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Extreme Climates Flashcards

1
Q

What are the five geological indicators?

A

Palaeomagnetism
Presence of liquid water
Cold/Ice
Hot/Dry
Flora/Fauna

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2
Q

What does palaeomagnetism show?

A

Mineral alignment is igneous and sedimentary rocks are aligned with Earths magnetic field therefore can determine palaeoaltitudes

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3
Q

How do we know of liquid water presence?

A

Ripples, cross bedding, fluvial channels, conglomerates

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4
Q

How do we know a palaeoclimate was cold/icy?

A

striations, dropstones, till/diamictite, ice rafted detritus

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5
Q

How do we know a palaeoclimate was hot/dry?

A

evaporates (hypersaline)
requires a restricted basin

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6
Q

What do flora/fauna tell us about palaeoclimates?

A

known climatic ranges
palm trees, cold blooded animals ie alligators in the artic

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7
Q

What do geochemical indicators show?

A

chemical measurements of sediments/fossils that record temperature through 18O

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8
Q

What are foraminifera?

A

single celled zooplankton, calcareous shell
planktonic or benthic

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9
Q

Why are foraminifera useful in the reconstruction of past climates?

A

As they grow their shells, they take in oxygen isotopes from seawater which tells us about the climate

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10
Q

What is the 18O water cycle?

A

16O is preferentially evaporated from seawater
18O is preferentially removed by precipitation
High latitude precipitation becomes very enriched in 16O
Extremely 16O enriched water is locked up in high latitude ice sheets
Global seawater becomes comparatively enriched in 18O

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11
Q

When is 18O in foraminifera shells high and low?

A

increases in glacial periods
decreases in ice melt warm climates

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12
Q

What phases do oxygen isotopes prefer?

A

16O prefers less dense phase
18O prefers more dense phase

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13
Q

What is the biggest Carbon reservoir?

A

sedimentary rocks

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14
Q

What are organic carbon sinks?

A

Photosynthesis
Formation of C org which can be buried in C org-rich sediments

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15
Q

What are inorganic carbon sinks?

A

Formation of CaCO3 minerals
Burial on seafloor carbonate ooze, limestone or chalk

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16
Q

What are characteristics of snowball earth?

A

Glacial deposits (dropstones, diamictites) at low latitudes
cap carbonates

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17
Q
A
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18
Q

What is a mass extinction?

A

A widespread and relatively rapid decrease in biodiversity
When the rate of extinction > rate of speciation

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19
Q

What are the big five mass extinctions?

A

End Ordovician 440Ma
Late Devonian 365Ma
Permian Triassic 252Ma
Triassic Jurassic 201Ma
Cretaceous Paleogene 66Ma

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20
Q

What extinctions are related to ice house conditions?

A

End Ordovician
Late Devonian
Triassic Jurassic

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21
Q

What was the largest mass extinction?

A

Permian Triassic
96% marine species
70% terrestrial species

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22
Q

What LIPs have temporary correlation with mass extinctions?

A

Siberian Traps - PT
Viluy - Late Devonian
Central Atlantic Magmatic Province - TJ
Deccan Traps - KT

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23
Q

How does volcanism affect climate?

A

Release of GHGs (CO2, Cl, SiO2 - block up sunlight)
Ocean acidification
Acid rain
Release of organic carbon from Corg rich sediments

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24
Q

What are the transitions of icehouse/hothouse during the Cenozoic?

A

hothouse warming conditions Paleocene, Eocene (66-34)
cooling conditions Oligocene and Miocene (34-5)
icehouse in Pleistocene (<2.7)

