Earth Life Support Systems

Question 1

What is an open system?

Answer 1

A system with inputs and outputs of energy and matter across the system boundaries

Question 2

What is a closed system?

Answer 2

A system with inputs and outputs of energy across the system boundaries, but no input or outpout of matter

Question 3

What is an isloated system?

Answer 3

A system with no inputs and outputs of energy and matter across the system boundaries

Question 4

What is the ‘Goldilocks Zone’?

Answer 4

Some scientists believe that the key to understanding the evolution of life on Earth is the presence of a medium that allows organisc molecules to mix and combine to form more complex structures: water. 71% of the Earth’s surface is covered by liquid water. This is because the Earth is the ‘right’ distance from the sun for water to exist in large quantities in liquid form - not too hot, not too cold. The Goldilocks, or Habitable Zone, of a star is a function of its temperaturre (5500K for our sun’s surface) and distance from it (93 million miles for the Earth). On Mercury, 48 million miles from the sun, surface temperatures of 430C mean that only water vapour can exist; on Mars (141 million miles, -65C), water exists at the poles in the form of ice (although recent evidence suggests there might be very small amounts of liquid water too)

Question 5

Where is there water on Earth?

Answer 5

Oceans occupy 71% of the Earth’s surface, and moderate temperatures by absorbing heat, storing it and releasing it slowly. Ocean currents redistribute heat from the equatorial regions towards the poles, preventing excessive heating and cooling of different parts of the planet. Water vapour is a greenhouse gas, and can absorb outgoing long-wave radiation, helping maintain a global average surface temperature of 15C (approx 35C warmer than it would be without the greenhouse effect). Water droplets and ice crystals in clouds reflect back 20% of incoming solar radiation, lowering surface temperatures.

Question 6

What is the importance of water to life on Earth?

Answer 6

Water makes up 65-95% of all living organisms. Water is crucial for growth, reproduction and other metabolic functions. Plants are nearly all autotrophic (manufacture their own food), and need water for photsynthesis, respiration and transpiration. Photosynthesis in plants involves the production of glucose from the combination of carbon dioxide and water, utilising solar radiation. Water is used in industry, to generate electricity, to irrigate crops, for recreation and leisure, for drinking water and sanitation. In people and animals, water is the medium for all chemical reactions, and for vital processes such as blood and nutriet circulation. Respiration in plants and animals converts glucose to energy through its reaction with oxygen, releasing water and carbon dioxide in the process. Plants require water to retain rigidity, otherwise they wilt, and as a medium in which to transport minerals from the soil. Respiration in plants and animals converts glucose to energy through its reaction with oxygen, releasing water and carbon dioxide in the process. Transpiration of water from lead surfaces colls plants, whilst humans sweat and dogs pant to achieve the same evaporative cooling.

Question 7

What is the global water cycle?

Answer 7

Land surface (39, 000km^3x10^3) to Oceans (1.37 million km^3x10^3) via river runoff/groundwater flow (40km^3/yr)
Oceans to Atomsphere (13km^3/yr) via evaporation (425km^3/yr)
Atmosphere to Oceans via precipitation (386km^3/yr)
Atmosphere to Land surface via precipitation (111km^3/yr)
Land surface to Atmosphere via evapotranspiration and sublimation (71km^3/yr)

Question 8

Why can the global hydrological cycle be thought of as a closed system?

Answer 8

There are only inputs and outputs of energy (solar radiation and radiation out to space) and no inputs or outputs of matter (no matter on Earth leaves Earth)

Question 9

Is the volume of water on the planet fixed?

Answer 9

Yes because it does not enter or leave the global hydrological cycle system. However, it can be redistributed between stores.

Question 10

Where is Earth’s water?

Answer 10

The oceans comprise nearly 97% of all water on Earth, fresh water makes up just 2.5% of all global water and of this 68.7% (2% of water on Earth) is found in glaciers and ice caps (Antarctica and Greenland). Just 30.1% of all fresh water (0.7%) is found in underground rocks called aquifers, whilst the atmosphere accounts for a tiny 0.001% of all global water. Some water transfers rapidly between stores (daily evapotranspiration, precipitation and river runoff); transfer into and out of the atmosphere is particularly rapid, with an average residence time of just 9 days. In contrast, some water may be locked in stores such as ice sheets or the deep ocean from hundreds of thousands, or even millions of years. The water cycle circulates 505, 000km^3 of water between stores on an annual basis.

Question 11

What is evaporation?

Answer 11

The change of phase of water molecules from liquid to gaseous water. It requires an input of energy to overcome the bond strength that keeps water molecules bound in liquid form. The energy is stored in the form of latent heat, which can be released back into the atmosphere when condenstation occurs. In the drainage basin, water may evaporate from lead surfaces (intercepted water), from the ground surface or from the soil. The rate at which evaporation occurs depends on a number of factors. Temperature and sunlight: higher temperatures and greater exposure to sunlight provides more of the energy needed for bond breaking. Humidity: no matter how hot it is, if the air is saturated (100% humidity - completely ‘full’ of water vapour molecules), evaporation cannot take place. Wind speed: stronger winds constantly replace air into which water has just evaporated with new, ‘dry’ air, so evaporation can continue.

Question 12

What is transpiration?

Answer 12

A form of evaporation, but it takes place through plant matter, rather than from open surfaces. Water taken up through plant roots can be emitted as water vapour via pores on the underside of leaves (stomata). Its rate is governed by the same factors that influence evaporation rate; it is also affected by vegetadtion type, with some species, especially in water-scarce environments, exhibiting characteristics to minimise transpiration loss (low-growing tundra plants stay out of the wind, waxy cuticles on pine needles or leaves/spines with a very small surface area)

Question 13

What is sublimation?

Answer 13

The change of phase of water from ice, straight to water vapour, without passing through the liquid water phase. It represents a transfer from ice caps, ice sheets, glaciers and sea ice stores to the atmospheric system

Question 14

What is river runoff?

Answer 14

The channelised transfer of water from the land surface to the oceanic store (although some rivers do discharge into lakes, which are still part of the land surface store). Some land surface water may also enter rivers as groundwater flow, direct from bedrock.

Question 15

What is condensation?

Answer 15

Condensation is the phase of change of water vapour to liquid water. It occurs when the air is cooled to dew point, at which temperature it becomes saturated with water vapour (cold air cannot hold as much vapour as warm air), so some of the water must condense out. The tiny droplets of water vapour may coalesce to form clouds, which are the visible aggregates of water (or ice crystals) that float in the air

Question 16

Why might cooling occur?

Answer 16

Air warmed by contact with warm land or sea surface rises through the atmosphere in a process called convection. As it rises, the atmospheric pressure falls, and the ‘parcel’ of rising air expands (adiabatic expansion), ‘pushing’ against the surrounding atmosphere. This work requires energy - the parcel loses internal energy and cools. An air mass moving horizontally over a cool surface (a glacial lake). This sideways movement is known as advection - mist over water (fog). An air mass rising to cross a mountain range. A relatively warm air mass micing with a colder one

Question 17

What is a lapse rate?

Answer 17

They descrive how temperature changes with height through the atmosphere. Typically, temperature decreases with altitude, as air molecules are further from Earth’s surface, which is a source of radiation. If temperaure increases with altitude, it is known as a temperature inversion

Question 18

What is the Environmental Lapse Rate (ELR)?

Answer 18

The ELR is the vertical temperature profile of the lower atmosphere at any given time. On average the temperature falls by 6.5C for every kilometre of height gained.
Think of this as the ‘background lapse rate’, how the temperature of most of the atmosphere is changing. It’s important as this will affect what happens to parcels of air within the atmosphere.

Question 19

What is the Dry Adiabatic Lapse Rate (DALR)?

Answer 19

The DALR is the rate at which a parcel of air (less than 100% humidity so condensation is not taking place) cools. Cooling, caused by adiabatic expansion, is approx 10C/km

Question 20

What is the Saturates Adiabatic Lapse Rate (SALR)

Answer 20

The SALR is the rate at which a saturated parcel of air (one where condensation is occuring) cools as it rises through the atmosphere, because condensation releases latent heat, the SALR, cools at around 7C/km, lower than the DALR.
Latent heat - condensation involves forming bonds between water molecules, which releases therman energy (latent heat), this result is slower cooling, relative to a dry parcel of air.

Question 21

How do clouds form?

Answer 21

Imagine that the atmosphere at the Earth’s surface is 13C, but a small parcel of air is warmed by the sun to 18C. The warmer parcel of air is less dense and therefore buoyant relative to the surrounding atmosphere. It rises as a convection current - a process known as atmospheric instability. As it rises, it cools at 10C/km (DALR). When it reaches a height of 1km, it has cooled to 8C, which is dew point. The parcel of air becomes saturated, and water vapour starts to form, so 1km is the base of the cloud layer. There is still a situation of atmospheric instability, as the parcel is still warmer than the surrounding atmosphere (8C v 6.5). Although the parcel is now cooling at 7C (SALR) due to the release of latent heat associated with condensation. At a height of 4km the parcel of air reaches the same temperature as the surrounding atmosphere (-13C); the atmosphere is now stable, which means that now further convection rising will occur, as the parcel of air is of the same density as the surrounding atmosphere. This is the top of the cloud layer.

Question 22

What causes fog?

Answer 22

If dew point is at ground level, condensation will occur at ground level, producing mist and fog, this often occurs after cloudless nights in autumn and winter, when the little heat that the Earth stores up during the day readily escapes into space at night (radiative cooling)

Question 23

What is absolute instability?

Answer 23

When the parcel of air is warmer, and therefore less dense than the surrounding atmosphere, and so it rises in a convention current

Question 24

What is absolute stability?

Answer 24

When the parcel of air is cooler, and therefore more dense than the surrounding atmosphere, the parcel cannot rise and so may sink to lower altitudes.

Question 25

What is conditional instability?

Answer 25

When there is absolute stability in the lower atmosphere, but ELR flattens off at higher altitudes (maybe due to a warm, high altitude wind), this means that a parcel of air cannot rise in th elower atmosphere, but can rise if it is in the upper atmosphere, instability is conditional on the parcel being at the right place in the atmosphereic profile.

Question 26

What are cumuliform clouds?

Answer 26

They have flat bases and considerable verticle development, they are most commonly formed through convection, associated with heating of the Earth’s surface and overlying atmosphere through solar insolation. Cumulus clouds may bring showers, but cumulonimbus clouds are the result of intense convection, reaching heights of 10-12km and are associated with thunderstorms and heavy rain

Question 27

What are stratiform clouds?

Answer 27

Clouds that form in long layers, typically associated with advection, where an air mass moves horizontally across a cooler surface, reducing the temperature of the air mass uniformly over a large area. They can bring persistent rain of light/moderate intensity.

Question 28

What are cirrus clouds?

Answer 28

High altitude, wispy clouds formed from ice crystals, they do not produce precipitation and so have little influence on the water cycle.

Question 29

What is precipitation?

Answer 29

Water and ice that falls from clouds towards the ground. Rain and snow are the most common forms, but it also includes hail, sleet and drizzle. Precipitation forms when water in the atmosphere cools to its dew point and condenses into tiny water droplets or ice particles to form clouds. These particles collide and merge (aggregate) until they reach a critical mass and gravity overcomes the updraft of air that is holding them aloft, they fall from the cloud as precipitation. Precipitation varies in character, and this impact the drainage basing hydrological cycle:
Most rainfall is transferred rapidly from where it falls into streams and rivers via overland flow and throughflow. In contrast, snowfall is stored as interception storage (on vegetation) or surface storage, possibly for weeks or months in the high latitude or altitude locations, before being delivered to rivers and streams when the spring thaws arrive. This accounts for a considerable lag time between precipitation and runoff. Precipitation intensity refers to the volume falling in a certain time period - high intensity precipitation (10-15mm/hr) is likely to resuly in rapid overland flow. Precipitation duration refers to the length of time that a precipitation event lasts - low pressure systems bring frontal rainfall to the UK that can persist for many hours. In semi-arid part of the world, precipitation may be so seasonal that rivers do not flow during the dry season.

Question 30

What is dynamic equilibrium?

Answer 30

A situation in which a system oscillates around a balanced or steady state. Disturbances which threaten to take the system away from this condition are detected, and mechanisms induced that return the system to a state of balance.

Question 31

What is a negative feedback loop?

Answer 31

Loops that are responsible for the maintenance of dynamic equilibrium. If a system moves away from its optimal, balanced state, negative feedback loops are triggered, which return conditions to ‘normal’. The system is therefore self-correcting.

Question 32

What is positive feedback?

Answer 32

A loop which causes a system to spiral away from dynamic equilibrium, they occur when a change to the system causes the same change to occur again, but with greater intensity.

