EAE 14 - Other climate proxies

Question 1

Dendroclimatology

What is Dendroclimatology?

Answer 1

Using tree rings to reconstruct climate

_{EAE 17aa}

Question 2

Dendroclimatology

Why is Dendroclimatology useful?

3 points.

Answer 2

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

_{EAE 17ab}

Question 3

Dendroclimatology

Why are Dendroclimatology’s benefits?

4 points.

Answer 3

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

_{EAE 17ac}

Question 4

Dendroclimatology

What are the approaches for dendroclimatology?

4 points.

Answer 4

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}

Question 5

Dendroclimatology

How are vessels distributed in wood?

Answer 5

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}

Question 6

Dendroclimatology

What is Ecological Amplitude?

2 points.

Answer 6

• 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}

Question 7

Dendroclimatology

What are the climatic constrains to plant growth?

3 points.

Answer 7

• Temperature
• Radiation
• Water

_{EAE 17ag}

Question 8

Describe

Important principle in dendrochronology: Replication

3 points.

Answer 8

• 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}

Question 9

Dendroclimatology

What is Cross-dating?

4 points.

Answer 9

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}

Question 10

Dendroclimatology

What is detrending?

Answer 10

Identifying and removing the age trend

Young trees grow faster than old trees.

_{EAE 17aj}

Question 11

Dendroclimatology

What other factors can be examined in Dendroclimatology?

3 points.

Answer 11

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

_{EAE 17ak}

Question 12

Dendroclimatology

What proxies do we measure in corals?

3 points.

Answer 12

• Oxygen isotopes (δ¹⁸O)
• Trace elements
• Luminescence

_{EAE 17al}

Question 13

Coral dating

What do oxygen isotopes reveal?

2 points.

Answer 13

• Proxy for ocean temperature
• Influenced also by precipitation

_{EAE 17am}

Question 14

Coral dating

What do trace elements reveal?

4 points.

Answer 14

• 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}

Question 15

Coral dating

What does luminescence reveal?

Answer 15

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

_{EAE 17ao}

Question 16

Coral dating

How is luminescence investigated?

Answer 16

By scan under UV/visible light

Luminescence intensity or ratios of luminescence in colour bands

Provides very high resolution!

_{EAE 17ap}

Question 17

What is a reconstruction?

Answer 17

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}

Question 18

What can we can reconstruct?

7 points.

Answer 18

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

_{EAE 17ar}

Question 19

What is the New Global Temperature Reconstruction?

4 points.

Answer 19

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

_{EAE 17as}

Question 20

What are Diatoms?

Answer 20

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}

Question 21

Why is diatom analysis useful?

2 points.

Answer 21

• 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}

Question 22

How are diatoms preserved?

2 points.

Answer 22

• 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}

Question 23

What assumptions are made in diatom analysis?

Answer 23

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}

Question 24

How can pollen be used as a proxy?

5 points.

Answer 24

• 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}

Question 25

What are the problem with using pollen as a proxy?

3 points.

Answer 25

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}

Question 26

What are plankton?

Answer 26

Diatoms that float through the upper part of the water column

Term comes from Greek work planktos = wanderer, drifter

_{EAE 17az}

Question 27

What are benthos?

Answer 27

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}

Question 28

Where are diatom particularly important.

Answer 28

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

_{EAE 17bb}

Question 29

What are the 2 main types of diatoms?

Answer 29

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

_{EAE 17bc}

Question 30

How are Diatoms contained?

3 points.

Answer 30

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}

Question 31

Why are lakes important in studying climate change?

Answer 31

Lakes are important sentinels of climate change

pH is an indicator of humidity

Runoff and weathering

Atmospheric deposition

Organic acids by vegetation

_{EAE 17be}

Question 32

What are ‘Transfer functions’?

Answer 32

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}

Question 33

How is pollen represented in ‘diagrams’ vs Vegetation?

5 points.

Answer 33

• 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}

Question 34

How is radiocarbon dating useful?

Answer 34

• 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}