EAE 14 - Other climate proxies Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Dendroclimatology

What is Dendroclimatology?

A

Using tree rings to reconstruct climate

EAE 17aa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Dendroclimatology

Why is Dendroclimatology useful?

3 points.

A
  • Understand recent and ongoing changes
  • Put change into pre-industrial context
  • Help model the future

EAE 17ab

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Dendroclimatology

Why are Dendroclimatology’s benefits?

4 points.

A
  • Annual (even seasonal) resolution
  • Absolute dating to calendar year
  • Long record relative to instrumental data
  • Widespread

EAE 17ac

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Dendroclimatology

What are the approaches for dendroclimatology?

4 points.

A

Tree corer:

  • fast, portable and nondestructive tool
  • Samples living and dead trees

Full discs

  • Helpful for dead wood
  • Sampling needs licenses / approvals from authorities

EAE 17ad

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Dendroclimatology

How are vessels distributed in wood?

A

Ring porous: The diameter of the pores in early wood is muh larger than latewood

Semi ring porous: The pores are more numerous in earlywood

Diffuse porous: The size of pores and distribution is more regular

EAE 17ae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Dendroclimatology

What is Ecological Amplitude?

2 points.

A
  • A tree species will be more sensitive to changes in environmental conditions at the margins of its ecological distribution
  • Includes: Latitude, longitude, elevation, topographical position

EAE 17af

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Dendroclimatology

What are the climatic constrains to plant growth?

3 points.

A
  • Temperature
  • Radiation
  • Water

EAE 17ag

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe

Important principle in dendrochronology: Replication

3 points.

A
  • Reduce variability in measurements within a single tree and between trees
  • Maximise environmental signal and reduce error
  • Usually want >30 samples per site

The growth of each ring in each tree is influenced by its immediate surroundings (e.g. trees nearby, moisture sources, soil structure), its individual genetics/biology, the specific impacts on the tree during its life (e.g. damage/fire/insect attack/canopy openings, called “releases”), as well as the broader climate. As dendroclimatologists, we are usually interested in extracting the climate signal only.

EAE 17ah

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Dendroclimatology

What is Cross-dating?

4 points.

A

Matching ring width patterns among cores

Various sources of samples:

  • Recently alive trees
  • Trees felled for lumber (may be 100’s of years old)
  • Long dead timber
  • Burried timber (or drowned in the construction of a dam)

EAE 17ai

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Dendroclimatology

What is detrending?

A

Identifying and removing the age trend

Young trees grow faster than old trees.

EAE 17aj

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Dendroclimatology

What other factors can be examined in Dendroclimatology?

3 points.

A
  • (Quantitative) wood anatomy
  • Stable isotope composition
  • Wood density

EAE 17ak

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Dendroclimatology

What proxies do we measure in corals?

3 points.

A
  • Oxygen isotopes (δ¹⁸O)
  • Trace elements
  • Luminescence

EAE 17al

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Coral dating

What do oxygen isotopes reveal?

2 points.

A
  • Proxy for ocean temperature
  • Influenced also by precipitation

EAE 17am

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Coral dating

What do trace elements reveal?

4 points.

A
  • Geochemical proxies for Temperature/Salinity/Precipitation
  • Sr/Ca widely used as an excellent proxy for sea surface temperature (SST)
  • Mn/Ca and Ba/Ca also used occasionally as a proxy for precipitation
  • Sub-annual resolution and annual cycles in geochemical tracers if measured at high enough resolution!

EAE 17an

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Coral dating

What does luminescence reveal?

A

Proxy for precipitation/runoff/flood due to incorporation of soil-derived humic acids transported to the reef during major flood events

EAE 17ao

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Coral dating

How is luminescence investigated?

A

By scan under UV/visible light

Luminescence intensity or ratios of luminescence in colour bands

Provides very high resolution!

EAE 17ap

17
Q

What is a reconstruction?

A

Approach to and result of “piecing together” or building a picture of the past temporal and spatial characteristics of a climate variable from one or more predictors

EAE 17aq

18
Q

What can we can reconstruct?

7 points.

A
  • Past temperature
  • Precipitation
  • Vegetation
  • Streamflow
  • Sea surface temperature
  • Climate “modes”
  • Other climatic or climate-dependent conditions.

EAE 17ar

19
Q

What is the New Global Temperature Reconstruction?

4 points.

A
  • New database
  • Multiple methods
  • Same input data
  • Strong agreement between methods esp. at multidecadal frequencies

EAE 17as

20
Q

What are Diatoms?

