ELSS- CASE STUDY- arctic tundra

Water and carbon cycles specific to tundra, including rates of flow and distinct stores

WC

• low evapotranspiration, much of suns energy spent melting snow to ground temps remain low and surface and soil water frozen for most of year

• Low annual precipitation (50–350mm) with most falling as snow

• Limited groundwater + soil moisture- permafrost= barrier to infiltration, percolation and groundwater flow

• Extensive wetlands, ponds, lakes on tundra during summer. Temporary water store impedes drainage, lays on top of permafrost

• Small stores of moisture in atmosphere- low temperatures which reduce absolute humidity

CC:

• Permafrost= carbon sink (1600GT of carbon) due to low temps which slow decomposition of dead plants

• During growing season plants input carbon rich litter into soil, decomposition increases releasing co2 into atmosphere through respiration

• In winter there are pockets of unfrozen soil + water- release co2 and ch4. Snow cover can insulate microbes, slow decomposition

• NPP low due to short growing season

• Amount of carbon in tundra is 5x greater than the above ground biomass

Physical factors- temp, rock porosity, relief

• Limited groundwater and soil moisture- permafrost= barrier to infiltration, percolation and groundwater flow

• Low annual precipitation (50-300mm) with most falling as snow

• Low rates of evaporation—> suns energy in summer spent melting snow, ground temps remain low and surface + soil water frozen for most of the year

• Extensive wetlands, ponds and lakes on tundra during the summer.

• Temporary store of water impedes drainage as it lays on top of permafrost which is impermeable

• Limited transpiration due to sparseness of vegetation and short growing season

• As the permafrost melts and exposes darker land and water surfaces, these surfaces reflect less sunlight (lower albedo) and more solar radiation is absorbed causing the surface to warm and more ice to melt (positive ice-albedo feedback).

• In areas without permafrost, rates of infiltration, percolation and groundwater recharge can increase.

• With a deeper active layer, there is more water available to run-off into rivers and cause flooding, particularly during early summer when snow and lake ice also melts. 

• As temperatures warm due to climate change (indirect human factor), a greater amount of water is locked up as ground ice/snow melts. This increases the depth of the active layer and the size of meltwater pools, wetlands and lakes. As the scale of these changes can be vast, they can potentially enhance natural processes on a global scale.

• Small stores of moisture in the atmosphere—> low temperatures, reduce absolute humidity

• Melting of snow, river and lake ice and the uppermost active layer in summer and spring increases river flow.

 

 

Physical factors affecting flows and stores in the carbon cycle, including temperature, vegetation, organic matter in soil and the mineral composition of rocks

Temp:

• low temperatures, unavailability of liquid water for most of the year limit plant growth. Total carbon store of biomass is relatively small

• Low temps and waterlogging slow decomposition and respiration and flow of co2 in atmosphere

• Snow cover in winter may insulate and allow for some decomposition despite low temps

• Temperatures can go below -40 degrees in winter, few plants and animals have adapted to this extreme environment—> biodiversity is low and the ecosystem is mainly treeless

• Once the permafrost begins to melt, it releases more methane which enhances the greenhouse effect, causing further warming (positive feedback loop), melting more ice to water, changing the nature of water stores and increasing water flows, especially during the warmer summer months.

 

Vegetation

• PSS and NPP low, growing season lasting barely 3 months

• But long hours of daylight in the summer

• During growing season, plants input carbon rich litter to the soil and decomposition increases releasing co2 into the atmosphere through respiration

• Vegetation cover can insulate the permafrost, if this is removed it can cause melting.

• Further in the north, plant cover is discontinuous with extensive areas of bare ground.

Organic matter

• carbon mainly stored as decomposed plant remains frozen in permafrost

• Most of this carbon has been locked away for at least 500,000 yrs

Rocks

• Impermeable permafrost, rock permeability, porosity and mineral composition of rock exert little influence on water and carbon cycle.

• Crystalline rocks

• Porous and permeable rocks may not allow water through if they are frozen, therefore water percolation and groundwater flow/recharge is more likely in the summer months when ground ice melts.

Seasonal changes

• Porous and permeable rocks may not allow water through if they are frozen, therefore water percolation and groundwater flow/recharge is more likely in the summer months when ground ice melts.

