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ESSHP: Section 2 > Lecture 19: Ice Age Earth IV Asia & Tropics > Flashcards

Lecture 19: Ice Age Earth IV Asia & Tropics Flashcards

1
Q

What are the 6 reasons for studying past climate change in Asia and the tropics?

A 
Population >3 billion
Ocean-atmospheric circulation: ITCZ, Asian monsoon and ENSO 
Unique: no ice present 
New Archives 
Hominid evolution and early agriculture 
Himalayan uplift: causing the quaternary
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2
Q

What is the Asian monsoon characterised by?

A

Seasonal reversal of wind directions that results in dramatic seasonal changes in precipitation patterns

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3
Q

How much of the annual precipitation that Asia receives occurs in summer?

A

90%

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4
Q

What is the driver of the Asian Monsoon?

A

Strong pressure gradients that alter between summer and winter seasons

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5
Q

What happens to the driver of the Asian monsoon in summer?

A

Heating of Asian landscape that draws moisture laden air from the SW pacific

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6
Q

What happens to the driver of the Asian monsoon in winter?

A

The heating takes place over the SW pacific which switches the pressure gradient between land and ocean

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7
Q

What are the three locations where there are different monsoon climates?

A

Indian Seasonal monsoon
East Asian Seasonal monsoon
Western Pacific Summer Monsoon

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8
Q

What are loess deposits and how do they occur?

A

These are huge deposits of fine grain material that accumulate in to a landform as a result of the monsoon winds switching directions as the seasonal transition takes place

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9
Q

How small are the grains that make up the loess deposits?

A

10-50 micro metres

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10
Q

Where are the biggest loess deposits found and what size are they?

A

Loess Plateau in Yellow River, North China. 3x size of UK (450,000km^2)

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11
Q

What happens to Loess deposits as they evolve over time?

A

They form highly fertile soils that which were used for agriculture but are highly susceptible to erosion

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12
Q

How thick are loess deposits typically?

A

10-50m thick

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13
Q

Which monsoon season do loess deposits typically form during?

A

Dry winter monsoon because the winds from the N, W and NW regions are strongest in this season and so drive dust down to accumulate in one area

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14
Q

What regions do the winds in the winter monsoon originate from?

A

Taklaman and Gobi deserts

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15
Q

Are the Asian monsoon winds that drive the formation of loess deposits strongest during glacial or interglacial periods? why?

A

Glacial - the Asian winter monsoon season is colder and thus more amplified

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16
Q

What adverse impact do the changes in the Asian climate during the monsoon have and how does this affect loess deposits?

A

It impacts on vegetation and animals which can either strengthen or weaken the loess deposits as the plants can secure the previously unconsolidated material

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17
Q

What is the name for the soils that form as a result of vegetation strengthening the unconsolidated loess deposits?

A

Palaeosols

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18
Q

What can the soil structure alternating between palaeosols and unconsolidated material serve as?

A

A proxy for interglacial and glacial periods - palaeosols will form during one as a result of changes in climate and the vegetation and during the other the unconsolidated material will keep the same

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19
Q

What supported the idea that Asian soil structures were a good climate proxy?

A

They matched up with the marine isotope stage record

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20
Q

What did the Asian soil structures appear to correlate with?

A

sub-milankovitch periodicity

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21
Q

Where are ice cores found in Asia and the tropics?

A

At high altitude

22
Q

What is a strong source of ice cores in Asia and the tropics and what is it sometimes called?

A

Tibetan Plateau - called the third pole sometimes because it has four ice caps

23
Q

What are the four ice caps on the Tibetan plateau?

A

Dunde, Gulyia, Dasuopu, Puruongangri

24
Q

Where was what is thought to be the oldest core recovered from the tropics found and how old is it dated at?

A

Gulyia ice cap and is thought to be 600,000 years old

25
Q

What does the gulyia ice core hopefully contain information on?

