Geog mock xoxoxo

Threats to the Earth's life support systems

- Climate change
- Pollution
- Lack of resources fuelled by over population

Open systems:

- : materials / energy can leave or enter the system

Closed systems:

- contained systems from which materials and energy can't leave or enter

- The water and carbon cycles are both \________ systems

closed

Residence times

- The average length of time in which something is stored in a particular state

The Goldilocks Zone

- The area around a star that allows for the conditions on a planet in which life can exist (including extremophiles)
- Presence of an atmosphere, this allows for gases to be used by organisms
- Correct temperature for liquid water on the planets surface (between 0oC and 100oC)
- Temperature is controlled by the planets distance from the star which it is orbiting, the distance from a star in which life can exist is the 'Circumstellar Habitable Zone' (CHZ)

Biosphere:

- : all living matter on earth

Hydrosphere

surface water

Lithosphere

the earth's crust

Atmosphere

- gases that surround the earth

Cryosphere

- all ice on earth

Why is water essential for life?

- It is essential for many processes, including photosynthesis, hydrolysis and power generation
- Up to 60% of the human body is water
- Water regulates global temperatures
- 71% of the earth's surface is covered by water

Important properties of water

- Good solvent, allowing for transport and reaction of chemicals within organisms
- High specific heat capacity, this results in a relatively constant temperature
- High latent heat of vaporisation, this cools animals down when they sweat or pant
- Good heat conductor
- Allows for light to penetrate, this is essential for plant life below water
- When solid it has a lower density, therefore ice floats creating an insulating layer, regulating water temperature below
- High surface tension, allowing for life on the surface of water
- Exhibits capillary action due to cohesive and adhesive forces, allowing for transport in plants

Spatial distribution of water

- 30% of fresh water is stored in aquifers, mostly found in porous/permeable rocks such as chalk or limestone, they therefore have an uneven distribution
- Some areas have very few aquifers (e.g. North America & Eastern Russia), other areas have large aquifer stores (e.g. Western Russia & South America)
- 68% of fresh water is found in ice, therefore cold countries posses a large amount of global fresh water (e.g. 60% of fresh water is found in Antarctica)
- Water vapour is found in greater concentrations at the equator where temperatures are higher

How might climate change effect residence times of water?

- Increasing melting rates of glaciers reduce residence times in ice
- Increased rate of evaporation reduces residence times in oceans
- Human use of ground water reduces residence times in aquifers

Factors affecting infiltration

- Amount, intensity, duration and type (e.g. rain or snow) of precipitation
- Base flow (the sustained flow in a river, mostly from groundwater), this influences how much excess water from precipitation can be drained
- Soil characteristics, soils such as clay absorb little water causing large amount of runoff, other soils such as sand allow for a high rate of infiltration
- Soil saturation, previously saturated soil prevents further infiltration causing surface runoff
- Land cover, vegetation slows infiltration by interception, surfaces such as tarmac are impermeable, and ploughing farmland influences infiltration rates
- Gradient of land, rainfall on steeply sloped land will runoff more quickly, reducing infiltration
- Evapotranspiration, water in surface soil will be quickly removed by plants

Infiltration Excess flow:

- Surface water increases by precipitation at a greater rate than infiltration capacity
- Occurs on surfaces with poor permeability e.g. compacted surface in deserts or saturated surface soil
- Occurs over the slope simultaneously, but water accumulates downslope
- Sub-surface flows not necessary

Saturated Overland Flow:

- Soil becomes saturated, preventing further infiltration, excess water becomes surface runoff
- Usually occurs after long periods of rain once soil has become saturated and down slope where the water table is nearer the surface, at this point water may exfiltrate from the soil
- Occurs in well vegetated areas
- Sub-surface flows are important as they raise the water table

Factors affecting overland flow:

- Type and volume of precipitation
- Relief (gradient of land)
- Soil type / land cover

