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Global Environmental Change > Revision > Flashcards

Revision Flashcards

1
Q

What are Heinrich Events?

A

Periods of massive iceberg discharges into the North Atlantic Ocean, resulting in significant climate and ocean circulation disruptions.

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2
Q

How are Heinrich Events identified in the geological record?

A

They are identified by layers of ice-rafted debris (IRD) in marine sediments, indicating large-scale iceberg melting.

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3
Q

What causes Heinrich Events?

A

Heinrich Events are thought to be triggered by the collapse of ice sheets due to climate instability or internal ice sheet dynamics.

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4
Q

During which time period did Heinrich Events primarily occur?

A

They occurred during the last glacial period, approximately between 60,000 and 10,000 years ago.

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5
Q

What is the impact of Heinrich Events on ocean circulation?

A

Freshwater influx from melting icebergs reduces ocean salinity, weakening the density-driven sinking of water in the North Atlantic, which is a key component of AMOC.

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6
Q

How do Heinrich Events affect global climate?

A

They can lead to abrupt cooling in the Northern Hemisphere and possibly trigger changes in monsoon systems and precipitation patterns globally.

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7
Q

What is the significance of Heinrich Event H1?

A

H1 occurred around 16,500 years ago and is associated with significant climate shifts and disruptions to ocean circulation.

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8
Q

How do Heinrich Events interact with Dansgaard-Oeschger cycles?

A

Heinrich Events often punctuate cold phases of D-O cycles, with iceberg surges coinciding with the coldest stadials and contributing to abrupt climate transitions.

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9
Q

What ice sheet is responsible for Heinrich events?

A

The Laurentide Ice Sheet releasing in to the Labrador Sea

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10
Q

What modern climate risks might be compared to Heinrich Events?

A

Rapid ice sheet melt and freshwater influx from Greenland and Antarctica today could mimic similar disruptions to ocean circulation and global climate.

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11
Q

What are Dansgaard-Oeschger events?

A

Dansgaard-Oeschger events are rapid climatic oscillations during the last glacial period, characterized by abrupt transitions from cold (stadial) to warm (interstadial) conditions, primarily recorded in Greenland ice cores through isotopic data.

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12
Q

What isotopic evidence indicates D-O events?

A

The δ¹⁸O (oxygen isotope) values in Greenland ice cores increase sharply during D-O events, reflecting rapid warming and changes in precipitation source regions.

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13
Q

What is the duration of warming phases in D-O events?

A

Warming phases occur over decades to centuries, with interstadial conditions persisting for hundreds to a few thousand years.

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14
Q

What is the proposed role of the Atlantic Meridional Overturning Circulation (AMOC) in D-O events?

A

Variability in AMOC strength and stability is thought to modulate heat transport to the North Atlantic, driving the rapid temperature shifts observed in D-O events.

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15
Q

How do D-O events correlate with Heinrich Events?

A

Heinrich Events often occur at the end of a prolonged stadial phase following a D-O event, potentially triggered by ice sheet destabilization due to accumulated glacial stress.

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16
Q

How do methane concentrations vary during D-O events?

A

Atmospheric methane levels increase during interstadials, reflecting expanded wetland areas and increased biological activity in warmer, wetter climates.

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17
Q

How do ice core records distinguish stadials and interstadials?

A

Stadials exhibit lower δ¹⁸O values and reduced dust concentrations, while interstadials show higher δ¹⁸O and increased atmospheric methane, indicating warmer, wetter conditions.

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18
Q

What external forcings might influence D-O events?

A

Factors like solar activity, volcanic eruptions, and orbital parameters may modulate the timing or amplitude of D-O events.

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19
Q

What is IRD- Ice Rafted Debris?

A

The debris consists of lithogenic materials sourced from the bedrock underlying ice sheets, particularly the Laurentide Ice Sheet. The IRD layers are often associated with reduced foraminiferal content, abrupt shifts in stable isotopes (e.g., δ¹³C and δ¹⁸O), and variations in sediment grain size.

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20
Q

Frequency of Heinrich Events Over 80,000 Year?

A

There have been 6 Heinrich events ove the past 80,000 years spaced irregularly, occurring approximately every 7,000–10,000 years.

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21
Q

Heinrich events- surface cooling

A

Surface Cooling: Reduced heat transport led to significant cooling in the North Atlantic region, amplifying the glacial conditions (stadials).

