glacial

• Accumulation


  Addition of mass (precipitation, usually snow) to the glacier

  
• Ablation


  Loss of mass from the glacier (meltwater, avalanches, sublimation, evaporation, and other processes)
• Glacial budget


  The mass balance of a glacier, i.e the difference between accumulation and ablation
• Positive glacial budget


  Accumulation exceeds ablation, so the glacier is advancing

  
• Negative glacial budget


  Ablation exceeds accumulation, so the glacier is retreating
• Glacial budgets fluctuate yearly, with more ablation in the summer months and more accumulation in winter months
• Natural system


  Specific interactions within their development and sustaining that allow glaciers to work

  
• Open system


  There are inputs from outside the system's set area
• Closed system


  All of the inputs and processes occur within the system's set area
• Inputs to a glacier system

  • Precipitation (snow, hail)
  • Avalanches from other areas
  • Debris eroded and falling into the system

  
• Outputs from a glacier system

  • Meltwater
  • Calving (large pieces of glacier breaking off at the snout)

  
• Glacial energy


  Kinetic energy as the glacier moves, allowing erosion to occur. Gravity forces the glacier downhill.

  
• Glacial stores


  • Ice
  • Sediment from erosion
  • Meltwater lakes/channels

  
• Subglacial, englacial, supraglacial


  Types of glacial stores (underneath, within, on top of the glacier)
• Flows


  Transfer of mass or energy, such as ice to meltwater, and compressional flow of the glacier
• Dynamic equilibrium


  A state of balance where the processes causing the balance are continual, so the mass of the glacier does not change annually

  
• Equilibrium line


  The area where mass gain = mass loss on a glacier
• Positive feedback loop


  A process occurs, which causes another process to occur, heightening the first process
• Negative feedback loop


  The process that occurs is counteracted by an opposing process, causing the effects to cancel each other out
• Polar environments are located at the poles (high latitudes) of the Earth within the Arctic Circle (66°N) and the Antarctic Circle (66°S)

  
• The maximum extent of ice sheets in polar regions occurs within the coldest, winter months

  
• Polar environments


  • Consistently below freezing temperatures with little rainfall
  • Slow nutrient cycles and deprived soils
  • Only highly adapted vegetation can grow

  
• Alpine environments


  • Fluctuating annual temperatures, with milder summers and heavy snowfall in winter
  • Adapted animals can move to higher altitudes
  • Quicker nutrient cycle and more fertile soils
• Periglacial environments


  Areas on the edge of colder environments where the ground is permanently frozen (permafrost)

  
• Periglacial environments


  • Consistently cold temperatures with low precipitation
  • Slow nutrient cycle and infertile soils
  • Permafrost makes it hard for plants to grow
• Glacial environments are areas where temperatures are consistently cold enough to sustain glaciers or ice sheets, in both polar and alpine areas

  
• The most recent major ice age occurred in the Pleistocene era, spanning from around 2.5 million years ago to 11,700 years ago

  
• Fluctuations in global temperatures during the Pleistocene ice age

  • Glacial period (colder temperatures, glacial advances and sea levels falling)
  • Interglacial period (warmer temperatures, glacial retreats and sea levels rising)

  
• The Last Glacial Maximum was around 21,000 years ago, when a much larger area of the northern hemisphere was completely covered by ice

  
• Glacial periods are characterized by glacial advances, where temperatures are cooler and glaciers expand, causing sea levels to fall

  
• Interglacial periods are characterized by warmer temperatures, causing glacial retreats and sea levels to rise

  
• The most recent period of glacial advance (Last Glacial Maximum) occurred

  21,000 years ago

  
• The present distribution of cold environments is much more isolated in comparison to the Last Glacial Maximum period

  
• This interactive timeline outlines global temperature trends since the last glacial maximum

  
• A much larger area of the northern hemisphere was completely covered by ice, including the majority of the UK, during the Last Glacial Maximum

  
• The world is currently in an interglacial period, meaning temperatures are higher and the majority of our glaciers are retreating

  
• Glaciers


  • They have advanced and retreated in correlation with the world's glacial and interglacial periods
  • The majority of glaciers are currently thought to be retreating due to increased temperatures

  
• Historically, global temperatures have been increasing since the Last Glacial Maximum, but there have been smaller global coolings in recent history that have affected the mass balance of glaciers

  
• The 'Little Ice Age' between 1300 and 1870 has been the most significant global cooling in recent history

  
• During the Little Ice Age, glacial advance in the Alps was a very prevalent issue, with heavy snowfall and avalanches being common and posing a risk to life