Proxies 1

Question 1

What is a Proxy?

Answer 1

A stand-in variable (for desired but unobservable variables ex. temperatures, salinity, nutrient content, oxygen content, CO2 concentrations, wind speed, productivity).

Question 2

What are some target ocean-climate variables for palaeoceanographic proxies?

Answer 2

Hydrological cycle, water column thermal, nutrient structure, interaction with the atmosphere, biology and evolution.

Question 3

What are the three ocean climate proxies?

Answer 3

Micropaleontological/paleontological, geochemical proxies, lithological…

Question 4

How do Palentological/micropaleontological proxies link to climate/envo conditions?

Answer 4

Species composition, shell preservation and evolutionary response

Question 5

What is required to be able to use paleontological/micropaleontological proxies?

Answer 5

An understanding of the (environmental) TOLERANCE of species and species COMBINATIONS.

Question 6

What is assumed when using paleontological proxies?

Answer 6

That preference remains unchanged over the application period

Question 7

What are paleontological proxies used for and how are they linked?

Answer 7

Sea surface temperature, ocean stratification, sea-ice extent, sea level, upwelling (seasonality), water depth, dissolved oxygen, nutrient availability

Question 8

How is palaeontology different to biostratigraphy and geochemical methods?

Answer 8

Reflection….

Question 9

An example of how to use the microfossils…

Answer 9

First link how forams live today - modern patterns of fossil assemblage - and what climate zones they can be found today and then study the microfossil further down the core…

Question 10

What are the climate zones from polar to tropical…?

Answer 10

Polar, subpolar, cool subtropical, subtropical, tropical. Varying from the average temperature of 0 to 30 degrees celsius.

Question 11

What are fully quantitative assemblage based methods? (SST)

Answer 11

Statistical analysis of the relative abundance of plankton species in sea floor sediment samples linked to sea surface temperatures.

Question 12

What are transfer functions?

Answer 12

Equations used to estimate past SST (sea surface temperatures) but also other parameters by using microfossil relative abundance data.

Question 13

What time span is palaeontology in deep-sea sediments good for?

Answer 13

Global climate history over PAST 1 ma years - important before geochemical methods…

Question 14

Give an example of a paleontological proxy and reflect around it…

Answer 14

MODERN global crocodilian distribution has a critical thermal minimum - coldest month mean temp of 5 degrees celsius

Question 15

What are some limitations of micropaleontological methods?

Answer 15

Assumptions that species had same ecology and biology but could have responded to en environmental change, core tops for calibration may not be representative of the overlying column as for the ground-truthing may have been transported or perhaps fragile species selectively dissolved… For early Cenozoic and Cretaceous interpretations to be made about ecology and biology due to extinction…

Question 16

What is measured when using geochemical proxies?

Answer 16

INORGANIC chemistry shells, teeth, minerals, diagenetic mineral coatings - stable isotopes, radiogenic isotopes, trace metal ratios, metal/element concentration and ratios… ORGANIC chemistry (organic remains, plankton bodies) - organic carbon (13C), organic biomarkers (TEX86, plant wax n-alkanes…)

Question 17

Which oxygen isotope is the most abundant?

Answer 17

16O (99.757%)

Question 18

Write down the equation for oxygen isotopes….

Answer 18

See answer in file….

Question 19

What factors are affecting 18O of foraminiferal shells and why/how????

Answer 19

Continental glaciation, evaporation and precipitation affecting the 18O in seawater… The seawater conditions are affected by seasonality, depth habitat and ontogenetic migration (different life stages migrate into different habitats) which affect the temperature affect the shell…

Question 20

Explain the hydrological cycle fractionation and how it affects the ice storage on land effect?

Answer 20

Processes: Evaporation and condensation influence the ratio of heavy oxygen 18O to light 16O in OCEANS.

Question 21

What can 18O be measured in? Give an example…

Answer 21

The foraminifera 18O paleothermometer can be measured in foram shells from a core top sample below the CTD

Question 22

In isotopically identical waters does calcite shells precipitate in cold water with high or low 18O? Why?

Answer 22

High 18O, since there is more 18O than 16O left behind since then more of the 16O then have been evaporated, condensed and precipitated/transported to form ice sheet which means cooling of Earth and therefore cooler water temperatures…

Question 23

In isotopically identical waters does calcite shells precipitate in warm water with high or low 18O?

Answer 23

Low 18O

Question 24

What happened 34 Ma ago?

Answer 24

Earth went from Ice-free (greenhouse conditions) to continental ice growth, south Antarctica probably was glaciated for the first time…

Question 25

What problem do you run into when using 18O paleothermometry? Look further into…

Answer 25

You need to know 18O in the seawater to be able to calculate seawater temperature from calcite 18… to overcome the problem other independent temperature proxies are needed but there are few options… Foraminifera shell Mg/Ca (planktonic and benthic) which are temperature-dependent (higher temp easier to incop. Mg into CaCO3 crystal lattice) OR Organic biomarkers (TEX86, UK37 from algae organic molecules, but only gives sea surface temperatures).

Question 26

What is ocean climate variables that are detectible from ocean sediments?

Answer 26

Ex 1. Ocean-climate variable: sea surface temperature – linked to – Climate system component: regional surface ocean temperature/ocean heat transport/latitudinal thermal gradients.
Ex 2. Ocean-climate variable: Atmospheric CO2 – linked to – Climate system component: Greenhouse climate forcing: carbon system.
Ex 3. Ocean-climate variable: Ocean acidity – linked to – Climate system component: ocean carbon storage; carbon system.