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22
Q

Bipolar Seesaw

A

The bipolar seesaw refers to the inverse temperature relationship between the Northern and Southern Hemispheres during abrupt climate events, driven by heat redistribution via oceanic and atmospheric pathways. Cooling in the Northern Hemisphere due to a weakened AMOC leads to compensatory warming in the Southern Hemisphere.

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23
Q

Impacts of Heinrich events on tropical regions and Monsoons

A

Weakened AMOC dye to influx of freshwater- leads to reduced heat transport to high latitudes-= causing in North Atlantic
- Also reduces moisture transport
- Weakened Indian Summer monsoon

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24
Q

What primary driver causes the bipolar seesaw?

A

Changes in the Atlantic Meridional Overturning Circulation (AMOC), which modulate heat transport between the hemispheres.

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25
Q

How was the bipolar seesaw identified?

A

By synchronizing ice core records from Greenland and Antarctica using markers like volcanic ash layers, methane (CH₄) concentrations, and isotopic data (δ¹⁸O and δD).

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26
Q

What is the timing lag between Greenland and Antarctic temperature changes during a D-O event?

A

Antarctic warming typically lags behind Greenland warming by approx 200 years but can be up to 1000

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27
Q

What happens during a Greenland stadial (cold period)?

A

Freshwater from ice sheet discharges weakens the AMOC, reducing heat transport northward, cooling the Northern Hemisphere, and causing heat buildup and gradual warming in the Southern Hemisphere.

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28
Q

What happens during a Greenland interstadial (warm period)?

A

The AMOC recovers, resuming northward heat transport, leading to rapid Northern Hemisphere warming and gradual cooling in the Southern Hemisphere.

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29
Q

How do Greenland and Antarctic temperature changes differ in shape during DO events?

A

Greenland: Rapid warming (up to 16°C) followed by gradual cooling (sawtooth pattern).
Antarctica: Gradual warming during Greenland’s cold periods (stadials) and slow cooling during Greenland’s warm periods (interstadials).

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30
Q

Dendrochronology mismatch

A

10,000 ^14C years correspond to ~11,600 calendar years.

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31
Q

How do tree rings show 14C levels in the atmosphere over time?

A

Trees grow by adding a new ring of cells each year. Each ring contains a record of the carbon absorbed by the tree during that year, including the 14C present in the atmosphere.

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32
Q

Date of Last Glacial Maximum?

A

21,000 years ago

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33
Q

The Holocene

A

(Started ~11,700 years ago), marked by stable, warm interglacial conditions.

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34
Q

What is a termination?

A

A rapid transition from a glacial to an interglacial period marked by significant warming and ice sheet melting.

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35
Q

Which proxies would you use for surface water changes?

A

Foraminifera δ¹⁸O: Indicates surface water temperature and salinity changes.
Ice-Rafted Debris (IRD): Tracks iceberg discharge events (Heinrich Event)

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36
Q

Which proxies would you use for intermediate and deep-water flow changes?

A

Neodymium (Nd) isotopes: Tracks changes in water mass sources.
Carbon isotopes (δ¹³C in benthic foraminifera): Indicates deep-water ventilation and nutrient content.

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37
Q

Heinrich Events - 𝜀Nd.

A

Increased εNd in the North Atlantic suggests reduced input from NADW and increased influence of southern-sourced waters. In Dansgaard-Oeschger events, variability in 𝜀Nd reflects rapid shifts in ocean circulation.

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38
Q

How do Nd isotopes help in tracing water mass sources?

A

Different water masses, like North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW), carry distinct Nd isotopic signatures, which can be used to track shifts in ocean circulation patterns over time.

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39
Q

Cladogenesis

A

– evolutionary split event
– sets of branches form “clades”
– development of sister species

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40
Q

Why is the record of hominin evolution considered patchy?

A

The record of hominin evolution is patchy because fossil finds are rare and often focus on a small part of Africa, and fossilization is a rare process.

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41
Q

What makes the relationship between environmental change and hominin evolution difficult to establish?

A

The relationship is difficult because there is often no direct link between environmental conditions and individual hominin finds, and climate evolution is mostly inferred.

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42
Q

Sulfate from ocean salt and dust from land

A

Fluctuated throughout Holocene- evidence for changes in wind strength

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43
Q

Evidence for IRD in the Holocene

A

Sediment core records with 10Be from ice cores

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44
Q

Millennial timescale change in the N Atlantic during the Holocene

A
  • Weak compared to glacial
  • some evidence for changes in ice rafting and sea ice extent
  • drivers unclear- could be solar forcing
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45
Q

14C and 10Be

A

Produced in the upper atmosphere through bombardment by cosmic particles

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46
Q

What is the key difference between calendar years before present and 14C years before present?

