Periglacial Environments

Periglacial Environments

1. Cold but non-glacial. No glacial cover - not related to placement of glaciers

   • Cold place all year round, only some seasonal warming

2. Tundra

   • Coldest biome
   • Vegetation growth hindered by low temp and short growing season
   • Dwarf shrubs, sedges, grasses, mosses and lichens
   • Don't get established vegetation

3. Permafrost

   • Soil/bedrock that is perennially frozen over long timescale (>2 years)
     • Permanently frozen ground must be frozen 2+ years to be classified as permafrost
   • Polar permafrost
     • Due to cold temp in high latitudes
     • 80% of Alaska covered by permafrost
   • Alpine permafrost
     • Himalayas - high mountain chains, not cld place but cold altitudes.
     • Due to cold temp. in high altitude areas
   • Subsea permafrost
     • Layers of permafrost under the sea
     • Low temp. of sea bed/relic from colder times
   • Arctic circle = area with most permafrost
     • Too cold to be glacial (mean annual temp. -5 degrees.
   • Continous permafrost: always cold, surface always cold
   • Discontinuous: warmer areas, some areas permafrost others soil
   • Sporadic: summer temps. above freezing - some areas permafrost but not cold enough continously to be everywhere
   • Temp. profile
     • Lowest temps. closest to surface
     • Permafrost gets warmer as you get deeper down
     • In summer, ground surface is slightly warmer and colder part shifts downwards
       • Depends on ground diffusivity
     • Ground diffusivity = how heat moves through the ground
     • Geothermal gradient = depth point where seasonal temp. no longer affects soil temp.
   • Thickness controls
     • Mean annual surface temp., ground conductivity and geothermal heat flux
       • Winter temp. = -30 degrees, summer +5/10 degrees. Gradient of permafrost will change
         • Geothermal heat flux = how much permafrost is growing in winter compared to melting in summer
     • Surface albedo
       • Short-wave radiation
         • Lots of ruination absorbed: increased melting: less permafrost created
   • Climate change
     • Permafrost = climate phenomenon
     • WILL be changes in distribution if climate warms as prediced
     • Will cause large realises of greenhouse gases
       • Permafrost contains twsicas much carbon as there is atmospheric carbon dioxide
   • Hydrology in Permfrost
     • Groundwater flow
       • Restricted by frozen ground
         • Between active layer and top of permafrost in summer months
     • River flow
       • Strong seasonal regimes