Climate reconstructions through terrestrial archives (and corals)

Question 1

What do we need to consider when looking at different climate archives

Answer 1

Consider:
How formed
Ideal records: continuous record with no breaks
Resolution and ages

Question 2

What are the other important aspects of climate archives to consider?

Answer 2

Mode of formation (biological growth, or accumulated through transport via water (rivers, ocean currents), wind and ice
Ideal records continuous record with no breaks
Resolution and ages

Question 3

What are the different climate archives?

Answer 3

Instrumental
Historical
Tree rings
Ice cores
Lake sediments
Coral reefs
Speleothems
Ocean sediments
Continental coastal

Question 4

What are the characteristics of tree ring archives?

Answer 4

Deposition
Annual
Individuals up to 500 years

Question 5

When do tree rings tend to be more visible?

Answer 5

Rings tend to be more visible in temperate zones with seasonality

Spring/summer- Rapid growth (wood is less dense): early wood

Late summer/autumn: slow growth (wood is denser): late wood

Question 6

What do thinner and thicker tree rings mean?

Answer 6

Thinner annual rings reflect years of lower precipitation
Thicker rings reflect years of higher precipitation

Question 7

How do trees respond to their environment?

Answer 7

In years with lots of precipitation, they grow faster than in years in less precipitation, they grow faster than in years with less precipitation

Question 8

What are some things to consider with tree rings?

Answer 8

Rings may be more visible in temperate zones with seasonality
Spring/summer part: rapid growth (wood is less dense); early wood
Late summer/autumn part: grows slower and is denser: late wood

Question 9

What can mid summer droughts result in?

Answer 9

Could result in several rings being formed in a given year
Some tree species may miss rings

Question 10

What is necessary to know about using tree rings as a climate archive?

Answer 10

Sample trees (coring), fix and polish
Scan samples with a scanner
Measure tree ring with generally with software with 0.01mm precision
Cross date, check for missing rings

Question 11

How do tree rings compare to other archives?

Answer 11

Information provided by tree rings in comparison with other archives?
- Relatively reliable proxy data
- High resolution (annual)
- Relatively short intervals 400 to 1000 years
- Cross matched records can cover - 10,000 years

Question 12

Where are there fully anchored and cross-matched chronologies for?

Answer 12

Central Europe: last 12,460 years (oak and pine)
Ireland: last 7429 years (oak)
England: last 6939 years (oak)
Southwest US: last 8500 years (bristlepine)

Question 13

What is radiocarbon dating?

Answer 13

Not an exact calendar age
Matched to calibration curves, developed from tree rings (previously dated by dendrochronology)

Question 14

What information can be gathered from vegetation/biome reconstructions?

Answer 14

Carbon stored in different biomes
Responses to changing climate
Testing models

Question 15

How are vegetation biome reconstructions sampled?

Answer 15

• Sampling
• Sampling preparation
• Identification pollen

Question 16

What are the steps involved in biomization?

Answer 16

1. Pollen taxa are assigned to one or more plant functional types
2. Plant functional types are assigned to biomes according to their bioclimatic range
3. Construction of biome-by-taxon matric
4. Calculation of affinity scores for all pollen samples (score of each biome is the sum of the square roots of the percentage (above 0.5%) of each taxon present in the biome

Question 17

What is biomization?

Answer 17

Biomization is quantitative procedure used to reconstruct past biomes by analysing the pollen record and assigning plant functional types (PFTs) to different plant taxa

Question 18

What is the BIOME 4 model?

Answer 18

Biogeochemistry-biogeograpahy model that predicts global vegetation distribution based on:
- Monthly mean temp
- Precipitation
- Sunshine fraction
- Soil texture
- Depth
- Atmospheric Co2

Question 19

What are the differences between the FAMOUS and HadCM3 models?

Answer 19

FAMOUS model- less expensive to run
HadCM3 model- more expensive to run

Question 20

What are the inputs and outputs in lake level reconstructions?

