Ice Ages

Question 1

Famous scientists that discovered the cause of ice ages

Answer 1

Louis Agassiz - discovered the boulders around the world come from ice, not water
Milutin Milankovitch - calculated how the orbit of Earth changes over time, which explains how ice age changes over time

Question 2

What are paleoclimate archives and proxies?

Answer 2

Archives
- corals, marine and lake sediments, tree rings, ice cores, speleothems

Proxies (physical and chemical properties)

• metal concentration in corals
• oxygen isotopic ratios in ice cores
• chemical changes in speleothems
• biological changes in tree rings

Question 3

When was the last glacial maximum?

Answer 3

• 21,000 years ago, ice sheets reached their maximum
• in the north, ice covered Greenland, Russia and North America
• in the south, larger ice sheet size, mountain glaciers in NZ

Question 4

How long did interglacial conditions (warm) prevail in the Pleistocene glaciation?

Answer 4

• about 10%

Question 5

What was Milankovitch’s Hypothesis about how ice age changes?

Answer 5

• varying orbital geometry influences climate by changing seasonal and latitudinal distribution of solar radiation to the Earth (insolation)
• summer insolation at the higher northern latitudes (65°N) is critical to the decay of ice sheets

Question 6

What are the 3 factors that affect insolation?

Answer 6

1. Eccentricity (Orbit)
   - Earth’s orbit is not a perfect circle, can change from time to time
   - 2 periods (100,000 yrs and 400,000 yrs)
   - by itself, not much effect on insolation. strong effect when combined with precession
2. Obliquity (Tilt)
   - changes in tilt amplify or suppress the strength of the seasons, especially in the high latitudes
   - 1 period is 41,000 years
   - responsible for most of the insolation in high latitudes
3. Precession (Wobble)
   - one period is 23,000 years, takes 11,500 years to alternative between pointing at Vega and the North Star
   - responsible for most of the insolation in the low-mid latitudes

Question 7

What is aphelion and perihelion?

What are the effects of precession on the seasons today?

Answer 7

• aphelion: furthest point from the sun
• perihelion: closest point to the sun

TODAY
In June:
- northern hemisphere (summer) is not too warm
- southern hemisphere (winter) is colder than average
In December:
- northern hemisphere (winter) is not too cold
- southern hemisphere (summer) is warmer than average

NEXT 11,5000 YEARS
In June:
- northern hemisphere (summer) is warmer than average
- southern hemisphere (winter) is not too cold
In December:
- northern hemisphere (winter) is colder than average
- southern hemisphere (summer) is not too warm

Question 8

Why is the summer insolation at the higher latitudes so important for forming glaciers?

Answer 8

• high northern latitudes has huge continents, ice sheets can build up there