Carbon

Question 1

What are the sizes of the major stores of carbon ?

Answer 1

Lithosphere - 99.985%
Hydrosphere - 0.0076%
Pedosphere - 0.0031%
Cryosphere - 0.0018%
Atmosphere - 0.0015%
Biosphere - 0.0012%

Question 2

What is the global distribution of the Cryosphere ?

Answer 2

Cryosphere - polar regions and highland areas of Himalayas and Patagonia

Question 3

What is the global distribution of the Atmosphere ?

Answer 3

Mainly over North America, Europe and Asia - the major sources. These are highest in autumn and winter when trees lose their leaves and photosynthesis slows down - in the spring and summer the opposite happens.
South Africa, Java, China and South America are high, especially over summer due to burning of forests

Question 4

What was the global distribution of the hydrosphere ?

Answer 4

Highest concentrations in the Atlantic and Bay of Bengal. These can be seen to be mirroring the warm ocean currents e.g. the Gulf Stream, which keeps carbon at the surface whilst cold water takes carbon to the bottom of the ocean

Question 5

What was the global distribution of the lithosphere ?

Answer 5

Hydrocarbons are mainly found concentrated in North America, Former USSR, and the Middle East.

Question 6

What was the global distribution of the biosphere ?

Answer 6

Higher content in TRF due to lush vegetation. Also high in other forests due to high amount of biomass. Grasslands and deserts have less biomass.

Question 7

What was the global distribution of the pedosphere ?

Answer 7

Highest concentration in northern latitudes e.g. Boreal forest due to slower decomposition in soils.

Question 8

What are the factors driving change in the magnitude of the biosphere ?

Answer 8

Photosynthesis - light energy converts CO2 into glucose, releasing O2

Respiration - O2 absorbed and CO2 is released (50% of CO2 absorbed by photosynthesis is returned this way

Combustion - CO2 rapidly released due to fires e.g. lightning strike

Decomposition - of leaf litter by bacteria, fungi etc. CO2 released into air and ground forming humus.

Question 9

What are the factors driving change in the magnitude of the cryosphere ?

Answer 9

Reduced rate of decomposition therefore CO2 is stored and has been for 1000s of years - perhaps 2.5 times the amount in the atmosphere

Question 10

What are the factors driving change in the magnitude of the Hydrosphere

Answer 10

Diffusion - ocean ventilates CO2 out and dissolves CO2 in during acidification

Calcification - shells and coral take carbon ions and convert into carbonate to build shells

Compaction - marine plants and animals (fish) die and decompose on sea bed, compacted under sediment to form hydrocarbons

Shells and coral dissolve releasing CO2 whilst others are compacted under sediment

Phytoplankton - microscopic organism convert CO2 via photosynthesis

Question 11

What are the factors driving change in the magnitude of the Lithosphere ?

Answer 11

Hydrocarbons formed from organic matter (living things) e.g. fish, plants etc

Sedimentary rocks formed from inorganic matter as shells and coral compacted into rocks e.g. limestone

Tectonic uplift - reveals sedimentary rock formed in ocean

Volcanic activity - releases CO2 back into atmosphere

Weathering - breakdown of rock in-situ.

Carbon in atmosphere mixes with H2O to create carbonic acid which dissolves rock into calcium ions which run-off takes to ocean

Question 12

How does the magnitude of the stores vary over time ?

Answer 12

These stores e.g. plants, coral, sedimentary rocks, vary due to changes in the fluxes e.g. diffusion, ventilation etc. Some of these fluxes are part of the fast carbon cycle (rapid, years, decades, centuries) e.g. diffusion, photosynthesis. Whilst others are part of the slow cycle (millions of years) e.g. compaction and weathering.

There is variance of these stores due to whether something is a sink (absorbs more CO2) e.g. plants, oceans, rocks, permafrost, shells/coral, soil, hydrocarbons, rainforest or whether it is a source (produces more CO2) e.g. decomposition, agriculture, humans, fires, volcanoes.

