Glaciation - Unit 2 Flashcards
Climate change?
The significant change in the patterns of average weather that a given region experiences
Natural causes of long term climate change?
Result in glacial and interglacial periods
Milankovich cycles
Stadials and interstadials
Aphelion?
The point during the Earth’s orbit around the sun where it is most distant
Perihelion?
The point during the Earth’s orbit around the sun when it is closest to the sun
Describe the eccentricity cycle
Stretch
Involves the shape of the orbit changing from circular to elliptical and back again every 100,000 years.
This varies the intensity of insolation received at the Earth’s surface through the year
Describe the obliquity cycle
Axial tilt
The tilt of the axis changes from 22° to 24.5° over a time period of approximately 40,000 years. The greater the tilt the more extreme the seasons become
Describe the precession cycle
Wobble
The axis wobbles with a periodicity of 21,000 years, changing the position of the seasons on the orbit.
What is a climatic ‘tipping point’?
A threshold that, when exceeded, can lead to large changes in the state of a system
Give an example of climate change due to the tipping point being reached
Changes to ocean currents
Explain what happens during a thermohaline conveyor current (changes to the ocean currents)
- In the tropics, ocean water absorbs heat from atmosphere
- Warmed water is carried north by surface currents
- Immense amounts of stored heat energy is transferred from one part of the world to another
- Evaporation occurs
- Salinity increases
- Salt water is denser than fresh water so eventually sinks and returns to the tropics at lower depths in ocean
- For this reason, it is referred to as a thermohaline conveyor current
CASE STUDY
The Younger Dryas
- About 12,800 years ago
- Melting freshwater from end of the Devension flowed into North Atlantic
- Made surface water less dense, keeping current from sinking
- Thermohaline conveyor stopped transporting heat to Northern Hemisphere
- Air became colder for more than 1000 years
- This period sent Northern Hemisphere back into conditions almost like the last Ice Age
Natural causes of short term climate change?
Volcanic eruptions
How do volcanic eruptions affect climate change?
Explosive eruptions with high VEI (Volcanic Explosivity Index) can inject large quantities of dust and gasses (e.g. sulphur dioxide) into stratosphere
- Blocks incoming insolation
- Stratospheric pollution may remain for several years
- Spreads to cover most of the globe
Causes of changes through historical time including the Little Ice Age
Both natural and anthropogenic:
Sunspot activity, global warming
How does sunspot activity lead to climate change?
- Sunspots are areas of intense activity on sun’s surface
- Result in more insolation reaching Earth
