Systems

• System


  A set of interrelated elements of both components ( stores ) and processes ( links ) that form a working unit
• Open system


  A system where energy and matter can be transferred from neighbouring systems as an input, and to other systems as an output
• Inputs

  • Precipitation
  • Energy - kinetic, thermal and gravitational potential energy
  • Material from glacial erosion, deposition, weathering and mass movement - typically sediment
• Outputs

  • Melting
  • Evaporation
  • Sublimation
  • Deposited material - sediment
• Throughputs


  Material passing through a system that consists of stores ( sediment held in a glacier ) and flows ( transfers like basal sliding of ice )
• Equilibrium


  When a system's INPUTS = OUTPUTS

  Eg. when the rate of ice added to a glacier = the rate of loss from melting
• Dynamic equilibrium


  When a system self regulates itself by producing a response to a disturbance in order to restore equilibrium
• Ablation


  Includes all losses of ice from a glacier, including melting, evaporation, sublimation and iceberg calving
• Sublimation


  The direct change of state from sold ( ice ) to gaseous ( water vapour )
• Accumulation zone


  The upper section of the glacier where accumulation exceeds ablation

  Inputs > outputs
• Ablation zone


  The lower section of the glacier where ablation exceeds accumulation

  outputs > inputs
• Equilibrium line of latitude (ELA)

  The altitude at which there is a balance between accumulation and ablation

  inputs = outputs
• Glacier Mass Balance ( or glacial budget )


  Mass Balance = Accumulation - Ablation

  
  

  If the number is positive, the glacier is bigger

  If the number is negative, the glacier is smaller
• Positive Mass Balance

  When accumulation > ablation, therefore inputs > outputs, therefore a net gain of ice, therefore an increasing volume of ice, therefore the glacier will advance

  
  

  This is typically in the winter season
• Negative Mass Balance

  When ablation > accumulation , therefore outputs > inputs, therefore a net loss of ice, therefore the glacier will retreat up the valley

  
  

  This is typically in the summer season
• Past and present distributions of cold environments

  • Todays glaciers cover 10% of the earth's surface
  • Ice ages occur roughly every 200-250 million years
  • The last ice age was known as the Pleistocene glaciation
  • We are now in an interglacial period- ice still covers part of the earth's surface but has retreated to polar areas
  • We are currently in the Holocene Epoch
• Pleistocene Glaciation

  • Part of the quaternary era
  • Covered 30% of the earth's surface
• Ice age

  A period of long term reduction in the earth's surface temperature
• During an ice age there are:

  Glacials:

  • Periods of cold and dry climate where land and sea ice masses grow and valley glaciers advance
  • The last glacial ended 10,000 years ago
  • During glacial periods there is 30% ice coverage on earth

  Interglacials:

  • Warmer periods where ice masses reduce and valley glaciers begin to retreat
  • We are currently in an interglacial period known as the Holocene
  • During interglacial periods there is 10% ice coverage on earth
• Glacier

  A mass of ice in motion
• The main areas of glacial activity:

  • North of the Arctic Circle: Greenland Ice sheet
  • South of the Antarctic Circle: Antartica Ice sheet
• Glacier system Inputs

  • Precipitation - in the form of rain, hail or snow
  • Sediment - Rocks or eroded material
  • Kinetic Energy - Movement of ice
  • Thermal Energy - Solar radiation
  • Gravity - Gravitational Potential Energy (GPE)
• Glacier system outputs

  • Sediment - Rocks or eroded material deposited when ice melts
  • Ablation - Melting
  • Calving - Large rocks or ice break off
• Glacial Positive feedback loops

  Ice mass melts > less ice to reflect solar radiation > low albedo > climate warms > increased ablation > glaciers retreat

  Ice mass grows > more ice to reflect solar radiation > high albedo > climate cools > increased accumulation > glacier advances
• Physical factors influencing a glaciated landscape:

  • Climate - wind, precipitation, temperature > macro scale
  • Geology - lithology and structure > regional scale
  • Latitude and altitude > micro scale
  • Relief and aspect > micro scale
• Impact of latitude on glacial landscapes

  P: Latitude has a micro influence on the regional climate

  
  

  E: Increased latitude > increased curvature > increased dispersed radiation > decreased temperature > decreased ablation and increased accumulation > formation of ice sheets

  
  

  E: The Arctic and Antarctic Circles have cold and dry climates at a high latitude > allows large stable ice sheets to form

  
  

  L: Micro impact at a regional scale as it determines the glacier type and therefore the rate of erosion
• Curvature of the earth