Carbon sequestration - when CO2 is removed and held in solid or liquid long-term store/sinks.

The carbon cycle operates at 3 levels, plant e.g. a tree, sere e.g. an ecosystem, continental e.g. global.

The Boreal Forest an example of a sere (a community of plants in a particular environment). High carbon content due to slower decomposition due to climatic conditions, waxy nature and smaller surface area of pine needles, and presence of peat which contains 30% of all carbon stored on land. Peat is formed from decaying plant matter in waterlogged conditions, sequestering carbon for thousands of years.

Siberian Tundra regions (continental scale) - as permafrost melts carbon stored as methane and CO2 is released. This carbon has accumulated over 2.5m years as 8+ ice advances have broken down material and then released or trapped it in tens of metres of soil. There is also negative feedback as higher temperatures have stimulated plant growth which at present absorbs more CO2 so it is currently a sink.

The atmosphere - varied through time - 500m 7000ppm, 2m 180ppm, today c.400ppm. Due to changes in temperature e.g. plant growth, colder oceans absorb more.

Question 13

How does the carbon cycle change over time due to natural variation?

Answer 13

Cold temperatures
Low co2 every 100,000 years
Less transfer pedosphere
Less flow into hydrosphere
Less decomposition
Less forest cover
More weathering

Hot temperatures
More co2 every 100,000 years
Melting of permafrost (Siberia) release of CO2 and methane

Volcanic eruptions
542-251 million years more active
130-380 million tonnes/year

Wildfires
Indonesia (97/13)
Noticeable spike
Sink to source

Question 14

How does the human impact change the carbon cycle over time ?

Answer 14

Hydrocarbons for energy and power
Increased since Industrial Revolution, dramatic increase since 1950s (ninefold increase), 2013 - 61% higher than 1990
Top 3 emitters (China, USA, India) all growing
Burning fossil fuels and industry responsible for 78% of increase in last 40 years.
What is the relative importance?
Very important in terms of long term stores - 70-100 million years old
87% of CO2 emissions

Land use change, e.g. urbanisation, transport, industry, cement production
Important stores (vegetation and soils) replaced
Urban pop to reach 60% by 2030, growing 1.3 million people a week
What is the relative importance?
Can have big impact on small-scale carbon cycles
Urban - 2% land use but 97% of CO2
Cement - 2.4%-5% of global emissions

Deforestation - releases CO2 quickly with no time for new vegetation to grow
Replaced with grassland therefore absorption reduced
13 million ha cut down every year
What is the relative importance?
20%-30% of all CO2 emissions
Changes forests from sink to source

Agriculture - fertilisers based on fossil fuels, machinery emissions, livestock e.g. cows releasing methane,rice paddies produce methane, ploughing breaks down organic matter quicker releasing carbon
Movement to meat diets - emissions from animals up 11% (2001-11)
Rice yields up 25% due to more CO2, but methane up 40%
44% from Asia for last 10 years
What is the relative importance?
Rice 10-20% - staple for 50% of the world
Cattle in USA responsible for 20% of USA methane

Question 15

What is the carbon budget and how does it vary?

Answer 15

The balance of carbon between the different stores.
No sphere is in balance with any other.

The hydrosphere, pedosphere and biosphere are the main sinks. The lithosphere is the main source

The greatest exchange of carbon is between the atmosphere and both the hydrosphere and the biosphere

The atmosphere absorbs the most amount of carbon followed by the biosphere and then hydrosphere

There is more carbon being given out than being absorbed the budget is not in dynamic equilibrium

The natural sources of carbon are far greater than human sources, however human sources are causing an increasing imbalance

Question 16

What is the impact of the carbon cycle on the land?

Answer 16

Carbon fertilisation - more CO2 means more photosynthesis and more plant growth.