Question 33

What is interception? (store)

Answer 33

Precipitation that lands on vegetation leaves, stems, branches or trunks is said to be intercepted. Interception rated depend on:
Type of vegetation: coniferous woodland typically intercepts 35% of rainfall, deciduous woodland 25% and grassland 15%. This is a function of interceptive surface area, cohesive properties (waxiness) of the leaf surface and number of layers to the vegetation.
Season: deciduous trees have much higher levels of interception in summer months.
Type of precipitation: snow experiances the highest levels of interception, followed by rain, and hail the least.
Duration of rainfall event: leaves have an interception capacity, at which point they cannot intercept any more water without displacing water already stored on the leaf. Therefore interception slows down during long duration events, once capacity has been reached.
Intensity of precipitation: more intense means less intercepted.

Question 34

What is surface storage? (store)

Answer 34

Water temporarily held on the Earth’s surface. Water will be stored if:
Precipitation rate > infiltration rate (rain falls faster than the ground soaks it up)
Topography causes surface water to accumulate in diips and depression - this is known as depression storage, and can encompass anything from a puddle to a lake.
Underlying geology, or human land use (impermeable concrete), result in very low infiltration rates.
Precipitation falls in a form that does not infiltrate.

Question 35

What is soil water? (store)

Answer 35

Water temporarily held in the soil. Water stored in the soil in three forms:
Hygroscopic water: a film of water, only a few molecules thick, that is bound so tightly to soil particles through electrostatic attraction that it cannot be displaced from them.
Capillary water: further from soil particles, so the electrostatic forces that bind them are weaker, as such, capillary water can be detached from soil particles, to be evaporated at the surface, or when absorbed by plant roots.
Gravitational or free water: found in the middle of the pores between soil particles, because it is further away from the particles, there is no electrostatic attraction at all, water can be used for evaporation, root uptake, or drainage into the bedrock, this water does not remain in the soil for ling, unless topped up with new rainfall.

Question 36

What is groundwater? (store)

Answer 36

Water stored in the bedrock. A water-bearing rock is called an aquifer; an example is the chalk aquifer underlying the London basin. Within the bedrock, we often find the water table - the level below which the rock is saturated. Above the water table, we find that zone of aeration, in which pore spaces are likely to contain a mixture of air and water molecules. The water table is a mobile layer, and will rise through the rock profile following periods of heavy rain, and fall in response to prolonged drought.

Question 37

What is vegetation storage? (store)

Answer 37

Water taken up through root uptake, and stored in the biomass of living plant matter. It is used for metabolic processes within the plant, and may be lost to the atmosphere via transpiration.

Question 38

What is channel storage? (store)

Answer 38

As well as being an output, we can consider water in the river channel to be in storage as well.

Question 39

What is throughfall and stemflow? (vertical transfers)

Answer 39

This describes the transfer of intercepted water from leaves to the ground surface. Throughfall occurs when water drips off leaves, whereas stemflow involves water running down tree trunks/plant stems. In areas of heavy rainfall, such as tropical rainforests, leaves have evolved elongated drip-tips to shed the heavy rainfall via efficient through fall, otherwise the weight of intercepted water could be damaging.

Question 40

What is infiltration? (vertical transfer)

Answer 40

Infiltration is the vertical movement of water from the Earth’s surface into the soil, under the influence of gravity. The maximum rate at which a particular soil can absorb water is known as its infiltration capacity. This depends on soil type, geology, relief, antecedent conditions and land use.

Question 41

What is percolation? (vertical transfer)

Answer 41

The downwards movement of water from the soil into the underlying bedrock, under the influence of gravity.

Question 42

What is capillary action? (vertical transfer)

Answer 42

The drawing up of water through the soil profile, against the force of gravity, to be evaporated at the surface. This is possible due to the electrostatic properties of water molecules, whichgive them a cohesive nature.

Question 43

What is root uptake? (vertical transfer)

Answer 43

The absorption of water, and dissolved minerals, from the soil into plant roots for use in metabolic processes.

Question 44

What is overland flow? (horizontal transfer)

Answer 44

Water running downslope across the Earth’s surface. There are two schools of thought as to how this process comes about:
If precipitation rate > infiltration rate, overland flow will occur. This means that overland flow is promoted by extremely intense rainfall, and/or by soils with low infiltration capacities.
Regardless of precipitation rate, all soils will be able to absorb rainfall. The only situation in which overland flow will occure is therefore when the soil is completely saturated with water already, so infiltration is impossible. This situation is called saturated overland flow.
Overland flow is the fastest way to transfer water from where the rain falls to a channel

Question 45

What is throughflow? (horizontal transfer)

Answer 45

Throughflow is the lateral transfer of water through the soil profile. It is driven by gravity, and will occur at a greater speed in sandy soils (high porosity), if the soil is on a steeper slope, or if the soil has small channels/tunnels (from burrowing animals or decayed plant roots) through it. It is slower than overland flow.

Question 46

What is groundwater flow (base flow)? (horizontal flow)

Answer 46

The lateral transfer of water through the bedrock. The rate depends on teh permeability of the rock. Permeability can take two forms:
Primary permeability (porosity) descrives the ability of water to travel through small pore spaces between individual grains within a rock (sandstone).
Secondary permeability (perviosity) describes the ability of water to travel along cracks, joints and bedding planes within a rock structure (limestone). Whilst some limestones are capable of transmitting water extremely quickly through a series of underground caves and rivers, in general, groundwater flow is the slowest lateral transfer of water.

Question 47

What is evaporation? (output)

Answer 47

The change of phase of water molecules from liquid to gaseous water. It requires an input of energy to overcome the bond strength that keeps water molecules bound in liquid form. The energy is stored in the form of latent heat, which can be released back into the atmosphere when condenstation occurs. In the drainage basin, water may evaporate from lead surfaces (intercepted water), from the ground surface or from the soil. The rate at which evaporation occurs depends on a number of factors. Temperature and sunlight: higher temperatures and greater exposure to sunlight provides more of the energy needed for bond breaking. Humidity: no matter how hot it is, if the air is saturated (100% humidity - completely ‘full’ of water vapour molecules), evaporation cannot take place. Wind speed: stronger winds constantly replace air into which water has just evaporated with new, ‘dry’ air, so evaporation can continue.

Question 48

What is transpiration? (output)

Answer 48

A form of evaporation, but it takes place through plant matter, rather than from open surfaces. Water taken up through plant roots can be emitted as water vapour via pores on the underside of leaves (stomata). Its rate is governed by the same factors that influence evaporation rate; it is also affected by vegetadtion type, with some species, especially in water-scarce environments, exhibiting characteristics to minimise transpiration loss (low-growing tundra plants stay out of the wind, waxy cuticles on pine needles or leaves/spines with a very small surface area).

Question 49

What is evapotranspiration? (output)

Answer 49

The combined loss of water to the atmospheric system. We can distinguish between potential evaporation (PET), which describes the amount of evapotranspiration that would take place from an environment given a limitless energy supply (a measure of energy available) and actual evapotranspiration (AET), which describes the amount of evapotranspiration that actually takes place from an envrionment (a measure of water and energy avaliable).

Question 50

What is the pattern of actual evapotranspiration around the world?

Answer 50

Highest levels are found between 15 degrees North and South of teh equator (tropical rainforests), where there is abundant water supply and high levels of solar insolation all year round. Lowest levels are found in the world’s hot deserts at approx. 30 degress North and South of the equator; despite extremely high insolation, AET is very low due to the limited water supply. Lowest levels are also found in the Arctic and Antarctic circles, where solar energy, not moisture is the limiting factor.

Question 51

What is the pattern of potential evapotranpiration around the world?

Answer 51

Levels of PET are still very high in tropical rainforest regions, where PET=AET. This tells us that water is not a limiting factor at all, and that there is always enough water to be lost to the atmosphere through ET, given the energy available. Greatest difference can be seen in the hot deserts, which have extremely high PET (higher than tropical rainforests - lack of cloud cover means more insolation). Polar regions have extremely low PET (the same as AET), as energy is the limiting factor here, not water.

Question 52

What is river runoff? (output)

Answer 52

Rivers represent the loss of water from the drainage basin system, usually to the oceanic system (although sometimes to a lake system). A river’s discharge is the volume of water that flows past a given point every second, and is measured in cumecs. Calculated using:
Discharge (Q) = Cross-sectional Area of Channel (CSA) x River Velocity (V)

Question 53

What is leakage? (output)

Answer 53

Some water may enter the oceanic system directly from aquifers as groundwater flow, rather than being transported through rivers first.

Question 54

What is the water budget?

Answer 54

The water balance equation describes the balance of inputs, outputs and storage within the open system of a drainage basin. Precipitation = Evapotranspiration + Streamflow +/- Change in Storage
P=ET+Q+/-AS
Inputs = Outputs +/- Change in Storage

Question 55

What is soil mositure surplus?

Answer 55

Occurs when all pore spaces in the soil are full of water (saturated)

Question 56

What is soil mositure utilisation?

Answer 56

Describes a phase when soil water is being lost (percolation, capillary action, evaporation and root uptake) faster than it is replenished by infiltration

Question 57

What is soil moisture recharge?

Answer 57

Occurs when the water lost during the utilisation phase is replenished

Question 58

What is field capacity?

Answer 58

The point at which recharge is complete, and the soil enters a state of water surplus again

Question 59

On a hydrograph what is the approach segment?

Answer 59

The river’s discharge before the rainfall event occurs

Question 60

On a hydrograph what is the peak rainfall?

Answer 60

The time (usually hour) during which most rainfall falls

Question 61

On a hydrograph what is the rising limb?

Answer 61

The time during which river discharge is increasing in response to the rainfall event, due to instantaneous channel catch and rapid surface runoff

Question 62

On a hydrograph what is the peak discharge?

Answer 62

The time of maximum discharge

Question 63

On a hydrograph what is the lag time?

Answer 63

The time between peak rainfall and peak discharge, the steeper the rising limb the shorted the lag time

Question 64

On a hydrograph what is the falling limb?

Answer 64

The time during which river charge is deceaseing towards normal levels; water from the rainfall even is still reaching teh river, but in a slower, more staggered manner due to throughflow. It is gentler than the rising limb

Question 65

On a hydrograph what is the base flow?

Answer 65

The proportion of a river’s flow (usually ever-present in UK rivers) that comes from teh slow seepage of groundwater into river channels from bedrock

Question 66

On a hydrograph what is the stormflow?

Answer 66

The rapid response of a river to rainfall event - the proportion of discharge that comes from surface runoff (usually finished in hours) or throughflow (days)

Question 67

Drainage basin and precipitaion characteristics of a ‘flashy’ hydrograph?

Answer 67

Basin size: small basins often lead to rapid water transfer
Drainage density: a high density speeds up water transfer
Rock type: impermeable rocks encourage rapid overland flow
Land use: urbanisation encourages rapid water transfer
Relief: steep slopes lead to rapid water transfer
Soil water: saturated soil results in rapid overland flow
Rainfall intensity: heavy rain may exceed the infiltration capacity of vegetation, and lead to rapid overland flow

Question 68

Drainage basin and precipitaion characteristics of a low, flat hydrograph?

Answer 68

Basin size: Large basins result in a relatively slow water transfer
Drainage density: a low density leads to slower transfer
Rock type: permeable rocks encourage a slow transfer by groundwater flow
Land use: forests slow down water transfer because of interception and root uptake
Relief: gentle slopes slow down water transfer
Soil water: dry soil soaks up water and slows down its transfer
Rainfall intensity: light rain will transfer slowly

Question 69

What is a river regime?

Answer 69

A graph that describes the annual pattern of dischage; it primarily reflects changes to the seasonal balance between precipitation and solar insolation

Question 70

What is the cryosphere?

Answer 70

The part of the Earth’s systems that are composed of ice; primarily ice caps, but also glaciers, sea ice and permafrost. It forms an important part of the global and the drainage basin hydrological cycle

Question 71

What is the impact of cryospheric process on the global hydrological cycle?

Answer 71

Ice caps (Antarctica and Greenland ice caps) represent a major store of water within the terrestrial component of the global water cycle. Inputs to this store are precipitation in the form of snow, which does not melt in the low temperatures and become buries under subsequent snowfall; over time, it becomes compressed to from glacial ice. Water is lost from ice stroes through ablation - either melting or sublimation, which is teh phase change of water from ice directly to water vapour. Glaciers, especially where they flow into the sea, may experiance calving, where blocks of ice break away and become icebergs within the ocean water store.

Question 72

What is the impact of cryospheric processes on the drainage basin hydrological cycle?

Answer 72

Depending on latitue, altitude and/or season, drainage basins may experiance an input of precipitation in the form of snow. This may melt when temperatures increase, or accumulate over years to form glacial ice. Drainage basins’ ice stores are depleted through ablation and, in some cases, calving. Meltwater represents an important component of river flow in some high latitude and high altitude catchments, the exact contribution will vary seasonally. Rapid thawing of upland snow in the British wainter is a common cause of flooding in downstream lowland areas

Question 73

What is the atmosphere?

