Week 4

Question 1

What are the changes occuring on the Orbital Time Scale?

Answer 1

• Axis Tilt (currently 23.5)
• Shape of earths revolution around the sun
• Shift of the seasons (precession)

Question 2

How often do Orbital scale Changes occur

Answer 2

23,000 and 413,000 year cycles

Question 3

What proxie data allows us to observe these cycles?

Answer 3

• 3 Myrs - 800Kyrs (marine sediments)

- 800 Kyrs (Ice cores)

Question 4

what major characteristics of our climate does orbital scale effect?

Answer 4

• Monsoons
• Polar Ice Sheets
• GHGs concetrations

Question 5

Describe earths Eccentric orbit

Answer 5

elliptical ,with the perihelion being 153 Mkm away and the Aphelion being 158 Mkm away

Question 6

What are the 3 main components that drive orbital climate change? describe them and their timescales.

Answer 6

1. Earths tilt, 41,000 year cycle, fluctation from 22.2-24.5 degrees
2. Earth’s eccentricity
   becomes more elliptical (or less), 2 cycles which occur at 100,000 and 413,000 years
3. Precession
   changes in solstice and equinox positions. 23,000 year cycle

Question 7

How does the earths tilt effect the climate?

Answer 7

• Larger tilt angle means warmer summer at poles and colder winter at the poles. Smaller angles means more neutral seasons.

Question 8

What is Precession, how does it effect climate.

Answer 8

The slow rotation of the elliptical orbit of the earth around the sun.

Question 9

Difference between poles and equator with respect to response to orbital cycles

Answer 9

Poles are affected more by long term cycles where as equator is effected by short term cycles

Question 10

Variability between NH and SH with respect to orbital scale cycles

Answer 10

if NH and SH react in the same manner, it is either precession or eccentricity, if they have opposite reactions, it is the earths tilt.

Question 11

List the Three orbital scales in order from shortest cycle period to longest.

Answer 11

1. Precession
2. Earths tilt
3. Long, short eccentricity

Question 12

If all cycles are occuring simultaneously, how can one detangle them from climate data?

Answer 12

Through spectral analysis requiring a time series.

Question 13

What is the relation of monsoons to orbital scale cycles?

Answer 13

Varying orbital scale cycles result in increased insolation, and increased insolation is associated with stronger monsoons (specifically summer) due to great uplift overland.

Question 14

What cycle does the disappearing of the sahara follow

Answer 14

the 23,000 year precession based cycle.

Question 15

What causes lakes like the sahara to exist?

Answer 15

Increase in solar radiation, therefore more precipitation

Question 16

What are some evidence of heavy monsoons in the sahara. Give brief descriptions of each

Answer 16

1. Sapropels, lack organic rich sediment deposited in lakes at times of monsoons, shows up as black sections in sediment cores. (use O18 for dating)
2. Paleoriver beds satellite evidence that riverbed sediment is under sand in desert.
3. Freshwater diatoms found in the atlantic sediments off the coast of africa

Question 17

Accumulation Vs. Ablation

Answer 17

• Accumulation = + mass balance
• Ablation = - mass balance
  Equilibrium : Accumulation = Ablation

Question 18

Specify the Milankovich theory and how it relates to ice growth

Answer 18

Ice grows during low summer insolation (less ablation)
lowest summer insolation
- is when earth has the lowest tilt angle, - Solstice is farthest from the sun (Preccesion)
- Max eccentricity

Question 19

How does orbital time scale cycles relate to ice development (and the study of it).

Answer 19

We know when the lowest insolation will occur in the summer therefore we know when there will be max ice growth.

Question 20

Give paleoclimate evidence of Orbital scales control over Ice development (3 archives, detail as to how their used)

Answer 20

1. Marine Foraminifera
   - made shells which were used for O18, ocean sediments!
2. Coral Reef Terraces
   - showed the height of the ocean, this showed how much water was stored in ice, used radiometric dating.
3. Tree-Grass pollen

Question 21

Todays orbital scale positioning

Answer 21

Tilt = 23.5
Precession = 0.8+
Eccentricity = Close to min 

All is headed toward the coldest summer!