Accumulation & Ablation

- Glaciers and icecaps form at polar latitudes and high altitudes
- Inputs cause accumulation, these include precipitation, avalanches, refreezing melt water and desublimation
- Outputs cause ablation, these include melting, carving, evaporation and sublimation
- Mass balance - the relationship between inputs and output
Positive regime \= growing, Negative regime \= shrinking
- Accumulation occurs higher up glaciers and ablation lower down, there is an equilibrium zone in the middle where inputs \= outputs, as the climate warms this moves up slope
- Factors affecting accumulation and ablation:
Temperature, Wind, Type and volume of precipitation

Percolation & Groundwater

- Water percolates through rock by gravity pulling it though weak rock (sedimentary rocks e.g. sandstone which has large pore spaces, voids and weaknesses)
- When water reaches dense and impermeable rock (confining layer of clay or granite) it will flow horizontally
- Water will percolate through the unsaturated zone to the saturated zone / groundwater (the surface of which is the water table)
- Factors affecting percolation
Gravity, Geology (permeability, porosity, structures like joints)

Air parcels and Air masses

- Air masses are volumes of air defined by their temperature and water vapour content
- Air masses are large, they may cover thousands of miles
- Air parcels form within air masses and have different characteristics
- Air parcels form due to differential heating due to the albedo effect, human activity, and due to the surface beneath the air

How does vegetation effect flows of water?

- Interception, broader leaves increase the amount of precipitation which is intercepted; the larger the interception period (delay), the greater the loss by evaporation. Interception also reduces the velocity of drips, therefore reducing soil erosion
- Leaf drip, leaves with a waxy cuticle and drip tips cause water to quickly drip off, whereas leaves with hairs retain the moisture
- Stemflow, smooth bark and angled branches will allow for increased stem flow. The presence of pollutants on bark may decrease pH of water, leading to chemical weathering
- Throughflow, the type of plants in an area will influence soil type and roots may weather roots (biological weathering), increasing porosity
- Transpiration, water is evaporated from stomata on leaves which drives capillary action through xylem, causing water uptake in the roots due to the transpiration stream. The plant type influences the stomatal density on leaves.
- Infiltration, plant type influences soil type, increased detritus / lead litter will increase soil permeability by adding organic matter
- Through fall (fall of droplets from leaf drip), tree height influences the distance over which droplets fall and therefore their kinetic energy, 9+m allows for terminal velocity to be reached
- Surface run-off, plant type influences soil type and therefore permeability of soil surface, roots can trap surface water causing reduced surface run-off, shade from plants will reduce water evaporated from ground causing increased surface water

Why does temperature change with increasing altitude?

- Temp. of dry air drops by 10oC per 1000m increase in altitude (dry adiabatic lapse rate)
- Molecules at higher altitudes experience less pressure as there is less weight of air molecules above them, therefore molecules spread out (adiabatic expansion)
- The more spread-out molecules are, the less able they are to retain heat energy
- Saturated adiabatic lapse rate, temperature of saturated air drops by 7oC per 1000m increase in altitude as condensation releases latent heat
- Environmental lapse rate, temperature that air actually drops per 1000m increase in altitude is actually around 6.5oC as the DALR and SALR are theoretical
- Lapse rates are important as they allow for the dew point at a specific location to be calculated

- Process of cloud formation:

1. Air rises and cools by roughly 10oC per 1000m
2. As air rises, relative humidity increases
3. Air reaches dew point (100% saturation), and condensation begins to occur
4. As saturated air rises it continues to cool by 7oC per 1000m

Cloud formation

- Clouds are a mass of water droplets or ice crystals suspended in the atmosphere
- Importance of clouds:
Spread the sun's energy from the tropics to the poles (planetary heat regulation)
Reflect light back to space (albedo effect), causing cooling (planetary heat regulation)
Some clouds act as an insulative layer, contributing to warming (planetary heat regulation)
Move water across the planet, determining the location of water stores (water distribution)
Clouds help meteorologists to predict weather (weather prediction)
- Evaporation occurs when heat energy is used to break bonds between water molecules
- Humidity:
Absolute humidity is the measure of actual water vapour in the air (g/m3)
Relative humidity is the ratio of absolute humidity to the theoretical maximum for a given temperature and pressure (%)
- Dew point or saturation point is reached when the 100% relative humidity is reached
- Clouds form when dew point is reached, this may be due to an increase in water vapour content or decrease in temperature (warm air can hold more water vapour)
- Conditions required for cloud formation:
Rising air (low atmospheric pressure) carrying water vapour OR Air is saturated due to decreasing temperatures
A nuclei for water to condense around (dust)

- Cumuliform:

Large clouds with flat bases, formed at high altitudes
Formed by when air warms at the earth's surface and rises by convection, as the air rises it expands and saturation point is reached causing condensation.
These deep convective clouds have little influence on global temperatures as they have both a large albedo effect and a large insulating effect.