Answer 73

The layer of gases, approximately 100km thick, that surrounds the Earth and is attracted to it by gravity

Question 74

What is the biosphere?

Answer 74

The total sum of all living matter on Earth; plants, animals, bacteria, fungi

Question 75

What is the carbon flux?

Answer 75

The transfer of carbon between or within stores, measured in gigatonnes of carbon dioxide equivalent per year (GtC/yr)

Question 76

What is carbonification?

Answer 76

The transformation of dead organic matter (plant or animal) into fossil fuels through the application of heat and pressure over millions of years

Question 77

What is the carbon sink?

Answer 77

A store of carbon that absorbs more carbon than it releases over a year

Question 78

What is a carbon store?

Answer 78

A ‘reservoir’ of carbon, which can be contained in gaseous, mineral, organic or dissolved form

Question 79

What is erosion?

Answer 79

The breakdown and subsequent removal of rocks by moving agents (rivers, glaciers, waves, wind)

Question 80

What is foraminifera?

Answer 80

A type of marine micro-organism with a calcium carbonate exo-skeleton

Question 81

What is a GtC?

Answer 81

A Gigatonne of Carbon Dioxide Equivalent per Year - the unit used by the UN’s Intergovernmental Panel on Climate Change to measure the amount of carbon in various stores. One Gigatonne amounts to 1 billion tonnes

Question 82

What is the hydrosphere?

Answer 82

A discontinuous layer of water at or near the Earth’s surface. It includes all liquid and frozen surface waters, groundwater held in soil and rock and atmospheric water vapour

Question 83

What is the lithosphere?

Answer 83

The crust and uppermost mantle; this constitutes the hard and rigid rocky outer layer of the Earth

Question 84

What is subduction?

Answer 84

The descent of the Earth’s crust into the upper mantle along a destructive plate margin

Question 85

What is tectonic uplift?

Answer 85

The process whereby rocks are raised upwards due to the forces created at plate margins, this can elevate rocks that previously formed the sea bed above sea level

Question 86

What is weathering?

Answer 86

The breakdown of rocks in situ by a combination of weather, plants and animals

Question 87

Where is the Earth’s carbon?

Answer 87

Atmosphere, Biosphere (living organisms), Hydrosphere (especially oceans) and Lithosphere (Earth’s crust)

Question 88

What is the volume of carbon stored in sedimentary rocks?
What is the volume of carbon stored in the deep ocean?
What is the volume of carbon stored in fossil fuels?
What is the volume of carbon stored in the terrestrial biosphere?
What is the volume of carbon stored in the soil?
What is the volume of carbon stored in the oceans surface?
What is the volume of carbon stored in the atmosphere?
What is the volume of carbon stored in the oceanic biosphere?

Answer 88

100 million GtC
37, 000 GtC
4, 100 GtC
3, 100 GtC
1, 500 
900 GtC
800 GtC
730 GtC

Question 89

Is carbon one of the most abundant chemical elements on Earth?
How much of our bodies is made up of water and carbon?

Answer 89

4th largest after hydrogen, helium and oxygen, it is essential to life on Earth
83%

Question 90

Why is carbon diverse?

Answer 90

It can exist as a gas or as a soild. Its imprtance lies in its ability to bond with other elements and it is estimated that it forms the basis of all known compounds. Carbon is ubiquitous on Earth, being found in the lithosphere, in the hydrosphere, in the atmosphere and throughout the biosphere.

Question 91

Why is carbon important to life on Earth?

Answer 91

Amino acid is the building blocks of proteins. All amino acids are forms of hydrocarbons, carbon atoms are the basis of life itself. Life as we know it is based on carbon: it is present in nearly every molecule and structure within organisms in the living world and in humans. Carbon-based crude oil is the new raw material for the manufacture of a wide range of products, including plastics, paint and synthetic fibre. Carbon is a significant raw material for manufacturing. Oil is fundamental in the manufacture of plastics, paints and synthetic fibres such as polyester. Carbon based energy sources remain of great importance to the global economy: coal, oil, natural gas, and, in some parts of the world, fuelwood. Carbon is the foundation of virtually all human activities, currently some 80% of the world’s primary energy is supplied by fossil fuels. Fuelwood is an important energy source in LIDCs. Timber is used in construction and paper making while agriculture crops not only provide food but also material such as cotton and oils for products like soap.

Question 92

What is the slow carbon cycle?

Answer 92

Carbon stored in rocks, sea-floor sedimnets and fossil fuels are locked away for millions of years. The total amount of carbon flux through the slow cycle is between 10 and 100 million tonnes per year - a small raction of the overall flux total. CO2 diffuses into the ocean from the atmosphere, where marine organisms such as molluscs and coral polyps build thier shlls and skeletons by combining dissolved carbon with calcium to form calcium carbonate. When the organisms die, their remains sink to the sea bed, where, over millions of years, burial, heat and pressure will convert the shells and skeletons into carbon-rich sedimentary rocks. Typical residnece times of carbon held in rocks is 150 million years. Other sedimentary rocks may form when layers of fluvially-transported sediment, eroded or weathered from the terrestrial environment accumulate on sea/lake beds. Organic tissue may undergo the same process, but will form fossil fuels such as oil and natural gas. On land, the burial and compression of tree andplant matter in tropical and sub-tropical swamps 300 million years before present saw the formation of most of the Earth’s coal. Carbon may be lost from this long-term store if rocks on the ocean floor are subducted at destructive plate margins; the carbon may then enter the asthenopheric mantle store, but it may be vented back into the atmosphere as elevated above the ocean surface, where they become vulnerable to chemical weathering processes such as carbonation, in which rainwater containing carbonic acid (from dissolved CO2) reacts with the calcium carbonate; CO2 is released into the atmosphere, and aqueous carbon compouds are returned to the oceans via river runoff.

Question 93

What is the fast carbon cycle?

Answer 93

Carbon circulates most rapidly between the atmosphere, the ocean surface, the biosphere (living organisms) and soils. These transfers are between 10 and 1000 times faster than transfers within the slow cycle, and are responsible for 10-100 billion tonnes of carbon flux per year. Land plants and phytoplankton in the oceans absorb CO2 through the process of photosynthesis, combining the molecules with water to make glucose. This is the basis of all food chains, as it converts solar energy into chemical energy, which can be ingested by non-autotrophic species. Respiration by plants and anumals oxidises glucose; a product of this reaction is CO2, which is released into the atmosphere. Decomposition of dead organic matter by detritivores (bacteria, fungi) also releases CO2 to the atmosphere. Organic matter may be buried in anaerobic conditions before it can decay; this carbon may be transformed into fossil fuels (carbonification) and enter the slow cycle. There is also fast exchange of carbon between the atmosphere and the ocean. Atmospheric CO2 diffuses into the surface ocean water; this is a reversible process, and CO2 can be released from the ocean back to the atmosphere. This is called natural or oceanic sequestration, and carbonatoms that are sequestered in this manner have a typical residence time in the ocean of 350 years. Aqueous carbon in the ocean may be incorporated into the shells and skeletons of marine organisms, which represents the transfer of the carbon from the fast to the slow cycle.

Question 94

How is precipitation a part of the carbon cycle?

Answer 94

Atmospheric CO2 naturally dissolves in rainwater to form weak carbonic acid; raided atmospheric concentrations of CO2 die to anthropogenic emissions have increased acidity of rainfall (and therefore the volume of the carbon flux). Knock-on effects include increased rates of chemical weathering and acidification of oceans, which can be damaging to marine life

Question 95

How is weathering a part of the carbon cycle?

Answer 95

Weathering is the in situ breakdown of rocks at or near the Earth’s surface through physical, chemical or biological processes. A lot of chemical weathering involves rainfall water which contains dissolved CO2 (carbonic acid), derived from the atmosphere or the soil (once the rain has fallen). Carbonic acid can slowly dissolve limestone and chalk rocks in the process known as carbonation.
Calcium carbonate + carbonic acid -> Calcium bicarbonate + Carbon dioxide
This process releases carbon into streams, rivers and oceans. Some CO2 is also released into the atmosphere. The process occurs more quickly under soil cover, as high concentration of carbon dioxide in soils makes more concentrated carbonic acid. It is estimated that chemical weathering transfers 0.3 billion tonnes of carbon into the oceans every year. Physical weathering such as freeze-thaw breaks rocks into smaller fragments through mechanical force, but does not involve any chemical change in rock minerals, and therfore does not result in a carbon flux. It does, however, expose a greater surface area of rock to chemical weathering processes. Biological weathering can involve chemical decomposition of rocks; chelation occurs when plant matter decomposes to form humic acids, which attack certain rock minerals. This process is important in tropical rainforests, where there is abundant leaf litter and decomposition is rapid in the hot, humid conditions.

Question 96

What is photsynthesis within the carbon cycle?

Answer 96

Photosynthesis in land plants and phytoplankton is responsible for the flux of 120 gigatonnes (120 billion tonnes) of carbon per year from the atmosphere to the biosphere. Carbon dioxide + Water -> Glucose + Oxygen
Glucose will be used in plants for respiration, reproduction, growth and other life processes. It is also available to be passed on to other organisms via the food chain. Carbon can be stored in trees for decades or centuries

Question 97

What is respiration within the carbon cycle?

Answer 97

The carbohydrates (glucose) produced in photosynthesis (whether retained in the plant or passed to animals through consumption) is oxidised in respiration, creating carbon dioxide and water, and releasing energy, which powers metabolic processes. 
Glucose + Oxygen -> Carbon dioxide + Water
Respiration and photosynthesis are at the heart of the fast cycle. Together, they exchange one thousand times the volume of carbon per year that is moved through the entire slow carbon cycle.

Question 98

What is decomposition within the carbon cycle?

Answer 98

Detritivores (also known as saprophytes) feed on dead organic matter. They include bacteria and fungi, and are responsible for the decomposition of plant and animal remains. As part of this process, CO2 is released into the atmosphere, and aqueous carbon compounds called humus (a nutrient rich, black, jelly-like substance) into the soil. Decomposition is a series of chemical reactions, and takes place quickest in hot, humid conditions (tropical rainforests). It is slowest in the absence of either heat (tundra) or water (hot desert)

Question 99

What is combustion within the carbon cycle?

Answer 99

Natural combustion involves the oxidation of carbon stored in biomass. As long as sufficient oxygen is present, combustion releases CO2 into the atmosphere, as well as other gases such as sulphur dioxide and nitrous oxides. Combustion is part of the natural life cycle of many ecosystems, such as Australia’s eucalyptus forests, or the pine forests of California’s Sierra Nevada mountatins. The trees in these forests contain high quantities of oils, which makes them highly combustible. Period burning, maybe triggered by a lightening strike, clears deadwood, thins litter from the forest floor, adds nutrients to the soil in the form of ash, and thins the forest canopy to increase light levels. Combustion of biomass can also be caused by human activities, including unintentional setting of wild fires (e.g. discarded cigarette butts), or delicate clearance of grassand or forest to clear space for agriculture. Combustion of fossil fuels in transport and industry contributes 10Gt of CO2 into the atmosphere every year from the geological store.

Question 100

What is oceanic sequestration? (the physical, inorganic, pump)

Answer 100

The take up of carbon from the atmosphere. This results from the mixing of surfaces and deep ocean water by oceanic currents, creating a more even distribution of carbon within the ocean, both vertically and latitude. CO2 enters the ocean from the atmosphere by diffusion; surface currents such as the Gulf Stream then transport this water around the globe, with many flows heading from the equator to the poles. In high latitudes, ocean water is colder and denser. It sinks in a process known as down-welling; dissolved carbon is transported to the deep ocean, where is can be retained for centuries. This process occurs strongly in the North Atlantic, off the coast of Greenland. Eventually deep ocean currents bring the carbon to areas of up-welling (e.g. west coast of South America). The cold, carbon-rich water returns to the ocean surface, from where it can diffuse back into the atmosphere.

Question 101

What is oceanic sequestration? (the biological, organic, pump)

Answer 101

The ocean takes up carbon from the atmosphere. Globally, nearly half of all carbon fixation by photosynthesis (50Gt/yr) takes place in the oceans, largely through phytoplankton. This drawing down of carbon into the ocean is known as the biolofical pump. Phytoplankton is then eaten, and the carbon is passed through the oceanic food chain. When marine organisms die, they may sink to the ocean floor, where they carbon in their organic matter accumulates; over a very long time scale, this can lead to fossil fuel formation. Alternatively, organic matter may decompose in the warm, oxygen-rich surface waters, releasing aqueous CO2. Marine organisms such as tiny coccolithophores, molluscs and crustaceans extract calcium and carbonate ions from the sea water to manufacture plates, shells and skeletons. Most of this carbon-rich material will sink to the ocean floor whe the organism dies; eventually, burial, heat and pressure sill lead to lithification (the formation of sedimentary rocks). The biological pump therefore represents a method of transfer of carbon from the fast to the slow cycle.

