The Carbon Cycle Flashcards
(11 cards)
What is the carbon cycle and what type of system?
Process by which carbon is stored and transferred
It is a closed system
What are the flows of carbon between stores?
Photosynthesis
Combustion
Ocean uptake and loss
Sequestration
Respiration
Decomposition
Weathering
What is photosynthesis role in carbon cycle?
Transfers carbon stored in atmosphere to biomass
Plants and phytoplankton use energy from sun to convert c02 to glucose and water enabling plants to grow
Carbon passed through food chain
What is combustion role in carbon cycle?
Transfers carbon stored in living, dead or decomposed biomass to atmosphere by burning
What is ocean uptake and loss role in carbon cycle?
C02 dissolved from atmosphere to ocean. Also transferred to oceans when taken up by organisms that live there - uptake
Carbon transferred from ocean to atmosphere when carbon rich water from deep in the oceans rises to surface and releases c02 - loss
What is sequestration role in carbon cycle?
Carbon from atmosphere can be sequestered (captured and held) in sedimentary rocks or as fossil fuels
What is respiration role in carbon cycle?
Transfers carbon from living organisms to atmosphere
Plants and animals break down glucose for energy, releasing c02 and methane in the process
What is decomposition role in carbon cycle?
Transfers carbon from dead biomass to atmosphere and soil
After death bacteria and fungi break organisms down. Co2 and methane released
What is weathering role in carbon cycle?
Chemical weathering transfers carbon from atmosphere to hydrosphere and biosphere
Atmospheric carbon reacts with water and forms acid rain. When this falls on rocks a chemical reaction occurs and dissolves rocks
What are the changes in the carbon cycle over time dude to natural variation?
Volcanic activity - Carbon stored within the Earth in magma is released during volcanic eruptions, majority enters atmosphere as CO2. This returns carbon that has been trapped for millions of years in
rock deep with the Earth’s crust back to the atmosphere.
In the past, e.g. the Paleozoic era, volcanoes were much more active than they are today. A vast
amount of co2 was emitted into the atmosphere, where it remained for a long time.
Recent volcanic eruptions have released much less CO2, than human activities (e.g. fossil fuel
burning). Currently, volcanoes emit between 130 and 380 million tonnes of CO2 per year.
However, there is potential for a very large eruption to disrupt the carbon cycle significantly.
Supervolcanoes, e.g. the Yellowstone Caldera, have the potential to emit large quantities of CO2.
Wildfires - natural events that can alter the magnitude of carbon stores.
They rapidly transfer large quantities of carbon from biomass to the atmosphere as a result of combustion.
As wildfires result in a loss of vegetation in the short term, photosynthesis decreases so less
carbon is removed from the atmosphere.
In the longer term, however, fires can encourage the growth of new plants. Secondary
succession can occur as plants recolonise the area. As succession takes place more carbon will
be taken from the atmosphere due to photosynthesis.
Depending on amount and type of regrowth, fires can have a neutral effect on the amount of atmospheric carbon.
wildfires tend to be restricted to small parts of the Earth’s surface they can have regional impacts.
In 1997-8 and again in 2013 there were many huge fires in Indonesia that burned out of control for months. Smoke from these fires spread across parts of south-east Asia, affecting the lives of millions. The fires released a large quantity of CO2 into the atmosphere, causing a noticeable spike in the rising trend of carbon emissions recorded since the late 1950s.
In 2018 the wildfire season involved wildfires on multiple continents. Some fires were in areas
accustomed to wildfires, but numbers and size were greater than usual. In California, for
example, over 5000 fires burned.
Others were far more rare events eg) wildfires broke out north of the Arctic Circle in Scandinavia in July.
Large wildfires can turn forests from being a carbon sink to being a carbon source, as combustion returns huge quantities of carbon back to the atmosphere.
What are changes to the carbon cycle over time due to natural variation?
Hydrocarbon fuel extraction and burning - Fossil fuels are mainly composed of carbon and hydrogen, so are known as hydrocarbons.
Extracting and combustion of fossil fuels releases CO2 into the atmosphere.
Without human intervention, the carbon would remain sequestered in the lithosphere for thousands or millions of years to come.
Today, most of the world’s gas and oil is extracted from rocks that are 70-100 million years old.
The carbon has remained locked up in these deposits for all that time but, when burnt to generate energy and power, the stored carbon is released as CO2 into the atmosphere,
accelerating the cycling of this carbon.
• Since the Industrial Revolution, fossil fuels have been burnt in increasing quantities, emitting
CO2 into the atmosphere (see graph below). The increase since 1950 has been particularly
dramatic, driven by the rapid industrialisation of developing nations (such as India and China)
as well as the continued demand from the world’s industrialised nations such as the USA.
• Since the 1950s carbon dioxide in the atmosphere has been measured by the Hawaiian Volcanic
Observatory, their research showing an alarming increase in levels of atmospheric CO2 (see
graph below).