- Stratiform:

Low thin clouds which form layers
Formed when an air mass moves horizontally across a cool surface, such as the ocean, and advection occurs (mixing and turbulence). As the air cools, condensation occurs.
These optically thick clouds are made of spherical water droplets, they reflect a significant amount of solar radiation and have little insulating effect, so overall they have a cooling effect.

- Cirrus:

Wispy clouds at very high altitudes
Formed of tiny ice crystals high in the atmosphere and don't produce precipitation, so have little effect on the water cycle.
These optically thin clouds reflect few of the suns rays but do absorb some outgoing thermal radiation, so overall they have a warming effect

- Atmospheric stability:

Air parcels cooler than atmospheric air, they sink and warm causing a high atmospheric pressure and lack of cloud formation
Typical weather conditions are dry and clear with large diurnal temperature changes

- Atmospheric instability

Air parcels are warmer than atmospheric air, they rise and cool causing a low atmospheric pressure and clouds form as air cools to dew point
Typical weather conditions are clouds and precipitation that minimise diurnal temperature change

Conditions required for precipitation:

- Droplets collide to form larger droplets (coalesce)
- Droplets freeze and crystalise
- Droplets / crystals become too heavy and fall due to gravity

Forms of precipitation

- Snow is unaltered crystals
- Sleet is slightly melted crystals
- Rain is melted snow
- Hail is refrozen ice

Frontal rain

- when a warm air mass meets a cool air mass, the warm air mass is pushed up as it is less dense, thus creating the 'front'. As the warm air moves up it cools and clouds form by condensation, these clouds then produce precipitation.

Orographic rain

- when a saturated air mass moves over an area with raised topography, such as a mountain, the air increases in pressure and condensation is forced. Clouds form and precipitation occurs over the mountains

Convective rain

- forms over a warm surface as the air above the ground warms has a high absolute humidity due to evaporation. The unstable air rises by convection and cools, cumulus clouds form at the dew point. This continues until the clouds become large and precipitation occurs.

Drainage basin

- the area of land drained by a river and its tributaries (river system)

river system inputs

rain and aeolian sediment

river system outputs

- include discharge into oceans and sediment

River discharge

- , the volume of water passing a given point in a given time, measured in cubic meters per second (CUMECS)

Storm hydrographs measure

- fluctuating streamflow, they show the pattern of discharge of a river at a specific gauging station after a specific rainfall event

Importance of hydrographs

They can be used to compare how different drainage basins respond to rainfall events
Speed and scale of the rise in discharge can be used to assess the risk of flooding
They allow for the effects of river management to be monitored.

- Measuring rainfall:

Met office uses automatic rain gauges and wetness sensors to calculate humidity

- Measuring sea ice:

Nasa's 'Earth Observing System' satellites measure microwave energy radiated from the earths surface, showing how much solar energy is reflected. Due to the albedo effect, sea ice is indicated by increased radiation

Why is carbon essential for life?

