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ESSHP: Section 2 > Lecture 15: Palaeoenvironmental Reconstruction > Flashcards

Lecture 15: Palaeoenvironmental Reconstruction Flashcards

1
Q

What happened as a result of WW2 that benefited science exploration?

A

Developments in technology and data collection allowed for the expansion of oceanography

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2
Q

What did the expansion of oceanography lead to the discovery of?

A

In 1947 seismologists embarked on an adventure in which they found ocean cores at margins.

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3
Q

What happened to the ocean cores that were collected in 1947 and when? what was their significance?

A

they were assessed for their magnetic patterns during the 1950s and 1960s. They would then form part of the revolutionary plate tectonic theory

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4
Q

What did the revolutionary nature of the ocean cores that were collected in 1947 serve to do?

A

Because they were so revolutionary, they provoked large amounts of funding in to research

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5
Q

What projects were created following the massive imbursement of funding during the mid 20th century?

A

1964: US-based deep sea drilling project
1968: Glomar Challenger built (ocean-drilling vessel)

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6
Q

What did John Imbrie produce in the 1970s?

A

Model demonstrating the link between insolation changes driven by Milankovitch cycles and global ice volume

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7
Q

How was Imbrie’s model created?

A

assessing the chemical composition of oxygen isotopes that made up foraminifera shells in ocean cores.

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8
Q

Why did Imbrie look at the chemical composition of oxygen isotopes in foraminifera shells?

A

Because they reflected the chemical composition of ocean water which convey ice state.

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9
Q

How good were the models that Imbrie produced?

A

Very good - they explained 95% of the variance in oxygen isotopes

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10
Q

When was Greenland actually recognised?

A

end of 19th century

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11
Q

When did the proper discovery of Antarctica happen?

A

1820 - Russian, American and Englishmen all claimed to have found the continental ice shelf it had.

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12
Q

When was the SIRE project coordinated and what was it?

A

1950s - drilling programme in Antarctica, Greenland and Alaska

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13
Q

What is an unexpected place that ice core records were found?

A

Tropics

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14
Q

How thick is the Antarctic ice sheet and what period does it cover?

A

4.5km thick.

Covers the snowfall record throughout the quaternary

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15
Q

How thick is the Greenland ice sheet and what period does it cover?

A

2.4km thick

Not as long as the Antarctica at all

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16
Q

What are the oldest cores found in Antarctica and Arctic?

A

Antarctica: 800kya
Arctic: 130kya

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17
Q

What core was found in 2017 but what is a problem with it?

A

Extended back 2.7mya but has a fragmented record

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18
Q

What is the diameter and length of typical ice cores?

A

10cm diameter

3km length

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19
Q

What do ice cores records contain?

A

high-resolution annual snow bands over time that contain bubble with air and dust.

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20
Q

What is important about ice core records for a global understanding?

A

there is data available for both hemispheres

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21
Q

What other proxy confirms the validity and strength of ice cores?

A

There is correlation with marine records that also contain evidence of global ice volume

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22
Q

What climate theory is strongly confirmed by the correlation between ice core records and marine sediment records?

A

It supported the theory proposed by Louis Agassiz that milankovitch cycles correlated with glaciation period.

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23
Q

Why do we need more information about past climates other than just glacial and interglacial cycles?

A

Because the earth system is much more complex than this

24
Q

What are instrumental climate records?

A

Records that come from our actual measurement at the time.

25
Q

When do most instrumental climate records stretch back to what ways were they collected?

A

100-150 years

collected by remote sensing and meteorology

26
Q

What are historical records?

A

Weather observations, ship logs, books and stories

27
Q

What is the oldest instrumental record but what is the problem with it

A

Central England Temperature Record (1659-1722). From 1722 they started to record temperature indoors

28
Q

What is the most common method for gaining long-term perspectives?

A

Climate proxy techniques

29
Q

What are 5 climate proxy techniques?

