EQ1 How does the carbon cycle operate to maintain planetary health?

Question 1

What is phytoplankton’s role in the carbon cycle?

Answer 1

Phytoplankton sequester atmospheric carbon during photosynthesis in surface ocean waters.
Carbonate shells move into the deep ocean water through the carbonate pump and action of thermohaline circulation.

Question 2

Explain thermohaline circulation

Answer 2

Slow, large-scale seawater movement between all of the oceans, caused by differences in temperature (hotter waters near equator due to solar radiation, note water has low albedo) and density (hotter water temperatures at equator, resulting in higher rates of evaporation, e.g North Atlantic Conveyor. Evaporation leaves salt behind, increasing density of water due to more salt presence. This results in the more dense water sinking downwards, subsequently warmer water upwelling from intermediate depths to replace it, bringing with it nutrients, oxygen and heat as well as fresh CO2 to diffuse into the atmosphere.

Question 3

How is biological carbon stored or returned to the atmosphere?

Answer 3

Biological Carbon, can be stored as dead organic matter in soils, or returned to the atmosphere via biological decomposition over several years.

Question 4

Define terrestrial stores

Answer 4

Land based primary producers (plants), sequester carbon through photosynthesis.

Question 5

What is the minimum temperature photosynthesis occurs at?

Answer 5

6°C, this is why there is a high rate of photosynthesis that occurs in the Amazon rainforest. High rates of photosynthesis = high rates of transpiration, therefore there is more water present in these areas, resulting in more rainfall. Linking to a short residence time, compared to polar regions, where very little evapotranspiration occurs resulting in a longer residence time.

Question 6

What is the residence time of water for the following:
1. Oceans
2. Icecaps
3. Groundwater

Answer 6

1. 3,600yrs
2. 15,000yrs
3. up to 10,000yrs

Question 7

What is outgassing?

Answer 7

The primary source of CO2 is outgassing from earth’s interior at midocean ridges, hotspot volcanoes, and subduction related volcanic arcs (mostly from the metamorphism of carbonate rocks subducting with the ocean crust)

Question 8

Explain the formation of Oil, as well as Coal

Answer 8

Crude Oil:
Phytoplankton and other marine organisms, die and sink to the ocean floor. It then compacts over millions of years under sediment etc. Oxygen absence, meant that the fossils changed into Kerogen, under heat and pressure, kerogen changes into oil or gas.

Coal: Provides 40% of worlds electricity (approx.)
Plants, trees etc. Died and fell into swamps… The conditions meant that the organisms could not completely decay. Over millions of years of intense heat and pressure coal formed.
Ranked by carbon content:
Lignite
Anthracite

Higher grade of coal = cleaner burning

Extracted through underground mining and surface mining.

Used mostly to produce electricity.

Question 9

Why can the discovery of oil reserves be harmful to the environment etc.?

Answer 9

The use of seismic surveys, use reflected sound waves to detect oil… Which can harm marine life due to the sounds being mistaken for other animals ~

Question 10

What are the geological processes that release carbon into the atmosphere?

Answer 10

Chemical Weathering:
Simple:
Weathering consumes CO2, weathering products carried to ocean, carbonate sedimentation on sea floor, sediments subducted, partial metlint releases CO2, CO2 rises with magma, volcanoes release CO2 back into atmosphere.

Detailed:
1. Atmospheric CO2 and water react to form Carbonic Acid
2. Falls with rain, although weak, it reacts with surface rock minerals, dissolving them into ions e.g calcium.
3. Calcium ions drain in the rivers and oceans, where they combine with bicarbonate ions and precipitate out as minerals such as calcite.
4. Submarine deposition and burial turn calcite sediment into limestone.
5. Sea floor limestone is subducted under continental margin by slab pull
6. Some carbon rises back up to the surface as magma
7. The magma degasses, releasing CO2 back into the atmosphere

Outgassing:
Pockets of CO2 are released through Volcanic eruptions
Hot springs and Geysers
Direct emissions from fractures in earth’s crust.

Question 11

At what stage is CO2 released from hydrocarbons, and limestone?

Answer 11

CO2 is only released when the hydrocarbons are burnt or when limestone is used in cement.

Question 12

What is a natural variation in carbon fluxes?

Answer 12

Geographical Patterns
Since climate controls fluxes, CO2 varies with latitude… Levels are higher in northern hemisphere, due to more landmass.

Question 13

Explain the natural greenhouse effect as well as naming GHGs

Answer 13

Short wave radiation comes in from the sun through the greenhouse gases and heats objects inside. Objects get warmer and give out long wave radiation… some long wave radiation cannot get back out, and remains inside… resulting in a rise of temperature.

Greenhouse Gasses:
Carbon Dioxide
Methane
CFCs (link to Montreal protocol 1989)
Nitrous Oxide

Question 14

Explain what the Enhanced Greenhouse Effect is

Answer 14

Human activities are adding more greenhouse gases as time goes on. This means an increasing amount of outgoing longwave radiation is trapped and our planet is increasingly becoming warmer.

Question 15

Give examples of human activities contributing to an increase of greenhouse gas concentrations

Answer 15

Burning of fossil fuels.
Deforestation.
Agriculture.
Industrial processes.

Question 16

Define the term Carbon Sink

Answer 16

A carbon reservoir that takes in an sequesters more carbon than it releases. Carbon Sinks can serve to partially offset greenhouse gas emissions. Forests and oceans are both large carbon sinks.

Question 17

Where is solar energy potential at its greatest?

Answer 17

Equatorial Areas, where there is the most focused solar radiation.