Question 102

Where is the Arctic tundra?

What is tundra?

Answer 102

The Arctic tundra occupies more than 8 million km^2 in northern Canada, Alaska (USA) and Sibera (Russia), approx. between 55 and 70 degrees north of the equator. It covers 8% of global surface area. To the south lies the boreal forest biome (coniferous trees), sometimes known as taiga. To the north is the is the Arctic Ocean or polar desert. The southern edge of the tundra is the tree line - the line north of which trees are unable to grow due to an unsuitable climate. This equates approx to the 10C July isothern (the line north of which July temperatures are colder than 10C).
The tundra is underlain by permanently frozen ground, or permafrost, which can extend to depths of over a kilometre. On the southern margins of the tundra, it may be sporadic or discontinuous. During the summer months, the top metre or so may melt and create an active layer, the melt water cannot drain due to the impermeable permafrost beneath, so it becomes saturated and marshy.

Question 103

Why is biodiversity low in the tundra?

Answer 103

Few plants and animals are adapted to this extreme envionment and the tundra ecosystem is treeless, except for a few species (willow) that have adapted dwarf varieties that cover the ground in a low-growing carpet, to reduce exposure to the desiccating wind. As you progress north through the tundra biome, vegetation cover becomes more sparse, reflecting the increasingly harsh abiotic conditions.

Question 104

What is the climate of the Arctic tundra?

Answer 104

Cimate conditions in the Arctic tundra are severe, and become more extreme at higher latitudes. For eight or nine months a year, there is a negative heat balance, with temperatures below freezing. As a result, the ground is permanently frozen, with only the top metre or so thawing out druing the brief summer. Average temperatures are below freezing for eight months a year. The coldest months are January (average -26.5C) and February (average -28C). The sun does not rise above the horizon for several weeks during December-January. June, July, August and September are the only months when average temperatures are above freezing. July is the warmest month (7.6C). Precipitation levels are low, with an annual average of just 412mm. This will fall as snow for much of the year. The warmer months are also the wetter months, with August seeing the most precipitation (66mm).

Question 105

What is precipitation like in the Arctic tundra? (water input)

Answer 105

Low annual precipitation (50-350mm), with most falling as snow. The low temperatures reduce the capacity of the atmosphere to store water vapour, limiting the opportunities for condensation, cloud development and precipitation.

Question 106

What is the atmosphere like in the Arctic tundra? (water store)

Answer 106

Low temperatures reduce absolute humidity, meaning small stores of atmospheric moisture - cold air can’t hold much water vapour.

Question 107

What is the surface storage like in the Arctic tundra? (water store)

Answer 107

High levels of surface storage of water for 8-9 months a year in the form of snow. During the summer months, whilst the snow melts, surface storage remains high, as permafrost prevents the infiltration and percolation of the meltwater into the ground, so it remains as lakes, ponds and marshes.

Question 108

What is the soil water/groundwater like in the Arctic tundra? (water store)

Answer 108

Limited liquid soil water and groundwater stores, due to presence of permafrost preventing infiltration and percolation. There is, however, frozen water stored within the permafrost.

Question 109

What is the interception like in the Arctic tundra? (water store)

Answer 109

Limited interception due to sparse nature of vegetation, and the fact that it is all at ground level anyway, so there is not the opportunity for multi-layered interception; however, snow has higher interception rates than rainfall.

Question 110

What is the vegetation storage like in the Arctic tundra? (water store)

Answer 110

Low levels of vegetation storage due to low biomass; plants that can grow in the tundra are often adapted to have low water requirements, as what little precipitation there is, is often in an inaccessible form (snow/ice).

Question 111

What is infiltration/percolation like in the Arctic tundra? (water transfer)

Answer 111

Limited due to impermeable permafrost.

Question 112

What is surface runoff like in the Arctic tundra? (water transfer)

Answer 112

Surface runoff is very low (often zero) for much of the year due to below-freezing temperatures and precipitation falling as snow. In the short summer, regimes show an increase in discharge as meltwater flows down channels.

Question 113

What is throughflow and groundwater flow like in the Arctic tundra? (water transfer)

Answer 113

These two flows are negligible, due to the presence of permafrost. During the short summer, the uppermost metre of the soil may thaw to create an active layer, in which some lateral movement of water may occur.

Question 114

What is transpiration like in the Arctic tundra? (water output)

Answer 114

Low transpiration levels due to low biomass and short growing season.

Question 115

What is evaporation like in the Arctic tundra? (water output)

Answer 115

Low evaporation levels due to low temperatures. Much of the sun’s energy during the short summer is expended melting snow, and is therefore not available for ground absorption. Ground temperatures therefore remain low (further limited by the permafrost beneath), which ingibits convection. Furthermore, evaporation requires a liquid store, which is not available for most of the year.

Question 116

What is river runoff like in the Arctic tundra? (water output)

Answer 116

River discharge is very low (often zero) for much of the year due to below freezing temperatures and precipitation falling as snow. In the shoret summer, river regimes show an increase in discharge as meltwater flows down channels.

Question 117

What is the permafrost like in the Arctic tundra? (carbon store)

Answer 117

The permafrost is a vast carbon store, containing an estimated 1600GT of carbon globally. The carbon is stored in the form of undecomposed and partially decomposed plant matter. Decomposition is so slow because of the very low temperatures. The amount of below-ground carbon in tundra soils is five times greater than above ground carbon in biomass.

Question 118

What is the vegetation like in the Arctic tundra? (carbon store)

Answer 118

Tundra biomass is small (between 4-29 tonnes/hectare), depending on density of vegetation cover. This is because climatic conditions - low temperatures and low moisture availability - inhibit plant growth. There is only a short growing season. This can all be seen in the low NPP figures of less than 200g/m^2/year.

Question 119

What is photosynthesis like in the Arctic tundra? (carbon flux)

Answer 119

Plant growth is resticted to the brief summer (although growth can be rapid in this time). As such, relatively little carbon is fixed from the atmosphere over the course of the year (low NPP figures).

Question 120

What is decomposition like in the Arctic tundra? (carbon flux)

Answer 120

During the short growing season, the tundra plants input carbon-rich litter into the soil. Decomposition is much slower than in other biomes due to the lower temperatures. However, this process does transfer carbon to the soil store, and carbon dioxide and methane to the atmosphere through microbial respiration. Some microbial activity will persist throughout the year, especially in pockets of unfrozen soil in the southern tundra, or if snow cover insulates the soil.

Question 121

What is the permafrost like in the Arctic tundra? (carbon flux)

Answer 121

There are concerns that global warming will cause the tundra permafrost to become a net carbon source, rather than the sink it has been for thousands of years. Melting permafrost releases trapped methane and carbon dioxide, which, in turn, can cause global temperatures to rise further; this is an example of a positive feedback cycle. However, this relationship is not clear-cut; whilst there is evidence for increased carbon emissions from permafrost in recent decades, this may be counted by increased plant growth due to higher temperatures and more atmospheric carbon dioxide. More biomass may mean more carbon re-entering the soil store as litter; if so, this may negate the increased carbon emissions.

Question 122

What are the physical factors that influence the water cycle in the Arctic tundra?

Answer 122

Average temperatures are wll below freezing for most of the year, so most water is stored as ground ice in the permafrost layer. During the short summer, the shallow active layer (top metre) of the ground thaws, and liquid water can flow on the surface; meltwater forms millions of pools and shallow lakes, which stud the tundra surface. Drainage is poor; water cannot infiltrate the soil because the permafrost is impermeable. Furthermore, much of the geology of Arctic and sub-Arctic Canada is impermeable crystalline rocks, associated with an ancient shield. For up to 8-9 months a year, sub-zero temperatures prevent evapotranspiration; in summer, some evapotranspiration occur from standing water, saturated soils and vegetation. Humidity is low all year round due to low temperatures and low rates of evapotranspiration. Precipitation is low due to low atmospheric moisture levels. The ancient shield geology that underlies much of the tundra has been reduced to a gently undulating plain by hundreds of millions of years of erosion and weathering. Minimal relief, and chaotic glacial deposits, impede drainage and contribute to waterlogging in the summer months.

Flux of carbon dioxide to atmosphere

Question 123

What are the physical factors that influence the carbon cycle in the Arctic circle?

Answer 123

The rocks underlying the tundra exert little influence on its carbon cycle, due to the barrier provided by the permafrost layer. Low temperatures and waterlogging slow decomposition rates, and the flow of carbon dioxide to the atmosphere via microbia respiration. Low temperatures, the unavailability of liquid water and parent rocks containing few ‘useful’ minerals limit plant growth. The total carbon store in the biomass is therefore relatively small. Averaged over the year, photosynthesis and NPP are both low, with the growing season lasting barely 3 months. Long hours of summer daylight provides some compensation. Carbon is mainly stored as partly decomposed plant remains, frozen in the permafrost. Most of this carbon has been locked away for at least the past 500, 000 years.

Question 124

What are the major challenges to oil and gas production in Alaska?

Answer 124

The North Slope stretches from the Brooks mountain range to the shores of the Beaufort Sea (part of the Arctic Ocean), ranging from 68N to 71N. Oil and gas was discovered in Prudhoe Bay in 1968, but the extreme cold, long periods of darkness in winter, permafrost and an active melting layer in the summer, remoteness and poor accessibility, fragile wilderness of great ecological value are some major challenges for development.

Question 125

What is the timeline for oil and gas production in Alaska?

Answer 125

1968: oil and gas discovered at Prudhoe Bay on Alaska’s North Slope
Late 1960s/early 1970s: massive investment in pipelines, roads, oil production plants, gas processing facilities, power lines, power generators and airstrips
1977: start of oil production; opening of Trans-Alaska Oil Pipeline to Valdez, on Alaska’s south coast. High global energy prices and US desire to be self-sufficient in energy (and reduce reliance on volatile Middle East) drive development
1988: peak productioin (2 million barrels/day)
Early 1990s: North Slope accounts for a quarter of all domestic US oil production
2006: 6400 barrels of oil spilled on Alaska’s North Slope following pipeline rupture
2014: production declined to 479, 000 barrels/day (6% of American production) as production costs on North Slope rise, and the US oil shale industry grows
2015: President Obama bans oil drilling on the Arctic National Wildlife Refuge, adjacent to Prudhoe Bay oil field
2021: Trump allows sale of drilling leases to ANWR, Biden declares 10 year delay

Question 126

What is the impact of local melting of permafrost on the water and carbon cycles in Alaska?

Answer 126

Melting permafrost releases trapped carbon dioxide and methane to the atmosphere. On the North Slope, estimated CO2 losses from permafrost vary from 7 to 40 million tonnes per year, whilst CH4 losses range from 24, 000 to 114, 000 tonnes/year (which indicated the inherent uncertainty about the magnitude of the flux). Additionally, warmer soils leads to increased microbial activity, so rates of decomposition are faster, further accelerating CO2 release. Melting of permafrost and snow cover increases river run off, making flooding more likely. More surface water storage during the summer, and more evaporation from these stores to the atmosphere.

Question 127

What is the impact of gas flares and oil spills on the water and carbon cycles in Alaska?

Answer 127

Flux of carbon dioxide to atmosphere

Question 128

What is the impact of vegetation destruction on the water and carbon cycles in Alaska?

Answer 128

Reduced photosynthesis and NPP, so reduced flux of carbon from atmosphere to biomass. Reduced vegetation storage of water, and reduced transpiration; reduced interception.

Removal of vegetation for construction of oil and gas production infastructure. Pollution events can degrade vegetation. Due to extreme cold, vegetation takes a very long ime to recover from destruction or degradation.

Question 129

What is the impact of strip mining on the water and carbon cycles in Alaska?

Answer 129

Artificial lakes creates, further increasing surface storage.
Mining aggregates (sand and gravel) for use in construction.

Question 130

What is the impact of road construction and explosions used to prospect for oil and gas on the water and carbon cycles in Alaska?

Answer 130

Disruption of drainage networks

Question 131

What is the impact of abstraction of water from creeks and rivers on the water and carbon cycles in Alaska?

Answer 131

Localised reduction of river discharge.

Used in industrial processes.

Question 132

What does the strategy of insulated ice and gravel pads do to reduce the impact of development on the water and carbon cycles?

Answer 132

Construction and operation of oil and gas installations, settlements and infastructure, diffusing heat directly to the environment. Dust deposition alongside roadsides darkens snow surfaces, decreasing albedo. Removal of vegetation cover, which forms a protective blanket over permafrost stopping direct exposure to solar energy in summer.

