carbon cycle fluxes in more depth

How is precipitation a flux?

Atmospheric C02 dissolves in rainwater to form weak carbonic acid.

Why is the acidity of precipitation rising?

Rising concentrations of C02 in the atmosphere due to anthropogenic emissions

What harmful effect can the increased acidity of ocean surface waters have on marine life

coral bleaching

What is the average amount of the flux or carbon from the atmosphere to land plants and phytoplankton (oceans) via photosynthesis

120 gigatonnes (GT) a year

How do plants make chemical energy (glucose)?

Using the sun’s energy, C02 from the atmosphere and water

How much C02 is released into the atmosphere by respiration from plants

Much less than initially absorbed and varies by plant type and environmental conditions.

Fast growing plants

Higher photosynthesis and higher respiration rate. Still absorbs more than released - carbon sink. useful in sequestration but only for short periods

Slow growing plants eg. oaks,redwoods

Store large amounts of carbon in biomass, low respiration rate, act as long term carbon sinks, making them essential for reducing atmospheric C02

Environmental Conditions Affecting CO₂ Release - light availability

low light = less photosynthesis = more C02 released than absorbed

eg. Under dense canopy forests, shaded plants may act as CO2 sources

Environmental Conditions Affecting CO₂ Release - temperature

higher temperature increase respiration rates, this can lead to trees releasing more C02 then they store.

eg. Amazon Rainforest may shift from a carbon sink to a carbon source under global warming

What do decompose organisms do?

Breakdown dead organic matter, extracting energy and releasing c02 to the atmosphere

What do rates of decomposition depend on?

Climatic conditions

Where do the fastest rates of decomposition occur?

Humid environments such as the tropical rainforest

Where do the slowest rates of decomposition occur?

Cold environments such as tundra, drylands such as tropical desert and permafrost regions

weathering definition

the in situ breakdown of rocks at or near the Erth’’s surface by chemical, physical and biological processes

My most common example of chemical wealthering

rainwater is a weak carbonic acid which slowly dissolves limestone and chalk in a process known as carbonation

What does carbonation do?

carbonation releases carbon from limestones to streams, river, oceans and the atmosphere.

When is the process most effective?

Beneath a soil cover because the higher concentration of CO2 in the soil makes rainwater highly acidic

What is the estimated volume of carbon chemical weathering transfers to the atmosphere and oceans every year

0.3 billion tonnes

Example of the effectiveness of solution weathering on limestone

Norber Brow in the Yorkshire Dales - limestone has been lowered by nearly half a meter over the past 13,000 years

Physical weathering impact

Freeze thaw, increases surface area exposed to chemical attack

Biological weathering impact - important in humid tropical environments where decomp is rapid and forest trees provide abundant litter

Chelation - rainwater mixed with dead and decaying organic material in the soil forms humic acids, which attack rock minerals

Combustion

when organic material reacts or burns in the prescence of oxygen

What gases does combustion release?

CO2, sulphur dioxide, nitrogen oxides

Wildfires cause by lightning are essential to the health of some ecosystems such as

Coniferous forests of the Rocky Mountains

What slows the decomposition of forest littler

Long cold winters - however fires shift this jam, freeing carbon and nutrients that were previous inaccessible to trees

Positives of wildfires

• opens up forest canopy

• creates new habitats

• increases biodiversity

Why would humans burn forests?

• deliberate firing of forest and grassland

• clear land for cultivation

• improve quality of grazing

Burning fossil fuel transfers how much of the geological carbon stored in the atmosphere, oceans, and biosphere?

nearly 10 GT of C02 annually

Respiration definition

Process in which carbohydrates fixed in photosynthesis care converted into C02 and water

physical pump (inorganic) definition

Involves the mixing of surface and deep ocean waters by vertical currents creating a more even distribution of carbon

Where does downwelling occur?

North Atlantic between Greenland and Iceland

Process of physical pump before downwelling

Surface ocean currents transport the water and its dissolved C02 polewards, where it sools and becomes more dense = therefore, it sinks

Process of physical pump after downwelling

Downwelling carries dissolved carbon to the ocean depths where individual carbon molecules may remain for centuries. eventually deep ocean currents transport carbon to areas of upwelling. there cold, carbon rich water rises to the surface and C02 diffuses back into the atmosphere

biological pump (organic)

carbon exchanged between the oceans and atmosphere through the actions of marine organisms

Globally, where does nearly half of all carbon fixation by photosynthesis take place?

In oceans

What drives the biological pump?

Marine Organisms - phytoplankton

Biological pump process

Phytoplankton floating near the ocean surface combines sundlight, water and dissolved C02 to produce organic materal. Whether consumed by animals in the marine food chain or through natural death, carbon locked in the phytoplankton either accumulates in sediments on the ocean floor or is decomposed and released into the ocean as C02

Other organism examples + what they do

Tiny Coccolithophores, molluscs and crustaceans extract calcium ions from sea water to manufacture plates, shells and skeletons of calcium carbonate.

These end up in ocean sediments and ultimately get lithified to form chalk and limestone

lithified

compressed and compacted into solid rock

Vegetation, especially rainforests and boreal trees contain huge stores of carbon - how

Atmospheric C02 is extracted through photosynthesis and is locked away for decades