Links and interdependence Flashcards
Carbon cycle- permafrost
- Melting permafrost releases carbon
- Atmospheric carbon causes eustatic sea level rise
- More clean liquid water could store more carbon
- Increased runoff causes more soil to be washed away, including the carbon within it
- Humidity increases decomposition, so increases release of carbon
In the atmosphere
- Carbon dioxide is a greenhouse gas
- Carbon dioxide is needed for photosynthesis
- Biomass stores carbon and water, and extract water from soils and transpire it
- When water is evaporated, carbon dioxide is exchanged between the ocean and the atmosphere
In the oceans
- Ocean acidity increases when carbon exchange into the oceans exceed carbon exchange into the atmosphere
- Higher sea temperatures mean less carbon dioxide can be dissolved into it and stored
- Atmospheric carbon dioxide levels influence sea temperatures and the thermal expansion of oceans (eustatic sea level rise)
In the biosphere and pedosphere (vegetation and soil)
- Water availability is a limiting factor in photosynthesis and so carbon intake
- This then influences input of organic material back into the soil where it can be decomposed
- The moisture content of the air influences the rates of decomposition and release of carbon into soils and atmosphere
In the cryosphere
- Atmospheric carbon dioxide determines the greenhouse effect and therefore the melting of sea ice, permafrost and glaciers
- Melting exposes land and sea surfaces which absorb more solar radiation and so temperatures raise further
- Permafrost melting exposes organic material to decomposition, adding carbon to the atmosphere
Impacts of population growth on the water cycle
• Rapid population growth, economic growth, deforestation and urbanisation have modified water and carbon stores and the rates of flows.
• The human impact on the water cycle is clearest in rivers and aquifers. Rising demands have created shortages.
(e.g. In the Colorado River Basin, USA, surface supplies have fallen as water is extracted from the rivers and diverted for agriculture and domestic supplies. Huge volumes are stored in reservoirs such as Lake Mead. The river does not even reach the sea anymore in its natural mouth in Mexico.)
Human activity causing changes in carbon stores
- Fossil fuels represent 87% of global primary energy consumption.
- Exploiting these resources has removed billions of tonnes of carbon from storage in the lithosphere. 8 billion tonnes of carbon a year are transferred to the atmosphere by fossil fuel combustion.
- Land Use change (mainly deforestation) adds 1 billion tonnes a year.
- The excess carbon is mainly stored in the atmosphere.
- Around 2.5 million tonnes is stored in the ocean and another 2.5 million in the biosphere.
- Large scale deforestation has reduced global forest coverage by nearly 50%
- So, the amount of carbon in biomass storage has declined greatly
Phytoplankton in the oceans absorb…
…more than half of fossil fuel carbon dioxide (much more than tropical rainforests)
Phytoplankton are threatened by…
…acidification of oceans, due an increase in carbon absorption
Soil is being degraded by…
…deforestation and poor farming practises
10cm of soil takes ????? to form
2,000 years
Erosion costs ???? a year
$490 billion
Over ??? of wetlands have been drained
50%
Carbon stored in wetlands are depleted as…
…they are removed for urban growth
Mass balance equation
Inputs - outputs
Undisturbed tropical rainforest
Inputs = 30.4 tonnes/ha
Outputs = 24.5 tonnes/ha
Mass Balance = 5.9 tonnes/ha
Above ground biomass = 180 tonnes/ha
Below ground biomass = 226 tonnes/ha
Total stores = 406 tonnes/ha
10 years after deforestation
Inputs = 12.3 tonnes/ha
Outputs = 25.1 tonnes/ha
Mass Balance = -12.8 tonnes/ha
Above ground biomass = 43 tonnes/ha
Below ground biomass = 150 tonnes/ha
Total stores = 193 tonnes/ha
Water cycle- climate change
- Climate change is already modifying the cycle
- Global warming has increased evaporation, and therefore the amount of vapour in the atmosphere
- More water vapour (a GHG) has a positive feedback effect of raising temperatures, increases evaporation and precipitation
- Increased precipitation increases runoff and flood risk
- Atmospheric water vapour releases latent heat when it condenses. This added energy in the atmosphere, storms and hurricanes may become more powerful and frequent
- Global warming is accelerating the decline retreat of glaciers and sea ice melting. There, cryosphere storage is reduced. This reduces the albedo of the Earth, so it absorbs more solar radiation, another positive feedback effect
Carbon cycle- climate change
- Climate change brings rising temperatures, but it also changes rainfall amounts depending on geography. Some places receive more, some less
- Higher temperatures increase decomposition and accelerate carbon transfer from soil to atmosphere
- In humid areas, there may be a change to more arid conditions as deserts advance into grasslands, and grasslands advance into tropical forests. This will then reduce carbon stored in biomass
- More carbon in the atmosphere affects primary productivity
As temperatures rise, so does primary production, and so plant growth. But as temperatures increase, this benefit may be cancelled out by droughts. Between 2000 and 2009, there was a small net decrease in NPP.
[No answer]
Tipping points for tropical forests
While warmer temperatures will increase photosynthesis, and so growth, too much of a rise may start a forest die back. A 4°C rise in temperatures will kick off 85% of forests, while a 2°C increase will kick off up to 40%
Tipping points for tundra
- Warming global temperatures will accelerate the melting of tundra permafrost, allowing the coniferous forests of the Northern Hemisphere (called the Taiga in Russia and Boreal forests in North America) to advance northwards
- Carbon locked in permafrost will be released as it melts, increasing decomposition of the vast stores of carbon they contain
Ocean acidification
Acidification of the oceans as they absorb more carbon will reduce photosynthesis by phytoplankton, reducing ocean carbon stores
Overall, climate change will see:
- More carbon stored in the atmosphere
- Less carbon stored in oceans and the biosphere
- Carbon flows changing geographically