- Carbon is an essential element for forming biomass
- Organic compounds such as proteins, carbohydrates and lipids all require carbon
- Carbon's molecular structure allows for its atoms to form long chains, with each link leaving two potential bonds free to join to potential atoms

Importance of studying the carbon cycle

- Carbon storage and fluxes of CO2 are important indicators of the health of ecosystems
- Energy resources e.g. fossil fuels and biofuels are key parts of the cycle
- Atmospheric CO2 levels are the main cause of climate change

- Physical carbon pump:

1. CO2 in the atmosphere dissolves in the surface ocean, forming carbonic acid and carbonates
2. The thermohaline circulation system pumps carbon rich surface water into the deep ocean by downwelling
3. Dissolved carbon is stored for up to 1250 years in the deep ocean
4. Dissolved carbon may be used by marine biota to form carbonates for shells and skeletons

biological carbon pump

- Biological pump:
1. Phytoplankton and other photosynthesising marine biota fix carbon to form biomass, this occurs in the surface ocean
2. Carbon is passed up the food chain
3. Dead marine biota and faecal matter fall to the ocean floor and form calcareous ooze

calcareous ooze

- Calcareous ooze is made up of shells, skeletons and dead biological matter, as layers slowly build up on the ocean floor pressure increases.

calcareous ooze 2

1. Calcium carbonate detritus undergo compaction, cementation and recrystallisation, becoming sedimentary rock such as limestone
2. Biomass (dead flesh and plant matter) undergo thermocatalytic reactions, forming insoluble geopolymer compounds which form the basis of crude oil and natural gas

- Tectonic activity moves sedimentary rock over thousands of years towards plate boundaries and crust surfaces

1. Weathering and erosion remove particles of rock into rivers and soils. Rainwater contains weak carbonic acid which dissolves limestone and chalk by carbonation, releasing carbon into rivers and atmospheres.
2. Oceanic crust sinks in subduction zones, heat causes decarbonation and carbon dissolves into magma and upward moving fluids. Degassing releases CO2 into the atmosphere at volcanoes and vents, releasing 300 million tons of CO2 annually.

Fast carbon cycle

Predominantly biotic components
Carbon trapped in stores for millions of years
Infrequent fluxes between stores

Slow carbon cycle

Predominantly abiotic components
Carbon trapped in stores for a short time e.g. hundred years in a tree
Frequent fluxes between stores

Forests and the carbon cycle

- Photosynthesis in terrestrial ecosystems absorbs 123 PgC annually, but respiration, decomposition and combustion release 118.7 PgC annually, it therefore acts as a carbon sink
- Through deforestation humans are increasing CO2 emitted by combustion and decomposition, while decreasing CO2 fixed by photosynthesis, this is causing terrestrial ecosystems to become less effective carbon sinks.

Carbon and the oceans

- The ocean absorbs 80 PgC annually and releases 78.4 PgC annually, it therefore acts as a carbon sink
- This has enabled the oceans to absorb 50% of anthropogenic CO2 since the industrial period
- When carbon dioxide dissolves in oceans it forms carbonic acid, decreasing the pH of the ocean, since the industrial period oceans have become 30% more acidic
- Increased ocean acidity reduces the available carbonate ions for hard shelled organisms and corals to use, therefore reducing the formation of sedimentary rock
- If the ocean becomes too acidic then organisms' shells may begin to dissolve, reducing how much carbon that the oceans can absorb

- Downwelling:

This occurs at the polar regions; warm surface currents cool at the poles, becoming denser due to thermal contraction. Also, as ice forms, salt concentrations increase, increasing the density of the water. Due to the increased density, the water sinks into the deep ocean

- Upwelling:

Deep ocean currents resurface in areas such as the Indian ocean, this is partially due to currents becoming trapped by coasts and winds creating surface currents away from the shore, reducing pressure and allowing for water to rise. Also, decreased salinity and increased temperatures increase the temperature of deep water.

The thermohaline circulation system is responsible for

- regulating global temperatures, circulating nutrients, and driving the physical carbon pump.

CO2 dissolves in surface currents and is transferred to the deep ocean

in areas of downwelling, this carbon will be stored until upwelling occurs.

In areas of upwelling

carbon rich deep ocean water rises to the surface and CO2 is released back into the atmosphere.

Due to climate change, water temperatures at the poles is increasing

- reducing ice formation and therefore reducing the density differences. This is reducing the rate of downwelling and, as a result, the thermohaline circulation system is slowing. This is an issue because transfer of carbon to the deep ocean sink is reducing.

There is global variation in carbon storage due to

- climatic conditions creating different biomes, each with different vegetation, soil types, nutrient cycles and water cycles.

