Lec 2 - Atmosphere, CO2, Tectonics, Climate Flashcards
How thick is the atmosphere?
200-400km
relatively thin compared to Earth diameter!
What are the layers of the atmosphere, from the ground up?
- troposphere
- stratosphere
- mesosphere
- thermosphere
What defines the layers of the atmosphere?
- the Temperature Profile (change in temperature with height)
- pauses in temp profile at the start of each layer
- ‘inversions’ in the direction of temperature change
In what atmospheric layer does most weather occur?
troposphere
How does the thickness of the troposphere vary?
- 8-10km at poles, 16km over tropics
- due to thermal expansion
What causes the inversion in the temperature profile of the Stratosphere?
absorption of UV radiation by ozone, causing hot air to rise
What is the coldest atmospheric layer?
mesosphere - radiation absorption only occurs in the bottom layer
What is the atmosphere made of?
- gases
- suspended particles (aerosols)
- liquid/solid water
How well are gases mixed in the atmosphere?
- <80km = well-mixed (homosphere)
- > 80km - separated by gravity (heterosphere)
What are the permanent gases of the atmosphere?
- N
- O
- Ar
- Ne
- He
- K
- Xe
- H
What are the main variable gases of the atmosphere?
- water
- CO2
- O3
- methane
What classifies a gas as permanent/variable?
residence time = reservoir size/flux rate
How abundant is water in the atmosphere?
- ranges from 0-5% of air
How much of the atmosphere is CO2?
0.039%
How is CO2 added to the atmosphere?
respiration, volcanic activity, decay, combustion
How is CO2 removed from the atmosphere?
- photosynthesis
- long term: weathering
What does ozone do in the atmosphere?
- pollutant in lower atmosphere
- absorbs UV radiation in upper atmosphere
How is methane released into the atmosphere?
fossil fuels, livestock, digestion, agriculture (esp rice)
What are the two main types of continental chemical weathering?
- hydrolysis
- dissolution
What controls chemical weathering rates?
- temp increases
- precipitation increases
- temp/precipitation impact vegetation/productivity
What kind of feedback is chemical weathering?
negative loop
What kind of feedback loop does water vapour cause?
- positive feedback!
- more water = GHG Effect, so more heating = more evaporation = more water in atmosphere
What is the Gaia hypothesis?
- living things regulate climate
- based on CO2 cycle, photosynthesis affecting weathering, and plankton storing CO2 in shells
What is the polar position hypothesis?
- the position of continents determine ‘ice house’ intervals
- suggests ice sheets should appear on continents near polar latitudes, and no ice sheets should appear outside of these latitudes
- BUT - based on records, not all continents in polar positions develop ice sheets (ex Pangaea - CO2 compensates for weaker sun, no ice!)
How could tectonics control CO2?
- Volcanoes - add CO2
- weathering - remove CO2
What is the BLAG Hypothesis?
- most CO2 in atmosphere is expelled from margins of converging plates (volcanoes), and divergent plates (ocean ridges)
Why is there more weathering with more uplift?
- mass wasting
- earthquakes
- steep slopes
- heavy precipitation
- glaciers
How might uplift weathering be a feedback?
more uplift weathering means more CO2 removal, but as rocks in other areas age, they remove less and less CO2. Maybe these two effects balance out?
