Earth’s Life Support Systems SG4
How do the Water and Carbon Cycles Operate in Contrasting Locations?
Arctic Tundra
An Introduction to the Arctic Tundra
Arctic Tundra
- A periglacial environment, which has frozen ground known as permafrost.
- There are long cold winters and short cool summers, and little precipitation.
- In Alaska, Canada, Greenland and Russia
- 60oN of Equator
Climate in Kaktovic, North Slope, Alaska: Limitations of Climate Graphs:
Only shows average temp/rainfall per month – doesn’t
Low annual precipitation (50-350mm)
show variation within month
8-9 months of the year temps below 0oC
The scale could be unsuitable/difficult to read
High temp range = 23o Only shows rainfall, not total precipitation – in Alaska
Temps can fall below -40o in winter most precipitation falls as snow.
Average temp of -12.2oC
The Water Cycle in the Arctic Tundra
Precipitation Low – 50-350mm annual precipitation with most falling as
snow.
Transpiration Low – sparseness of vegetation cover and short growing
season.
Evaporation Low – most of the sun’s energy in summer is expended melting
snow so ground temperatures remain low. Also, surface and
soil water are frozen most of the year.
Groundwater Store Low – permafrost prevents infiltration, percolation and
groundwater.
Stores of Moisture in the Atmosphere Low – due to low temperatures which reduce absolute
humidity.
River Discharge Summer – High – melting of snow, river and lake ice and upper
permafrost increases river flow.
Winter – Low – water freezes so lower river discharge.
Surface Storage Summer – High – extensive wetlands, ponds and lakes on the
tundra.
Winter – Low – water freezes and turns to ice.
Natural Factors Affecting the Water Cycle in the Arctic Tundra
Temperature
Evaporation – low temp means water is frozen, so less evaporation
Transpiration – cold temps mean less vegetation, so less transpiration
Infiltration – ground is frozen, so little infiltration
Atmospheric Store – less evaporation means less water vapour in the atmosphere
Ground Store – permafrost prevents infiltration, so little ground store
Surface Storage – water stored in rivers/lakes is frozen
, Rock Permeability and Porosity
Permeability – the ability for fluids to flow through rocks, high permeability results in rapid flow.
Permeability is low in the Arctic Tundra as the ground is frozen as permafrost meaning water
can’t infiltrate it. When it thaws, the ground is too saturated for water to infiltrate in.
Porosity – the percentage of void space in a rock. The ratio of the volume of the voids or pore space
divided by the total volume.
For most of the year the pore spaces will be filled with ice but in summer it will thaw, as
temperatures rise slightly.
The top active layer of the permafrost will get bigger as the permafrost thaws, increasing
groundwater stores and infiltration.
Relief
Relief – the height and shape of the land.
Erosion and weathering over millions of years has flattened out the land. This is mainly due to ice
sheets from the last Ice Age eroding the land, making it flat and gently undulating.
In areas of steep relief, the main flow would be surface runoff, so surface storage will be
high.
In areas of gentle relief, the main flow would be infiltration, but this will not happen in the
Arctic Tundra (due to the permafrost) so surface storage will be high.
The Carbon Cycle in the Arctic Tundra
The contribution of carbon being given off by the permafrost might amplify human impacts by 30%
Permafrost contribute to the release of 3GT carbon per year
The Tundra is a carbon sink – more carbon stored than released
Slow release of carbon due to extreme cold temperatures, so little decomposition by bacteria and
fungi
Carbon storage in permafrost globally is 1600GT
Tundra contains nearly ½ of all global soil carbon in the permafrost
Photosynthesis Small – there is little vegetation so a small flow of carbon.
Concentrated to summer.
Respiration Small – very little vegetation due to cold climate.
Decomposition Small – plants are partially decomposed but get frozen in the
permafrost. Less leaf litter.
Soil Respiration Small – soil is frozen as permafrost for most of the year,
though respiration occurs through talik.
Biomass Small – vegetation is sparse and there is little photosynthesis.
Atmosphere Small – more is removed through photosynthesis than is
released from the permafrost.
Soil Large – frozen into the permafrost for >10,000 years.
