WCC: Carbon Cycle - Natural Causes of Change in the Carbon Cycle Flashcards
Changes in the carbon cycle over time, to include natural variation: wildfires and volcanic activity.
How would cold conditions impact chemical weathering?
It would be more active as cold water can hold more carbon dioxide
How would cold conditions impact decomposition? How would this impact the carbon cycle?
It would decrease as decomposers would be less effective, so carbon transfer to soils would be reduced.
How would cold conditions impact ocean stores? How would this impact the carbon cycle?
Ocean stores would be smaller as less water would have flowed into the oceans due to it being locked up as snow and ice on land. There would be less sediment transfer along rivers and less build-up of sediments on the ocean floor, reducing sedimentary rock stores.
How would cold conditions impact soil? How would this impact the carbon cycle?
Soil would be frozen over vast areas of land, stopping transfers of carbon.
How are wildfires started?
Lightning strikes
Human accidents or arson
What are the 3 main natural variations that cause change in the carbon cycle over time?
Natural climate change - temperature
Wildfires
Volcanic activity
How have global climates changed throughout the Quaternary geological period?
Climates have fluctuated considerably between warm interglacial periods and cold glacial periods
Briefly describe the nature of the relationship between CO2 and temperature
Trends in temperature and CO2 over time mirror each other. Increased CO2 levels increase temperatures and lower CO2 levels decrease temperatures, but temperature change also has an impact on CO2 levels.
Give evidence for the mirrored relationship between CO2 and temperature
Data obtained from ice cores in the Antarctic ice sheet shows that over the past 800,000 years, there have been several regularly occurring glacial periods interspersed with warmer interglacial periods. CO2 levels have risen and fallen along with these temperature changes.
Name the carbon stores and transfers which would be directly impacted by temperature changes.
Weathering (chemical) Vegetation Decomposition Ocean store Soil transfers Permafrost
How would colder conditions impact vegetation? How would this impact the carbon cycle?
Forest coverage would differ in total area and geographical location. This would affect the significance and distribution of photosynthesis and respiration.
Where has the recent rise in temperature been particularly noticeable?
High latitudes for example tundra regions in Siberia, Russia
What noticeable effect has the recent rise in temperatures had on tundra regions?
Melting permafrost resulting in a positive feedback loop
Describe the positive feedback loop occurring in tundra regions due to recent rises in temperature.
Carbon stored within the permafrost is being released as it melts in the form of CO2 and methane. In the atmosphere, these gases further enhance the greenhouse effect, leading to increased warming and subsequent .melting.
What is biomass combustion?
The burning of living and dead vegetation
What are the 4 different cycles the carbon cycle can be divided into?
Fast organic carbon cycle
Fast inorganic carbon cycle
Slow organic carbon cycle
Slow inorganic carbon cycle
Dsecribe the fast organic carbon cycle.
Operates from months to centuries and includes transfers of carbon via living things between atmosphere, soil and biosphere
What is the fast inorganic carbon cycle?
Ocean-atmosphere exchange of carbon dioxide through diffusion
What is the slow organic carbon cycle?
The long-term sequestration of carbon in the remains of plants and animals over hundreds of millions of years
What does the slow organic carbon cycle create?
Fossil fuels - coal, oil, natural gas
What is the slow inorganic carbon cycle?
The sequestration of carbon from the atmosphere in the hydrosphere and then sedimentary rocks which are brought back to the surface through tectonic activity and then weathered
What 5 areas does biomass combustion occur most frequently in?
- Boreal forests in North America, Russia, Scandinavia
- Savannah grasslands in Africa
- Tropical forests in Africa, SE Asia, South America
- Temperate forests of US and Europe
- Agricultural areas of US and Europe
In what ways do wildfires emit carbon?
Combustion of vegetation
Decomposition of vegetation (soil respiration)
In what ways do wildfires result in the storing of carbon?
