ELSS 2.a tundra

a case study on the arctic tundra

water cycle in the tundra - general

• low annual precipitation of 50-350mm, mainly snow

• low temp, low evapotranspiration, suns energy spent on melting snow, most water remains frozen

• usually low run off but melting of active layer causes rapid increase in runoff and flow

• low underground stores as permafrost is barrier to infiltration and percolation

• in summer temp stores cant drain due to permafrost

• atmosphere has low stores due to low temp

• low flows via vegetation as few veg and short growing season, not a big store

physical factors affecting the water cycle in the tundra

• geology - hard crystalline rocks add to permeability

• temp - low temp keeps water stored as permafrost, short summer melt causes some water to flow on surface (but thats the active layer)

• low evapotranspiration although som ein summer

• relief - gentle relief helps store water in summer - waterlogged soils

human factors affecting the water cycle in the tundra

• oil and gas explores increase melting of snow cover and permafrost, flooding is more likely

• creates extensive wetlands in summer, can increase evaporation and disrupt drainage networks

• artificial lakes made by strip mining stores of water, also extracted from creeks and used locally in industry

general facts on the tundra

• 8 million km² of arctic tundra in Alaska, North Canada and Siberia

• low average temps between 0-30 degrees for 8-9 months of the year

• remaining months have ave temps below 0 degrees

• permafrost, thaws to depth of about 1 metre in summer (called the active layer

• summer is June-sept

the impact of increasing temperatures on the tundra

• more than 40% of worlds permafrost at risk of thawing, even if global warming is limited to international goal of 2 degrees

• permafrost covers 5.8 miles² and 2.5 million m² could thaw at 2 degrees

• 92 GT of carbon change by 2100

• with increasing temp, permafrost layer decreases in size and active layer grows

• processes occurring in active layer are more plentiful during high temp in summer and into rest of country

management strategies

• infrastructure on gravel pads protects the permafrost from melting

• buildings and pipelines built on piles allows cold air to circulate, which stops permafrost from melting

• drilling for oil with newer techniques allows access to oil km away from the drill sites, reducing impact on vegetation and permafrost

• improved tech in oil detection reduces need for exploration wells

• refrigerated supports on trans-alaskan pipeline, buildings and infrastructure stabilise permafrost temperature

carbon cycle general info for tundra

• vegetation - low NPP (200/m²/year) so low biomass

• atmosphere - CO2 released into atmosphere all year but most during growing season via respiration

• soil/ground - permafrost stores increase carbon even though accumulation is slow, there is 5x more carbon here than above ground - concerns about permafrost becoming a carbon source rather than a sink due to global warming

• photosynthesis - sequestration of CO2 is low - in summer there is rapid growth but still limited biomass for photosynthesis

physical factors influencing the carbon cycle in the tundra

• geology - little impact on flows, impermeable permafrost overlying hard crystalline rock, most carbon stored in permafrost

• temperature - reduced temp slows photosynthesis and respiration so limited flow of CO2 to atmosphere

• biomass - small due to lack of water and sun

• methane hydrates - tipping point, made due to anaerobic microbial action and forms when temps are cold and/or pressure is high enough, as in ocean beds

• methane hydrates also form on land in tundra, both above and below permafrost line, when melts it releases trapped methane

human factors influencing the carbon cycle in tundra

• oil and gas explore melts permafrost releasing stored c carbon

• building for oil and gas industry - deposition of dust on roads so ice and snow absorb more sun - removal of vegetation which previously insulsated the permafrost and reduces photosynthesis, increasing CO2 - increased microbial activity in warmer soil causes more deposition and more carbon emissions - gas flaring and oil spills put CO2 into the atmosphere

trans-alaskan pipeline

• created for 8 billion USD

• oil pumped through pipeline at 80 degrees

• warm oil contributes to thawing of permafrost

• built 3 metre above ground to span rivers and allow migration of caribou and other wildlife

• network of 12 pumping stations control flow of oil and close down sections in event of spillages