Water

Question 1

Last glacial period

Answer 1

20,000 years ago
Stockholm covered in 2km of ice
During glacial maximum, sea level dropped by c. 120m

Question 2

Foraminifera

Answer 2

Marine microorganisms, typically <1mm
Used as paleoenvironment indicators
One species coils to the right in ice-free conditions while coiling to the left when sea-ice is common
CaCO[3] in their shells contains oxygen or both isotopes O18 and O16. O16 is light and evaporates more readily and is also 500 times more prevalent.
Sea-ice grows from precipitation from above. Water vapour is rich in O16, so the ice traps it and becomes rich in O16. Thus, the sea-water becomes enriched in O18.
If precipitation occurs in an inter-glacial period, the O16 and O18 levels remain constant.
The relative proportion of O18 to O16 in foraminifera shells shows how ice and sea-levels changed in the past.
BUT, when it’s cold, foraminifera preferentially absorb more O18. This complicates the issue

Question 3

Frequency of climate variation and what it’s dependent on

Answer 3

Eccentricity: Earth’s elliptical orbit changes shape by up 6% over a 100,000 year period
Tilt: The tilt of the Earth’s rotation axis relative to the orbital plane varies by within a c. 2.6 degrees range
Precession: The Earth’s axis wobbles like a top with 2 periods. 19,000 years and 23,000 years

These 3 factors affect the intensity of radiation incident from the Sun on Earth. The three variations interact to sometimes create anomalously hot or cold seasons in temperate latitudes where ice sheets can form.

Relative importance of each variation is not constant.

Once change occurs, there’s rapid change due to positive feedback. E.g. with lots of ice, radiation is reflected. But once it melts, more radiation is absorbed by sea-water. As temperatures rise, more ice melts.

Question 4

Effect of volcanic eruptions on climate

Answer 4

Cause short-term effects

E.g. Mt Pinatubo (Phillipines, 1990) reduced the mean surface temperature by 0.5 degrees celsius for 2 years

Question 5

Ice cores

Answer 5

Calcium:
Concentrations how much wind-blown dust there was. This is higher when the edges of the ice sheet are too cold for vegetation.

O18 vs. O16
When it’s cold, there’s less H20 molecules with O18 in the ice as these have more mass and need more energy to evaporate.

Methane and CO[2] can be extracted directly from bubbles in the ice