Production of new vegetation
Decomposition of vegetation (soil storage)
What percentage of a forests carbon does a wildfire emit into the atmosphere?
10-20%
Why do wildfires only emit a small percentage of a forest’s carbon into the atmosphere?
Wildfires kill trees but do not entirely consume them
What determines whether a forest becomes a net source or a net sink after a wildfire?
The balance between production and decomposition
What type of carbon cycle are the impacts of wildfires involved in?
Fast organic carbon cycle
What 3 factors make wildfires more likely to turn forests into carbon sources?
Larger fires
More frequent fires
Presence of peat
Which 5 carbon cycle stores and transfers are directly affected by wildfires?
Vegetation storage Decomposition Soil respiration Combustion Atmospheric storage
Give 2 reasons for the increase in magnitude and frequency of wildfires.
Warming temperatures
Changing precipitation levels
How much of the Earth’s land area do wildfires burn annually?
3-4 million km^2
How much carbon do wildfires release into the atmosphere annually?
Over 1 billion tonnes
Give an example of how wildfires can regional impacts.
In 1997-98 and 2013 many huge fires in Indonesia affected the lives of millions of people as smoke spread across SE Asia
How much CO2 do volcanic eruptions emit annually?
130-380 million tonnes
What do the USGS say about the contriubtion of volcanic activity to global warming?
The CO2 released in recent volcanic eruptions has never cause detectable global warming of the atmosphere?
What are 2 reasons for recent volcanic eruptions not causing a detectable increase in the Earth’s temperatures?
CO2 emissions are counterbalanced by sulphur dioxide emissions
Not enough CO2 compared to human activities
Why do sulphur dioxide emissions counterbalance the warming effect of CO2 emissions from volcanic eruptions?
Sulphur dioxide is converted into sulphuric acid, which forms fine droplets. This increases the reflection of radiation from the Sun back into space, cooling the Earth’s lower atmosphere.
Give evidence to support that not enough CO2 has been emitted from volcanic activity compared to human activity to cause detectable global warming
Present-day sub-aerial and submarine volcanoes have released less than 1% of the CO2 released currently by human activities
How does volcanic activity release carbon?
Carbon rich sediments are dragged into the mantle during subduction. Volcanic eruptions release the carbon into the atmosphere as volcanic gases e.g CO2
How can volcanic activity result in the absorption of carbon from the atmosphere?
Volcanoes erupt lava, forming igneous silicate rocks that will slowly weather. This converts atmospheric CO2 to carbonate minerals in solution. These become ocean sediments and may become sedimentary rocks,
Briefly describe what impacts volcanic activity has on the carbon cycle.
Large quantities of CO2 are immediately returned to the atmosphere. However CO2 can be very slowly absorbed from the atmosphere due to the formation of igneous rocks.
By looking at temperature changes and atmospheric CO2 changes over time, which change appears to occur first?
Temperature change
What do some scientists believe causes the cycle of glacial and interglacial periods?
Orbital change
How does orbital change cause the cycle of glacial and interglacial periods?
Regular cycles of orbital eccentricity causes slight variations in the amount of sun’s radiation that warms up the Earth.
How does the cycle of glacial and interglacial periods cause changing atmospheric CO2 levels?
Orbital change triggers temperatures to rise at the end of a glacial period. The warming of oceans and melting of frozen land surface releases a surge of CO2 into the atmosphere.
Explain the relationship between temperature and atmospheric CO2 over time through cycles of glacial and interglacial periods.
Rising temperatures at the end of glacial periods causes a surge of CO2 into the atmosphere. This enhances the greenhouse effect, amplifying the warming trend and creating a positive feedback loop.
How much of the most recent post-glacial warming is believed to have occurred after the rise in atmospheric CO2? What does this suggest about the relationship between atmospheric CO2 and climate?
90%, suggesting rises in atmospheric CO2 are a major cause of global warming, rather than increased temperatures being the reason for increased atmospheric CO2.
