W + C: The Water Cycle Flashcards
What is the global distribution and size of major stores of water?
There is a fixed amount of water on Earth and in its atmosphere. The majority of the water is saltwater (97.4%) and only 2.6% is freshwater. Of freshwater, 79% is from ice caps and glaciers, with 20% groundwater and 1% easily accessible surface freshwater (which in itself is 52% lakes, 38% soil moisture, 8% atmospheric water vapour, 1% rivers and 1% organisms).
• water on or close to the Earths surface is called the Hydrosphere.
What is oceanic water?
Although the ocean contains 97% of the earths water, oceanographers have only explored 5%. The salt allow the water to stay as a liquid water below 0 DC. They are an alkaline with a pH of 8.14 that has fallen from 8.25 in the last 250 years due to the increase in carbon.
What is Cryospheric water?
The cryosphere describes area where water is a solid. There are 5 locations: Sea Ice (Artic Ocean); Permafrost (frozen ground in Alaska); Ice Caps (Iceland); Ice Sheets (Greenland); Alpine Glaciers (The Alps).
What is sea ice?
doesn’t raise sea level when it melts, because it forms from ocean water. Ice shelves are platforms of ice that form where ice sheets and glaciers move out into the ocean (exist mostly in Antartica and Greenland).
What are ice sheets?
mass of glacial land ice extending more than 50,000km2. The Antartica and Greenland ice sheets account for >99% of the freshwater ice on earth. form when winter snow fall doesn’t entirely melt in the summer. Over 1000s of years, the ice layers build up and compress. Constantly moving downhill due to their weight. If Greenland sheet melted, sea levels would rise by 6m, if Antartica sheet melted, would be roughly 60m
What are ice caps?
thick layers of ice on land that are smaller than 50,000km2- usually found in mountainous areas. Dome-shaped and located over the highest points of an upland area. Become the major source for many glaciers.
what are alpine glaciers?
thick masses of ice found in deep valleys and upland hollows.
What is permafrost?
ground (soil or rock) that remains at or below 0 DC for at least 2 consecutive years. Thickness varies from 1-more than 1500m. Melting permafrost is releasing huge amounts of carbon dioxide and methane.
What is terrestrial water?
4 broad classes: Surface water (rivers, lakes, etc.); Ground water (water that collects underground in the pore spaces of rocks); soil water; Biological water (water stored in biomass - e.g. plants and animals)
Wha is surface water?
Rivers —> act as both a store and a transfer of water (transfer water from the ground, soils and the atmosphere to a store). Lakes —> collections of freshwater found in hollows on the land surface. Wetlands —> areas of marsh, fen, peatland or water, with a dominance of vegetation.
What is ground water?
30% of all freshwater is stored in rocks deep below the ground, forming vast reservoirs known as aquifers - which are commonly found in porous (contain lots of air pockets) and permeable (allow water through) rocks such as chalk and sandstone. Upper layer of saturated rock is called the water table (boundary between saturated and unsaturated) and it rises and falls due to: groundwater flow and water abstraction. Management of the water table needs to be maintained at the same level (state of equilibrium).
What is soil water?
vary in their capacity to store or transfer water (soil water budget). Porous sandy soil holds very little water but allows the transfer of water. Clay soils store a huge amount of water, but allows very little transfer.
What is biological water?
varies widely around the globe depending on the vegetation cover and type. Areas of dense rainforest store much more water than deserts. Many plants are adapted to store water in large quantities.
What is atmospheric water?
This exists in all 3 states, most common of which is gas (water vapour). Water vapour absorbs, reflects and disperses incoming solar radiation helping the atmosphere regulate its temp. Cold air cannot hold as much water as warm air, hence the air over the poles being dry in comparison to the tropics. An increase in water vapour —> increased atmospheric pressure; positive feedback as this will then lead to a rise in water vapour level as the air is warmer. Clouds are a visible mass of water droplets or ice crystals suspended in the atmosphere. They form when the air becomes saturated due to either cooling air or an increase in water vapour.
How is the lithosphere a subsystem?
water stored in the crust and upper mantle.
• All the water within the rocks too.
What’s a cascading system?
Water moves between these stores at different rates and remains in storage for different periods of time. In moving from one store to another, water moves through different ‘spheres’ (Biosphere, lithosphere, hydrosphere, atmosphere and cryosphere)
How do processes drive change in state?
