A Regional Approach All elements of physical geography integrated in the ecoregion approach of Robert Bailey, UCLA Geographer, U.S. Forest Service
General circulation perspective Intertropical Convergence Zone (ITCZ) – brings summer rains in equatorial & tropical latitudes Subtropical High – brings drought, annually or seasonally Polar Front – brings precipitation in the midlatitudes Polar Easterlies – the cold landscapes of tundra and ice caps Organized by basic climate processes controlling precipitation and temperature
Organization 1st – climate 2nd – soils 3rd – landforms & hydrology 4th – biogeography with discussion of geology because geology plays an important role in deserts in defining meso-scale landform regions
Ice Cap Climate Dominated by dry, frigid air masses Average temperature below freezing most or all year World’s coldest surface air is found in Antarctica in S. hemisphere winter Glaciers accumulate snow and ice despite low precipitation (<80mm/yr in Antarctica) Precipitation exceeds small evapotranspiration demand Examples: Antarctica, North Pole, Greenland
Tundra Climate harsh winters low average temperatures little snow or rainfall too short summer season for trees. Influenced by permafrost, a layer of permanently frozen subsoil in the ground. The surface soil, which tends to be rocky, thaws in summer to varying depths. The combination of frozen ground and flat terrain impedes drainage of water. Held at the surface or soaking the upper layer of soil, the water forms ponds and bogs in low areas
Soils Experience overturning from permafrost activity
Soils: Position is very important Upland soils: entisols Poorly developed Lowland soils: histosols Peat – plant accumulation
In low-lying areas where water collects from permafrost melting, get accumulation of organic remains of plants called PEAT. Name for soils: histosol
Why does peat accumulate ? Production by plants exceeds decomposition Abundant growth due to available moisture during growing season Preservation of plants (cool conditions) Saturated conditions - slow, anaerobic decomposition by methanogenic bacteria When plants decay (with drying & warming), release of methane
River Ice River ice is a unique aspect of Arctic Hydrology. All rivers experience some ice effect, yet in some instances, runoff events associated with river ice have produced extreme and dangerous flooding events. River Ice interacts and obstructs the passing of floods. The blockage causes water levels far higher than those experienced for the same flows under open water conditions.
YUKON RIV HARD LIFTED AND SHIFTED SHEETS Shifted ice – large ice sheets that have moved short distances from their original locations as rising water levels create wider areas of open water into which the ice can move http://aprfc.arh.noaa.gov/rwpindex.php
TYPICAL RUN OF ICE May be 10-20 miles in length Reach of large moving sheets (nr breakup front) Reach of mixed sheets, pans, and chunks Reach of mostly chunks Subsequent runs are mainly chunks http://aprfc.arh.noaa.gov/rwpindex.php
YUKON RIVER Ice run – a continuous length of moving ice http://aprfc.arh.noaa.gov/rwpindex.php
NULATO RIVER ICE JAM Ice jam – an ice run that has stopped moving due to any of a variety of reasons; this very small jam has broken sheet ice holding back a small run of chunk ice http://aprfc.arh.noaa.gov/rwpindex.php
ICE JAM IMPACTS Upstream from the jam... Fast water level rise Packed ice chunks Potential flooding http://aprfc.arh.noaa.gov/rwpindex.php
Flooding impact Water outside the channel http://aprfc.arh.noaa.gov/rwpindex.php
KUSKO RIV ANI VILLAGE FLOODING Village flood – water spreading into a village that covers roads or threatens buildings http://aprfc.arh.noaa.gov/rwpindex.php
Source: Solomon, 2000 Effect of Latitude or Altitude
-severe winters -short growing season, cool summer; too little warmth for tree growth -arctic or alpine Tundra
Small growing season Dwarf Willow Dwarf Birch Generates dwarf forms adapted to survive in Cold and Windy winters
The arctic tundra lies between the Boreal Forest and the permanently frozen polar regions –It is a treeless biome characterized by extreme cold, wind, and permafrost –Permafrost is continuously frozen subsoil Long, bitter-cold winters characterize the tundra
SNOW AND MICROCLIMATE The snow on top helps protect the tundra plants underneath from the worst of the cold above. When it is very cold outside, take a thermometer and measure the temperature underneath the snow, and you will see that it is quite a bit warmer! This helps not only the tundra, but small rodents such as the red-backed vole.
Light and heat may not be the only limiting factors for plant growth Days are long and temperatures may reach the teens in summer Wind and moisture deficit are also important Thin, active layer holds limited moisture. Small, leathery leaves, closely spaced to protect stomata Hairs limit air circulation Flowers are small Plants often occur in tufts for protection Prostrate growth - stems spread out over ground with little vertical growth - especially willow Arctic tundra
Lichens Common Fungal layer Algal layer Mutualism: Relationships between fungi and hosts that are mutually beneficial Symbiosis: intimate association between two distantly, related species that are mutually benefiting from this association Food for Caribou
Adaptations to Light Conditions -Perennials Tundra Flowers These plants come back every year. Short flowering & reproductive season
Low Arctic Tundra Extends north from treeline along a line from Northern Alaska to northern Quebec and southern Baffin Island (10 degree C isotherm) Cold, with low precipitation Nearly the entire area is underlain with permafrost Almost complete vegetation coverage (except unfavourable areas) Dominated by dwarf shrubs (birch and willow) Vegetation traps snow and provides shading from summer heating Peat accumulation at poorly-drained sites Any black spruce is very stunted and abraded by snow Major summer range and calving grounds of some of Canada's largest caribou herds
Mid Arctic Tundra Transitional band between high and low arctic Plant cover more than 50% in most areas but bare ground still exists locally Vascular plants more common than in high arctic - willow common Cumberland Sound, Baffin Island, Nunavut, Canada
Wetland Environments Cover 14 to 18% of Canada Mainly just to the south of treeline in discontinuous and sporadic permafrost Pockets further north Major carbon sink Potential future source of greenhouse gases (methane) Hydrophyllic vegetation present due to water table at or above mineral soil
Example of Plants Sedge Willow-herb Cotton grass has seeds that are dispersed across the tundra by the wind.
Animals of the Tundra – Color Adaptations Arctic Hare Arctic Fox Lemming These animals turn white in order to camouflage themselves from predator or prey
Animals of the Tundra – Cold Adaptations Polar bears shelter in dens in winter and to have cubs Arctic ground squirrels hibernate
Animals of the Tundra Muskox dig through snow in winter for food, if snow is frozen solid, they could die Caribou migrate south during winter in search of food
Birds of the Tundra Snow geese migrating north in summer Tundra birds help to distribute seeds. When they eat bright colored berries, they fly to other areas and leave the seeds to grow.
The Arctic Fox eats birds and rodents. Caribou eat lichen. The Musk ox eat lichen, moss, grass, and leaves. Lemming eats grass & other vegetation. The Polar bear eats large & small mammals, birds, fish, berries, and leaves. Food Sources
Hansen, Scientific American, March 2004 Arctic Warming at the Front Line of Global Change
Dramatic changes in Artic Sea Ice 1979-2003: Progressive Loss of Arctic Ice Imagine an ice-free Arctic
Source: Corell, R. W., 2004: Impacts of a warming Arctic. Arctic Climate Impact Assessment (www.acia.uaf.edu) Cambridge University Press (www.cambridge.org).www.acia.uaf.edu
The increase in growing season length over the last 50 years averaged for eight stations in Alaska having the longest and most consistent temperature records. Gradual Loss of Tundra (purple) as growing season lengthens
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