• As the active layer thaws and summer temperatures are not as cold, more plants can grow for longer, adding more litter to the soil adding to the ice-albedo feedback.

• Frozen surface storage will be higher in winter and in many places, non-existent in summer

• In the tundra diurnal changes have a minimal impact as for several months of the year the sun has either set or risen. The impact of change is spread over several weeks so is more appropriate as a seasonal change.

• Seasonal change in the tundra has massive impact on stores as permafrost melts leading to surface lakes and ponds with higher rates of evaporation in summer and more movement into the thawed soil allowing throughflow to occur.

• Average temperatures below freezing so water stored in permafrost. In summer the active layer melts creating meltwater pools.

• In summer wetlands, ponds and lakes increasing in extent increasing rates of evaporation. Removal of vegetation reduces transpiration.

• Influence of seasonal change on the tundra WC -Snowmelt forms many pool and shallow lakes because drainage is poor and water cannot infiltrate the soil as there is still permafrost at depth  • Some evapotranspiration will occur as temperatures are higher and snow has melted however humidity remains low, as rates are minimal due to low temperatures • Snowmelt results in more evaporation as more water is in rivers

• Influence of seasonal change on the tundra CC - Waterlogging of the soil and low temperatures slow decomposition and respiration and the flow of CO2 into the atmosphere • Snowmelt provides water for plant growth along with higher temperatures, although photosynthesis and NPP are low with short growing season and low temperatures • Snowmelt exposes the active layer so this melts and releases carbon to the atmosphere.

• In the night, no photosynthesis occurs, more in the daytime when there is sunlight

 

 

 

Impact of developing oil and gas industry on water and carbon cycles

• Trump has emphasised the potential for oil drilling in the ANWR. Biden finalized legislation to ban fossil fuel drilling on almost half of the national petroleum reserve. Oil tax provides jobs and free public services. However many are scared about the impact and damage caused due to climate change, particularly in coastal communities. One of the most important issues is the cost.

• Permafrost covers almost ¼ of land mass in N hemisphere

Coal strip mining WC:

• Activities (e.g., construction, dust deposition and vegetation removal) caused lowering of albedo/localised melting of the permafrost layer increases surface run-off and river discharge increasing flooding. , reduce infiltration and percolation, increase surface runoff

• In summer wetlands, ponds and lakes increasing in extent increasing rates of evaporation. Removal of vegetation reduces transpiration.

• Strip mining creates artificial lakes disrupting drainage and leads to further melting. Quarrying makes holes

• Localised surface run-off is reduced as water is abstracted for use in industry and building of ice roads

• Creates artificial lakes like taliks- disrupt drainage

Coal strip mining CC;

• Mining removes vegetation and topsoil which are active sinks that absorb atmospheric carbon dioxide. More atmospheric carbon, less PSS, lower NPP. Global scale. +ve feedback loop.

• US: Appalachia region, mountaintop mining destroyed forests acting as carbon sinks- approx 1.1 million hectares

• Carbon stored in rocks released- impacts slow carbon cycle

• Methane emissions—> coal mines release methane.

• Methane is 20x more influential than carbon dioxide

Oil and gas drilling WC

• On the land oil production will require miles of new roads (one estimate is 280 miles) new drilling pads, pipelines, pumping stations and airports. All these will damage the fragile arctic ecosystems, leading to a loss of habitat, fish and wildlife. This will create more impermeable surfaces which will increase surface runoff and cause more flash floods.

• The drilling pads would require massive quarrying of local rivers to produce gravel for construction sites, again leading to a loss of important riverine ecosystems. The quarrying would create huge holes in the landscape, as well as interfering with both the permafrost and the natural drainage systems.

• Drilling creates about 40,000m3 of oily waste per well. This has to be disposed of so pits would need to be dug in the sands and gravels. However the waste may seep through the sand and into water supplies, as well as killing local fish and birds

 

Oil and gas drilling CC

• The area would produce over 50,000 tons of nitrous oxides which contribute to both acid rain and global warming.

• Oil and gas production, which can cause localised melting of the permafrost and snow cover, thus increased run off and river discharge

• Disturbs slow carbon cycle, introduces carbon to fast carbon cycle. Drilling, transporting and refining oil and gas results in significant emissions- 5.1 billion tonnes of co2 in 2022.