Tropical and subtropical rainforests are the

- due to the year round warm and humid conditions which allow plants to continuously grow and sequester carbon

Temperate biomes are large

terrestrial stores of carbon as they cover an extensive land mass and store substantial amounts of carbon in the soil

Savannah and desert biomes are

- less significant carbon stores as the hot, arid conditions prevent substantial plant growth, therefore limiting carbon captured by photosynthesis, subsequently limiting the soil store (desert soil carbon content < 1%)

Tundra is the smallest terrestrial biome

- in terms of carbon storage as the harsh conditions minimised plant growth

Measuring changes in the carbon cycle

- Monitoring stations use sensors to collect data on the chemical composition of the atmosphere, including CO2concentration which is measured in Parts per million (ppm)
- The remote research observatory in Mauna Loa, Hawaii has measured a 30% increase in atmospheric CO2concentration since 1960
- Satellites also be used to monitor CO2 levels globally
- Satellite imaging is used to estimate carbon stored in terrestrial stores such as tropical rainforests by monitoring forested landmass
- Flux towers are used in rainforests to measure fluxes of carbon between the forest and the atmosphere, as well as changes in climatic conditions

Flashy

Susceptible to flash floods
Short lag time
High peak discharge
Steep rising limb

Non-flashy

Flooding is rare
Long lag time
Low peak discharge
Shallow rising limb

Madeira Basin, Amazon Rainforest Case study

- Rainforests cover over 20 million km2 of land globally
- The Amazon rainforest contains 20% of all species on earth
- Rainforests absorb up to 25% of anthropogenic carbon

Madeira Basin, Amazon Rainforest Case study - climate

- Annual rainfall of 2300mm
- Average temperatures of 25oC, with peaks of 40oC

Madeira Basin, Amazon Rainforest Case study -Human activity:

- 17,500 km2 of the Amazon is destroyed each year
- Since 1970, 20% of the primary rainforest has been degraded or destroyed, reducing its carbon sequestering power by 30%
- 30% of anthropogenic carbon emissions globally are from deforestation
- 75% of Brazil's emissions are due to deforestation
- Global population growth is driving demands for food and fuel, in turn this is driving a demand for land in the Amazon rainforest and therefore deforestation

Madeira Basin, Amazon Rainforest Case study -Characteristics of the water cycle:

- The Amazon River accounts for 1/6 of the worlds river discharge
- The Madeira river is the largest tributary of the Amazon
- Rainfall is evenly distributed year-round with heavy rainfall most afternoons, there is a monsoon season during which there is particularly heavy rainfall
- Due to the dense vegetation, 90% of precipitation is intercepted and 50% is immediately returns to the atmosphere by evapotranspiration
- There is rapid run-off due to the well-drained soils and intense rainfall
- There is a large atmospheric water store due to high temperatures lowering the relative humidity
- Large stores of water in aquifers
- Large stores of water in biomass

Madeira Basin, Amazon Rainforest Case study -Factors influencing the water cycle:

- Much of the underlying geology is ancient, impermeable, crystalline rocks such as granite, causing rapid run-off in some areas
- In basins, permeable and porous rocks like limestone store large amounts of water
- Extensive lowlands allow annual flooding which stores large amounts of water
- Steep slopes in the Andes mountains allow rapid run-off
- Year-round high temperatures fuel a rapid water cycle and high humidity
- High temperatures drive convection which produces thunderstorm clouds

Madeira Basin, Amazon Rainforest Case study- Impacts of deforestation on the water cycle

- Reduced vegetation reduces the rate of evapotranspiration, which in turn reduces cloud formation and precipitation
- By 2080, summer rainfall in the Madeira basin could reduce by 80%
- Less rainfall is intercepted, increasing surface runoff, which drives increased soil erosion
- Temperatures rise due to reduced cloud cover reducing the albedo effect

Madeira Basin, Amazon Rainforest Case study- Impacts of farming on the water cycle

