The Arctic Tundra - case study

The Arctic Tundra

-occupies 8 million km2
-N. Canada, Alaska and Siberia
-extends from the northern edge of the boreal coniferous forest to the arctic ocean
-its southern limit approximates 10 degrees calcium July isotherm
Climate conditions are severe and become more extreme with latitude
For 8 - 9 months a year it has a negative heat balance
Average monthly temps below freezing
It is permanently frozen with only the top metre thawing in the summer
Permafrost underlies much of the tundra and is an important feature in the regions water cycle
During the winter the sun remains below the horizon and temps reach -40
Long hours of daylight in the summer provide some compensation for brevity of the growing season
Few plants and animals have adapted to living there
Biodiversity is low and apart from a few dwarf species the ecosystem is treeless
In the southern areas - low arctic - the conditions are less extreme, vegetation provides continuous ground cover

Water cycle in the tundra
Low annual precipitation (50-350 mm) with most falling as snow
Small stores of moisture in the atmosphere owing to low temperatures which reduce absolute humidity
Limited transpiration because of the sparseness of the vegetation cover and the short growing season
Limited groundwater and soil moisture stores. Permafrost is a barrier to infiltration
Accumulation of snow and river/lake ice during the winter months. Melting of snow, river lake ice and the uppermost active layer of permafrost in spring and early summer results in sharp increase in river flow

Carbon cycle in the tundra
Permafrost is a vast carbon sink
Globally…