Natural Factors Affecting the Carbon Cycle in the
Arctic Tundra
How do the Water and Carbon Cycles Operate in Contrasting Locations?
Arctic Tundra
An Introduction to the Arctic Tundra
Arctic Tundra
- A periglacial environment, which has frozen ground known as permafrost.
- There are long cold winters and short cool summers, and little precipitation.
- In Alaska, Canada, Greenland and Russia
- 60oN of Equator
Climate in Kaktovic, North Slope, Alaska: Limitations of Climate Graphs:
Only shows average temp/rainfall per month – doesn’t
Low annual precipitation (50-350mm)
show variation within month
8-9 months of the year temps below 0oC
The scale could be unsuitable/difficult to read
High temp range = 23o Only shows rainfall, not total precipitation – in Alaska
Temps can fall below -40o in winter most precipitation falls as snow.
Average temp of -12.2oC
The Water Cycle in the Arctic Tundra
Precipitation Low – 50-350mm annual precipitation with most falling as
snow.
Transpiration Low – sparseness of vegetation cover and short growing
season.
Evaporation Low – most of the sun’s energy in summer is expended melting
snow so ground temperatures remain low. Also, surface and
soil water are frozen most of the year.
Groundwater Store Low – permafrost prevents infiltration, percolation and
groundwater.
Stores of Moisture in the Atmosphere Low – due to low temperatures which reduce absolute
humidity.
River Discharge Summer – High – melting of snow, river and lake ice and upper
permafrost increases river flow.
Winter – Low – water freezes so lower river discharge.
Surface Storage Summer – High – extensive wetlands, ponds and lakes on the
tundra.
Winter – Low – water freezes and turns to ice.
Natural Factors Affecting the Water Cycle in the Arctic Tundra
Temperature
Evaporation – low temp means water is frozen, so less evaporation
Transpiration – cold temps mean less vegetation, so less transpiration
Infiltration – ground is frozen, so little infiltration
Atmospheric Store – less evaporation means less water vapour in the atmosphere
Ground Store – permafrost prevents infiltration, so little ground store
Surface Storage – water stored in rivers/lakes is frozen
, Rock Permeability and Porosity
Permeability – the ability for fluids to flow through rocks, high permeability results in rapid flow.
Permeability is low in the Arctic Tundra as the ground is frozen as permafrost meaning water
can’t infiltrate it. When it thaws, the ground is too saturated for water to infiltrate in.
Porosity – the percentage of void space in a rock. The ratio of the volume of the voids or pore space
divided by the total volume.
For most of the year the pore spaces will be filled with ice but in summer it will thaw, as
temperatures rise slightly.
The top active layer of the permafrost will get bigger as the permafrost thaws, increasing
groundwater stores and infiltration.
Relief
Relief – the height and shape of the land.
Erosion and weathering over millions of years has flattened out the land. This is mainly due to ice
sheets from the last Ice Age eroding the land, making it flat and gently undulating.
In areas of steep relief, the main flow would be surface runoff, so surface storage will be
high.
In areas of gentle relief, the main flow would be infiltration, but this will not happen in the
Arctic Tundra (due to the permafrost) so surface storage will be high.
The Carbon Cycle in the Arctic Tundra
The contribution of carbon being given off by the permafrost might amplify human impacts by 30%
Permafrost contribute to the release of 3GT carbon per year
The Tundra is a carbon sink – more carbon stored than released
Slow release of carbon due to extreme cold temperatures, so little decomposition by bacteria and
fungi
Carbon storage in permafrost globally is 1600GT
Tundra contains nearly ½ of all global soil carbon in the permafrost
Photosynthesis Small – there is little vegetation so a small flow of carbon.
Concentrated to summer.
Respiration Small – very little vegetation due to cold climate.
Decomposition Small – plants are partially decomposed but get frozen in the
permafrost. Less leaf litter.
Soil Respiration Small – soil is frozen as permafrost for most of the year,
though respiration occurs through talik.
Biomass Small – vegetation is sparse and there is little photosynthesis.
Atmosphere Small – more is removed through photosynthesis than is
released from the permafrost.
Soil Large – frozen into the permafrost for >10,000 years.
Natural Factors Affecting the Carbon Cycle in the
Arctic Tundra