If CO2 is doubled plant growth might increase from 12-76%

70% of greening (1982-2015) thought to be due to rising CO2

Negative feedback - more CO2 = more plants = less CO2

However….
Plant growth limited by other factors e.g. availability of water, nutrients especially nitrogen, sunlight

If plants grow faster can become more susceptible to diseases

Water stressed plants become more susceptible to fire and insects

Evidence that plants in Northern Hemisphere have slowed their growth in summer and seen an increase in burning.

Little agreement on which regions will benefit the most due to differences in climate and vegetation.

Increase in temperatures will lead to increase in decomposition in the soil therefore leading to increase in CO2 - 55 trillion kg by 2050.

Question 17

What is the impact of the carbon cycle on the atmosphere?

Answer 17

Incoming shortwave (UV) radiation heats the earth’s surface (although some is reflected back out by clouds etc)
The earth’s surface radiates this heat out as longwave (infrared) radiation which heats the air above it
Some of this longwave radiation escapes back out into space whilst some is trapped by the greenhouse gases e.g. CO2, methane, water vapour…making the earth warmer
The average temperature of our planet is 15℃, without the greenhouse effect it would be -18℃
The enhanced greenhouse effect is due to an increase in anthropogenic gases
An increase in these gases results in more longwave radiation becoming trapped, further increasing the temperature of the planet.
The balance between the incoming and outgoing radiation is called the radiative forcing

The evidence:
20 of the warmest years on record have been in the last 22 years
Overall there has been an increase in global average temperature, since 1880 by over 1 degree
Every month of the year is seeing an increase.
Comparison of CO2 levels and Antarctic temperatures for the last 800,000 years show a strong correlation.

The future:
RCP (representative concentration pathways) predict between 450 and 1300ppm and 2 and 6 degrees by 2100

Question 18

What is the impact of the carbon cycle on the ocean?

Answer 18

Ocean acidification
As CO2 increases in the atmosphere so does CO2 increase in the seawater.
As more CO2 accumulates in the ocean, the pH of the ocean decreases showing a negative correlation.
30% of anthropogenic emissions are diffused into the ocean
Dissolving CO2 creates carbonic acid which increases the acidity - ocean acidification
Carbonic acid (H2CO3) reacts with carbonate ions to form bicarbonate
Less carbonate means…
Less calcification (creation of calcium carbonate)
More energy needed to build shells which are thinner and more fragile
More acidic water will also dissolve shells of organisms making them pitted and weak.
Coral reef loss - providing food and livelihood for 500 million as well as coastal protection from sea level rise and storm surges
However, more acidic the better it dissolves calcium carbonate rocks, therefore more carbonate so ocean can absorb more CO2.
Warmer ocean will lead to less phytoplankton (grow in colder, nutrient rich water) therefore limiting ability to take in carbon via photosynthesis - positive feedback
Increase in CO2 could lead to carbon fertilisation (however most species are not helped) - negative feedback
The ph of the oceans has decreased.In 1885 the ph was 8.2 yet by 2005 it had decreased to 8.1. In the future it is predicted to drop at a much faster rate - it dropped 0.1 in 120 years yet it could drop by 0.3 in just 89 years.

What are the causes of sea level change?
Melting of terrestrial ice - increase temperatures in summer and less precipitation in winter
Thermal expansion - as water heats up it expands. Half of rise due to this
Sea levels rose by almost 6 inches in the 20th Century. Projected to rise by 0.8-2.0m by 2100.

Albedo - the fraction of sunlight that is reflected:
Ice is around 0.9
Open water is 0.1
Ice melts leading to decrease in albedo therefore water absorbs more short wave radiation and therefore…
The amount of ice in the Arctic has dramatically decreased from around 7 million Km2 in 1980 to 3 million in 2012. Every month throughout this period has seen a decline. The oldest ice has also seen a rapid decline.
As the ice melts this will lead to greater likelihood of potential resources being exploited which will lead to disagreements over territorial claims e.g Russia. This has already led to an increase in militarisation of the area. There will also be potential for reduced shipping distances through the Northwest Passage