Energy in the form of latent heat is either absorbed or released depending on the process. Supplying or removing Heat energy to or from a substance causes it to change State.
What is evaporation?
occurs when energy from the sun hits the surface of the water/land and causes the liquid to turn to gas. The rate of this depends upon;
- Amount of Solar Energy
- availability of water
- humidity of the air (the more humid the air, the closer to saturation point the air is so less evaporation will occur)
- the temp of the air (warmer air can hold more water than cold air).
What is condensation?
the direct cause of precipitation, occurs when;
- the temp of the air is reduced to the dew point (e.g. when a cold winters night - heat radiates away from the earth and ground gets cooler)
- and when air rises, it cools, as it cools, it expands (adiabatic cooling) and this can occur when air is forced over hills- this is the orographic effect.
What is the formation of clouds?
atmosphere is full of gas particles (water vapour) and also tiny particles of salt/dust (aerosols) - both vapour and aerosols constantly bump into each other. When air is cooled, some vapour sticks to aerosols (condensation). The warmer the air is, the more water vapour it can hold.
- Clouds form when the air rises, becomes saturated and cannot hold any more water. This can happen in 2 ways:
—> the amount of water in the air has increased
—> the air has cooled to its dew point.
Finally, as water droplets group together, they become heavy and gravity pulls them down as raindrops. If the air is cold enough, the ice crystals remain frozen and fall as snow.
How does cloud formation happen at the equator?
high evaporation, air rises - cools - condenses to form Low Pressure Zones (ITCZ - Inter-Tropical Convergence Zone). Mid-Latitudes - convergence of warm tropical air and cold Artic air. Localised scale - thunderstorms from intense convective activity.
What are cloud condensation nuclei’s?
For clouds to form, there have to be tiny particles of other substances (e.g. dust or salt)
- they give water a surface to condense on - this encourages clouds to form, rather than allowing moist air to disperse.
What is frontal rainfall?
- Areas of warm and cool air are blown towards each other by the wind.
- The lighter, less dense warm air is forced to rise over denser cold air
3.- Frontal rain, produces a variety of clouds which brings moderate to heavy rainfall.
— the UK experiences a lot of frontal rainfall because we have weather systems called depressions that brings lots of cold and warm air together.
What is relief rainfall (also called orographic rainfall)?
- The Prevailing wind picks up moisture from the sea
- The moist, warm air is forced to rise up the mountain, cool and increases forming clouds.
- the air drops down over the mountain, warming as it does. As it warms, it condenses the amount of water it can hold, meaning little rainfall occurs here. This is called the rain shadow effect.
What is conventional rainfall?
- The surface of the earth is heated by the sun
- The warm surface heats the air above it, hot air always rises and as it does, the air begins to cool and condensate
- Convection produces cumulus-nimbus clouds (heavy, dark and towering storm clouds), which produce heavy rain and possible thunder and lightening.
How do cryospheric processes affect the magnitude of stores over time and space?
ice is another large store of water, that over-time has fluctuated massively. In the short-term snow accumulates and adds to the mass of the glacier or ice sheet. In recent years, the climate has warmed - so ice stores shrink and retreat (positive feedback). As glaciers melt, sea levels rise which could destabilise ice shelves causing more calving and further melting.
What are the processes of change at a local scale - hillslopes?
- hillslopes are considered to be the most important local unit of study by hydrologists.
- Consists of multiple water stores which operate over short timescales
- The most influential process is infiltration and the rapid transfer of water overland is a major cause of flooding.
- Affected by a variety of natural and human factors. Different types of water storage.
What is the soil water budget?
describes the changes in the soil water store during the course of the year due to infiltration.
- Winter - precip exceeds potential evapotranspiration (water rising as vapour from the ground or released from the leaves) leading to a water surplus, soils saturated, higher river levels and overland flow (rainfall exceeds infiltration capacity).
- Summer - Evapotranspiration exceeds precipitation meaning that the soil dries up.
- Autumn - Evapotranspiration starts to fall, therefore soil water is replenished (recharged)
- Spring - plants start to grow again and potential evapotrans increases as temps get higher and plants start photosynthesising more. Infiltration and percolation will also refill the water table.