- Slash and burn clearing leaves a shallow layer of fertile soil which can support agriculture for a short amount of time
- Extensive monocultures of cash crops e.g. soya deplete soil nutrients
- Fertilisers used are washed into rivers, polluting freshwater ecosystems
- Increased surface runoff increases sediment being washed into rivers, resulting in flooding
- In the Madeira basin, extensive drainage systems are used to drain the fields, increasing river discharge
- In 2014 the Madeira river flooded, causing cholera outbreaks and 70,000 were evacuated

Madeira Basin, Amazon Rainforest Case study -Impacts of dams on the water cycle

- Many hydropower dams, such as the Balbina Dam, have been created in Brazil
- Dams flood large areas of forest while reducing discharge downstream
- Dams trap sediment, causing a build up behind the dam
- Dams prevent several fish species from migrating upstream

Madeira Basin, Amazon Rainforest Case study- Characteristics of the Carbon cycle:

- The Amazon rainforest stores 17% global terrestrial vegetation carbon stock
- Rainforests naturally sequester carbon dioxide from the atmosphere through high levels of photosynthesis, acting as a carbon sink
- The dense vegetation in the Amazon stores a significant amount of carbon
- The ideal growing conditions allow the rainforest to have a high net primary productivity (NPP \= 2500 g / m2 / yr.)
- The Amazon rainforest accounts for 15% of global terrestrial NPP

Madeira Basin, Amazon Rainforest Case study- Factors influencing the carbon cycle:

- High temperatures promote rapid plant growth and rapid nutrient cycling (high levels of decomposition)
- Vegetation stores large amounts of carbon, 60% of rainforest carbon is stored in biomass
- The rapid nutrient cycle due to the moist, warm conditions results in detritus and soil being a less significant store of carbon in rainforests (TRF soils store 226PgC)
- Limestone and sandstone store significant amounts of carbonates

Madeira Basin, Amazon Rainforest Case study -Impacts of deforestation on the carbon cycle:

- Deforestation by slash and burn releases large amounts of CO2 into the atmosphere
- Increased soil erosion due to exposed soil and increased surface run-off leaves nutrient poor soil which can't support large amounts of biomass
- After deforestation most tropical areas become tropical grassland
- Grasslands store 90% less carbon than virgin tropical rainforests

Madeira Basin, Amazon Rainforest Case study -Impacts of farming on the carbon cycle:

- Soya plantations store 98% less carbon than virgin rainforests
- Farm machinery burns fossil fuels, releasing CO2 into the atmosphere
- Draining fields for agriculture allows peat to dry out, releasing methane and CO2

Madeira Basin, Amazon Rainforest Case study-Impacts of dams on the carbon cycle:

- Flooded forest rots, releasing methane and CO2
- Hydropower reduces reliance on fossil fuels, thus reducing CO2 released from power stations

Madeira Basin, Amazon Rainforest Case study -Managing the Amazon rainforest:

- Deforestation rates have reduced by 70% since the 1980s
- Brazil has formed national parks which are protected by legislation
- The UN-REDD scheme funds native groups, e.g. the Surui people, to plant seedlings, this is funded by selling companies 'carbon credit'
- The Muvuca farming method is used by many indigenous people in the Xingu region, this involves sowing a mix of 120 tree species in deforested regions and once the area has been reforested controlled cattle grazing and polyculture farming can be carried out amongst the forest. This has been supported by the Brazilian government
- Brazil has committed to reforesting 120,000km2 of rainforests by 2030
- The government in Brazil owns large amounts of land which is used for producing sustainable timber through a 25-year cycle of felling and replanting
- Use of natural fertilisers, e.g. charcoal and manure, reduces pollution of rivers and allows farmland to be used for permanent cultivation

Madeira Basin, Amazon Rainforest Case study - Positive impacts of these schemes on the water cycle:

- Protection of rainforests reduces flood risks
- Protection of rainforests maintains cloud cover, aiding to regulate the local climate
- Reforestation binds the soil, protecting from soil erosion
- Improved farming techniques reduces pollution of rivers

Madeira Basin, Amazon Rainforest Case study -Positive impacts of these schemes on the carbon cycle:

- Protection of rainforests protects the forest as a natural carbon sink
- Sustainable timber production protects forests as a carbon sink and the wood produced stores carbon
- Improving agricultural techniques reduces demand for land for agriculture and therefore reduces deforestation by slash and burn