Ocean salinity - evaporation or freezing of seawater increases salinity whereas precipitation or melting of snow leads to decrease.
Linear pattern especially around poles (low salinity 32ppt) and tropics of Cancer and Capricorn (high salinity 36-38ppt)
Less rain at tropics of Cancer and Capricorn and high temperatures
Equator - ITCZ , high rates of rainfall
Melting ice in poles, though freezing ice at other times
Water sinks in the Arctic since cold water denser than warm water and increase in salinity due to water freezing also makes water denser
Water rises around the Equator since warmer and less saline water rises to the surface
As oceans warm in poles and ice melts water will become less saline - warmer water and less saline water is lighter therefore disrupting thermohaline conveyor belt. Could have serious implications for Western Europe which is currently 5-10 degrees warmer than similar latitudes.

Question 19

How does the carbon and water stores and cycles support life on earth?

Answer 19

Carbon
essential for respiration and photosynthesis.
Creation of shells and coral in the oceans.
50% of biomass is made of carbon.
Provides energy e.g. hydrocarbons.
Is a greenhouse gas keeping the atmosphere at habitable levels

Water
Needed by all living organisms
Vital source of power and energy production.

Storage and cycling of these are vital and changes in the magnitude can have severe implications.

Question 20

What is the relationship between the water cycle and the carbon cycle in the atmosphere?

Answer 20

Hydrosphere - exchange of CO2 from the atmosphere into the hydrosphere

Atmosphere - carbon and H2O combine to form carbonic acid

Weathering - water in form of carbonic acid dissolves carbon rich rocks and rivers take these carbon ions to the sea where they are turned into calcium carbonate by shells and coral

Question 21

What role do feedbacks make within and between cycles ?

Answer 21

Ocean salinity - increase in CO2 leading to warming ocean and melting of ice which leads to less saline water and possible collapse of thermohaline conveyor.

Albedo - increase in CO2 leading to warming ocean, therefore less ice and less albedo therefore more warming.

Permafrost - higher temperatures leads to melting therefore more CO2 and more warming.

Global warming - increase in temperature leads to more evaporation, therefore more water vapour (GHG) therefore more warming.

Warmer oceans leads to reduction in absorption of CO2.

Question 22

How do humans intervene in the carbon cycle to influence transfers and mitigate the impacts?

Answer 22

Mitigation - attempts to slow down the process of global climate change, usually by lowering the level of greenhouse gases in the atmosphere.

Carbon Capture Storage (CCS) - converting CO2 into liquid under high pressure and transporting by ship or pipeline, storing it (sequestration) in depleted oil and gas fields several km below.
Good - capture 90%, forces out more oil and gas which would partly offset costs, traps the CO2, could also be stored in ocean.
Bad - forcing out more oil and gas just adds to problem, storing in ocean leads to acidification, very expensive - $800m Boundary Dam

Changing rural land use - ensuring carbon inputs are greater than losses
Grasslands - adding manure and fertiliser increases soil organic carbon (SOC) and plant productivity. Avoiding overstocking of grazing animals.
Croplands - mulching to add organic matter and stop release of carbon, less ploughing, use of animal manure to increase plant productivity, rotation of crops and improved varieties.
Forested land - protection of forests, reforesting/afforestation, agroforestry.

Aviation industry - 2013 produced 700m tonnes of CO2 and by 2020 will be 70% higher and could be 300-700% higher by 2050.
Movement management - towing aircraft whilst still on ground, avoiding stacking, adopting fuel efficient routes.
Flight management - 100% occupancy, cruising at lower speeds, matching aircraft to route.
Design and tech - increased efficiency, use of biofuels, improved aerodynamics, reduced weight, carbon capture with engines, maximising number of seats

Question 23

How have changes in the water and carbon cycles changed the TRF?

Answer 23

Annual rainfall around 2000mm and temperatures 27℃, as deforestation takes place atmosphere becomes less humid as evapotranspiration is reduced.

With few trees, most rainfall reaches the ground immediately, compacting it and encouraging overland flow. Exposed to the sun, the soil becomes very dry and vulnerable to erosion.

