L3 - Earth's Orbit and Climate Flashcards
Why are variations in the Earth-Sun geometry important for the climate system?
Because it influences the amount of solar radiation received by the Earth at varying latitudes
Which theory of climate change focuses on the Earth-Sun geometry?
Milankovitch
The Earth’s orbit day has 2 fundamental motions what are they?
- Daily Spin on its Axis
2. Yearly Revolution of the Sun
What is the current axis of rotation of the Earth?
23.5 Deg with seasonal variations
When do the two solstices occur?
June and December
During which solstice is the Northern Hemisphere pointing away form the sun?
December
When do the two equinoxes occur?
March and October
Northern Hemisphere Winter and Southern Hemisphere Summer occur close to what? and what does this mean?
Close to Perihelion (Close Pass) which means that Northern Hemisphere winters are warmer
Northern Hemisphere Summer and Southern Hemisphere Winter occur close to what? and what does this mean?
Close to Aphelion (Distant Pass) which means that Northern Hemisphere summers are cooler
What are the 3 orbital cycles?
- Obliquity
- Eccentricity
- Precession
What is the variation in cycle amplitude referred to as?
Modulation
Between what range does obliquity vary?
From ~21.5 to 24.5 Deg
What is the period of obliquity?
41,000 years
Are seasons exaggerated during large or small obliquities?
Large
Where do the largest changes in obliquity occur?
At High Latitudes
Eccentricity is determined by what formula?
SQRT (a2 - b2/a)
What is eccentricity?
The shape of the Earth
What shape is the Earth when eccentricity is at its max and min?
At the minimum it is closest to a circle and at the maximum it is 6% away from a circle
What is the period of eccentricity? (and why is it important)
100,000 years (links to the MPT!)
What is the period of precession?
23,000 years
What does precession cause?
A move of the cardinal points around the Earths orbit
During precession what shape does the elliptical orbit trace out?
A flower petal
Precession causes contrasts with perihelion and aphelion - what magnifies these contrasts?
High Eccentricity
Which cycles dominate changes in low and mid latitudes?
Precession
Which cycles dominate changes in high latitudes?
Obliquity
What is Spectral Analysis?
A time series analysis used to divide signals into composite frequencies to extract details on climate cycles
ablation>accumulation can occur from what temperature?
-10 Deg C
Give 3 methods of ablation
- Absorption of Solar Radiation
- Uptake of Latent Heat
- Iceberg Calving
The boundary between +ve and -ve mass balance is the what?
The Equilibrium Line
What does low summer insolation mean?
Snow and ice that has accumulated doesn’t melt, there is low obliquity and it is likely that there will be ice sheet growth
What does high summer insolation lead to?
Ice sheet removal
What 3 things influence ice sheet growth in addition to summer insolation?
- The position of the equilibrium line
- Albedo
- The Ice Elevation Feedback
What is bedrock response?
The response of an ice sheet to changing insolation is complicated by the response of the lithosphere to the ice sheet & ice sheet loading pushes the lithosphere down into the ablation zone
What are the 2 types of bedrock response, which is +ve and -ve feedback and which accounts for the most response?
- Elastic Response (-ve feedback) accounts for 30%
2. Viscous Respons (+ve feedback) accounts for 70%
Which ocean sediment gives the best records on ice volume?
Benthic Oxygen-18
What do lags occur between?
Between insolation and response for obliquity and precession
What is orbital tuning used for and how is it done?
For assigning dates to records by applying filters to isolate frequencies
What do stacks do?
Apply orbital tuning in an attempt to reference marine models that are representative of area and time
What can post-tuned stacks be compared to?
Obliquity and Precession
What has dominated climate power in the last 0.9 MY?
Eccentricity
In the oldest records what dominated power?
Precession
Between 2.75 MYA and 0.9 MYA what dominated power?
Obliquity
There has been substantial power at the 100,000 year period in the last 0.9 MY what does this mean?
That the largest variations have not occurred because of changes in Earth’s orbit - there must be another factor
For the 100,000 year power to be significant what does it need to produce?
Large Terminations like the MPT
What is one possible cause for the 100,000 year power significance and the MPT?
Ice Sheet Erosion of Regolith
