earth life support systems

Characteristics of tundra

• Canada, Siberia, Alaska, Russia

• 60 degrees north of the equator

• Is 8 million km2

• Ground is usually permafrost

• short summer 10 degrees, winter -30 degrees

• Low precipitation, low amount atmospheric moisture, limited groundwater and soil moisture

Why is the arctic tundra cold and dry all year

• angle that the sun touches the tundra

• Lower amount of evaporation and transpiration (due to lower energy)

• Area of high pressure

What physical factors influence the water cycle in the tundra

Temp- cold temp means ground ice is in the permafrost layer. Melts in short summer and forms shallow lakes. Humidity and atmospheric store is low. Infiltration is limited bc of permafrost, sub zero temps prevents evapotranspiration in winter but there is little in summer.

Rock permeability- low infiltration due to permafrost and crystalline and impermeable rocks, will also reduce the ground water store

Relief- rocks are ancient and has been weathered and eroded to an undulating plain. Gentle slopes mean little drainage and lots of water logging (high surface store)

Water cycle specific to the tundra (size of store/ rate of flows in the water cycle) precipitation, atmospheric store, evaporation rates, ground and soil store, snow and ice stores, surface water store

precipitation- low annual precip (50-360mm), low evapotranspiration due to low temp,

atmospheric store- small stores of moisture in the atmosphere meaning low temp which reduce absolute humidity, due to low evapotranspiration

evaporation rates- low rate, much of suns energy is expended melting snow so ground temp remains low and inhibits convection

ground and soil store- limited groundwater and soil moisture permafrost is a barrier to infiltration, percolation, and groundwater flow

snow and ice stores- accumulating of snow and river/lake ice. Melting of snow, river and lake ice and uppermost permafrost means increase in river flow.

surface water store- extensive wetlands ponds and lakes. When the permafrost melts it creates surface lakes

Permafrost in the arctic tundra

• affects the water cycle as the permafrost melts and collects on the surface as pools

• Permafrost melts in summer leading to land saturation quick

• Permafrost remains the longest and thaws the least on north facing slopes because it receives less sunlight and therefore colder

• Due to standing water it means that there’s no o2 so no anaerobic decomposition takes place and produces methane instead of co2 which then accelerates climate change

• Climate change leads to increase in summer snow meaning increase in temp and transpiration so more precipitation. Also leads to increase of river channels being silted up as melting snow means more erosion by surface run off leading to more sediment in rivers.

• Permafrost keeps carbon locked up as dead plants are frozen before they decompose and release co2

carbon cycle specific to the tundra (size of store/ rate of flows in the carbon cycle) soil, biomass, litter, decomposition, photosynthesis, plant growth

Soil store- globally, contains 1600GT of carbon, 5x bigger than biomass store

Biomass- net primary productivity is less than 200 g a year so small (4-29 tonnes per ha)

Litter store- during the growing season tundra plants input carbon-rich litter to soils but its small (litter input is only in growing season)

Decomposition- accumulation of carbon is due to low temp which slows decomposition or dead plants. Snow cover may insulate microbial organisms and allow some decomposition despite low temperature

Photosynthesis- slow, due to limited sunlight in winter and cold temp means little photosynthesis.

Plant growth- amount of plant litter is increasing and is slow rate. Higher temp has stimulated plant growth in the tundra and greater uptake of co2