• Methane leakage during drilling, processing and transportation.

• Flaring- burning of  gas produced during oil extraction when it cannot be captured (dispose of gas when it is not economically viable to capture, transport/ sell) releases co2

• New drilling techniques allow oil and gas to be accessed several km away from drilling site. Shell developed ‘snake drill’- allowing drilling across a wide area from a single drilling site. Fewer sites needed for drilling rigs, impact on vegetation and permafrost due to construction is reduced.

 

 Trans Alaskan pipeline WC

• Carries hot oil which can cause permafrost to thaw if not properly insulated- waterlogged hollows to form as frozen ground melts- thermokarst—> alases. Increases runoff and river discharge- flooding more likely.

• In summer, wetlands, ponds and lakes have become more extensive, increasing evaporation.

• Vegetation insulates permafrost- removing this removes the insulation so it thaws quicker

• But the structure is raised to prevent melting of permafrost- protects water and carbon cycle. There are also refrigerated supports used to stabilise the temperature of the permafrost- also impacts the carbon cycle. 

 

Trans Alaskan pipeline CC

• oil and gas management strategies, which aim to minimise disruption to the water cycle by protecting the permafrost, for example by elevating pipelines to allow cold air to circulate beneath them and provide insulation against the heat which would otherwise melt the permafrost. Both cycles are protected in this way.

• Facilitates extraction and transport of oil leading to greenhouse gas emissions

• Heat transfer from pipe—> melting permafrost

• By the early 1990s the North slope accounted for nearly 1/4 of the USA’s domestic oil production. Now, the proportion is less than 4%. This is because of the high production costs and the massive growth of the oil shale industry in the USA

• Construction and operation of oil and gas installations, settlements and infrastructure diffusing heat directly to environment

• Dust deposition along roadsides- darkened snow surfaces, less albedo—> more sunlight absorbed

• Removal of vegetation cover which would insulate permafrost—> reduces PSS

• On the north slope, estimated co2 losses from the permafrost range from 70 to 40 million tonnes/year

• Roads and other infrastructural features can be constructed on insulating ice or gravel pads, thus protecting the permafrost from melting so reducing the co2 and ch4 that is released. Spine road at Prudehoe Bay lies on a 2m deep pad.

Management strategies to moderate impacts of oil and gas industry

Arctic Foundations is doing brisk business selling thermosiphons- tubes that pull heat out of ground to keep permafrost from thawing under oil infrastructure. ConocoPhillips plans to make use of these devices at its Willow project in the National Petroleum Reserve, and its also building taller bridges and wider culverts to accomodate larger spring floods

Insulated ice and gravel pads

• roads and other infrastructural features can be constructed on insulating ice or gravel pads, protect permafrost from melting

• Spine road at Prudhoe Bay lies on 2m deep pad

Elevated on stilts

• buildings + pipelines on stilts

• Cold air circulate beneath

• Buildings generate heat- doesnt melt permafrost

Drilling laterally beyond drilling platforms

• oil and gas accessed several km from drilling site

• Shell developed ‘snake drill’ allowing drilling across wide area from single drilling site

Refrigerated supports

• Refrigerated supports on trans Alaskan pipeline to Stabilise temp of permafrost

Thermosyphons

• 124,000 used on trans Alaskan pipeline

• tubes that pull heat out of the ground to keep permafrost from thawing underneath oil infrastructure.

Cooling deceives are highly effective at mitigating the thawing of permafrost. However climate change can cause unsatisfactory cooling of the permafrost and if heat exceeds the cooling capacity, cooling devices like thermosyphons may not be able to prevent long term thawing. When more devices are in use the effectiveness increases. This will prevent carbon dioxide from being released from permafrost as it thaws, therefore contributing to the enhanced carbon cycle. This would therefore reduce the greenhouse gas emissions. This also contributes to the water cycle because when there is a reduced thawing of permafrost there is less water released from ice that is contained within permafrtost. Less evaporation.

• In the long term this facilitates more human activity- multiplier effect with human activity

• Local/ regional scale- conserves water cycle

• Infrastructure may need to be built for the workers