Roads and other infastructural features can be constructed on insulating ice or gravel pads, thus protecting the permafrost from melting.

Question 133

What does the strategy of elevating buildings and pipelines on piles do to reduce the impact of development on the water and carbon cycles?

Answer 133

Constructing buildings, oil/gas pipelines and other infastructure on piles allows cold air to circulate beneath these structures. This provides insulation against heat generating buildings, pipework, which would otherwise melt the permafrost.

Question 134

What does the strategy of drilling laterally beyond drilling platforms do to reduce the impact of development on the water and carbon cycles?

Answer 134

New drilling techniques allow oil and gas to be accessed several kilometres from the drilling site. With fewer sites needed for drilling rigs, the impact on vegetation and the permafrost due to construction is greatly reduced.

Question 135

What does the strategy of more powerful computers detecting oil and gas bearing geologiclal structures remotely do to reduce the impact of development on the water and carbon cycles?

Answer 135

Fewer exploration wells are needed thus reducing the impact on the environment

Question 136

What does refridgerating supports do to reduce the impact of development on the water and carbon cycles?

Answer 136

Refridgerated supports are used on the Trans-Alaska Pipeline to stabalise the temperature of the permafrost. Similar supports are widely used to conserve the permafrost beneath buildings and other infastructure.

Question 137

Where is the Amazon rainforest?

Answer 137

The Amazon rainforest occupies more than 6 million km^2 in South America. 70% of it is found in Brazil, with the remainder extending into Peru, Ecuador, Venezuela, Colombia, Bolivia and Guyana. It is part of a large region of tropical rainforest that extends into Central America, mainly between 15N and 15S of the equator. The Amazon Basin covers 32% of the land area in South America. Tropical rainforest (including tropical cloud forests and tropical monsoon forests) occupy 6% of global surface area.

Question 138

What is the climate of the Amazon rainforest?

Answer 138

High average annual temperatures between 25C and 30C, with little seasonal variation in temperature. The high temperatures are a result of high levels of solar insolation throughout the year. This is because the equatorial zones are less affected by the tilt on the Earth than higher latitudes, and so do not experiance seasonal variations in exposure to the solar radiation. Also the curvature of the Earth’s surface is less pronounced at the equatior, which means that the sun’s rays are more concentrated here. Annual temperatures, whilst high, are a little lower than in the hot desert biome, as high levels of cloud cover reduce levels of solar insolation relative to the often cloudless deserts. There is a higher diurnal temperature range than there is an annual tmperature range. High average rainfall (2286mm in Manaus, and > 2000mm in rainforest generally). Convectional rain falls all year round, although it is possible to identify a wetter season and a drier season. In Manaus, it is wettest in march (820mm), with a ‘dry’ seaspm om June-August (70mm). The timings of these wetter and dryer seasons depends on the location of the Intertropical Convergence Zone (ITCZ), which is a band of low pressure that migrates from the Tropic of Cancer (23N) to the Tropic of Capricorn (23S) and back again annually. The ITCZ position shows which places are receiving most solar insolation, and it brings with it the heaviest rainfall. As Manaus is so close to the equator, the ITCZ is close by for most of the year, bringing heavy rainfall, and it is directly overhead in March (hence the heaviest rain). In June, July and August, it migrates further north to the Tropic of Cancer, taking the rains further away from Manaus and bringing drier conditions. Between 50-60% of precipitation in the Amazon Basin is recycled by evapotranspiration back to the atmosphere, rather than leaving the system via river runoff. This occurs due to the high levels of solar radiation providing lots of energy for evapotranspiration. It is sometimes said that rainforests ‘make their own rain’, as a lot of the water vapour that condenses to form clouds and bring precipitation has come directly from the vegetation surface or from within the vegetation itself.

Question 139

What is precipitation like in the Amazon rainforest? (water flow)

Answer 139

High average annual rainfall (>2000mm). Rainfall fairly evenly distributed throughout the year though short drier season occurs in some places. High-intensity, convectional rainfall. Interception by forest trees is high (around 10% of precipitation). Intercepted rainfall accounts for 20-25% of all evaporation.

Question 140

When does convectional rainfall occur?

Answer 140

When there is intense heating of the Earth’s surface, often associated with high levels of solar insolation. As the Earth warms, it heats the overlying atmosphere, creating a ‘parcel’ of low density air that rises through the surrounding atmosphere. In the tropical rainforest, this is likely to be saturated with water vapour due to the high levels of evapotranspiration. As it rises, it cools through adiabatic expansion, until it reachs dew point, and condensation will occur. In tropical rainforests, this occurs on a near-daily basis, resulting in the formation of cumulonimbus clouds in the late afternoon, which bring heavy rainfall and thunderstorms.

Question 141

Why are interception rates high?

Answer 141

They are high because the canopy is very dense, and because trees are evergreen, meaning that there is no seasonal variation in leaf cover. Tropical rainforest trees have evolved drip tips to shed intercepted water efficiently via throughfall, otherwise the weight of water could tear leaves from trees.

Question 142

What is evapotranspiration like in the Amazon Basin? (water flow)

Answer 142

High rates of evaporation and transpiration due to high temperatures, abundant moisture and dense vegetation. Strong evapotranspiration-precipitation feedback loops sustain high rainfall totals. Around a half of incoming rainfall is returned to the atmosphere by evapotranspiration. Most evaporation is from intercepted moisture from leaf surfaces. Moisture lost in transpiration is derived from the soil via tree roots.

Question 143

How much precipitation is returned to the atmosphere through evapotranspiration?

Answer 143

Between 50-60% is returned. Tropical rainforests, potential evapotranspiration is very similar to actual transpiration, because the presence of water is not a limiting factor.

Question 144

What is Net Primary Production (NPP)?

Answer 144

Measures the volume of carbon ‘fixed’ by an ecosystem in photosynthesis per year minus the volume of carbon released by the same ecosystem back into the atmosphere via respiration.

Question 145

What is run-off like in the Amazon Basin? (water flow)

Answer 145

Rapid runoff releated to high rainfall, intensive rainfall events and well-drained soils. Depending on seasonal distribution of rainfall, river discharge may peak in one or two months of the year.

Question 146

What is the river discharge like in the Amazon Basin?

Answer 146

The Amazon has the highest discharge of any river on Earth. Its average at mouth is 175, 000 cumecs, which is nearly 5 times greater than the next largest river (the Congo)

Question 147

What is soil/groundwater like in the Amazon Basin? (water store)

Answer 147

Abundant rainfall abd deep tropical soils leads to significant water storage in soils and aquifers.

Question 148

What is the vegetation like in the Amazon Basin? (water store)

Answer 148

Rainforest trees play a crucial role in the water cycle, absorbing and storing water from the soil and releasing it through transpiration.

Question 149

What is the tropical rainforest dominated by?

Answer 149

Large trees, there is a dense canopy of interwoven tree crowns at approximately 30m with larger emergent trees reaching 50m. According to scientists of the RAINFOR consortium, there are 400 billion trees, belonging to 16, 000 different species in the Amazon Basin. Vegetation growth on the forest floor is relatively sparse due to the low light levels beneath the canopy.

Question 150

What is the effect of geology on a flood hydrograph in the Amazon Rainforest?

Answer 150

Impermeable catchments (e.g large parts of the Basin are an ancient shield area comprising impermeable, crystalline rocks) have minimal water storage capacity resulting in rapid run off. Permeable and porous rocks such as limestone and sandstone store rainwater and slow runoff.

Question 151

What is an ancient shield?

Answer 151

A geological region of ancient (at least 500 million years before present, but up to 3BaBP) igneous rocks, formed from volcanic eruptions in the distant past, but now tectonically stabe and inactive.

Question 152

What is the effect of relief on a flood hydrograph in the Amazon Rainforest?

Answer 152

Most of the Amazon basin comprises extensive lowlands. In areas of gentle relief water moves across the surface (overland flow) or horizontally through the soil (throughflow) to streams and rivers. In the west the Andes create steep catchments with rapid runoff. Widespread inundation across extensive floodplains (e.g. Pantanal) occurs annually, storing water for several months and slowing its movement into rivers.

Question 153

What is the Pantanal?

Answer 153

Low-lying wetland ecosystem in the Amazon Basin that provides surface storage of water.

Question 154

Where do the inputs of water come from in the Amazon Rainforest?

Answer 154

Come from precipitation, the moisture for this comes from evapotranspiration from rainforest trees (internal recycling), or advection (lateral movement through the atmosphere) of moisture evaporated from the Atlantic Ocean (8-10Gt/yr).

Question 155

What are the outputs of water in the Amazon Rainforest?

Answer 155

The outputs are river runoff (5.5 Gt/yr flowing via the Amazon into the Atlantic) or advection of atmospheric water vapour into neighbouring regions

Question 156

Where is carbon stored in the Amazon Rainforest?

Answer 156

Soil carbon storage averages between 90-200 tonnes per hectare. This is relatively low due to rapid uptake of soil carbon by roots, and due tot leaching of nutrients from rainforest soils (heavy rainfall).
Biomass (dry mass of living matter) in tropical rainforests is between 400-700 tonnes per hectare.
Large rainforest trees can store 180 tonnes/hectare of carbon above ground, and 40 tonnes/hectare of carbon in their roots. Overall, 60% of carbon is stored above ground, and 40% below ground.

Question 157

What is the climate of the Amazon Basin?

Answer 157

The Amazon Basin has an ideal climate for rapid plant growth, with high temperatures all year round (‘a 12 month thermal growing season’) and an abundant supply of water.
Warm, humid conditions promote very rapid cycling of of carbon between the atmosphere, the biosphere and the soil. Leaf drop from rainforest trees is a year-round process, but decomposition is extremely fast as the warmth and moisture allows bacteria, fungi and other detritivores to thrive, as well as speeding up chemical reactions. However, the carbon released through decomposition is rapidly take back into the biomass through efficient uptake into a dense, shallow root network.

Question 158

Rainforests account for how much land and how much NPP?

Answer 158

Despite occupying just 6% of the Earth’s surface, rainforests account for 30-50% of all global photosynthesis.
NPP is the amount of carbon ‘fixed’ plants in an ecosystem through photsyntheis on an annual basis. The faster and larger plants grow, the higher the carbon uptake and the higher the NPP. Tropical rainforests have the highest NPP of any biome on the planet and accounts for 15-20% of all global productivity.

Question 159

Is the Amazon Rainforest a part of the slow or fast carbon cycles?

Answer 159

Much of the rainforest carbon storage and fluxes take place within the fast carbon cycle. However, the underlying geology of much of the Amazon is ancient igneous rock, with few carbonate minerals, but, in the west of the Amazon Bais, close to the Andes, areas of limestone provide significant regional stores of carbon within the slow carbon cycle.

Question 160

Why is the Amazon Rainforest a carbon sink, and how much carbon does it release?

Answer 160

The Amazon Rainforest is a major global carbon sink, absorbing 2.4 billion tonnes a year.
The Amazon Basin releases 1.7 billion tonnes of carbon per year through decomposition of organic matter.

Question 161

How does human activity influence the water cycle in the Amazon Basin?

Answer 161

Deforestation in the Basin averaged approx. 17, 500 km^2/yr between 1970 and 2013. Since 1970, one-fifth of primary rainforest has been destroyed, although rates of deforestation have slowed in recent years. Major causes of deforestation in the Amazon are to create new agricultural land - especially cattle ranches and soya bean plantations; other causes include extraction of hardwood timber, settlement expansion and mining for iron ore, gold and other minerals. The Tucurui Dam and Reservoir, built on the Tocantins River, a tributary of the Amazon, between 1975-1984. The reservoir holds 45km^3 of water covering 2250km^2. It has a catchment area of 750, 000km^2.

Question 162

How does deforestation impact the water cycle and why? (interception)

Answer 162

Reduced interception and vegetation storage; increased proportion of rainfall becoming river runoff, changing the balance of ouputs from the system. Loss of rainforest canopy means that less water will be intercepted, and the loss of trees means a reduction in water taken into vegetation via root uptake.

Question 163

How does deforestation impact the water cycle and why? (river runoff and flooding)

Answer 163

Increased proportion of water leaving the system as river runoff. Converting rainforest to grassland increases runoff by a factor of 27, and over half of all rain falling on grassland goes directly into rivers. Less water is stored on or in vegetation, less can be lost through evapotranspiration, so, as per the water balance equation, more must be lost through runoff. In April 2014, devastating floods occured on the Madeira River, the largest tributary of the Amazon, in western Brazil. At Porto Velho, the river reached record levels of 19.68m above normal. Vast expanses of floodplain were submerged, 60 people died, 68, 000 people were evacuated and there were outbreaks of cholera and leptospirosis. The main cause of flooding was deforestation in the upper drainage basin, especially in Peru and Bolivia, where 30, 000km^2 of rainforest, much on the steep lower slopes of the Andes, was cleared between 2000-2012 to celar space for ranching and subsistence agriculture.

