CS.2 - Arctic Tundra

Introduce the AT

The Arctic Tundra occupies ~8 million km² in Northern Canada, Alaska, and Siberia.

Mean temperatures in the AT

below -15°C

Annual temperature fluctuations in the AT

36^oC — About 40°C

Summer temperatures in the AT

About 10°C for 1-3 months

Why is the AT mainly treeless

Permafrost prevents trees from anchoring their roots

Annual precipitation in the AT

150-250mm/yr - most ppt falls as snow

NPP of the tundra

Less than 200 g/m²/year

Carbon stored in plants per hectare

4-29 tonnes per hectare

What surface stores are formed in summer?

When active layer melts but the water cannot infiltrate due to permafrost - forms up to 3 million lakes in Alaska in summer

Little water can infiltrate into the permafrost, so there isn’t much _, limiting the _ store

Little water can infiltrate into the permafrost, so there isn’t much percolation, limiting the groundwater store

How much carbon has been stored in the Arctic Tundra for how long

1600 gigatonnes for 500,000 years (when the Pleistocene was at its peak)

• Contains so much partly decomposed plant matter that it’s one of the most significant carbon sinks in the world

The below-ground carbon store is _ than that stored in the above-ground biomass

The below-ground carbon store is 5 times greater than that stored in the above-ground biomass

What factors limit plant growth in the AT:

• Low temperatures

• Lack of liquid water

• Lack of nutrient content in the soil

What happens during the growing season (ref decomposition)

• Plants input organic matter, containing carbon, to the soil

• Microbes in the soil also become more active

  • Carbon dioxide is released to the atmosphere via respiration

Any decomposition even in winter?

• May be some microbial activity as snow insulates them and allows some decomposition… but v minimal

• Pockets of unfrozen ground (talik) release carbon dioxide and methane to the atmosphere

  • They stay thawed, so allow microbes to decompose previously frozen organic matter

What 4 physical factors affect the flows and stores in the water cycle of the AT?

• Temperature

• Rock permeability

• Rock porosity

• Relief

How does temperature affect stores/flows of water in the AT

• Sub-zero temps for most of the year ensure that water is mainly stored as ice (permafrost)

• Summer melt releases some of the stored water in the active layer

How does rock permeability influence flows/stores of water in the AT

Igneous and metamorphic rocks underlie the Alaskan Tundra.

This + the permafrost above make the land impermeable to water

How does rock porosity influence flows/stores of water in the AT

• Drainage is really bad in the Alaskan tundra - the soil/rock are waterlogged throughout the year

• This is bc of extensive glacial deposits that lie all over the denuded, flat plain

How does relief influence flows/stores of water in the AT

The landscape is largely flat, caused by millions of years of weathering and erosion.

Water just sits on the surface in summer when the active layer melts

What 4 physical factors influence the flows and stores of carbon in the AT

• Temperature

• Vegetation

• Organic matter in soil

• Mineral composition of rocks

Impact of vegetation on the CC in the AT

• Tundra plants grow slowly in cold temperatures

• With the short growing season, photosynthesis and NPP are low

• Carbon store in plants is therefore low, as are the accompanying fluxes like photosynthesis

Impact of temperature on CC in the AT

• Low temperatures slow fluxes such as decomposition and respiration

• Little photosynthesis

Impact of organic matter in soil on CC in the AT

• Cold temperatures inhibit decomposition so a lot of carbon is stored as partly decomposed plant remains in the permafrost

• Most has been stored for 500,000 years

Impact of mineral composition of rocks on CC in the AT

• There is hardly any weathering, physical or chemical, in the AT, on account of the low moisture availability and low temps

• In addition, the rocks are mainly igneous and metamorphic, which have a lower carbon content

• Carbon is not being released from the rocks via weathering. e.g. freeze thaw doesn’t occur as temps stay mostly below zero

FINISH WITH LAST TWO SPEC POINTS: IMPACT OF DEVELOPING OIL AND GAS INDUSTRY AND MANAGEMENT STRATEGIES USED TO MODERATE THE IMAPCTS OF THIS