A

Tree rings, ice cores, lake sediments, coral reefs, ocean sediments, continental coastal sediments

30
Q

What is one climatic parameter which is still not known much about that is very important?

A

cloud cover

31
Q

What determines which proxy technique is chosen to assess climate of the past?

A

The question to be answered - some proxies are records of certain environmental parameters while others are not

32
Q

What are the two types of isotope?

A

Radioactive: decay over time
Stable: do not decay and are present in earth system in different quantities

33
Q

What is the delta notation used for?

A

To indicate ratio of one isotope to another (typically the most common)

34
Q

How are measurements of isotopes taken?

A

Using Isotope-Ratio Mass Spectrometry (IRMS)

35
Q

How rare is the 18O isotope?

A

It only occurs once in every 500 atoms of oxygen

36
Q

What word is used to describe when there is a small or negative amount of 18O in the atmosphere?

A

depleted

37
Q

Why is there more 18O in ice and the atmosphere during warmer periods of earth history?

A

Because during that time, there is more energy to evaporate 18O from the oceans compared to when there is very little available and thus during colder periods there is less 18O. this means during warmer periods it is more easily precipitated to form ice

38
Q

Why is there less 18O in ice and the atmosphere during colder periods of earth history?

A

because there is less energy available to evaporate it and then be precipitated on the land (ice) to form ice

39
Q

What happens to the 18O concentration in foraminifera shells during warmer periods?

A

there is a lower concentration of 18O because it has all managed to be evaporated from the oceans due to the warmer temperatures and thus more abundant energy

40
Q

What are 4 bodies that oxygen isotopes are analysed in?

A

Speleothems
Lake Cores
Peat Cores
Teeth and Bone

41
Q

Why are biological proxies good for determining past climate?

A

Because they are sensitive to environmental indicators and preserve well in the sedimentary sequence. They also have undergone little evolutionary change in the quaternary so we can use knowledge of how it behaves today to determine changes and behaviour then

42
Q

What are some sedimentary sequences that biology is preserved in?

A

peatlands, lakes, marine sediment caves and river terraces

43
Q

What does pollen analysis consist of?

A

The discovery of pollen from plants (using the knowledge we have for that plant species today [because it has not evolved much since]) indicates the characteristics of the place they were preserved at.

44
Q

What can the presence of pollen also indicate? why?

A

Human activity - because we brought weeds and broadened the coverage of grassland

45
Q

What are Chironomids and how do they help with past climate analysis?

A

Types of mosquito (1200 species variations) which all have their own specific ecological requirements. The heads of insects preserve well in sedimentary record. We can then compare the fossils to what knowledge we have for them today to determine the environmental conditions at the specific time and place

46
Q

What is dendrochronology and how can it help with past climate analysis?

A

Analysis of HD annual tree growth bands. Minimal bands suggest stress on the tree at the time which means growing conditions were not ideal

47
Q

What environmental conditions are speleothems sensitive toward?

A

temperature, nutrient and oxygen conditions, PH

48
Q

What environmental conditions are trees sensitive toward?

A

temperature, moisture availability, volcanic eruptions

49
Q

What temporal resolution of climate record do trees have?

A

Annual (sometimes even double annual marking the start and end of growth seasons)

50
Q

What is important to remember about most dating techniques?

A

They are only suitable in specific environments or for specific materials. They also have a specific time interval they operate over

51
Q

What is the law of superposition?

A

sediments higher in a sequence were younger than those below

52
Q

Why is the law of superposition so important?

A

it means that we can identify time scale from looking at geological record

53
Q

Is the law of superposition always true?

A

no - there is some variability

54
Q

What is precision in climate estimates?

A

The variance in the results you have secured

55
Q

What is precision commonly represented as in reports?

A

Standard deviation

56
Q

What is accuracy in climate estimates?

A

The relationship between age estimate and the true age of the sample

ESSHP: Section 2 (14 decks)

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