2. Arctic tundra Flashcards
What area does the Arctic tundra cover?
Occupies 8 million km2 in northern Canada, Alaska and Siberia and extends from the northern edge of the boreal coniferous forest to the Arctic Ocean
What is the climate like in the Arctic tundra?
They become more severe as latitude increases
8/9 months of the year the tundra has a negative heat balance (loss of energy to the atmosphere)
Average monthly temperatures are below freezing and can reach -40
Mean annual precipitation is low
Describe the ground in the tundra:
Permanently frozen with only the top metre thawing during Arctic summer overlying a layer of permafrost
Describe the biodiversity in the tundra:
Biodiversity is low with few plants/animals adapted to the environment
Dwarf tree species present
What are the main features of the water cycle in the Arctic tundra?
- Low annual precipitation
- Small stores of moisture in the atmosphere
- Limited transpiration
- Low rates of evaporation
- Limited groundwater stores
- Sharp increase in river flow in summer
Describe low annual precipitation:
50-350mm per year
Most falls as snow
Describe small stores of moisture in atmosphere:
Leads to low temperatures and reduces absolute humidity
Why is there limited transpiration?
Due to sparseness of vegetation cover and short growing season
Why is there limited evaporation?
In summer the sun’s energy is used to melt snow, not for evaporation + soil is frozen
Why is there limited groundwater stores?
Permafrost is a barrier to percolation, infiltration, and groundwater flow
Why is there a sharp increase in river flow in summer?
The snow that has accumulated over summer melts, as well as the uppermost active layer of the permafrost – creates extensive wetlands that cannot be drained
How much carbon does the permafrost contain?
Globally estimated to contain 1600 GT of carbon
Why is there such high carbon content in permafrost areas?
Low temperatures slow down the decomposition of dead plant material
When is the largest flow of carbon?
Greatest in summer
Why is the flow of carbon greatest in summer x3?
- Active layer of permafrost thaws releasing CO2
- Plants grow rapidly so photosynthesis is concentrated
- Tundra plants input carbon-rich material into the soil which is decomposed and respired by microorganisms – emitting methane and CO2 (can also occur during winter when snow layer insulates microbes)
