Transcript 38Ecoregion_Tundra

Polar Landscapes
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
Organized by basic climate
processes controlling
precipitation and
temperature
• 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
Organization
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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
Polar Climates
Dominated by Polar High
Dense, cold air flows equatorward
Extreme Seasonal Changes
24 hr days in summer, 24 hr night in winter
Ice Cap Climate
Mean monthly
below zero
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
Poorly Developed
In Rocky Areas
Soils
Experience overturning from permafrost activity
Soils: Position is very important
Lowland soils: histosols
Peat – plant accumulation
Upland soils: entisols
Poorly developed
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
Landforms
&
Hydrology
Permafrost
Ice Wedge
Polygons
Pingo
Patterned
Ground
Solifluction
Rocky Uplands
Rivers
Permafrost Permanently
frozen water
in the ground
Underground mine in permafrost (Yakutsk,
Permafrost Institute, Dr. P. Konstantinov
When thaws, creates “thermokarst”
Pipelines Break
Roads Cave In
Buildings Collapse if not properly
insulated
Natural
permafrost
cycle
Northwest Territories
Northwest Territories
Pingo
Northwest Territories
Pingo
Can grow as water moves to ice core
Patterned Ground – Rocky & Flat
active layer “churning” sorts rocks
Northwest Territories
Solifluction: sloped ground in finer
materials flows (oozes)
Kinnard Research, Excavation, Yukon
Topographic
Position
Rocky uplands
patterned ground
Low slopes
solifluction lobes
Lowlands
ice wedge polygons
Rocky
Uplands
Felsenmeer – rock
block field broken
up by frost
weathering
Steep slopes with lots of frostweathered rock: Rock Glaciers
Ice core & seasonal
freeze/thaw
moves rocks
Rivers
Winter – frozen
Spring – thaw
Summer – very
aggressive
erosion
Sudden
Thaw
Floods
Lena
River
Siberia
Breakup Timing
http://aprfc.arh.noaa.gov/rwpindex.php
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
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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
Lena River Delta
Yukon R. Delta
Biogeography
Cold & Dry
Effect of Latitude
or Altitude
Source: Solomon, 2000
Tundra
-severe winters
-short growing season,
cool summer; too little
warmth for tree growth
-arctic or alpine
Small growing season
Generates dwarf forms adapted to survive in
Cold and Windy winters
Dwarf Willow
Dwarf Birch
Long, bitter-cold winters
characterize the tundra
• 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
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.
Arctic tundra
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
Lichens
Common
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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
Fungal layer
Algal layer
Fungal layer
Food for Caribou
Adaptations to Light
Conditions -Perennials
These plants come back every year. Short flowering &
reproductive season
Tundra Flowers
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
Willow-herb
Sedge
Cotton grass has
seeds that are
dispersed across the
tundra by the wind.
Source: Natural Resources Canada
http://atlas.gc.ca/english/facts/wetlands/wetlands_ewetdist2_e.html
Animals of the Tundra – Color
Adaptations
These animals turn white in order to camouflage
themselves from predator or prey
Lemming
Arctic Hare
Arctic Fox
Animals of the Tundra – Cold
Adaptations
Arctic ground
squirrels hibernate
Polar bears shelter
in dens in winter
and to have cubs
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.
Food Sources
The Musk ox eat lichen,
moss, grass, and leaves.
Lemming eats
grass & other
vegetation.
Caribou eat lichen.
The Polar bear eats large & small
mammals, birds, fish, berries, and leaves.
Arctic Warming at the Front Line of
Global Change
Hansen, Scientific American, March 2004
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).
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
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.