Question 164

How does deforestation impact the water cycle and why? (evapotranspiration)

Answer 164

Reduced importance of evapotranspiration output. With fewer trees to intercept precipitation, and to take up and store water from the soil, there is less water available for the outputs of evapotranspiration, which are so important in an undisturbed rainforest.

Question 165

How does deforestation impact the water cycle and why? (humidity)

Answer 165

Reduced atmospheric humidity. Less water lost through evapotranspiration means less atmospheric water vapour and lower levels of humidity.

Question 166

How does deforestation impact the water cycle and why? (cloud cover)

Answer 166

Reduced cloud cover and rainfall of a regional scale. With less water vapour entering the atmosphere through ET from trees, less condensation can occur; cloud cover is reduced and precipitation levels fall. A knock-on consequence of this is that the temperatures may increase, as the reduced cloud cover means higher rates of solar insolation. Whilst on a drainage basin scale, increased proportion of rainfall entering rivers as runoff can result in sever flooding at certain times, on a continental scale, river discharge is likely to decrease due to lower precipitation. The impacts on rainfall levels will affect entire regions, and extend beyound the boundaries of the tropical rainforests, as cloud formed over rainforests deliver rainfall to neighbouring areas. A study by Spacklen et al (2012) suggested that for more than 60% of tropical land surface, air that had passed over extensively forested land produced at least twice as much rain as air that has passed over little forest. The authors estimated that Amazonian deforestation could result in regional rainfall declines of 20%. The massive plumes of water vapour that travel south and east from the Amazon - ‘flying rivers’ - bring rainfall that irrigates some of the most important agricultural land in Brazil. A warmer, drier Amazon Basin may see increased incidents of drought; water stress and vegetation deaths will limit transpiration further in extreme cases. It also increases the likelihood of forest fires, which will impact the carbon cycle. In 2015-16, large areas of Brazil suffered their worst drought in nearly a century; areas around Sao Paolo were worst hit because the ‘flying rivers’ had stopped. Finally, trees release salts and organic fibres when they transpire, which become atmospheric aerosols. These act as condensation nuclei and assist in cloud and rain foramtion. Their loss inhibit cloud formation and reduces rainfall.

Question 167

How does deforestation impact the water cycle and why? (rainfall patterns)

Answer 167

Changes in rainfall patterns on a local scale. There is some evidence to suggest that deforested areas may experiance some increase in rainfall. Without the cooling effect of the trees, cleared land warms more quickly, setting up convective air currents above it. This localised low pressure draws in moist air from surrounding forested regions, increasing rainfall over the cleared land, but reducing rainfall in the forested areas.

Question 168

How does deforestation impact the water cycle and why? (soil water)

Answer 168

Reduced soil water. Increased surface runoff means that less water will infiltrate and be stored in the soil. Increased solar insolation (less cloud cover and no tree canopy) means that soil water that is present is more likely to be lost through evaporation.

Question 169

How does building dams and reservoirs impact the water cycle and why?

Answer 169

Increased surface storage; decreased river discharge; increased evaporation. Large reservoirs such as Tucurui represent the surface storage of biliions of cubic metres of water that would otherwide be leaving the Amazon drainage basin as river runoff. Locally, reservoirs will experiance increased evaporation rates due to increased volume of surface water, especially if atmospheric changes associated with deforestation occur (increased solar insolation, warmer temperatures)

Question 170

How do carbon emissions impact the water cycle and why? - this is a global issue with local/regional consequences, whereas deforestation and dam construction are local/regional consequences of local/regional actions

Answer 170

Decreased precipitation. One of the predicted consequences of global warming is that tropical rainforest regions such as the Amazon will experiance higher temperatures, and receive less annual rainfall (dry season will become much drier). This will lead to reduces vegetation growth and storage of water, reduced interception, reduced river runoff. One study by the Brazilian National Space Research Institute predicted that a tropical rainforest ecosystem would become unsustainable in large parts on the Amazon, and that between 30-60% would turn to savannah grassland.

Question 171

How does deforestation impact the carbon cycle? (biomass)

Answer 171

Reduced biomass storage. In undisturbed rainforest, biomass in trees represents 60% of all stored carbon in the ecosystem, with approx. 180 tonnes/hectare of above-ground stored carbon. Most of the remaining carbon is found in the soil, either in roots or as decomposed organic matter. Deforestation for timber extraction removes the biomass, and all the carbon in it, from the system. If trees are deforested and the biomass left to decompose, much of the carbon will enter the atmosphere as CO2; some will enter the soil store, but the lack of protective canopy will mean that this is rapidly lost to leaching and soil erosion. Finally, if the forest is burned, CO2 will be released directly into the atmosphere. Ash will transfer some carbon and other nutrients to the soil, but following a temporary increase in soil carbon, leaching and soil erosion will rapidly deplete the store. The ecosystems that replace the rainforest will not have as much stored carbon, because they are less productive, and have less biomass. Grassland typically has 16.2 tonnes/hectares of carbon, and a soya plantation just 2.7 tonnes/hectare. Of cource, we are not just losing the carbon already stored in rainforest biomass, but we are also preventing further carbon dioxide from being absorbed in the future by stopping photosynthesis from occurring.

Question 172

How does deforestation impact the carbon cycle? (decomposition)

Answer 172

Reduced decomposition. It has already been noted that deforestated areas are likely to experiance less rainfall, higher temperatures and stronger sunlight. These conditions are not good for detritivores, so rates of decomposition are reduced. This means that organic litter persits for longer, and there is less transfer of carbon from the litter to the atmosphere or to the soil.

Question 173

How does deforestation impact the carbon cycle? (leaching/runoff)

Answer 173

Increased loss of carbon via leaching or runoff. Without a protective tree canopy, tropical soils exposed to heavy rainfall events will erode rapidly, leading to high losses of carbon and other nutrients via river runoff and leaching. This also affects litter - carbon stored in dead organic matter is more likely to be transported out of the system in river runoff.

Question 174

How does deforestation impact the carbon cycle? (respiration)

Answer 174

Reduced respiration. With less biomass, there will be less respiration taking place.

Question 175

How do carbon emissions impact the carbon cycle?

- global consequences

Answer 175

Reduced biomass storage. One of the predicted consequences of global warming is that tropical rainforest regions such as the Amazon will experiance higher temperatures, and receive less annual rainfall. Water stress will see the death of much vegetation; much of the carbon stored in the dead organic matter will ultimately be returned to the atmosphere via decomposition or combustion (forest fires will be more common). With more carbon dioxide being released into the atmosphere, global warming will only be intensified (positive feedback loop).

Question 176

What are the effects on the water and carbon cycles by reforestation strategies to manage tropical rainforests?

Answer 176

The indigenous Surui tribe of Rondonia participate in a scheme that aims to protect primary rainforest on tribal lands from illegal logging and reforest areas degreaded by deforestation in the last 40 years. The Surui plant seedlings bred in local nurseries in deforested areas around their villages. The native species are chosen to provide them with timber for construction, food crops, and, through logging, a sustainable source of income.

Several forest restoration projects, sponsored by local authorities, NGOs and businesses are underway, although progress has been slow. One such scheme is the Parica Poject in Rondonia, in the western Amazon. This sustainable forestry scheme aims to develop a 1000km^2 commercial timber plantation on government owned, deforested land. The plan is for 20 million fast growing tropical hardwood seedlings to be planted on 4000 smallholdings, to mature over a 25 year period. Financial assistance is being given to smallholders to help with land preparation, planting and plot maintenance. Tree nurseries provide the seedlings for them. Timber will be exported along the Amazon and its tributaries through Manaus or Port Velho. Although this is a monoculture project, and will not replace the biodeversity of the lost primary rainforest, it is a sustainable scheme, and the trees will sequester CO2, reduce runoff and protect the soil from erosion and leaching.

Question 177

What are the effects on the water and carbon cycles by protected area strategies to manage tropical rainforests?

Answer 177

The Brazilian Government has commited to restoring 120, 000km^2 of rainforest by 2030. Since 1988, it has established many forest conservation areas; these Amazon Regional Protected Areas now cover an area 20x the size of Belgium. By 2015, 44% of the Brazilian Amazon comprised national parks and indigenous reserves where farming is banned.

Question 178

What are the effects on the water and carbon cycles by market-based strategies to manage tropical rainforests?

Answer 178

The Surui became the first indigenous group in Amazonia to sign up to the UN’s Reducing Emissions from Deforestation and Degradation (REDD) scheme. This scheme provides payment to the tribe for protecting the rainforest and abandoning logging. It is a market-based approach that grants carbon credits to the Surui, reflecting the carbon sequestration that takes place through maintaining intact rainforest. These credits can be purchased by international companies who exceed their annual carbon emissions quota, thus offsetting their emissions. In 2013, Natura (cosmetics TNC) purchased 120, 000 tonnes of carbon credits from the Surui - the first carbon credit sale by indigenous people in the Amazon.

Question 179

What are the effects on the water and carbon cycles by improved agricultural strategies to manage tropical rainforests?

Answer 179

Farming is the main cause of deforestation in the Amazon Basin, but the low fertility of the soils (virtually all nutrients were stored in biomass) meant that permanent cultivation was unsustatinable. After a few years, smallholders were forced to abandon plots as yields dropped; the abandoned land became low quality grassland. Large scale commercial ranching has a very low yield per unit area, with one hectare of grazing required per cow. Agricultural diversification can improve yields and protect soil nutrients. Soil fertility can be maintained by rotating crops and combining arable and pastoral practices. Integrating crops and livestock can result in a 5-fold increase in ranching productivity, which reduces the need for deforestation.

Sixteenth century European explorers noted high population densities in some Amazonian regions; it may have been possible to support large numbers of people due to the practice of supplementing soils with charcoal, waste and human manure. The resulting, so-called ‘dark soils’ retain fertility for much longer, as the charcoal attracts micro-organisms and fungi that are instrumental in the production of humus from organic matter. If these dark soils can be recreated, increased yields and more durable soil fertility would reduce the need to create new farmland through deforestation.

Question 180

In what ways are the water and carbon cycle linked in tropical rainforests in their natural state?

Answer 180

Photosyntheis requires plants to absorb both carbon dioxide and water, and tropical rainforests have the highest rates of photosynthesis of any biome. Trees represent major stores of both carbon and water, The higher the productivity, and the more biomass there is, the more carbon is fixed via photsynthesis and stores, the more water is taken up from the soil, and the more water is returned to the atmosphere via transpiration. High humidity and high rainfall levels promote rapid decomposition of organic matter, transferring carbon from the litter to the soil store. Respiration releases both water vapour and carbon dioxide into the atmosphere.

Question 181

In what ways are the water and carbon cycle linked in tropical rainforests following human activity?

Answer 181

Reduced transpiration following deforestation promotes hotter, drier conditions, which leadds to water stress and death of vegetation, resulting in the transfer of carbon dioxide to the atmosphere via decomposition or combustion (forest fires). Loss of protective canopy increases rates of leaching, meaning carbon nutrients are washed from the soil by rainfall. Reduced interception and vegetation storage following deforestation increases the proportion of rainfall that leaves drainage basins as river runoff (instead of ET); flashier hydrographs result in more frequent flooding events, and the loss of carbon in the form of litter (leaves, branches, trunks) washed downstream. Increased atmospheric carbon dioxide due to human emissions is predicted to create hotter, drier conditions in tropical rainforest regions; the reduced rainfall will result in water stress for trees, and reduced transpiration, which wil further reduce rainfall. As trees die, possibly to be replaced with savannah grassland, huge volumes of stored carbon will be released into the atmosphere; the reduced biomass will also have lower rates of photosynthesis, so less carbon dioxide is fixed in this manner. Reduced transpiration in a deforestated area creates hotter, drier conditions which are less favourable for bacteria, fungi and other decomposers. This means a slower flux of carbon from litter to soil stores. A larger build up of litter can also increase the risk of forest fires, and the transfer of carbon dioxidde to the atmosphere through combustion. Deforestation represents the removal of both stored carbon and water; the vegetation that replaces primary forest has less biomass (therefore less stored carbon), a lower interception capacity and less stored water.

Question 182

What human factors can disturb and enhance the natural processes and stores in the water and carbon cycles?

Answer 182

Land use changes, water abstraction, fossil fuel use

Question 183

What is the cahnge and systems theory?

