L3 - Earth's Orbit and Climate

Question 1

Why are variations in the Earth-Sun geometry important for the climate system?

Answer 1

Because it influences the amount of solar radiation received by the Earth at varying latitudes

Question 2

Which theory of climate change focuses on the Earth-Sun geometry?

Answer 2

Milankovitch

Question 3

The Earth’s orbit day has 2 fundamental motions what are they?

Answer 3

1. Daily Spin on its Axis

2. Yearly Revolution of the Sun

Question 4

What is the current axis of rotation of the Earth?

Answer 4

23.5 Deg with seasonal variations

Question 5

When do the two solstices occur?

Answer 5

June and December

Question 6

During which solstice is the Northern Hemisphere pointing away form the sun?

Answer 6

December

Question 7

When do the two equinoxes occur?

Answer 7

March and October

Question 8

Northern Hemisphere Winter and Southern Hemisphere Summer occur close to what? and what does this mean?

Answer 8

Close to Perihelion (Close Pass) which means that Northern Hemisphere winters are warmer

Question 9

Northern Hemisphere Summer and Southern Hemisphere Winter occur close to what? and what does this mean?

Answer 9

Close to Aphelion (Distant Pass) which means that Northern Hemisphere summers are cooler

Question 10

What are the 3 orbital cycles?

Answer 10

1. Obliquity
2. Eccentricity
3. Precession

Question 11

What is the variation in cycle amplitude referred to as?

Answer 11

Modulation

Question 12

Between what range does obliquity vary?

Answer 12

From ~21.5 to 24.5 Deg

Question 13

What is the period of obliquity?

Answer 13

41,000 years

Question 14

Are seasons exaggerated during large or small obliquities?

Answer 14

Large

Question 15

Where do the largest changes in obliquity occur?

Answer 15

At High Latitudes

Question 16

Eccentricity is determined by what formula?

Answer 16

SQRT (a2 - b2/a)

Question 17

What is eccentricity?

Answer 17

The shape of the Earth

Question 18

What shape is the Earth when eccentricity is at its max and min?

Answer 18

At the minimum it is closest to a circle and at the maximum it is 6% away from a circle

Question 19

What is the period of eccentricity? (and why is it important)

Answer 19

100,000 years (links to the MPT!)

Question 20

What is the period of precession?

Answer 20

23,000 years

Question 21

What does precession cause?

Answer 21

A move of the cardinal points around the Earths orbit

Question 22

During precession what shape does the elliptical orbit trace out?

Answer 22

A flower petal

Question 23

Precession causes contrasts with perihelion and aphelion - what magnifies these contrasts?

Answer 23

High Eccentricity

Question 24

Which cycles dominate changes in low and mid latitudes?

Answer 24

Precession

Question 25

Which cycles dominate changes in high latitudes?

Answer 25

Obliquity

Question 26

What is Spectral Analysis?

Answer 26

A time series analysis used to divide signals into composite frequencies to extract details on climate cycles

Question 27

ablation>accumulation can occur from what temperature?

Answer 27

-10 Deg C

Question 28

Give 3 methods of ablation

Answer 28

1. Absorption of Solar Radiation
2. Uptake of Latent Heat
3. Iceberg Calving

Question 29

The boundary between +ve and -ve mass balance is the what?

Answer 29

The Equilibrium Line

Question 30

What does low summer insolation mean?

Answer 30

Snow and ice that has accumulated doesn’t melt, there is low obliquity and it is likely that there will be ice sheet growth

Question 31

What does high summer insolation lead to?

Answer 31

Ice sheet removal

Question 32

What 3 things influence ice sheet growth in addition to summer insolation?

Answer 32

1. The position of the equilibrium line
2. Albedo
3. The Ice Elevation Feedback

Question 33

What is bedrock response?

Answer 33

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

Question 34

What are the 2 types of bedrock response, which is +ve and -ve feedback and which accounts for the most response?

Answer 34

1. Elastic Response (-ve feedback) accounts for 30%

2. Viscous Respons (+ve feedback) accounts for 70%

Question 35

Which ocean sediment gives the best records on ice volume?

Answer 35

Benthic Oxygen-18

Question 36

What do lags occur between?

Answer 36

Between insolation and response for obliquity and precession

Question 37

What is orbital tuning used for and how is it done?

Answer 37

For assigning dates to records by applying filters to isolate frequencies

Question 38

What do stacks do?

Answer 38

Apply orbital tuning in an attempt to reference marine models that are representative of area and time

Question 39

What can post-tuned stacks be compared to?

Answer 39

Obliquity and Precession

Question 40

What has dominated climate power in the last 0.9 MY?

Answer 40

Eccentricity

Question 41

In the oldest records what dominated power?

Answer 41

Precession

Question 42

Between 2.75 MYA and 0.9 MYA what dominated power?

Answer 42

Obliquity

Question 43

There has been substantial power at the 100,000 year period in the last 0.9 MY what does this mean?

Answer 43

That the largest variations have not occurred because of changes in Earth’s orbit - there must be another factor

Question 44

For the 100,000 year power to be significant what does it need to produce?

Answer 44

Large Terminations like the MPT

Question 45

What is one possible cause for the 100,000 year power significance and the MPT?

Answer 45

Ice Sheet Erosion of Regolith