Glacier - Interglacial cycles

Question 1

What was Ice Age Earth?

Answer 1

The presence of ice sheets on Earth
An unusual feature of Earth’s history
Over last billion years
- Global warming - “greenhouse”, ice-free
- Global cooling - “Icehouse”, ice-sheets

Question 2

What are we in now?

Answer 2

The Cenozoic ice age

Question 3

What happened 2.5mya in the Northern Hemisphere?

Answer 3

Ice sheets began

Question 4

What has happened over the Quaternary period?

Answer 4

Glacials and inter-glacials
Ice advance and retreat
Glacials have varied in intensity
Global impact

Question 5

What evidence do we use?

Answer 5

Terrestrial evidence
Marine sediment evidence
Ice-sheet core evidence

Question 6

What can Marine Sediment cores offer?

Answer 6

Organic origin containing mineral deposits
Slow by continuous accumulation of sediment of deep open ocean floors
Immune to major episodes of erosion
Can provide record of climate change throughout the Quaternary

Question 7

What do Ice-sheet cores do?

Answer 7

Show layers of snow fall
Compressing into successive layers of ice

Question 8

What does the ice consist of?

Answer 8

Water, air bubbles, dust, volcanic ash, sea salt
Providing clues about climate at the time they were deposited

Question 9

What does the water show?

Answer 9

Oxygen isotopes preserving the temperature

Question 10

What can air bubbles show?

Answer 10

Preserve past atmosphere

Question 11

What does dust, ash, and sea salt show?

Answer 11

Index of strength of atmospheric circulation (how windy)
Can date known volcanic eruptions
Indicate how surrounding areas have changes

Question 12

What are some causes of climate change over 100s thousands years?

Answer 12

• Orbital forcing
• Changing Earth’s orbit -> changing spatial + temporal distribution of solar energy
• Changes favour/hinder ice-sheet growth
  First discussed by Croll (1860s)

Question 13

What do the combined cycles show?

Answer 13

A continuous variable but predictable pattern of solar energy receipts

Question 14

What do Oxygen isotope fluctuations have cyclic periods of ?

Answer 14

41,000 years
19-24,000 years
100,000 years

Question 15

What are the limitations of Milankovitch cycles?

Answer 15

• 100,000-year glacial cycle has the strongest amplitude but the 100,000-year orbital cycle is relatively weak
• Need an amplification of climate response
  > ie positive feedback (ocean circulation)

Question 16

Was there a British and Irish Ice Sheet?

Answer 16

Yes, vast amounts of geomorphic evidence
- On land
- And below sea

Question 17

What did the glaciations of N. America involve?

Answer 17

Two major ice masses
- Formed over rocky mnts
- Fed by moist westerlies from pacific

Question 18

What did the Laurentide Ice Sheet cover?

Answer 18

Covered most of the rest of Canada and northern USA

Question 19

What happened to the North American ice sheets during the Last Glacial Maximum?

Answer 19

They joined with Greenland Ice Sheet
- Lots of geomorphological evidence

Question 20

What is less well-known about the North American Ice Sheet?

Answer 20

The elevation

Question 21

How can the North American Ice Sheet’s elevation be estimated?

Answer 21

Isostatic uplift

Question 22

How can you reconstruct the ice sheet?

Answer 22

Using numerical ice sheet modelling
- Use an understanding of glaciological processes
- Ice core records of climate change

Question 23

What are the issues with reconstructing the North America Ice Sheet?

Answer 23

Difficult to do using waxing and waning of sheet through time
Needs to be attempted to determine ice sheet volumes