A

past cycles and their impact upon the tropics and the monsoon climate

26
Q

What is one of the most notable sites that speleothem records are collected from in the tropics? what method is used to date them?

A

Dongge and Hulu Caves in China and they are analysed using Uranium-Thorium dating

27
Q

What did Wang et al. (2005) discover about the Asian monsoon from looking at speleothems in the Dungge caves?

A

That it had relatively linearly decreased in strength over time since around 9,000 years ago but there is a suggestion that it is currently undergoing a slight increase in strength

28
Q

What are 4 reasons why we are interested in changes in the tropics?

A

Hurricanes take place there, lightning strikes are more common, wetlands are highly concentrated in this region, there is a large amount of the world’s population here

29
Q

Why are wetlands in the tropics of interest?

A

because they are the biggest natural source of methane which is a highly potent greenhouse gas. There is also 50% of them in the tropics which makes the region interesting

30
Q

What are el nino and la nina characterised by?

A

El nino: increased warming across pacific ocean which has global consequences
la nina: the opposite/ relaxed conditions

31
Q

Why is el nino known as it is?

A

because it means little boy in spanish and was supposed to resemble the presence of Jesus as it was first noticed around Christmas time in South America which mostly speaks Spanish

32
Q

What was it estimated the 1998 El Nino cost the US?

A

$25bn

33
Q

What is the hypothesised link between climate change and el nino?

A

climate change associated with strong el nino events

34
Q

How well understood are the impacts of el nino?

A

Poorly

35
Q

What are porites corals similar to in terms of how they record changes in climate over time?

A

Dendrochronology

36
Q

How far back do records from porites corals stretch back to?

A

~1000 years

37
Q

What do the porites corals act as a proxy for?

A

sea surface temperatures

38
Q

What state can porites corals be in to be proxied?

A

Alive or dead

39
Q

What is a problem with porites corals currently as a proxy?

A

there are a lot of gaps in the record

40
Q

From what porites corals do tell us about the climate record, what do they present?

A

A different trend in the corals record to many records taken from the poles in ice cores

41
Q

Why were Tropical African lakes proxied and how?

A

They were proxied using geomorphological evidence, sedimentology, stable isotopes and organic matter from biological remains. Lower or higher levels indicate changes in either evaporation and precipitation which then link to other climate factors

42
Q

What were the 3 findings of research in to the African lake levels?

A

broad scale changes correlated with milankovitch periodicity
rapid low lake level events/changes in recent periods
Correlations of recent changes with North Atlantic Heinrich events

43
Q

What does archaeological evidence about the Sahara tell us?

A

It used to be a source of abundant tropical fauna and flora with extensive greener, unlike the dessert environment that it is today

44
Q

What is the archaeological evidence of what the Sahara used to be like supported by?

A

Palaeolithic cave art that shows animals of tropical fauna nature

45
Q

What evidence still exists today that supports the archaeological evidence of what the Sahara used to be like?

A

dwarf crocodiles still exit in Sahara desert waterholes

46
Q

Where did the evidence of what the Sahara used to be like come from?

A

A core taken from off the Western coast of Africa

47
Q

Why was the core taken form off the western coast of Africa taken there?

A

because the dust plume and evidence from that dessert travels across the region and usually ends up in that region where the core was taken

48
Q

What did DeMonocal et al. (2000) identify from the core that was taken off the western coast of Africa? When did it happen and what did it consist of?

A

The African humid period took place between the last ice age through to ~5.5kya - it was defined by an increase in summer radiation and precipitation

49
Q

What also changed during the African humid period and why?

A

Terrigenous % was less than normal because there was more vegetation and precipitation that would have stabilised the sand and reduced dust flow.

50
Q

What is terrigenous %?

A

The percentage of dust that originates from the terrestrial sphere

51
Q

What took place at the very end of the African humid period and why?

A

Sudden dramatic increase in terrigenous % possible because of the sudden reaction of the vegetation to excessive humid conditions but the definitive reason is uncertain.

ESSHP: Section 2 (14 decks)

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