Chemical and biogeochemical effects Flashcards
How does the ability of the oceans to absorb CO2 change as atmospheric CO2 changes?
The ability of sea water to absorb CO2 drops as atmospheric CO2 increases
How do phytoplankton respond to iron availability?
If there is more dust present, there is more iron available … this encourages phytoplankton growth
What chemical processes do we need to consider in our models?
- Ocean chemistry
- Role of ozone
- Atmospheric chemistry
- Methane lifetime
- Volatile Organic Compounds (VOCs)
What is the average pH of the oceans?
pH 8
How does the ocean act as a biological pump?
- Phytoplankton absorb CO2
- Zooplankton consume phytoplankton
- Respiration returns CO2 to the atmosphere
- Some organic matter sinks to the deep ocean … net uptake of CO2
Where is CO2 recycled in the ocean?
In the upper 1 km
What % of organic matter sinks to the deep ocean?
5-10%
What is phytoplankton growth limited by?
- Light
- Nutrients (nitrogen, phosphorous, iron)
In what regions is iron a major limiting nutrient?
- Equitorial pacific
- Southern Ocean
How is iron delivered to the ocean?
Through dust
Where in the ocean do your find nutrient ‘deserts’?
The centre of gyres
Who proposed the iron hypothesis?
John Martin
What is the iron hypothesis?
- Fertilise low-chlorophlull zones
- Create algal blooms
- Boost primary productivity
- Drive down CO2
How many studies on iron fertilisation experience have shown a CO2 draw down?
Only one of over 12 studies … (Boyd, 2000: showed a doubling of biomass and a CO2 draw down)
When were commercial iron fertilisation experiments banned?
2013
Which convention prevents iron fertilisation experiments?
The UN convention on biological diversity
How much dust was dumped into the oceans after the Pinatubo eruption?
40,000 tonnes
How could the relationship between iron availability and climate cause a positive feedback loop?
-warmer, wetter climate … less dust … less iron deposition … fewer nutrients … fewer phytoplankton … less oceanic CO2 absorption
How could the relationship between iron availability and climate cause a negative feedback loop?
-arid regions get drier … more dust … more iron deposition … more nutrients … more phytoplankton … more oceanic CO2 absorption
What is DMS?
Dimethyl Sulphide … emitted by phytoplankton as a natural byproduct of metabolism
What is one hypothesis for why DMS is emitted?
To protect phytoplankton from UV radiation
What does DMS do?
- gives the sea water its smell
- forms natural aerosol
What is the chemical formula for DMS?
(CH3)2S
What happens to DMS in the atmosphere?
Oxidised and condensed into aerosols
What is the CLAW hypothesis?
A negative climate feedback loop
- ocean warms
- enhanced phytoplankton growth
- enhanced DMS production
- More aerosol produced
- More cloud condensation nuclei
- Ehanced cloud area
- Enhanced albedo … reflecting sunlight
Who proposed the CLAW hypothesis?
C-Charlson
L-Lovelock
A-Andreae
W-Warren
When was the CLAW hypothesis first proposed?
1897
What is the controversy surrounding the CLAW hypothesis?
Lovelock (one who originally proposed the hypothesis) contracted this in The Revenge of Gaia … could it be a positive loop instead? … increased stratification … reduced upwelling … less DMS production …
How much is the stratosphere cooling?
0.5ºC a decade
What is chemistry of the ozone dependent on?
Temperature
What is occurring in polar regions due to reducing stratospheric temperature?
More polar stratospheric clouds are generated … these provide the surface on which chemical reactions occur that creates the ozone hole
What is the atmospheric lifetime of methane and what does this mean?
12 years … meaning half is removed in 12 years
Why does methane emission rate affect its lifetime?
More emissions reduces OH concentration, increasing methane lifetime
What is the OH radical important for?
Important for chemical reactions that remove methane from the atmosphere … it is described as the ‘atmospheric detergent’
What is produced in the oxidation of methane?
Stratospheric water vapour
What is stratospheric water vapour important for?
The formation of stratospheric clouds which accelerate ozone depletion
Why do plants produce VOCs?
Unsure of this … requires a lot of energy from the plant so there must be a reason for this … communication? protect against predation?
How does a warming planet affect VOC emissions?
Warmer temperatures cause more VOCs to be emitted … due to increased metabolism