Few trees remain, so little interception or evapotranspiration.

Rates of runoff will increase, with an increased risk of flooding.

It is estimated that deforestation will affect places downwind, perhaps reducing rainfall by up to 20%.

Half of the world’s rainforests have already been wiped out for commercial farming, mining, logging, settlements - often resulting in fires.

Photosynthesis ceases and respiration drops.
Rain washes ash into ground (increasing carbon content) and rivers.

Decomposers largely absent.

Replacing rainforest with crops etc reduces effectiveness of carbon cycle.

Question 24

What relationships are there between the water, carbon cycle and the environment in the TRF?

Answer 24

Absorb huge amounts of CO2 and 28% of world’s oxygen.

Rainforests allow a considerable amount of water to be returned to the atmosphere through evapotranspiration.

The canopy intercepts up to 75% of the rainfall, the other 25% is evaporated. Of this 75%, half is used by the plants and the other half either infiltrates into the ground or runs-off to the river.

Warm and wet climate ideal for plant growth, promoting photosynthesis and respiration.
Wood is 50% carbon so a huge carbon store and sink.

Decomposition is active due to climatic conditions

Question 25

17. How has human activity affected the TRF? - use an example

Answer 25

Indonesia
1960s - 80% was rainforest but since then there has been massive deforestation.
Demand for paper, pulp, plywood, palm oil and disputes over land rights led to rise.
One of the highest rates in the world - under 50% remains.

1 million hectares cleared each year - 70% on mineral soils and 30% on peat. The peat, once exposed, is easily eroded by wind and rain. The increased rates of decomposition have turned them into a source not a sink.
Last couple of decades fires have been common as a quick way of clearing land for palm oil.

Now the world’s 3rd largest emitter of greenhouse gases - 85% from rainforest and peatland loss.

1997-98 - huge fires, more than 8 million hectares had been burnt. Estimated that these fires produced more CO2 than all the living things on earth remove from the atmosphere in one year.

Question 26

What is the impact of precipitation on drainage basin stores and transfers in a named river catchment?

Answer 26

River Exe, Exmoor, flows for around 80km to the sea at Exmouth.

Water balance: precipitation (1295mm) = evaporation +/- soil water storage (451mm) + runoff (844mm) - therefore around 65% of precipitation runs-off - this is quite high, due to:
Area - 600㎢, source in hills of Exmoor, flatter in the south.
Geology - over 80% is impermeable rocks e.g. Devonian sandstones
Drainage ditches to drain peatlands reduce soil water storage
High levels of precipitation
However, long lag time due to:
Land use - Almost 70% grassland, 15% woodland and farmland. 3% peat bogs

Question 27

What factors affect securing sustainable water supply (&/or flooding) in a named catchment ?

Answer 27

The River Exe catchment
Wimbleball Reservoir -
1979 River Haddeo, upland tributary, dammed to create Wimbleball Reservoir.
Surface area of 150ha
Supplies water to Exeter and parts of East Devon.
Regulates water flow, flattening the regime, reducing risk of flooding or drought.

Peatland restoration on Exmoor - Exmoor Mires Project
Drainage ditches have been built in the past to make peat bogs suitable for farming. However, this has increased speed of water flow to the Exe and reduced water quality carrying more silt.
As peat has dried out, decomposition has taken place, releasing CO2 and CH4.
Peat has also been dug as a fuel.
The mires project has restored peat bogs (mires) by blocking drainage ditches - aim 2000ha.
More water storage in upper catchments, ensuring steady supply of water through the year
Improved water quality - slower flow means less sediment carried to rivers, good for salmon.
More carbon storage - water content increases and returns ground to saturated, boggy conditions. This helps to keep carbon in the peat.
Improved opportunities for education, leisure, recreation.
Improved grazing and water supply for animals.
By 2020, 2750ha had been restored and 250km ditches blocked, raising water table by 2.45cm.