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25
what were the temperatures during the early Eocene?
12-16 degrees warmer than today
26
What period is the best for recent geological analogues for anthropogenic climate change?
Cenozoic
27
How do we know that climate has changed over the past 66Ma?
Marine Sediment Archives Core Sample Preparation Foraminifera
28
How do we use marine sediment archives to examine climate change?
Topographic highs on the seafloors are drilled above the carbonate compensation depth (CCD) Cores extend back to the late Cretaceous
29
What is the marine snow line?
Carbonate compensation depth CCD Line above which white calcium carbonate is preserved CaCO3 rich sediments contaon abundant calcareous microfossils
30
Where are marine sediments archives from the Atlantic ocean stored?
Bremen core repository
31
What happens in core sample preparation?
Small calcium carbonate microfossils are separated from the sediment
32
What are the four foraminifera depth habitats?
Mixed layer planktic foraminifera = 0-60m (photosynthetic algae) Deeper dwelling planktic foraminifera = 100-200 Epifaunal benthic foraminifera = seafloor infaunal benthic foraminifera = shallow depth below seafloor
33
How do work out the age of a marine sediment core and identify which part of geological record its from?
Generate an age model
34
What are the types of age models?
Biostratigraphy Magnetostratigraphy Chemostratigraphy Orbital Tuning
35
How is biostratigraphy used as an age model?
Morozovella subbotine (56-53Ma) vs morozovella velacoensis (60-56Ma) abundance
36
How is magnetostratigraphy used as an age model?
Changes in earths magnetic field are recorded by orientation of minerals in deep sea sediments Boundaries between normal and reverse polarity zones can be correlated to the Global Polarity Time Scale
37
How is chemostratigraphy used as an age model?
Based on rough biostratigraphic framework Use thickness of core between dated events to calculate sedimentation rates
38
How is orbital tuning used as an age model?
Variations in earths eccentricity and obliquity and precession control the latitudinal of solar insolation received by earth Processes leave a cyclical imprint in high resolution palaeoclimate records such as 13C and 18O
39
What is eccentricity?
Shape of earths orbit
40
What is obliquity?
Angle of earths orbit
41
What is precession?
Direction of tilt of earth
42
What carbon stores are released during hydrothermal events?
Methane hydrates Permafrost LIP Volcanism Oxidation of peat or marine Corg
43
What is the MMCO?
Middle Miocene Climatic Optimum Brief warming period
44
When did the uplift of the Himalayas start?
During the Eocene epoch
45
When did the Antarctic continent become covered by an ice sheet for the first time?
Eocene/Oligocene Transition (EOT)
46
What was the CO2 trend in the Eocene?
Long term atmospheric CO2 decline since the Early Eocene
47
What are causes for Antarctic glaciation?
Declining atmospheric C02 Influence of orbital cyclicity Antarctic circumpolar current
48
How does orbital cyclicity cause Antarctic glaciation?
Orbital parameters favouring reduced seasonal contrast and cool summers in the southern hemisphere would enable continent-scale glaciation of Antarctica
49
How does Antarctic circumpolar current cause Antarctic glaciation?
Opening of the Drake Passage resulted in development of the Antarctic Circumpolar Current (ACC) and thermal isolation of the Antarctica by the Eocene/Olgiocene Transition
50
What is the more rapid decrease of CO2 since the end of the Miocene linked to?
Further increases in weathering and decreases in outgassing resulted in onset of widespread northern hemisphere glaciation
51
What is the duration of glaciation cyclicty?
41kyr
52
When did the glacial-interglacial cycle intensify and switch to 100kyr cyclicity?
Since 1Ma, following the Mid-Pleistocene Transition (MPT)
53
What 41kyr cycles forced by?
Obliquity Tilt of axis from 22.1 to 24.5 degrees with a periodicity from one to the other and back again of 41kyr
54
When do glaciations take place in terms of obliquity?
During low obliquity when seasonal contrast is reduced allowing milder/wetter winters (favouring snow accumulation) and cooler summers (limiting snow melt)
55
What are methods and archives used to analyse Quaternary climate change?
Ice cores Pollen assemblage Foram assemblage d13C and Circulation
56
What are the accumulation rates of ice in Greenland and Antarctica?
Greenland: ~50cm/yr Antarctica: <5cm/yr
57
What do air bubbles in ice do?
record atmospheric composition based on 18O
58
What causes different d13C in water?
Different histories of photosynthesis/respiration
