Unit 4 - Greenhouse Gas Concentrations Flashcards
What are the three main units used for measuring gas concentrations in the atmosphere?
Answer: Parts per million (ppm), parts per billion (ppb), and parts per trillion (ppt)
What is the gross primary production of photosynthesis?
120 GtC/year
GtC standds for gigatons of carbon
How much GtC/year does respiration release?
60 GtC/year
What is net ecosystem production (NEP)?
the difference between the amount of carbon fixed by an ecosystem through GPP and the total ecosystem respiration (includes autotrophic and heterotrophic)
NEP = GPP - (autotrophic respiration + heterotrophic respiration)
What is net biome production (NBP)?
the net amount of carbon accumulated in an ecosystem after accounting for all carbon gains and losses, including natural disturbances, human activities like harvesting, and natural processes
NBP = NEP - disturbance/harvest
What is Net Primary Production (NPP) and how is it calculated?
Answer: NPP is the carbon accumulated through photosynthesis minus respiration. It equals 60 GtC/year, calculated as the difference between gross primary production (120 GtC/year) and plant respiration (60 GtC/year).
Explain the CO2 fertilization effect and one of its limitations.
Answer: CO2 fertilization is the enhancement of plant growth and photosynthesis due to increased atmospheric CO2 levels. One key limitation is that saturation effects are expected, meaning there is a limit to how much additional CO2 can benefit plant growth.
Increased CO2 concentrations results in higher NPP through:
- Higher photosynthesis activity
- Improved water-use efficiency → plants reduce their stomatal opening so that’s why water use is more efficient
Explain the solubility pump
Solubility Pump → based on CO2’s high solubility in water
- Exchange occurs in surface layer (50-100m depth) of ocean
- Driven by CO2 partial pressure differences between the atmosphere and ocean
- with low atmospheric CO2 pressure, the ocean outgases CO2 to the atmosphere
- with high CO2 pressure, CO2 is dissolved in the surface water of the ocean
- Also influenced by water temperature and wind speed
Explain the physical pump
Physical Pump → driven by ocean circulation patterns
- Annual exchange exceeds 90 GtC
- Net absorption of 1.7 GtC by the ocean more than release
- Regional variations: warm regions are sources (at high temperatures, water can take less carbon), cold regions are sinks
- a temperature increase of 1 degrees celsius leads to a CO2 flux of around 4 Gt C
Saturation effect in CO2 fertilization
there is a limit to how much additional CO2 can benefit plant growth
What do high temperatures do to CO2?
High temperature changes may convert CO2 sinks to sources
How much CO2 does the ocean have versus atmosphere?
Oceans contain 50 times more dissolved CO2 than atmosphere
What are the three forms of dissolved inorganic carbon in seawater and their percentages?
- Bicarbonate ion (HCO3-): 91%
- Carbonate ion (CO32-): 8%
- Dissolved CO2: 1%
How does a 1°C temperature increase affect ocean CO2 release?
Answer: A 1°C temperature increase:
- Raises CO2 partial pressure by 4.2%
- Results in ~4 GtC release to atmosphere
- This is double the current annual anthropogenic CO2 uptake
What is the biological pump in ocean-atmosphere CO2 exchange?
Answer: The biological pump refers to the role of phytoplankton and plankton in CO2 exchange. They absorb CO2 during photosynthesis, convert it into organic matter or limestone, and when they die, their organic matter sinks to the ocean bottom, sequestering carbon through sedimentation.
Explain the Simple IPCC Carbon Cycle Model
- basic conceptual model that represents the global carbon cycle as a series of “boxes” or reservoirs that exchange carbon with each other
- shows carbon fluxes between reservoirs, basic exchange rates between boxes and anthropogenic inputs to the system