A

Calendar years are directly dated, while 14C years are based on radiocarbon dating, which requires calibration due to variations in radiocarbon production.

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47
Q

What role do tree ring ages and U-Th ages play in calibrating 14C dating?

A

Tree ring and U-Th ages provide precise calendar dates that help calibrate and correct 14C age estimates.

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48
Q

How does the Earth’s magnetic field affect radiocarbon dating?

A

A weaker Earth’s magnetic field, particularly before ~7000 years ago, allowed more cosmic rays to reach the atmosphere, increasing radiocarbon production

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49
Q

How do changes in the carbon cycle impact 14C dating?

A

Variations in old carbon storage, especially in the deep sea, can alter the amount of radiocarbon available in the atmosphere, affecting 14C age estimates.

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50
Q

What is the effect of solar radiation changes on radiocarbon dating?

A

Changes in solar radiation influence cosmic ray flux, which in turn affects radiocarbon production rates.

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51
Q

Solar cycles (Schwabe cycle- sunspots

A

11 year between 1645 and 1715 low number of sunspaces

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52
Q

El Nino Southern Oscillation

A

Cyclicity-3-7 yrs
Change temp-1C regionally
Water pushed to west of Pacific ocean making a pile of warm water. In El Nino, this push is reduced meaning portion of warm water travelled to the east and puts a lid o the east ocean

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53
Q

La Nina

A

Strengthens the westerly push of water west of the pacific ocean. Intensification of trade winds

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54
Q

What is the Urey reaction?

A

The Urey reaction involves the chemical weathering of silicate minerals, where atmospheric CO₂ reacts with silicate rocks to produce bicarbonates and silicate sediments, sequestering carbon.

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55
Q

Why is the Urey reaction important for understanding climate change on geological timescales?

A

It acts as a long-term negative feedback mechanism, stabilizing Earth’s climate by removing atmospheric CO₂, which directly impacts global temperatures.

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56
Q

What geological event is associated with enhanced silicate weathering rates?

A

The uplift of the Himalayan-Tibetan Plateau, which increased rock exposure and weathering rates, leading to significant CO₂ drawdown.

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57
Q

How was the role of the Himalayan uplift in weathering identified?

A

Through increased sedimentation rates, shifts in isotopic records such as strontium isotopes in marine carbonates, and evidence of accelerated erosion coinciding with the uplift.

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58
Q

What is the climatic impact of the Himalayan uplift?

A

Decline in atmospheric CO₂, driving long-term global cooling and potentially influencing glacial cycles.

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59
Q

What is the role of topography in WAIS stability?

A

The West Antarctic Ice Sheet is largely grounded below sea level, making it susceptible to marine ice sheet instability (MISI), where retreat of grounding lines can trigger rapid ice loss.

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60
Q

Transitioning out of
the ice age- the Holocene

A
  • Higher sea levels
  • Changes in vegetation
  • Increasing air/ocean
    temperatures
  • Opening of travel routes
  • Formation of lake
  • More exposed land
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61
Q

When was warming reversed?

A

About 12.6kyr (Younger Dryas) for about 2kyr

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62
Q

Holocene Climate
Optimum (5000-3000
BC)

A

1-2° C warmer
NH summer, but
temporally and
spatially variable.

63
Q

Why are high latitude areas preferred for glaciation?

A

High latitude areas are preferred for glaciation due to low (negative) net solar radiation.

64
Q

What role do relief and aspect play in ice growth?

A

Ice growth depends on land relief. Aspect (the direction the land faces) affects incoming solar radiation and precipitation.

65
Q

How does continentality influence ice sheets?

A

On ice sheets, the distance from the ocean is the fundamental factor influencing rates of accumulation and ablation.

66
Q

Mass Balance

A

Balance between accumulation and
ablation.
Positive: growth of ice
Negative: loss of ice

67
Q

Post Glacial sea level rise

A

Appears progressive with the exception of meltwater pulses
Sea level near present level by mid to late Holocene

68
Q

How does Antarctica strongly affect Earth’s climate?

A

Antarctic Bottom Water and ocean circulation
Strong pole-equator thermal gradients, influencing westerlies
Responsible for low latitude deserts

69
Q

What is Deuterium and its role in climate studies?

