Lecture 12:Turmoil in the Greenhouse Flashcards
What is the Cenozoic era most commonly recognised for?
When aspects of life as they are known today started to emerge
What was the name of the extinction event at the end of the cretaceous period in the Mesozoic? Breakdown the abbreviation.
KPG/End Cretaceous extinction event. KPG refers to K (Cretaceous) and PG (Paleogene)
What was the major warming event that took place during the Cenozoic?
Palaeocene-Eocene Thermal Maximum (PETM Maximum)
Describe the correlation of carbon dioxide and atmospheric temperature up to the Miocene epoch?
there is some correlation between them, however this starts to disappear as the Miocene approaches. the co2 stabilises while temperature shows an increase
What do temperature records of the cenozoic era come from?
Foraminifera Shells
Explain how foraminifera shells are a proxy for temperature
Their shells are made up of calcium carbonates that include oxygen. The isotopic composition of the oxygen molecules is dependant on temperature. When the climate is colder, the shells are made up more of 18O whereas when the climate is warmer the shells feature an increase in the concentration of 16O.
Why is 18O more present in foraminifera shells during colder periods?
18O is harder to evaporate because it is denser, this means during colder periods when there is less thermal energy to evaporate the oxygen molecules, they are unable to be evaporated and so remain in the ocean where they will be the last isotope left to form the foraminifera shells that lie at the bottom of the ocean
Aside from foraminifera shells, how does the oxygen isotopic signature convey temperature?
During the colder periods, 16O is the only oxygen isotope that can be evaporated and thus eventually precipitated. When it is precipitated, and because it is cold, it forms ice and so in colder periods the oxygen isotopic signature of ice/glaciers is more concentrated with 16O
What makes the analysis of foraminifera shell formation more complex?
During colder periods the foraminifera naturally prefer to use 16O even though there is less of it in the oceans as it has been precipitated on land. So you have two conflicting source of foraminifera formation.
What do foraminifera shells also tell us about the earth system?
Changes in the biosphere and the carbon cycle
How do calcium carbonate shells (foraminifera shells) provide information about the carbon cycle?
They use carbon in their shell formation, as well as the oxygen, and the isotope which is preferred is 12C. This means if the shells are made up more of 12C then it suggests that there is an abundant supply. The supply of this isotope increases with temperature so when there is more of it present in the record we can say that it was a warmer period (e.g. PETM)
What event demonstrated how 12C increased with temperature?
Paleocene-Eocene Thermal Maximum (PETM)
What transition occurred in the animal ecology following the KPG extinction?
During the cretaceous, the dinosaurs were present and when they became extinct, the environmental niches left behind were replaced with mammals
What was the rate of increase in mammal mass following the KPG extinction?
They grew at a linear rate from 150g to 1kg on average across 1myr
Who claimed that the increase in mammal size following the KPG extinction was a result of increased oxygen?
Falkowski et al. (2005)
Why was Falkowski et al.s theory proved wrong?
Oxygen levels were already quite high and were higher than today - for the transition from dinosaurs to mammals Tim lenton believes that there must have been a reduction in oxygen levels