Alaska, Arctic Tundra Case study

Area:
- 8 million km2 in northern Canada, Alaska and Siberia
- Between 60oN and 75oN

Alaska, Arctic Tundra Case study
Climate:

- Cold temperatures: avg. winter temps. \= -34oC, avg. summer temps. \= 7oC
(low temperatures due to unconcentrated solar insolation and the albedo effect)
- Extreme seasons due to variation in daylight hours throughout the year
- 50 - 350mm of precipitation annually, mostly snow
- The arctic region is the fastest warming area globally

Alaska, Arctic Tundra Case study
Vegetation type:

- Cotton grass, lichens, bearberry
- Plants must be low lying and compact to protect it from the wind
- Plants must be able to withstand waterlogged soils and annual freezing

Alaska, Arctic Tundra Case study
Human activity:

- Oil drilling and pipelines, 50% of Alaska's economy is oil based
- Prudhoe Bay is a major oil extraction site in Alaska, oil is transported to a port via the 1300km Trans Alaskan Pipeline
- Tourism, such as tours to see the polar bears and northern lights
Significant infrastructure is required for accessing

Alaska, Arctic Tundra Case study
Characteristics of the water cycle:

- Water is stored in permanent ice year round
- Seasonal rivers and lakes from meltwater and surface runoff from rain in the summer
- There is very limited evapotranspiration due to the low temperatures and lack of vegetation
- The atmospheric store of water is low as the low temperatures increase relative humidity

Alaska, Arctic Tundra Case study
Characteristics of the carbon cycle:

- 50% of global soil carbon is stored in the tundra permafrost, making it a large carbon sink which is important to protect (tundra soil stores 1600PgC)
- Permafrost forms a layer of up to 600m of frozen dead organic matter, storing carbon
- Limited growing season (50-60 days), low light intensity and low temperatures result in a low NPP of 200 g / m2/ yr.
- Arctic ocean accounts for 14% of global ocean carbon

Alaska, Arctic Tundra Case study
Factors influencing the carbon cycle:

- The shallow active layer provides very limited soil for plant growth in the summer months
- The low temperatures allow for permafrost to remain frozen year-round, trapping methane and preventing detritus from decomposing

Alaska, Arctic Tundra Case study
Impacts of human activity on the water cycle:

- Increased melting of the permafrost is forming new lakes and increasing river discharge
- Gravel extraction from rivers and mines is impacting river systems and creating new lakes
- Water extraction for factories is disrupting natural drainage systems

Alaska, Arctic Tundra Case study
Impacts of human activity on the carbon cycle:

- Up to 40 million tonnes of CO2 is released from the melting permafrost on the North Slope in the Arctic National Wildlife Refuge per year
- Urban heat islands are being created around infrastructure, causing permafrost to melt
- Road construction removes the insulating layer above the frozen permafrost and reduces the albedo effect, causing increased melting

Alaska, Arctic Tundra Case study
Managing the impacts of drilling and pipelines:

- The Arctic National Wildlife Refuge has been created by the US government and is protected by legislation, meaning that any infrastructure project requires stringent planning
- Modern technology such as lateral drilling allows for smaller drilling sites to access large areas of oil, limiting the damage to permafrost
- Use of insulated, raised pipes minimises heat reaching the ground and melting permafrost
- Refrigeration systems can be used under pipes to ensure that the permafrost doesn't melt

Diurnal change

- changes throughout the day

Seasonal change

- changes throughout the year

Long term change

- slow change over hundreds or thousands of years

Diurnal changes in the water cycle

- Minimally significant as these changes are very short term
- Little diurnal change at poles (24hr daylight/night), large diurnal change at equator

Diurnal changes in the water cycle
Day:

- Temperatures increase during the day due to sunlight, increasing evapotranspiration
- The absolute humidity increases but the condensation point also increases
- The water content in the air increases
- Rising humid air causes cumuliform clouds to form
- Convectional rainfall is likely in the afternoon once clouds reach maximum water capacity
- Frontal rain may occur in the morning when cool night air meets warm air currents