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A LEVEL GEO
Arctic Tundra (CARBON CYCLE (the permafrost is a vast carbon…
A LEVEL GEO
Arctic Tundra
ARCTIC TUNDRA
occupies some 8 million km^2
northern Canada, Alaska & Siberia
extends from the northern edge of the boreal coniferous forest to the Arctic Ocean
southern limit = 10°C July isotherm
climatic conditions = severe, becomes more extreme with latitude
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summer = ground is permanently frozen, top metre for thawing
winter = Sun remains below the horizon, temperatures plunge to below -40°C
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plants and animals
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apart from a few dwarf species, ecosystem is treeless
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WATER CYCLE
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low rates of evaporation -> much of the Sun's energy [summer] is expended melting snow
ground temperatures remain low -> inhibit convection
limited groundwater & soil moisture stores
permafrost is a barrier = infiltration, percolation, recharge & groundwater flow
accumulation of snow and river/lake ice -> [winter months]
melting of snow, river & lake ice + uppermost active layer of permafrost [spring / early summer] -> results in sharp increase of river flow
extensive wetlands, ponds and lakes [summer]
temporary store of liquid water -> permafrost impedes drainage
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CARBON CYCLE
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[in the past] -> permafrost functioned as a carbon sink
[now] -> global warming has raised concerns that it is becoming a carbon source
outputs of carbon has increased -> higher temperatures have simulated plant growth and greater uptake of CO2