ELSS

• Explain why natural systems are in dynamic equilibrium

  They are dynamic in the sense that they have continuous inputs, throughputs, outputs and variable stores of energy and materials
• Explain a negative feedback loop in a drainage basin

  - Unusually heavy rainfall will increase the amount of water stored in aquifers

  - This raises the water table which increases the flow from springs until the water reverts to normal levels
• Describe what urbanisation is

  - The conversion of land use from rural to urban.

  - Farmland and woodland are replaced by housing, offices, factories and roads: natural surfaces such as vegetation and soil give way to concrete brick or tarmac
• Explain the impact urbanisation has on the environment

  - Artificial surfaces are largely impermeable, so they allow little or no infiltration and provide minimal water storage capacity to buffer run off

  - Urban areas have drainage systems designed to removed surface water rapidly (pitched roofs, gutters, sewerage systems) which allows high proportions of water from precipitation flows quickly into streams and rivers leading to a rapid rise in water level

  
  

  - Floodplains are natural storage areas for water, and urban development on floodplains reduces water storage capacity in drainage basins, increasing river flow and flood risks
• Explain the impact farming has on the carbon cycle

  The clearance of forest for farming reduces carbon storage in both above and below ground biomass

  - Soil carbon storage is reduced by ploughing and the exposure of soil organic matter to oxidation

  - Further losses occur through harvesting of crops with only small amounts of organic matter being returned to soils

  - Soil erosion accompanies arable farming

  - Erosion by wind is most severe when crops have been lifted and soils have little protection
• Explain the impact farming has on the water cycle

  - Crop irrigation diverts surface water from rivers and groundwater to cultivated land. some of this water is extracted by crops from soil storage and released by transpiration, but most is lost to evaporation and soil drainage

  - Interception of rainfall is less in forests, evaporation and transpiration from leaf surfaces is less

  - Ploughing increases evaporation and soil moisture lost, furrows ploughed downslope act as drainage channels, accelerating run off and soil erosion

  - Surface run off increases where heavy machinery compacts soils and result in peak flows on streams draining farmland
• Explain the change to the water cycle as a result of forestry

  - Higher rates of rainfall interception in plantations in natural forest. In Eastern England, interception rates for Sitka spruce are as high as 60%, Temperatures and evaporation are lower, interception is half

  - Increased evaporation - a large proportion of intercepted rainfall is stored on leaf surfaces and evaporated directly

  - Reduced run off and stream discharge. High interception and evaporation rates and the absorption of water by tree roots

  
  

  - Forest trees extract CO2 from the atmosphere and sequester it for hundreds of years. Most of the carbon is stored in woods however trees become an active carbon sink for the first 100 years after planting - after that, the carbon captured levels out and soil decomposers have a rotation period of 80-100 years
• Describe the water extraction on the River Kennet

  - Area of 1200 km"2

  - The upper catchment mainly comprises of chalk which is highly permeable

  - Chalk contributes most of the kennets flow

  - Supports biodiversity

  - Water filtered through chalk, is clear, has high oxygen, fast flowing, has salmon and trout, and otters
• How has water extraction affected the river kennet

  - Rates of groundwater have exceeded rates of recharge and falling water table has reduced flows by 10-14%

  - During the 2003 drought, flows fell by 20% and dry conditions of early 1990s by 40$

  - Lower flows have reduced flooding and temporary areas of standing water and wetlands on the floodplain

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• Describe an aquifer


  - Aquifers are permeable or porous water-bearing rocks such as chalk and New Red Sandstone

  - Groundwater is abstracted for public supply from aquifers by wells and boreholes

  - Water table - the aquifer of the upper surface of saturation is known as the water table

  - Height fluctuates seasonally and is affected by rainfall, drought and abstraction
• Describe an artesian basin

  - Sedimentary rocks from a syncline or basin-like structure, an aquifer confined between impermeable rock layers may contain artesian pressure

