overland Flow
Transfer of water over the land surface
Define Infiltration
Transfer of water from the ground surfaces into soil, where it may then percolate into underlying rocks
Define Throughflow
Water flowing through soil towards a river channel
Define Percolation
Water soaking into rocks
Define Groundwater Flow
Transfer of water very slowly through rocks
Why does the magnitude of global water stores change over time and space?
For example, seasonal changes that occur in the Arctic with the annual freezing and melting of the sea ice
(caused by processes such as evaporation and Sublimation)
How much does the global water stores change on a global scale?
Do not change significantly on a global scale
How much does the water stores (e.g. Soil storage) change on a local scale?
Can change significantly on a local scale (e.g by extreme events such as storms)
Describe Evaporation generally and on a Local and Global Scale
- Approx. 90% of atmospheric water storage is from evaporation of oceans and seas
- 10% comes from plant transpiration
- High levels of Evaporation can occur in tropical and desert areas (regional level)
- Increased global changes due to Evaporation are likely to occur due to climate change and increased atmospheric temperature
- Level of Evaporation on global scale for Ocean and sea level is minimal, but in drainage basin (local) Evaporation has large impact
- Lakes/rivers in areas with high maximum summer temperature experience high levels of Evaporation, so Hydrosphere storage will reduce significantly (causing droughts)
Describe Condensation
- Occurs when temperatures fall and humidity increases
- Tiny, microscopic water molecules which develop around dust and smoke particles (called aerosols) will be carried on the area invisibly. When they combine into larger molecules of liquid water or ice, they may be mist, fog or clouds
- This occurs on a global scale but could alter as climate change increases global atmospheric temperatures
Describe Cloud Formation
- Process where clouds form when water molecules aggregate
- Occurs when air temperature falls to a point where condensation of water vapour occurs (at dew point) or when humidity content has risen (so that water vapour can’t remain in that state and condenses)
- As water molecules aggregate, clouds form with tiny water/ice particles kept in the air by rising air currents
Describe causes of precipitation
- Occurs when water molecules within a cloud combine and become too large (called coalescence)
- Occurs of the droplet’s fall velocity is greater than the cloud’s updraft velocity (if droplets fall faster than the cloud moving upwards)
- Whether rain, snow or hail is the precipitation depends on the clouds surrounding temperature and height
Describe Cryospheric Processes
- After oceanic water, the largest store of water on Earth is frozen water (ice) in the Cryosphere
- 95% of frozen water is stored in the world’s two largest ice sheets covering Antarctica and Greenland
- Cryospheric processes such as accumulation and ablation change the amount of water stored as ice in the Cryosphere. The balance of accumulation and ablation varies with temperatures
- During cold global periods, inputs are greater than outputs in the Cryosphere (water is transferred to Cryosphere as snow and less water transferred away due to melting)
- During warm global periods, magnitude of Cryosphere Store reduces as losses due to melting are larger than inputs of snow
- On a long-time scale, snow falling on glaciers and ice sheets become compressed and enter long-term storage, forming layers of glacial ice (scientists have found ice over 400,000years in Antarctic)
- On short time scale, snow accumulated during winter adds to mass of glacier or ice sheet. In summer, melting occurs or ice calves (breaks away). On a glacier, the equilibrium line marks the altitude where annual accumulation and melting are equal.
Recently, climates have warmed causing the equilibrium lines to move to higher altitudes, most glaciers are shrinking and retreating
Example of Positive Feedback of melting freshwater ice
Melting of freshwater ice –> increases sea levels (total melting of all polar ice sheets can result in a 60m rise in sea level) –> increases water to the ocean store (Hydrosphere)