Week 2 - Intro To Environmental Change

Question 1

Why study past climate change?

Answer 1

Understanding the past helps us understand how the climate works - climate models, computer programs can predict how it’s going to change in the future

Question 2

What are Direct Societal Benefits and Academic Benefits of studying past climate change?

Answer 2

Direct - understanding the climate will help us predict future climate change

Academic - how climate influences, such as human evolution and civilisations collapses

Question 3

Name an example of Analogues for the future in terms of studying past climates.

Answer 3

How high did temperatures reach in the past the last time CO2 levels were this high?

Question 4

How do we benchmark climate models?

Answer 4

Run climate models backwards to see if they accurately predict past climate change (and how that compares to our palaeolimate reconstructions)

Question 5

Why do grain harvest records infer climate?

Answer 5

A certain type of climate gets more grain in a year

Question 6

What are proxies?

Answer 6

Physical, chemical or biological records that respond to changes in temperature or precipitation- in order to ‘reconstruct’ past climate change

Question 7

What is an archive and name an example.

Answer 7

Something that accumulates material over time

Sediments at the bottom of the lake, accumulation of sediment

Tree rings

Ice cores

Question 8

In a tree, what is the archive and what is the proxy?

Answer 8

The tree is the archive and the ring is the proxy (how wide it is could tell us about the climate at the time)

Question 9

Name 5 examples of archives (geological and biological material)

Answer 9

Ocean sediments

Ice cores

Lake sediments

Bog sediments

Trees

Question 10

Name 4 examples of proxies

Answer 10

Stable isotopes (18O, 13C)

Pollen

Diatom

Tree ring width

Question 11

What is paleolimnology?

Answer 11

The study of lake sediments

Question 12

How can a closed lake (one that has no flow of water) help us reconstruct past environmental change?

Answer 12

The lake level goes up if it gets ‘wetter’ (less evaporation and/or more precipitation) and goes down if it gets ‘drier’ (more evaporation and/or less precipitation).

Question 13

In lake sediments there is a light layer and dark layer forming every year. What are they?

Answer 13

Light layer is calcium carbonate

Dark layer is algae

Question 14

Though they have the same number of protons, what does Oxygen-18 have that Oxygen-16 does not have?

Answer 14

2 more neutrons

Question 15

In a lake, what does a change in the ratio of O18 and O16 indicate?

Answer 15

Changes in lake level - caused by how wet or dry the climate is

Question 16

What are Peatlands?

Answer 16

A mixture of more or less decomposed plant (humus) material

Accumulates in a water saturated environment

Absence of oxygen (anaerobic)

Question 17

Why does material not completely decompose in peatlands?

Answer 17

Because of anaerobic conditions as a result of no oxygen

Question 18

What are the two types of peatlands?

Answer 18

Ombrotrophic peatlands (bogs)

Minerotrophic peatlands (fens)

Question 19

What are ombrotrophic peatlands?

Answer 19

Receive water solely/mostly from mineral-poor precipitation falling onto their surface

Question 20

Minerotrophic peatlands (fens)

Answer 20

Influenced by mineral-rich groundwater from outside their own limits. Can turn into bogs

Question 21

What can ombrotrophic peatlands tell us about past environmental changes?

Answer 21

As they get most of their moisture from precipitation, any change in the hydrology of the bog (how much water there is) can tell us about precipitation and temperature

Question 22

What is Troels-Smith classification when analysing peat cores?

Answer 22

Visually identify stratigraphic units/layers (dark, lighter)

Mark the boundaries on the section/core

Record depth and nature of upper boundaries (sharp or diffuse)

Describe the physical components of each peat unit

Question 23

What are the 4 different peat components?

Answer 23

Turfa herbacea (stringy)

Turfa bryophytica (spongy)

Turfa lignosa (woody remains)

Substantia humosa (highly decomposed)

Question 24

What are the 3 components of Munsell Colour?

Answer 24

Munsell Hue (red, green, blue)

Munsell Value (light, dark)

Munsell Chroma (bright, vibrant)

Question 25

What proxies can be found in peatlands?

Answer 25

Plant macrofossils
Plant microfossils
Charcoal
Testate amoebae

Humification
Inorganic elemental chemistry
Isotopes - oxygen, hydrogen, carbon
Organic geochemistry

Question 26

What are plant macrofossils and plant microfossils?

Answer 26

Macro - vegetative parts, seeds, fruits

Micro - pollen, spores

Question 27

What is Humification?

Answer 27

A process of formation of humic substances (organic matter that has reached maturity) decomposed from plant remains

Decomposition of organic material in soils & peats

Question 28

What can Sphagnum (moss) tell us about past climate conditions?

Answer 28

Some species prefer wetter conditions and other species prefer dry conditions

Question 29

What are the 2 layers of peat bogs?

Answer 29

Upper acrotelm layer

Lower catotelm layer

Question 30

Which peat layer is below the water table (waterlogged)?

Answer 30

Catotelm layer

Question 31

When is a peat bog considered flooded?

Answer 31

When it rises above the acrotelm layer

Question 32

How does the water table influence decomposition rate in bogs?

Answer 32

Sediment in the acrotelm layer is exposed to oxygen in the air, aiding decomposition

Sediment in the catotelm layer is saturated in water, preventing peat from breaking down further

Question 33

What can higher water tables in peat bogs tell us about past climate?

Answer 33

Higher water tables are caused by wetter and or cooler (less evaporation) climatic conditions, resulting in less decomposed peats

Question 34

What can lower water tables tell us about past climatic conditions?

Answer 34

That the climate was warmer and/or drier, causing the peat to break down more as it sits in the acrotelm for longer

Question 35

As peat breaks down, what acids are produced?

Answer 35

Humic (dark brown)

Question 36

The more decomposition there is, the more ____ ____ will be produced

Answer 36

Humic acids

Question 37

What can a spectrophotometer tell us about peat samples?

Answer 37

It measures changes in colour over time, the darker the material is, the more humic acids there are (more decomposition), the less light will pass through.