Answer 183

Most natural systems, unaffected by human activity, exist in a state of dynamic equilibrium. They are dynamic in the sense that they have continuous inputs, throughputs, outputs and variable stores of energy and matter. In the short term, inputs, outputs and stores of matter such as water and carbon will fluctuate on a diurnal, seasonal or annual basis. In the long term, however, flows and stores usually maintain a balance, allowing the system to retain its stability. Negative feedback loops within systems restore balance. For example, unsually heavy rain in a drainage basis will lead to increased infiltration and percolation, and more water stored in aquifers. This will raise the water table, resulting in increased flow from springs (an output) until the water table is restored to normal levels. Or in the carbon cycle, burning fossil fuels may increase the atmospheric store of carbon, but the enhanced levels of atmospheric CO2 stimulates more photosynthesis (‘carbon fertilisation’) which may act to fix carbon from the atmosphere back into the biomass, restoring equilibrium.

Question 184

What are the consequences of urban land changes on the water and carbon cycles?

Answer 184

The conversion of land use from rural to urban - farmland and woodland replaced with housing, offices, factories and roads; natural surfaces (vegetation and soil) replaced with artificial surfaces (concrete, brick and tarmac).
Artificial surfaces are largely impermeable, resulting in lower soil/bedrock storage of water and increased runoff flows.
Drains, gutters and sewers are efficient means of removing stored surface water, further increasing the proportion of rain that is rapidly lost through runoff (throughflow replaced).
Urbanisation encroaches on floodplains, reducing natural water storage capacity of water meadows and other wetlands.

Question 185

What are the consequences of forestry land changes on the water and carbon cycles?

Answer 185

Most plantations are coniferous, with higher levels of interception than natural forests due to large surface area of needles, dense planting and evergreen nature. In eastern England, interception loss for Sitka spruce plantations is as high as 60%.
Increased evaporation, a large proportion of intercepted rainfall is evaporated directly into the atmosphere.
Reduced runoff and stream discharge due to increased interception and evaporation loss, and root uptake, vegetation storage and transpiration loss (350mm/yr from Sitka plantations is Derbyshire). This created flatter hydrographs; coniferous plantations in upland areas can often reduce water yield for public supply.
Clear-felling creates sudden but temporary changes in local water cycle, decreased interception and ET, increased stream discharge.
Increased carbon storage, in a typical UK plantation, mature trees contain 170-200 tonnes of C/hectare (ten times higher than grassland and 20 times higher than heathland); forest soil is an even larger store, around 500 tonnes C/hectare.
Forest trees extract atmospheric CO2 and sequester it for hundreds of years, with most carbon being stored in the woody trunk. However, forest trees are only an active carbpn sink for the first century after flanting, after which carbon capture levels reduce and is balanced by respiration and litter decomposition. Therefore, forestry plantations usually have a rotation period of 80-100 years, after which time trees are felled and reforestation occurs

Question 186

What are the consequences of farming land changes?

Answer 186

Clearance of forests for farming reduces carbon storage in above and below ground biomass.
Soil carbon storage is reduced by ploughing (carbon exposed to the atmosphere more readily oxidises).
Harvesting represents the loss of stored carbon (biomass) from the system, rather than returning to the soil through death and decomposition.
Soil erosion is increased in cultivated areas, especially after harvesting removes protective cover, this is further loss os stored carbon.
If grassland is converted to cropland, the impacts on the carbon cycle are less significant, as the crops generally have a larger biomass than the grasses they replace; however, carbon exchanges through photosynthesis are generally lower than in natural ecosystems, as crops’ growth cycles only occupy 4-5 months per year.
Crop irrigation removes water from rivers (decreasing output flows) or groundwater supplies (reducing stores), temporarily increased soil storage may result in more root uptake, vegetation storage and transpiration, although often we also see enhanced evaporation.
Interception of rainfall by annual crops is less than that of woodland or grassland, as is evaporation and transpiration.
Ploughing increases evaporation and soil moisture loss (more exposure to the atmosphere), and downslope furrows can increase rates and volumes of surfaceflow, accelerating soil erosion.
Heavy machinery compact soils, reducing infiltration and increasing runoff.
Agricultural areas often have flashier hydrographs than natural ecosystems.

Question 187

What water extraction is happening in the River Kennet Basin?

Answer 187

Water is extracted from surface and groudwater to meet public, industrial and agricultural deman. Direct human intervention in the water cycle changes the dynamics of river flow and ground water storage.
The River Kennet in southern England drains an area of 1200km^2 in Wiltshire and Berkshire.
The upper catchment is primarily chalk geology, which is highly permeable. Therefore the majority of the Kennet’s flow comes from groundwater.
The porous chalk filters the water effectively, making it very clear and clean, with high oxygen levels. The Kennet has many aquatic habitats and is home to species such as Atlantic salmon, brown trout, water voles and otter.
There are several urban areas within and close to the catchment, including Swindon (pop. 200, 000); the Kennet also supplies water for industrial, agricultural and public use. Thames water abstracts groundwater from the upper catchemnt from boreholes; none of this abstracted water is returned to the river as waste water.
As rates of groundwater abstraction have exceeded rate of recharge, the falling water table has seen the discharge of the Kennet fall by 10-14%.
During the 2003 drought, discharge fell by 20%, and in the dry period in the early 1990s, it fell by 40%.
Lower flows have reduced flooding and temporary surface storage in wetlands on the Kennet’s floodplain.
Lower groundwater levels have caused springs to dry up and have reduced the incidences of saturated overland flow.

Question 188

What are aquifers?

Answer 188

Permeable or porous water-bearing rock such as chald or new red sandstone.

Question 189

Why are aquifers useful to us?

Answer 189

The extraction of water from boreholes and rivers for use in public water supply, agriculture and industry.

Question 190

What water extraction is happening in London?

Answer 190

London is located in the middle of synclinal structure that form an artesian basin.
Groundwater is stored in a chalk aquifer, trapped between layers of impermeable London Clay (above) and Gault Clay (below).
Rainwater enters the aquifer at the edges of the basin, where the chalk strata outcrops at the surface as the North Downs (southern edge of the basin) and the Chiltern Hills (northern edge).
Once it has percolated into the chalk, groundwater then flows to the centre of the basin under gravitational force, pooling in the chalk at the lowest point, under London. This gravitational flow of water means that wells and boreholes in the London area are under positive artesian pressure.
Groundwater from the chalk atmosphere has been an important water source for London for centuries.
Overexploitation of the aquifer in the 19th and early 20th centuries saw the water table in central London fall by nealy 90m.
In the last 50 years, declining demand for water by industry and reduced rates of abstraction have allowed water tables to recover, at rates of 3m/yr in the 1990s. Such rapid rise threatened underground tunnels and building foundations.
To combat this threat, since 1992 Thames Water has been granted abstraction licences to slow the rise of the water tabe. This project has been successful, and the water table is now stable.

Question 191

What is groundwater?

Answer 191

Water stored within aquifers; emerging from springs and seepages, groundwater is major (and, in the UK, virtually ever present) contributor to river flow (its contribution is know as base flow in river discharge).

Question 192

What is abstraction?

Answer 192

The extraction of water from boreholes and rivers for use in public water supply, agriculture, industry, etc.

Question 193

What is the water table?

Answer 193

The uppper level of the saturation layer within the ground; usually, this is found somewhere within the aquifer, although it can rise into the soil or even into the surface. Its position is determined by climate (balance between rainfall and ET sees seasonal migration of the water table), exceptional weather/climate events (drought/extreme rainfall) and human activity (abstraction or artificial recharge)

Question 194

What is recharge?

Answer 194

The process by which groundwater stores are replenished as rainfall exceeds evapotranspiration. In southern England, this is typically between October and March.

Question 195

What is a syncline (or geosyncline)?

Answer 195

A geological basin-like formation, in which rock strata exhibit a concave dip.

Question 196

What is an artesian basin?

Answer 196

Synclines may be the site of artesian basins/artesian aquifers. If groundwater is held within permeable rock strata within a syncline structure, but is trapped by adjacent impermeable strata, the water can be under positive pressure. If a borehole is sunk into the aquifer rock strata, this pressure will flow up the borehole to the surface under its own pressure (doesn’t need to be pumped upwards)

Question 197

What is a potentiometric surface?

Answer 197

The level to which water can rise up a borehole sunk into artesian aquifer; its height is determined by the level of the water table in areas of the basin where recharge can occur (permeable rock is exposed at the surface)

Question 198

How does the use of fossil fuels contribute to the carbon cycle?

Answer 198

Whilst the use of fossil fuels as an energy source does predate the industrial revolution to a very limited extent, it is the exponential growth in their use over the past two centuries that has driven industrialisation and urbanisation. Despite the emergence of nuclear power and renewable energies, in 2013 fossil fuels still accounted for 87% of global energy consumption.
(37% oil, 27% natural gas, 23% coal, 7% HEP, 4% nuclear, 2% renewables)
Fossil fuel consumption releases 10 billion tonnes of CO2 anually. This increases atmospheric CO2 concentration by over 1ppm every year. It is estimated that, since 1750, cumulative anthropogenic CO2 emissions total nearly 2000Gt, three quarters of which comes from buning fossil fuels/ 879Gt of these have remained in the atmosphere, raising CO2 concentrations from 280ppm to over 400ppm.
Today, atmospheric CO2 concentrations are at their highest level for 800, 000 years at 416ppm. Anthropogenic carbon emissions comprise less than 10% of the annual fluxes of carbon to the atmosphere from natural sources (ocean, biosphere) but they have significant impact on the size of the atmospheric store. The decade 2000-2009 saw the fastest increase in atmospheric CO2 concentrations of any record. Without increased absorption of CO2 by oceans and plants, today’s atmospheric CO2 concentrations would already be over 500ppm

Question 199

What is carbon capture and sequestration?

Answer 199

Capturing the carbon from factory emissions and storing it elsewhere. CCS could eventually play an important part in reducing CO2 and other greenhouse emissions. For instance, 40% of the USA’s CO2 emissions come from coal and gas-fired power stations, and CCS could reduce these emissions by 80-90%. In the UK, a CCS pilot project is underway a Peterhead in northeast Scotlannd. Although the technology for CCs is feasable, its effectiveness is limited by economic and geological factors:
CCS involves big capital costs - a plan to capture 2 million tonnes of CO2 at the former Drax poer station in North Yorkshire was axed in 2016, the plan was to pump the carbon by pipeline to be stored in depleted gas reservoirs under the North Sea. CO2 can also be pumped into mature oilfields to recover oil that would otherwise be uneconomic to extract.
Large amounts of energy (typically 20%) of the power plants energy is needed to separate and compress the CO2.
There must be suitable geology for storage reservoirs, porous rock overlain by impermeable strata, which is not found everywhere.

Question 200

What are the seasonal changes in the water cycle?

Answer 200

In the UK, solar radiation peaks in mid-June. A typical solar input is June in southern England is around 800W/m^2, compared to 150W/m^2 in December; as a resuly, evapotranspiration is highest in summer and lowest in winter. In the driest part of the lowland eastern England, up to 80% precipitation may be lost to evapotranspiration in the summer. With high rates of ET, soil moisture utilisation will occur leading to reduced soil and groundwater storage, and reduced river discharge. In the winter, precipitation inputs exceed ET outputs, allowing for recharge of delpleted stores and increased river flow.

Question 201

What are the seasonal changes in the carbon cycle?

Answer 201

Seasonal variations in the carbon cycle are shown through variations in the NPP of vegetation; in the middle and high latitudes, photoperiod (day length) drives seasonal changes in NPP. In the tropics, photoperiod is very close to 12 hours throughout the year, so variations in NPP are driven by changes in water availability (migration of ITCZ). In the Northern Hemisphere summer, when deciduous trees are in full leaf, there is a net global flow of carbon from the atmosphere to the biosphere, which causes atmospheric CO2 to fall by up to 2ppm; in autumn and winter, photosynthesis ends as trees lose their leaves, and there is a return flux of CO2 to the atmosphere through litter decomposition. Even though the Southern Hemisphere trees are photosynthesising at their maximum rate at this time, the Northern Hemisphere signal is dominant, due to the concentration of land masses there (NH is 39% land, SH is 19% land), which are home to huge boreal and temperate forest biomes.
Oceanic plankton photosynthesis is stimulated by water temperature, sunlight intensity and photoperiod; algal blooms in the North Atlantic in mid-summer can be seen from space.

Question 202

What are the diurnal changes in the water cycle?

Answer 202

Lower temperatures at night reduce evaporation and transpiration.
Convectional precipitation, dependent on direct heating of the ground surface by the sun, is a daytime phenomenon, often most common in the afternoon when temperatures reach a maximum. This is particularly important in tropical regions, where the majority of precipitation falls as convectional storms.

Question 203

What are the diurnal changes in the carbon cycle?

Answer 203

During the daytime, CO2 flows from the atmosphere to vegetation; at night, this flux is reversed. Without sunlight, photosynthesis cannot occur, and plants lose CO2 to the atmosphere through respiration. The same diurnal pattern can be observed with phytoplankton in oceans.

