Ice ages

Question 1

Glacial-interglacial periods

Answer 1

• 2.5MYA to now
• initiated by Milankovitch cycles

Question 2

Milankovitch cycles

Answer 2

• eccentricity, obliquity and precession
• changes in the Earth’s orbit around the sun that influence how much sunlight the northern hemisphere receives
• Milankovitch argued that climate is greatly influenced by energy received in summer in the northern hemisphere as the northern hemisphere has more land and ice, so lower heat capacity

Question 3

eccentricity

Answer 3

• shape of Earth’s orbit around the sun
• varies from a circle to an ellipse
• every 96,000 years
• weakest effect of the Milankovitch cycles, but has significant seasonal effects when combined with precession

Question 4

obliquity

Answer 4

• tilt of the Earth’s axis of rotation
• varies between 21.8 and 24.4 degrees over a period of 41,000 years
• the larger the obliquity the greater the seasonal difference in solar energy

Question 5

precession

Answer 5

• Earth wobbles on its rotational axis
• makes seasonal variations more extreme in the norther hemisphere and less extreme in the southern hemisphere
• every 27,000 years

Question 6

Walker circulation

Answer 6

• developed 2MYA
• the atmospheric east-west component of the Hadley cell that controls rainfall in the tropics
• intensified gradient in sea surface temperatures between eastern and western pacific
• triggered the development of ENSO

Question 7

Mid-Pleistocene transition

Answer 7

• after 800,000YA the 41,000 year cycle between glacial and interglacial periods changes to a 100,000 year cycle
• the cycle become more intense and less stable, changes are more rapid once they are triggered as larger ice sheets are much more unstable

Question 8

the last ice age

Answer 8

• 21,000YA
• sea level 120m lower, meaning USA and Asia and UK and Europe were linked
• huge extent of ice caps covering Europe and Patagonia to New Zealand

Question 9

Heinrich events

Answer 9

• in Pleistocene
• large groups of icebergs break away from Laurentide glacier in North America and float across North Atlantic, hitting Northern Europe
• colder conditions in North America and Europe
• decrease in salinity in North Atlantic meant that NADW couldn’t form, switching off the global deep ocean conveyer belt
• worldwide climatic impacts

Question 10

evidence for Heinrich events

Answer 10

• marine sediment cores in Atlantic show sediment scattered by melting icebergs
• evidence of 2-3C temperature drop in Greenland ice-core records
• gouges in French coast where icebergs have run aground

Question 11

Holocene

Answer 11

• interglacial period 10,000Ya to now
• unstable period in global climate
• global temperatures have been a few degrees higher than present
• cold arid event 4,200YA linked to collapse of numerous civilisations
• little ice age