A

Deuterium is a stable isotope of hydrogen, containing one proton and one neutron. It is used in climate studies as a proxy for temperature, with its concentration in ice cores helping scientists infer past temperatures, as it varies with changes in temperature.

70
Q

What were the temperatures in Antarctica during the Last Glacial Maximum (LGM)?

A

Antarctic temperatures were 8-15°C colder during the LGM compared to present day.

71
Q

What changes occurred in Antarctica’s ice sheet during the Last Glacial Maximum (LGM)?

A

Interior Antarctica thinned
East Antarctica: minimal extension/thickening at margins
West Antarctica: considerable thickening/extension at margins

72
Q

What controls influence the Antarctic Ice Sheet regarding temperature and precipitation?

A
  • Distance from coast (continentality) and sea ice affect the ice sheet
  • Winter sea ice extent linked to ssNa flux
  • Winter sea ice was approximately double during glacial periods
  • Warming atmosphere and reduced winter sea ice promote increased precipitation in the interior
73
Q

cean Temperature and Sea Level’s Effect on Antarctic Ice
How do ocean temperature and sea level impact the Antarctic Ice Sheet?

A

Changes in sea level affect the availability of land and grounding line position (buoyancy)
Changes in ocean temperature affect basal melt rates

74
Q

Why do ice shelves matter in the dynamics of the Antarctic Ice Sheet?

A

Ice shelves act as buttresses, holding back the flow of ice. When ice shelves collapse, like in the Larsen B embayment, it leads to glacier acceleration and thinning.

75
Q

How does bed topography influence the Antarctic Ice Sheet?

A

-Controls the dynamics of ice streams
-Differentiates marine vs continental ice sheets
-Defines susceptibility to Marine Ice Sheet Instability (MISI) and pinning points

76
Q

What happened in the Weddell Sea during the Holocene?

A

Rapid deglaciation during the mid-Holocene due to atmospheric warming, sea level rise (SLR), and Marine Ice Sheet Instability (MISI).
Currently stable or re-advancing.

77
Q

What occurred on the Antarctic Peninsula during the Holocene?

A

Thinning was complete by early Holocene, followed by shelf collapse and reformation between 10-8 ka due to atmospheric and ocean warming triggers.

78
Q

How did the Ross Sea interior respond during the Holocene?

A

Asymmetric response: Lower reaches began thinning by 13 ka, while upper reaches continued thickening until around 7 ka due to sea level rise (SLR) and atmospheric warming.

79
Q

What happened in Mac. Robertson Land, East Antarctica, during and after the Last Glacial Maximum (LGM)?

A

Thickening in the interior post-LGM, with marginal retreat and thinning in coastal areas due to sea level rise (SLR), atmospheric, and ocean warming.

80
Q

Why is the topography beneath the Antarctic Ice Sheet so important to its stability?

A
  • Subglacial topography influences how ice flows
  • Influences regional variability in ice loss
  • Marine Ice Sheet Instability (MISI)
81
Q

How does Subglacial topography influences how ice flows?

A
  • Raised areas/ ridges slow down glaciers- help to stabilise ice sheet
  • Valleys/steep slopes can increase rate of ice flow
82
Q

How does Marine Ice Sheet Instability (MISI) influence ice sheet stability?

A

Where bedrock slopes downwards inland , as the grounding line retreats onto shallower land , the ice can accelerate rapidly leading to ice loss and potential sea level rise

83
Q

How can regional variability in topography affect the Antarctic ice sheet?

A

East Antarctica has a higher elevation and a more stable bedrock topography. However, regions like the Wilkes Land Basin and the Totten Glacier are vulnerable to changes in ocean temperature.

West Antarctica: West Antarctica has a lower elevation and a more complex bedrock topography, with many areas grounded below sea level. This makes it more susceptible to MISI and ocean warming.

84
Q

Evolution of Family Hominidae within the
Order Primates

A

Usually defined by the evolution of bipedal
locomotion

85
Q

Tools we can use to study human evolution

A

Genes and fossils

86
Q

Why is it so difficult to fuind fossil record of hominids?

A
  • preservation is an issue- e.g. weathering
  • Fossil record is incomplete
87
Q

Where are all settings for Early Human Evolution

A

East Africa Rift System Valley- graben structure

88
Q

First primates in the geological record

A

Late Cretaceous/early Palaeocene ~66mya

89
Q

When did hominids appear and spread?

