Chapter 6 - Greenhouse Climate

Question 1

Why is the south pole simulated to have such a high temperature during the cretaceous?

Answer 1

South pole 40 degrees higher in temperature due to the absence of the Antarctic ice sheet in the model. Today, the sheet reaches heights of 3-4km where temps are much colder than at SL due to lapse rate. This is then represented as the surface

Question 2

Problems with the cretaceous climate model?

Answer 2

Insufficient data about ocean circulation and models simulated continental freezing

Question 3

Problems with the geological data?

Answer 3

Foraminifera may have recrystallised while sitting at colder temperatures on seafloor. best samples indicate 5 degrees warmer

Question 4

Is icehouse or greenhouse more sensitive to co2 changes?

Answer 4

Icehouse is more sensitive. Even small decreases in co2 can greatly increase the positive feedback.
During greenhouse conditions there is little ice to produce positive feedback and co2 saturation plays a role

Question 5

Why were sea levels higher 100 mya?

Answer 5

1. Tectonically driven factors which altered the volume of ocean basins and their capacity to hold water
   
   2. Changes in water volume caused by climate
   3. High erosion of flat continents when SL rises and subsequent sediment deposition on the sea floor

Question 6

Hypothesis that SL is a long-term control of glaciation is NOT supported. Why?

Answer 6

Because glaciation is the cause of SL change, not the result of it.
Main control of glaciation is summer-season ablation

Question 7

What is the evidence for the asteroid impact 65 mya?

Answer 7

1. Iridium layer worldwide - mixed into sediment by burrowers
   
   2. Shocked quartz (shock laellae)

Question 8

Problems with determining climatic effects of Chicxulub impact?

Answer 8

The rapid changes are blurred by burrowing animals and bottom currents. Iridium layer can only be seen due to stark contrast, but other indicators are smeared.
Climate warming was already occurring - vegetation suggests a long term warming but this cannot be correlated to the impact. Initial co2 increase unlikely to have persisted

Question 9

Potential causes of the PETM?

Answer 9

Volcanic eruptions on the seafloor, comet impact, peat burning or tectonic instability

Question 10

What evidence shows the world was warmer 100 mya than today?

Answer 10

Negative oxygen isotope values (requires co2 release), temperature sensitive vegetation at high latitudes, carbonate ratio isotope values

Question 11

Which regions of continents were flooded during high SL 100 mya?

Answer 11

Continental margins with a low gradient.