A

Diatoms are unicellular microscopic algae (Bacillariophyta) which have been widely used to reconstruct depositional environments throughout the Quaternary and Holocene

(Vos & de Wolf, 1993; Lowe & Walker, 1997; Zong & Horton, 1999).

EAE 17at

21
Q

Why is diatom analysis useful?

2 points.

A
  • Diatom analysis facilitates the reconstruction of the water conditions in which the sediment was derived (freshwater, brackish water, marine water or a mix).
  • Such interpretations can be achieved because individual species are sensitive to ecological conditions such as salinity, trophic status and pH and can consequently only survive within certain thresholds of each environmental parameter.

EAE 17au

22
Q

How are diatoms preserved?

2 points.

A
  • Diatom preservation is good in most sediments due to the siliceous composition of the diatom frustule.
  • They are found in most water-lain deposits, but preserved in abundance in finer sediments such as silts and clays which experience much lower-energy depositional environments (and thus favour frustule accumulation with minimal fragmentation).

EAE 17av

23
Q

What assumptions are made in diatom analysis?

A

Analysis of present day species provides the means by which environmental characteristics are identified for the fossil diatom frustules within sediments.

It is assumed that diatoms employ uniformitarian principles; species present in today’s subaquatic environments require the same conditions (such as salinity, temperature and nutrient supply) as in the past.

In marine contexts, attempts to infer specific depositional environments from diatom assemblages (e.g. saltmarsh environments around/above Mean High Water, non-tidal lagoons).

EAE 17aw

24
Q

How can pollen be used as a proxy?

5 points.

A
  • Transportation takes pace through a number of mechanisms (wind, insect etc.).
  • Different plants produce differing amounts of pollen to ensure successful pollination.
  • The results of these factors mean that much more pollen is produced and released than is actively used in reproduction.
  • Much of this falls to the ground and becomes preserved within sedimentary deposits.
  • It is therefore possible to use the pollen preserved within sedimentary archives to understand the type of vegetation that existed at that location in the past.

EAE 17ax

25
Q

What are the problem with using pollen as a proxy?

3 points.

A

Concerns re is the pollen diagram a reliable, accurate and quantifiable reconstruction of the vegetation community that was present in the past?

Issues such as:

  • variations in pollen production
  • distribution mechanisms
  • post depositional preservation

must be taken into account

Consequently such palaeoenvironmental / palaeoecological interpretations must be undertaken with caution.

EAE 17ay

26
Q

What are plankton?

A

Diatoms that float through the upper part of the water column

Term comes from Greek work planktos = wanderer, drifter

EAE 17az

27
Q

What are benthos?

A

Diatoms that live on or in substrates.

Benthos are classified into different types according to the substrate to which they are attached.

Can live to depths limited primarily by light penetration.

EAE 17ba

28
Q

Where are diatom particularly important.

A

Especially important in oceans where they are estimated to contribute up to 45% of the total oceanic primary production.

EAE 17bb

29
Q

What are the 2 main types of diatoms?

A

CENTRIC - those that are circular with essentially radial symmetry PENNATE - those that are more elongate, with primarily bilateral symmetry.

EAE 17bc

30
Q

How are Diatoms contained?

3 points.

A

Diatom cells are contained within a unique silicate cell wall (SiO₄) comprised of two separate valves.

The cell wall is distinctive

  • provides rigidity
  • provides taxonomic characters
  • allows preservation in sediments

EAE 17bd

31
Q

Why are lakes important in studying climate change?

A

Lakes are important sentinels of climate change

pH is an indicator of humidity

Runoff and weathering

Atmospheric deposition

Organic acids by vegetation

EAE 17be

32
Q

What are ‘Transfer functions’?

A

aka inference models

Quantitative Inference Model based on modern material

Widely available to infer past environmental conditions from biostratigraphic indicators from sediments

Collected at a range of locations with different conditions

CORRELATION! Not experiment based

EAE 17bf

33
Q

How is pollen represented in ‘diagrams’ vs Vegetation?

5 points.

A
  • Both production & dispersal of polen is very variable
  • Site representation depens on size & nature of sampling locality
  • The importance of genera on a ‘diagram’ is complex & difficult to quantify
  • Many local factors are relevant
  • Some generalizations are possible.

EAE 17bg

34
Q

How is radiocarbon dating useful?

A
  • Radiocarbon is widely used in palaeoecological records.
  • Can date material back to about 50,000 years ago
  • ¹⁴C formed by bombardment of ¹⁴N by cosmic rays and then like stable ¹²C forms CO₂ that is incorporated into living organisms.
  • After death ¹⁴C decays to ¹⁴N and ratio of ¹²C to ¹⁴C determines the age of the fossil material assuming a s a balance between ¹⁴C production and decay.

EAE 17bh