  - Groundwater flowing to the surface is known as an artisan aquifer

  - Potentiometric surface is determined by the height of the water table
• Explain how fossil fuels have impacts on the carbon cycle

  - Fossil fuels have driven global industrialisation and urbanisation

  - Fossil fuels consumption releases 10 billion tonnes of CO2, to the atmosphere annually, increasing atmospheric CO2 by over 1ppm

  - estimated that 1750 cumulative anthropogenic CO2 emissions total nearly 2000 GT

  - 3/4 of these emissions have remained in the atmosphere raising CO2 concentrations

  - CO2 levels in the atmosphere are the highest for at least 800,000 years

  - Anthropogenic carbon emissions comprise less than 10% of the natural influx from the biosphere and oceans

  - Increased absorption of anthropogenic carbon by the oceans and biosphere, todays atmospheric CO2 concentrations would exceed 500ppm
• Explain what CCS is


  -The combustion of fossil fuels is from the atmosphere and oceans is the main driver of present day global warming

  - Capture and store CO2 released by power plants and industry

  - technology based at coal-fired power stations

  1 . CO2 is separated from power station emissions

  2. The CO2 is compressed and transported by pipeline to storage areas

  3. Injected into porous rocks deep underground where it is stored permanently
• Evaluate CCS


  - Could eventually play an important part in reducing CO2 and other greenhouse emissions

  - 40'% of all CO2 emissions are from coal and gas fired power stations and CCS has the potential to reduce these emissions by 80-90%

  - CCS at Peterhead in NE scotland has rising costs, designed to capture 2 million tonnes of CO2 was axed in 2016.

  - Plan was for the carbon to be transported by pipeline to the North Sea and depleted in gas reservoirs

  - Technology is feasible but effectiveness is limited due to economic and geological factors
• Explain the reasons why CSS effectiveness is limited

  - Involved big capital costs : the Draz and Peterhead projects will cost at least £1 billion

  - Uses large amounts of energy - typically 20% of a power plants output is needed to separate the CO2 and compress it

  - Requires storage reservoirs with specific geological conditions
• Explain the positive feedback cycles in the water cycle

  - Rising temperatures affect the water cycle at the global scale

  - Warm temperatures result in increased evaporation and therefore the atmosphere holds more vapour

  - This results in greater cloud cover and more precipitation

  - Which has an overall positive feedback effect because water vapour is a greenhouse gas, more vapour in the atmosphere increases absorption of long-wave radiation from the Earth causing further raise in temperature
• Explain how the positive feedback can result in negative feedback

  - More atmospheric vapour can induce negative feedback

  - More vapour creates greater cloud coverage which reflects more solar radiation back into space, as smaller amounts of solar radiation are absorbed by the atmosphere, oceans and land, average global temperatures fall

  
  

  - Above average precipitation increases river flow and evaporation, excess water reaches aquifers, increasing water storage in permeable rocks

  
  

  - During droughts, the system adjusts to lower temperatures by reducing run off and evaporation, helping to conserve groundwater stores
• Explain a negative feedback loop in the carbon cycle


  - Human activity burning fossil fuels has increased the concentration of CO2 in the atmosphere, the acidity of the oceans and the flux of carbon between stores

  - CO2 is released by stimulating photosynthesis (carbon fertilisation)

  - Excess CO2 is extracted from the atmosphere and stored in the biosphere

  - Eventually, the carbon makes its way into long term storage in soils and ocean sediments, allowing the system to return to a steady state
• Describe a positive feedback loop in the carbon cycle and in the Tundra

  - Global warming will intensify the carbon cycle, as it speeds up decomposition and release more CO2 into the atmosphere, amplifying the greenhouse effect

  
  

  - Global warming is occurring faster than in any other region (1.5-2.5 in the past 30 years)

  - As the arctic sea ice and snow cover shrinks, large expanses of sea and land are exposed, meaning that sunlight is absorbed, warming the tundra, and melting the permafrost
• Describe the importance of monitoring changes

  - As the damaging of the climate, accurate monitoring changes in global temperatures, sea surface temperatures, sea ice thickness and rates of deforestation is essential

  -GIS allows us to use these techniques on varied time scales which can then be mapped and show areas of change, and anomalies.
• Explain short term changes in a cycle

  DIURNAL

  -Change in a 24 hour period

  - Lower temperatures at night reduce evaporation and transpiration.

