Actic Tundra Flashcards
Where is the Arctic Tundra
8 million km2
Northern Canada, Alaska and Siberia
It extends from the northern edge of the boreal coniferous forest to the Arctic Ocean
What is the temperature in the tundra?
Climatic conditions are severe and become more extreme with latitude
For 8-9 months a year the tundra has av temp below freezing. Temperatures can plunge to -40oC
What is precipitation like in the Arctic Tundra?
Mean annual precipitation is low
How does the climate affect the ground and plants?
The ground is permanently frozen as permafrost with only the top metre or so thawing during the Arctic summer
Long hours of sunlight provide some compensation for the short growing season
How does the extreme environment affect plant and animal life?
Few plants and animals have adapted to the extreme conditions
Biodiversity is low and apart from a few dwarf species, the ecosystem is treeless
In the high Arctic plant cover is discontinuous with extensive areas of bare ground
In southern areas conditions are less severe and vegetation provides a continuous ground cover
Are there spatial variations in conditions in the tundra?
High Arctic plant cover is discontinuous with extensive areas of bare ground
In southern areas (low arctic) conditions are less severe and vegetation provides a continuous ground cover
What is precipitation like in the tundra?
Low annual precipitation with most falling as snow
Where is water stored in the tundra?
Small stores of moisture in atmosphere owing to low temp which reduces humidity
Limited ground water and soil stores as permafrost is a barrier to infiltration, percolation, recharge and groundwater flow
Extensive wetlands, ponds and lakes on the tundra during summer. This temporary store of liquid water is due to permafrost which impedes drainage
What flows of water are in the Arctic Tundra and how much water flows?
Limited transpiration because of spareness if the vegetation cover and the short growing season
Low rates of evaporation. Much of the suns energy in summer is used to melt snow so that ground temperatures remain low and stop convection. Also surface and soil water frozen for most of the year
What happens when the top layer of permafrost melts in the summer months?
Results in sharp increase in river flow
Where is carbon stored in the tundra?
The permafrost is a vast carbon sink. Globally it is estimated to contain 1600GT of carbon. The accumulation of carbon due to low temperatures which slow decomposition of dead plant material.
NPP is less than 200 grams/m2/year leading to low amount of carbon stored in biomass
What happens to the carbon cycle in the summer months in the tundra?
Flux of carbo occurs in the summer when the active top layer thaws. Plants grow rapidly in the short summer months which has long hours of sunlight allowing them to flower and fruit within weeks
Tundra plants input carbon-rich litter to the soil and CO2 is released into the atmosphere through respiration
However even in winter pockets of unfrozen soul in the permafrost act as a source of CO2
How has global warming affected the carbon cycle in the tundra and how do these processes exasperate global warming?
In the past permafrost acted as a carbon sink but today global warming has raised concerns that it is becoming a carbon source
Whilst outputs of carbon from permafrost have increased in recent decades, higher temperatures have stimulated plant growth in the tundra and greater uptake of CO2
It is possible that despite the warming the carbon budget remains in budget/ equilibrium
How does temperature affect the stores and flows of water in the tundra?
Average temperatures are well below freezing for most of the year so water is stored as ground ice in the permafrost layer
During short summer the active layer thaws liquid water flows on surface. Melt water forms hundreds of pools and lakes on the tundra landscape
Drainage is poor, water cannot infiltrate soil because of permafrost.
In winter subzero temp prevents evaporation
In summer some evapotranspiration occurs from standing water, saturated souls and vegetation. Humidity is low all year round and precipitation spare