Question 204

How do humans monitor changes in the carbon and water cycles?

Answer 204

Using the Keeling Curve - a zigzag due to uneven landmass in Hemispheres, winter has more CO2 emitted, summer has less emitted due to photosynthesis.
Mauna Loa is the perfect place to measure atmospheric CO2 concentrations because it is thousands of miles from any major industrial areas and is therefore unaffected by local CO2 emissions, giving a true global value. Before 1958, atmospheric CO2 was not directly measured. For pre-1958 values, we are reliant on proxy measurements - mainly by analysing air trapped in bubbles trapped in ice cores taken from the Greenland or Antarctic ice sheets.
Between 1958 and 2018, observed atmospheric CO2 in 1959 (first full year of recording) was 316ppm; in 2017, it was 407ppm - a growth of 91ppm or 29%.
April 2017 - the first time in the Keeling record that CO2 concentrations have been above 400ppm for an entire month; this is thought to be the first time that this has happened for 800, 000 years.
The Keeling curve has a characteristic ‘saw-tooth’ signature of monthly average readings, superimposed on the much smoother annual average line. This is because atmospheric CO2 concentrations are 2-3ppm lower in the Northern Hemisphere summer, due to high photosynthesis uptake by trees; the Southern Hemisphere does not counter balance this signal, as there is much less land mass there.

Question 205

How are the water anc carbon cycles monitored by remote sensing and GIS?

Answer 205

Given the potentially damaging impact of climate chage, accurate monitoring of changes in global air temperature, sea surface temperatures (SSTs), sea ice thickness and rates of deforestation is essential, because ground-based measurement of environmental change at a global scale is impractical, monitoring relies heavily on satellite technology and remote sensing. Continuour monitoring by satellites on a day-to-day, month-to-month or year-to-year basis allow changes to be observed on various time scales. Geographical Information Systems (GIS) allows this data to be digitally mapped and analysed, showing spatial and temporal trends and anomalies.

Question 206

What are the long term changes in the carbon and water cycles?

Answer 206

Over the last million years, the Earth’s climate has been highly unstable, with large fluculations in temperatures occuring at regular intervals.
These climatic shifts have has major impact on the Earth’s water and carbon cycles.
On longer timescales, global temperatures have been even more extreme; 250 million BP, average global temperatures reached 22C, 7-8 degrees higher than today.
During the warm interglacial periods, temperatures were similar to those of today or slightly warmer (+4C 120, 000 BP).
During the Last Glacial Maximum, 20, 000 BP, annual average temperatures in Britain were 5C colder than todat; Scotland, Wales and most of Northern England were covered in an ice sheet up to 1km thick.
There is a slow and irregular decent into a glacial, lasting approx. 100, 000 years, followed by a rapid rise to a more short lived (10-20, 000 years) interglacial.
In the past 400, 000 years there have been four major glacial cycles, with cold galcial periods followed by warmer interglacials.
Tyrrhenian Interglacial 130-120, 000 BP
Riss Glacial 108, 000 BP
Wurm Glacial 20, 000 BP
Holocene Interglacial 10, 000 BP-present

Question 207

What changes occur to the water cycle during glacial periods?

Answer 207

A transfer of water from the ocean store to the cryospheric store.
The shrinking ocean floor is manifest as a decrease in global sea levelsl - 20, 000 BP, at the height of the Wurm glacial, sea levels were 100-130m lower than today, creating land bridges between land masses that are today separated by by oceans (Australia/Papua New Guinea; Britain/Ireland; Britain/Europe; Russia/Alaska)
Ice sheets expanded from the polar regions (especially the Arctic) equator-wards, in Europe reaching as far south as the English midlands.
Similarly, alpine glaciers advance and merge, creating mountain ice caps at lower latitudes.
Less water is stored in biomass, partly because the advancing ice sheets destroyed huge areas ofboreal and temperate forest, and partly because tropical regions became considerable drier, and rainforest ecosystems were replace with grassland and desert.
Lower rates of ET in the cooler conditions meant less exchange of water between the atmosphere, oceans, biosphere and soils; the volume of water circulating was reduced (more locked up as snow and ice) and the rate of circulation also diminished.

Question 208

What changes occur to the carbon cycle?

Answer 208

Long term reconstruction of temperature records and CO2 concentrations based on ice core data reveal a close correlation between the two variables.
During glacial maxima, temperatures were up to 9C colder than 1950 levles, with CO2 at aroun 180ppm. During interglacials, temperatures were up to 4C higher, and CO2 concentrations were around 280ppm.
There is no clear explanation of why atmospheric CO2 storage decreases during glacial periods; it is possible that changing ocean circulations during glacials brings more nutrients to the surface, stimulating phytoplankton growth and fixing more CO2 through photosynthesis. Ultimately, through death and sinking, the carbon will end up in deep ocean storage.
The biosphere carbon store shrinks during glacials as boreal and temperate deciduous forest are covered by ice sheets replaced with tundra, and grassland encroaches on tropical rainforest. The colder, drier conditions also make for lower NPP values in biomes across the world. There is an overall decrease in carbon flux during glacials, with the fast carbon cycle operating less efficiently. The colder, drier conditions also make for lower NPP values in biomes across the world, as photosynthesis declines. The expanded tundra biome will sequester large amount of carbon in the permafrost.
Land under ice sheets will be unable to exchange soil carbon with the atmosphere through respiration and decomposition.

Question 209

What is the atmosphere store?

Answer 209

Store of both water and carbon. Some atmospheric CO2 dissolves in atmospheric moisture, and is rained out of the atmosphere in the form of carbonic acid.

Question 210

What is the vegetation and soil store?

Answer 210

Stores of both water and carbon. Water storage capacity of soils increases with organic content (more stored soil carbon = more stored soil water). Water enhances the rate at which many weathering processes occurs, which creates a flux of carbon from the soils and lithosphere to the ocean via river runoff.

Question 211

What is the cryosphere store?

Answer 211

Mostly a store of water, although permafrost traps a large volume of carbon in the form of frozen, undecomposed plant matter.

Question 212

WHat is the ocean store?

Answer 212

A store of both water and carbon.

Question 213

What are the links between the ocean and the atmosphere?

Answer 213

Atmospheric CO2 concentration determined intensity of greenhouse effect, which affect the rate of evaporation of ocean water. Ocean absorbs atmospheric carbon dioxide through solution to create shallow ocean carbon stores; over time, this may enter the deep ocean carbon stroes, the ocean stores 38.7 GtC

Question 214

What are the links between the atmosphere and vegetation and soils?

Answer 214

Atmospheric CO2 concentration affects the rate at which photosynthesis can occur (‘carbon fertilisation’ - higher CO2 = higher NPP) More vegetation = greater vegetation storage of water, more transpiration, more root uptake. Greater precipitation = higher NPP and more cabon sequestration and storage (lower precipitation = the opposite). Higher precipitation = faster decomposition and greater flux of carbon to the atmosphere. Increased atmospheric CO2 is predicted to create hotter, drier conditions intropical rainforests; water stress will resuly in reduced evapotranspiration, less atmospheric moisture (lower humidity), less cloud cover and further rainfall reduction. Reduced precipitation in tropical rainforest results in more death of vegetation and more forest fires, resulting in greater flux of carbon to the atmosphere. More vegetation storage of carbon = more root uptake and interception, and more ET of water to the atmosphere.

Question 215

What are the links between the ocean and cryosphere?

Answer 215

Atmospheric CO2 concentration determined intensity of greenhouse effect, which affect rate of sea level rise due to the transfer of water from cryospheric stores to ocean stores via meltwater runoff.

Question 216

What are the links between the ocean and vegetation and soils?

Answer 216

More vegetation storage of carbon (more biomass) = more root uptake and interception, and less river runoff to the ocean.

Question 217

What are the links between the atmosphere and cryosphere?

Answer 217

Atmospheric CO2 concentations determined the intensity of the greenhouse effect, which affects rate of melting of terrestrial frozen water stores. Melting of permafrost releases trapped carbon, increasing atmospheric carbon store.

Question 218

How do human activities cause changes in the water cycle?

Answer 218

Most evident on rivers and aquifers, rising demands for water and irrigation, agriculture and public supply, especially in arid and semi-arid environments, has created acute water shortages.
In the Colorado Basin in the southwest USA, surface water supplies have diminished as more water is abstracted from rivers, and huge amounts are evaporated from reservoirs such as Lake Mead.
In places such as coastal Bangladesh, over-pumping of coastal aquifers has led to incursion of salt water, contaminating groundwater and making it unfit for drinking and irrigation, this is illustrative of a decline in water quality in many parts of the world.
Compared to natural ecosystems, human activities such as deforestation and urbanisation reduces evapotranspiration and therefore precipitation, increases surface runoff, decreases throughflow and lowers the water table (decreases groundwater storage).
In the Amazon Basin, forest trees are a key component of the water cycles, transferring water tho the atmosphere through ET, which is then returned as precipitation, deforestation breakd this ‘recycling’ loop, causing climates to dry out preventing forest regeneration.

Question 219

How do human activities cause change in the carbon cycle?

Answer 219

Acidification of oceans through CO2 absorption threatens phytoplankton, which play a vital role in fixing CO2 through photosynthesis.
Soil carbon stores are being depleted through erosion and degradation caused by deforestation and agricultural mismanagement; draining of wetlands for agriculture or urban development leads to the oxidation and loss of stored carbon.
Massive deforestation has decreased global forest cover by 50%, in historic times, the amount of carbon stored in the biosphere, and fixed in photosynthesis, has declined steeply.
Of this 9 million tonnes of carbon entering the atmosphere every year, 2.5 billion tonnes are absorbed by the oceans, and 2.5 billion tonnes is absorbed by the biosphere, the remaining 4 billion tonnes remain in the atmosphere, where CO2 concentrations rise annually.
Land use change (primarily deforestation) transfers approx. 1 billion tonnes of carbon to the atmosphere annually.
Currently, approx. 8 billion tonnes of carbon is transferred to the atmosphere every year through the combustion of fossil fuels.
The world relies on fossil fuels for 87% of its primary energy consumption; the extraction of coal, oil and natural gas has removed billions of tonnes of carbon from the geological store, this process has gathered momentum in recent decades, with the industrialisation of the Chinese and Indian economies.

Question 220

What is the impact of long-term climate change on evaporation?

Answer 220

Global warming has increased evaporation and therefore the amount of water vapour in the atmosphere. Water vapour is a natural greenhouse gas, creating positive feedback loops. Water vapour is also a source of energy within the atmosphere, releasing latent heat when it condenses; with more energy in the atmosphere, extreme weather events such as hurricanes and mid-latitude storms become more powerful and frequent.

Question 221

What is the impact of long-term climate change on precipitation?

Answer 221

Increased precipitation will result in higher runoff and greater flood risk.

Question 222

What is the impact of long-term climate change on cyrospheric stores? (water)

Answer 222

Global warming is accelerating the melting of glaciers, ice sheets and tundra permafrost; the depletion of the cyrospheric store corresponds with a greater oceanic store (rising sea levels) and atmospheric store (via evaporation).

Question 223

What is the impact of long-term climate change on decomposition?

Answer 223

Higher temperatures will accelerate transfers of carbon from the biosphere and soil (litter stores) into the atmosphere by enabling faster chemical reactions; however, if there are regional reductions in precipitation, the reduction in moisture availability may counter balance this effect, resulting in a net decrease in decomposition flux.

Question 224

What is the impact of long-term climate change on the vegetation store?

Answer 224

In tropical regions, predicted increasing aridity is likely to see a replacement of large areas of forest ecosystem with savannah grassland; this will see a significant reduction in stored carbon within the biosphere. In contrast, warmer temperatures and increased precipitation in high-latitudes could see the polewards expansionof boreal forest, colonising areas previously defined by tundra vegetation; this could see a regional increase in vegetation carbon storage.

Question 225

What is the impact of long-term climate change on the cryospheric stores? (carbon)

Answer 225

Carbon frozen within the permafrost of the tundra is being released as temperatures rise above freezing, allowing oxidation and decomposition of organic carbon currently trapped in frozen peat deposits.

Question 226

What is the impact of long-term climate change on the oceanic stores?

Answer 226

Oceans will acidify as they absorb more CO2 (although warmer SSTs become, the less effective this transfer will become, as CO2 is more soluble in cold water). Also the acidification of ocean water will reduce the phytoplankton photosynthetic flux, reducing the oceans overall storage capacity.

Question 227

What is the impact of long-term climate change overall?

Answer 227

There will be increased storage of carbon in the atmosphere, a decrease of carbon stored in the biosphere, and possibly a similar decrease in ocean carbon stores; movement of carbon into and out of the atmosphere will vary regionally, depending on changes in rates of photosynthesis, decomposition and respiration.