  - Convectional precipitation, dependent on direct heating of the ground surface by the sun during the daytime falling in the afternoon after the temperatures have reached the maximum

  - Flows of carbon vary during day and night. During the day, CO2 flows from the atmosphere to vegetation

  - At night, the flux is reversed, without sunlight photosynthesis switches off and vegetation loses CO2 to the atmosphere

  
  

  SEASONAL

  - Seasons are controlled by variation in solar radiation

  - Solar radiation peaks in mid-June

  -Solar input in June peaks at 800 W/m"2, December it falls to 150 W/m"2

  Evapotranspiration is highest in the summer months and lowest in the Winter

  - Carbon is measured through NPP of vegetation

  - During northern hemisphere summer, there is a net global of CO2 from the atmosphere to the biosphere resulting in a 2ppm fall in atmospheric CO2 which is reversed during the winter
• Explain how and why Arctic sea ice is monitored

  - NASA Earth Observing System satellites have monitored sea ice growth and retreat since 1978

  - Measures microwave energy radiated from Earth's surface

  - Comparison of time series images to show changes
• Explain how Ice caps and glaciers are monitored


  - As well as ground-based estimates of mass balances, satellite technology

  - Measures surface height of ice sheets and glaciers using laser technology

  - Shows extent and volume of ice and changes
• Explain how sea surface temperatures (SSTs) are monitored

  - Radiometers measure the wave band of radiation emitted from the ocean surface

  - Changes in global SSTs and areas of upwelling and downwelling
• Explain how water vapour is monitored

  NOAA Polar orbiters

  - Measures cloud liquid water, total precipitable water

  - Long term trends in cloud cover and water vapour in the atmosphere
• Explain how deforestation is motired


  - ESA albedo images from various satellites

  - Measurements of reflectivity of Earth's surface and land use changes
• Explain how atmospheric CO2 is monitored

  NASA orbiting carbon observatory, ground based measurements at Mauna Loa, Hawaii since 1958

  - New satellite measurements of global atmospheric CO2 from NASA orbiting carbon observatory

  - Measures effectiveness of absorption of CO2 by plants

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• Explain how NPP in oceans is monitored

  - NASA MODIS

  - Measures net primary productivity in oceans and on land
• Describe what long term changes are

  - During the last 400,000 years, there have been 4 major glacial cycles with cold glacial followed by warm interglacial

  - Each cycle lasts around 100,000 years where around 20,000 years ago, the temperatures were 5C lower than they were today

  - During warmer interglacial periods, global temps have been more extreme and have reached 22C which is 7-8C higher than today
• Explain the long term changes to the water cycle

  - Net transfer of water from the ocean reservoir to storage in ice sheets, glaciers and permafrost

  - Sea levels fall by 100-300m and ice sheets and glaciers expand to cover 1/3 of continental land mass

  - As ice sheets advance, they destroy extensive areas of forests and grassland

  - The area covered by vegetation shrinks and the climate becomes drier
• Explain the long term changes to the carbon cycle

  - At times of glacial maxima, CO2 concentrations fall to around 180 ppm and warmer periods it can be 100ppm higher

  - No clear explanation however it is likely that excess CO2 goes from atmosphere to deep oceans and stimulated phytoplankton growth and bringing nutrients to the surface

  - Low ocean temperatures make CO2 more soluble

  - Carbon in vegetation shrinks as ice sheets occupy the land area

  - Soil being covered by ice means carbon can no longer be exchanged to atmosphere meaning less photosynthesis therefore less photosynthesis.