  • Determines how concentrated incoming solar radiation is at the surface
  • At the poles, solar radiation is dispersed over a much larger area > lower temperature
  • At the equator, solar radiation is concentrated over a small area > higher temperature
• Impact of altitude on glacial landscapes

  P: Altitude has a micro influence on regional climate

  
  

  E: High altitude > decreased temperature > increased accumulation > formation of valley glaciers

  
  

  Due to seasonal variation > dynamic glaciers

  
  

  E:

  • Temperatures decrease by 1 degree every 100 m
  • Higher rates of precipitation than in areas of high latitude eg. Lake District: average 2000 mm /year vs Vostok station, Antarctica: 4.5 mm/ year

  L: Micro impact at a regional scale as it determines the glacier type and therefore its rate of erosion
• The impact of climate on glacial landscapes

  Point: Climate has the most significant influence at a macro scale as it determines whether glaciers are present - if it meets the conditions for diagenesis to occur. This involves wind, temperature and precipitation

  
  

  E: Points include temperature, wind and precipitation

  
  

  Link: Climate is the most significant factor at a global scale due to climate patterns determining whether a glacier can form
• Impact of temperature on glacial landscapes: Diagenesis

  Temperatures need to be below the pressure melting point in order for snow to accumulate and diagenesis to occur. When snow falls it has a low density of 0.05 g/cm3 causing it to accumulate and compress. If the snow survives during the summer’s melting and compacts it becomes firn with a density of 0.4 g/cm3. Once temperatures drop below PMP, it freezes within the gaps of ice crystals. After many years, from 20 years to 1000, the pressure increases to a density of 0.8 g/cm^3 and glacial ice forms. This process is known as diagenesis.
• Impact of wind on glacial landscapes:

  Wind picks up material and uses it in aeolian processes such as erosion, deposition and transportation.
• Impact of precipitation on glacial landscapes:

  • Precipitation is the main input to the system of a glacier and determines its mass balance
  • It can be in the form of rain, sleet, hail or snow, depending on seasonal variation.  
  • Precipitation is affected by latitude and altitude
  • High latitude areas > decreased temperature > temperatures remain below PMP > decreased precipitation due to high pressure
  • High altitude areas > higher rates of precipitation due to relief rainfall > Eg. Lake District average rainfall/year: 2000 mm vs Vostok station, Antarctica: 4.5 mm
• High latitude

  Little seasonal variation > stable glaciers

  Example: Greenland
• High Altitude

  Seasonal variation > dynamic glaciers

  Example: Himalayas or Lake District
• Impact of relief on glacial landscapes:

  P: Steep relief gives more energy to a glacier

  E: Steep relief > increased GPE due to greater force of gravity > glacier will have more energy to move downslope > increased pressure on surrounding bedrock and mountainsides.

  E:

  L: Steep relief and north facing aspect > higher rates of erosion > micro scale impact
• Impact of aspect on glacial landscapes:

  P: The direction that a glacier faces impacts its ability to erode the surrounding landscape > influences where on the mountain landforms are created

  E:

  • Aspect away from sun - North facing in northern hemisphere > decreased temperature > decreased ablation and increased accumulation > inputs exceed outputs > increased diagenesis > positive mass balance
  • Aspect faces sun > increased temperature > increased ablation > negative mass balance

  E: Lake district corries mostly face north or northeast

  L: Localised impact > influences the direction of a landform
• Impact of geology on glacial landscapes: Lithology

  P: Geology determines the type of landforms - erosional and depositional

  E:

  • Windermere > weaker sedimentary rock > Eg. limestone > composed of calcium carbonate > chemically weaker > vulnerable to chemical weathering
  • BVG > resistant igneous rock > Eg. Granite or Basalt > composed of dense interlocking crystals > strong structure > more resistant to weathering or erosion

  E:

  • Windermere > depositional landforms > Kendal drumlins
  • BVG > erosional landforms > Red Tarn corrie

  L: Geology determines landform types but needs a cold climate first
• Lithology

  The chemical and physical composition of rocks

  This affects the impacts of weathering and erosion due how strong or weak the structure is
• Structure

  The properties of individual rocks including joints, bedding planes, faults and the permeability of rocks

  • Primary permeability: when a rock has pores which can absorb and store water eg. chalk
  • Secondary permeability: when water seeps into joints and cracks eg. limestone
• Pressure melting point (PMP)

  The temperature at which ice is on the verge of melting - typically 0°