L4 - Orbital Timescale Climate Variability

Question 1

What is Oxygen-18 in benthic forms used to reconstruct?

Answer 1

Ice Volume

Question 2

What is the temperature proxy used when using benthic forams?

Answer 2

Mg:CaCo3 ratios

Question 3

Which coral is used for reconstructing sea level and in what depths does it grow?

Answer 3

Acropora palmata

Question 4

How are corals dated?

Answer 4

Using U-Th dating

Question 5

What do you need to know about corals to correctly determine SL?

Answer 5

Rates of tectonic uplift

Question 6

Which sea has a different Oxygen-18 that means it can be used to determine SL?

Answer 6

The Red Sea

Question 7

What do ice sheets act as within the climate system?

Answer 7

A forcing mechanism

Question 8

What impact do ice sheets have on lower atmospheric air circulation during the glacial period?

Answer 8

They cause polar winds to be sent across the NW Atlantic

Question 9

What is the Modern Analogue Technique?

Answer 9

The expectation that similar climatic begins should foster similar assemblages of flora and fauna

Polar Assemblages – planktonic forams only
Subpolar Assemblage – more species

Question 10

Where is there evidence for cold N.Atlantic SST causing cooler, drier, duster conditions in Europe and Asia?

Answer 10

1. French Pollen Record
2. China (Glacial - loess vs. interglacial - clay rich soils)
3. Western Pacific

Question 11

Complete the Sentence:

The affects of the Glacial Maxima are…..

Answer 11

Global

Question 12

Give 3 examples of global evidence of the glacial maxima

Answer 12

1. Windblown Dust in the Arabian Sea
2. Pollen Records in NZ and S.America
3. Indication Ocean SST are cooler in the glacial maxima

Question 13

Why are G-IG variations symmetric despite out-of-phase insolation forcing?

Answer 13

G-IG CO2 variability

Question 14

Give 2 basic changes of CO2

Answer 14

1. Ocean cooling of 2 Deg C = -25-30ppm

2. Increasing salinity of 2.5% = +7ppm

Question 15

What impact does the glacial period have on the terrestrial biosphere and carbon inputs to the ocean?

Answer 15

The terrestrial biosphere decreases during the glacial and so adding 1-1.5% of carbon to the ocean would cause CO2 to rise by 40-60ppm

Question 16

What is the coral reef hypothesis?

Answer 16

That SL rise causes increased coral growth which reduces ocean alkalinity and corals used CaCO3 for their shells and so there is an increase in atmospheric CO2

Question 17

What role does Fe have on the biological pump?

Answer 17

It enhances it - this is greatest in the glacial period when there is more dust contains Fe

Question 18

What is the role of the Southern Ocean stratification?

Answer 18

During the glacial there is decreased vertical exchange which decreases CO2 outgassing and so atmosphere CO2 reduces

Question 19

What is the orbital monsoon hypothesis?

Answer 19

That strong summer radiation due to summer insolation gives strong summer monsoons and weak winter radiation gives strong winter monsoons

Question 20

Which records have shown there is a a strong precession component to the orbital monsoon hypothesis?

Answer 20

Chinese Speleothems