Week 9 Flashcards
1
Q
Earth’s Climate History
A
- Earth has been habitable for most of existence
- Earth naturally has a climate supporting life
- The Earth holds water oceans up to 4.5 Gyr ago
- The rock record shows the Earth has had water on its surface since almost the very beginning
2
Q
Faint Young Sun Paradox
A
- If the Sun were to reduce its energy by even a few percent, all the water on Earth would freeze
- When the Earth was young, the Sun had an energy output 25-30% lower than today
- The Sun’s weakened rays are strong enough to warm water at the equator, but much weaker at the poles, allowing ice to develop
- Atmospheric methane content, worked to regulate the Earth’s temperatures
3
Q
Rocks and the Atmosphere: Weather
A
- Human CO2 production is 90x greater than global volcanic CO2 production
- A lot of minerals will weather when exposed to water
- Calcium dissolved in water combines with carbonic acid to produce acid rain which dissolves rocks for carbonate shells and limestone
- Produces a carbon sink
4
Q
Carbon Sink
A
- When carbon is stored in rocks, it is removed from the atmosphere for a long geological time
5
Q
Rocks and the Atmosphere: Rocks
A
Rocks can drive climate change if:
- There is an abundance of fresh, exposed rock at the surface;
- There is sufficient precipitation to weather rocks, and;
- Given enough time.
6
Q
Rocks and the Atmosphere: Plants
A
If plants cover the rock, the process can be sped up by:
- Pulling CO2 from the air and putting it into the soil, promoting H2CO3 production.
- Breaking rocks apart with roots, creating more surface area to be weathered.
7
Q
Climate Change: The Polar Position Hypothesis
A
- This is the earliest and simplest hypothesis for climate change through Earth’s history
Is composed of two testable predictions: - Ice sheets appear on continents at or near the poles;
- No ice sheets should appear on Earth if there is no continental landmass near either pole.
8
Q
Climate Change: The BLAG Hypothesis
A
- This hypothesis attempts to link plate tectonics to atmospheric CO2
- Assuming most CO2 comes from volcanic activity (which is true pre-1900):
- Periods of rapid ocean-floor spreading and high global volcanism produce high atmospheric CO2 levels, thus warming the climate;
- Periods of slow ocean-floor spreading and low global volcanism produce low atmospheric CO2 levels, thus cooling the climate.
9
Q
Climate Change: Uplift Weathering Hypothesis
A
- This hypothesis uses the idea of weathering rocks as the main function of climate change, rather than the result of a feedback loop
- As rocks are more fractured, the available surface area that can be weathered increases
10
Q
Climate Change: Ocean Heat Transport Hypothesis
A
This hypothesis states, “sea levels control long-term Icehouse/Greenhouse climates, such that high sea levels produce warm climates, and low sea levels produce cool climates
11
Q
There are five main processes that drive ocean volume to change:
A
- Development of tall mid-ocean ridge spreading centres;
- Collisions between continents;
- Development of Basaltic plateaus;
- Water storage in Ice Sheets;
- Thermal Expansion of water
12
Q
The Snowball Earth
A
- For periods when the Icehouse is at a maximum, we use the term Snowball Earth
- Glaciers and Ice Sheets accumulate at the equator or tropical regions, meaning the whole Earth was at or near freezing (ie. Not too hot at the equator!)
- The most recent evidence of a Snowball Earth would be the global glaciation event occurring from 850 – 550 Myr ago
- During this period, glaciers had formed on every continent and at (nearly) every latitude
After naming the phenomenon, it was found the Earth had not completely frozen - Tropical Oceans remained slushy, yet near the freezing temperature; we call this period “Slushball Earth”
13
Q
Paleocene-Eocene Thermal Maximum (PETM)
A
- The PETM was an abnormal period of spiking global temperatures, with effects lasting for 20,000 years
- It is estimated that oceanic temperatures had risen by ~6°C
- A rapid peak in methane content in the atmosphere lead to this temperature increase
- Methane Clathrate: large pockets of stable methane dissolved into deep, cold water
14
Q
Climate Oscillations
A
- The Earth is known to swing in-and-out of glacial and interglacial periods
- Prior to human production of CO2, the atmospheric content was naturally dropping
- Low CO2 content is more conducive to cold climate
- Earth was moving towards icehouse conditions until the Industrial Revolution, where a dramatic increase in greenhouse gas production has forced the Earth into abnormal greenhouse conditions
15
Q
Climate Oscillations: Younger Dryas
A
- The Younger Dryas Event: after the glacial maximum 21kyr ago, global climate began steadily warming until 13kyr ago
- Lasting ~1300 years, the trend of steady global warming was broken by rapid and intense cooling at all latitudes
- The end of this period was marked by rapid and intense heating, where global temperatures rose ~7°C in 40yrs!
- This event is well-documented, despite its short geological time span, thanks to ancient pollen deposits from the White Dryas flower of the Arctic
- Scientists can correlate this event to a massive outflow of fresh glacial meltwater from the Great Lakes, occurring ~13kyr when the Laurentide Ice Sheet unblocked an ice-dam at the St. Lawrence River
- Thermohaline Circulation (see Chapter X) was interrupted by the massive influx of cold, fresh water, essentially ending the transport of warm, tropical water northwards
- As the out-flow of cold water slowed, climate should have warmed much faster; new findings show the likeliness of a meteor impact that prolonged the global cooling