59
What is stadial?
Cold periods
60
What are interstadials?
warm periods
61
What does rapid climate change in N Atlantic foram assemblage indicate?
Indicates extreme cooling in North Atlantic as only the polar-dwelling species N. pachyderma survuves
62
What is the AMOC?
Atlantic Meridional Overturning Circulation
63
What is deep water formation controlled by?
Sea water density
64
What is water density controlled by?
Controlled by temperature and salinity
65
What does the Gulf Stream do?
Brings warm, saline surface water to the North Atlantic, which cool as they meet cold currents from the Artic
66
What weakens the AMOC?
Freshwater input
67
What are the three models of overturning?
Interstadials/modern: strong deep AMOC=warm Glacial background: weaker shallower AMOC = cool Stadial: Collapsed AMOC = very cold
68
What was the Younger Dryas stadial?
End of deglaciation ~12ks Last time scotland had ice sheets - glacial readvance Controlled largely by moisture availability
69
What is the Bipolar seesaw?
Reduced AMOC = Northern Hemisphere dramatically cooled due to limited ocean heat transport northwards Conversely, Southern high latitudes warmed at the same time due to collapse AMOC
70
What was the global impact of the collapse of the AMOC?
Shift in thermal equator and atmospheric circulation
71
What is evidence of shift in thermal equator and atmospheric circulation?
Southward shift of storm track recorded by SW USA lakes Southward shift of ITCZ recorded by Brazilian stalagmites and Cariaco basin runoff Weakened monsoons in Asia recorded by stalagmites
72
Why does methane jump up during interstadial?
Bog Respiration? Permafrost melt?
73
What is the inter-glacial CO2 change?
Enhanced biological pump exported larged amounts of organic carbon from photosynthetic algae to the deep southern ocean during glacial episodes increased overturning during the deglaciation led to release of carbon from the deep ocean
74
75
What makes up anthropogenic climate change?
75% burning of coal oil and gas 25% Changes in land use
76
When was the last time global surface temperature was sustained at or above 2.5 degrees?
3Ma during the Mid-Pliocene warm period
77
When will we experience sustained 2.5 degrees warming?
By 2100 if ghg emissions stay closed to todays levels
78
What were the main characteristics of the mid Pliocene warm period?
Global mean surface temperature was 2.5-4 degrees Biomes expanded polewards Higher precipitation Stronger monsoons Sea level 5-25m higher than present Reduced ice sheets
79
Is there a link between extinction and CO2?
Yes
80
Why is there ocean deoxygenation during high CO2?
Increased nutrient supply from weathering Phytoplankton blooms
81
What is expected to happen to the AMOC with increased CO2?
Weakens Low confidence in magnitude of weakening
82
What would the collapse of the AMOC mean?
Southward shift of the ITCZ Weakening of African and Asian monsoons Strengthening of southern hemisphere monsoons Drying of Europe
83
What is the Kaya identity?
CO2 emissions = Population x GDP/Population x Energy/GDP x Carbon/Energy
84
What are anthropogenic sources of climate change?
Electricity 25% Land use and agriculture 24% Industry 21% Transport 14% Buildings 6% Fuel extraction 10%
85
What is the solution to anthropogenic sources of CO2?
Clean electricity Protect and plant trees Reduce meat consumption CO2 capture
86
What is NETs?
Negative Emissions Technologies
87
How can we remove CO2?
Terrestrial ~10s years Oceans ~ 100s years CaCO3 ~ 1000s years Weathering ~100,000s years
88
Which of the following is not likely to be associated with purely mantle derived volcanic emissions form an large igneous province: Ocean acidification; global warming; ocean anoxia; increasing continental weathering rates; acid rain; major negative carbon isotope excursion.
Major negative carbon isotope excursion
89
Which two mass extinctions are the Viluy and Siberian Traps LIP associated with respectively?
Late Devonian Permian Triassic
90
Which of the following carbon stores which could have contributed to early paleogene hyperthermal events is NOT sensitive to cyclical changes in earths orbit: Thermogenic methane; biogenic methane hydrates; permafrost; peat
Thermogenic methane
91
What was the early Eocene hothouse forced by?
High atmospheric CO2 levels from Deccan Traps
92
What are the properties of surface waters in the North Atlantic which cause them to sink and drive modern thermohaline circulation?
Cold and saline
93
True or false: Dissolution of calcium carbonates in the ocean leads to a reduction in atmospheric CO2
True

ES2001 (9 decks)

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