Answer 20

Input (precipitation + runoff + groundwater inflow)

Output (evaporation + groundwater outflow)

Question 21

What are the other influences on lake level fluctuations?

Answer 21

Soil type, vegetation, water depth, salinity, basin morphology, substrate geology, tectonics etc

Question 22

Where are lake reconstructions best carried out?

Answer 22

Best carried out in places where lake water level and precipitation and/or evaporation are closely related

Question 23

What are the ways to reconstruct lake levels?

Answer 23

1. Geomorphological evidence
2. Palynological evidence
3. Sedimentological evidence

Question 24

What are sediment shoreline deposits?

Answer 24

Grainsize decrease from the shoreline to the lake

Question 25

How do speleotems form?

Answer 25

Form through precipitation 100-1000 years

Question 26

What are the stages of speleothems?

Answer 26

Mineral deposition stage Limestone dissolution stage Water adulation stage

Question 27

What are speleothems?

Answer 27

Cave deposit Important climate archives, made out of calcium carbonate - Stalactite (accumulates from drip) - Stalagmite grows upwards - Pillar/column

Question 28

Where do speleothems occur?

Answer 28

Areas with carbonate rocks (limestone calcium carbonate or dolomite) Karst regions

Question 29

What can speleothems form?

Answer 29

Growth rings Rate depends on: - Amount of precipitation - Acidity and mineral content percolating water - Temperature and humidity in case

Question 30

What happens under perfect cave conditions?

Answer 30

Under perfect cave conditions, speleothem stable isotopes can preserve changes in the stable isotopic composition of the drip water

Question 31

How can the stable isotopes of speleothems be measured?

Answer 31

Using mass-spectrometers, scientists can measure the stable isotopes of the carbon and oxygen in the calcium carbonate

Question 32

What are speleothem deposits made up of?

Answer 32

Calcium carbonate

Question 33

What represents the oxygen isotopes?

Answer 33

Precipitated calcium carbonate represents the oxygen isotopes of the oxygen in the drip water

Question 34

How are isotopes different?

Answer 34

Number of neutrons

Question 35

What is Rayleigh fractionation?

Answer 35

the process where water isotopes in an air mass get progressively more depleted (more negative) through the process of heavier isotope being preferentially removed over time

Question 36

What are the causes for changes in speleothem oxygen isotopes?

Answer 36

1. a change in the source of the moisture for the precipitation of the speleothem 2. a change in its transport path 3. change in season of precipitation 4. climate change 5. cave temperature 6. evaporation 7. Mixing with other water (groundwater/river water)

Question 37

How are coral climate records characterised?

Answer 37

- biological - annual - 10-100s years

Question 38

What are corals?

Answer 38

Corals are marine animals, specifically cnidarians that form colonies of tiny individuals called polyps

Question 39

What are the four types of coral reefs?

Answer 39

Fringing reef Barrier reef Atoll reef Patch reef

Question 40

What can corals be important for?

Answer 40

Important archives Can inform about past tropical climate Able to provide high resolution (annual to sub-annual) records Well dated- annual density banding U/Th or 230^Th dating

Question 41

What is U/Th or 230^Th dating?

Answer 41

A radiometric dating method that measures the decay of uranium (²³⁸U) to thorium (²³⁰Th) to date calcium carbonate materials like speleothems, useful for ages up to ~500,000 years

Question 42

How can coral climate archives be reconstructed?

Answer 42

Age of seawater Temperature Hydrology Sea level

Question 43

Under equilibrium conditions rate of oxygen isotope would be a function of?

Answer 43

rate of oxygen isotope sea water Sea water temperature

Question 44

What are coral proxies?

Answer 44

Coral proxies are chemical signatures (like rate of oxygen isotopes and Sr/Ca ratios) in coral skeletons used to reconstruct past SST and salinity

Question 45

What can corals be used as indicators of?

Answer 45

Indicators of sea-level changes