week 6 Lecture part 2

Question 1

What is a Glacial period?

Answer 1

An interval of time marked by cold temperatures, when ice- sheets advanced to cover large parts of Earth’s surface

Question 2

What is a interglacial period?

Answer 2

An interval of time marked by relatively warmer temperatures, during which ice sheets are present only in polar and mountainous regions

Question 3

What is an ice age?

Answer 3

• A prolonged period of relatively lower temperature in which ice sheets are present on continents or the poles
• We are currently in an ice-age
• Glacial and interglacial periods occur within an ice age
• An ice age differs to a greenhouse climate state, when no ice is present

Question 4

What are two prominent proxies that can provide evidence for glacial interglacial cycles?

Answer 4

Marine oxygen isotopes

ice cores

Question 5

During glacial-interglacial cycles where is the majority of the time spent?

Answer 5

80% of time spent in glacial periods, interglacials

are the unique periods

Question 6

What characterises glacial periods?

Answer 6

Lower temperature
Less precipitation
Higher thermal gradients (greater temp range between tropics and poles)
CO2 stored in deep ocean
Lower sea level (60-120 m below present)
Growth of ice sheets

Question 7

What characterises glacial periods?

Answer 7

• Warmer
• Wetter
• Ice-sheets restricted to poles and mountain regions
• Higher sea level
• Higher CO2 and methane

Question 8

What are two positive feedback mechanism that promote ice sheet growth and decay?

Answer 8

Ice-albedo feedback

Bedrock feedback

Question 9

What is mechanism behind ice albedo feedback promoting ice growth?

Answer 9

Reduced solar insolation in summer
• Lower temperature
• Increased build up of snow and ice
• Increased albedo, leading to less
solar radiation absorbed

Question 10

What is mechanism behind Bedrock feedback promoting ice growth?

Answer 10

• Ice-sheet growth depresses underlying bedrock, but there is a delay
• Ice sheet remains at higher elevation
• Ablation is lower than if sinking had occurred instantaneously
• Promotes more growth

Question 11

What is mechanism behind ice albedo feedback promoting ice decay?

Answer 11

• Increased solar insolation in summer
• Higher temperature
• Melting of snow and ice
• Decreased albedo, leading to more
solar radiation absorbed

Question 12

What is mechanism behind Bedrock feedback promoting ice decay?

Answer 12

• Ice-sheet melt released pressure on
underlying bedrock, but there is a delay
• Ice sheet remains at lower elevation
• Ablation is higher than if rebound
had occurred instantaneously
• Promotes more melting

Question 13

How well do glacial-interglacial cycles compare to orbital theory?

Answer 13

insolation in the northern hemisphere is important.

but full interglacials only occur about every 5th peak in the precession cycle