A
  • First Hominids- late Miocene
  • Radiation of hominids - Pliocene
90
Q

Uplift of the Tibetan Plateau

A

Effect: Enhanced silicate weathering due to greater exposure of rocks to atmospheric processes.
Process:
CO₂ + water → carbonic acid.
Carbonic acid reacts with silicate minerals, releasing ions (e.g., bicarbonate).
Ions transported to the ocean.
In the ocean, bicarbonate and calcium form carbonate minerals that precipitate.

91
Q

Outcome of Tibetan Uplift

A

Outcome:
Sequestration of CO₂ in ocean sediments as carbonates.
Reduced atmospheric CO₂ → global cooling (negative feedback mechanism).

92
Q

Impact of Tibetan Uplift on Monsoons

A

Elevation and Heat Source: The uplift created a massive elevated landmass that acts as a heat source during summer, warming the overlying air.
Intensification of Monsoons: The warm air rises, creating a low-pressure system that draws moist air from surrounding oceans, strengthening the Indian and East Asian monsoons.
Rainfall Patterns: Enhanced monsoons brought heavier seasonal rains to South and Southeast Asia.

93
Q

Evolution of hominids habitats

A

Moved from a closed forest environment to more open spaces e.g. savanna grasslands

94
Q

Why is Tuff Useful for Dating Rocks?

A

Quick Deposition: Forms rapidly during eruptions, preserving a distinct time snapshot.
Widespread: Ash spreads over large areas, making tuff layers easy to correlate between locations.

95
Q

What is the Mid-Pleistocene Transition (MPT)?

A

A climatic shift between 1.2 million and 0.8 million years ago, where Earth’s glacial cycles changed from a 41,000-year periodicity to a 100,000-year periodicity.

96
Q

What was the glacial cycle pattern before the MPT?

A

Glacial cycles occurred every 41,000 years, driven by changes in Earth’s axial tilt (obliquity).

97
Q

What caused the longer glacial cycles after the MPT?

A

A shift to a 100,000-year periodicity, influenced by Earth’s orbital eccentricity and amplified by internal climate feedbacks.

98
Q

How did ice sheet dynamics influence the MPT?

A

Larger and more stable Northern Hemisphere ice sheets delayed melting, leading to longer glacial cycles.

99
Q

How did CO₂ levels contribute to the MPT?

A

Reduced atmospheric CO₂ levels during glacial periods prolonged cooling and strengthened longer glacial cycles.

100
Q

What role did tectonics and geography play in the MPT?

A

Mountain uplift (e.g., Himalayas) increased silicate weathering, reducing CO₂, while ocean circulation changes (e.g., the Bering Strait) affected heat and moisture distribution.

101
Q

What was the role of albedo feedbacks in the MPT?

A

Larger ice sheets increased Earth’s reflectivity, cooling the planet further and reinforcing longer glacial periods.

102
Q

What marked the termination of the MPT?

A

The establishment of strong 100,000-year glacial cycles with longer glaciations and abrupt deglaciations.

103
Q

How are dust records used to study global climate?

A

Dust patterns in marine sediments and ice cores align with global glacial-interglacial cycles, acting as proxies for past climate states.

High Dust = Glacial Periods
Low Dust = Interglacial Periods

104
Q

How does dust affect climate feedbacks?

A

Dust on ice sheets can lower albedo (reflectivity), contributing to melting during deglaciation.

Iron Fertilization: Dust provides iron to oceans, promoting phytoplankton growth, which can lower atmospheric CO₂ and enhance cooling.

105
Q

How did African climate change affect its variability?

A

The climate became more variable, with increased seasonality and fluctuations between wet and dry periods.

106
Q

hat evolutionary events occurred during periods of climate instability in Africa?

A

Major evolutionary events, including speciation, may have been climatically mediated, occurring during periods of climate instability.

107
Q

What characterises the African paleoclimatic history?

A

Changing patterns of wet-dry cycles, not a simple directional change from wet to dry, but step-like shifts in aridity.

108
Q

Stable climate episode

A
  • lakes and rivers more prominent
  • faunal dispersal via vegetated corridors
109
Q

Prior to 3mya - coastal Africa

A

Indian Ocean coastal forest crucial in African mammalian evolution because of climatic stability due to buffering influence of the ocean . During dry periods coastal strip was a refugium and a source of new species.

110
Q

What is the Aridity Refuge Model?

A

A hypothesis suggesting that climatic fluctuations during periods of aridity created refuges where species could survive, helping to preserve biodiversity and potentially contribute to speciation.

111
Q

How does the Aridity Refuge Model relate to African climate change?

A

During arid periods, species could retreat to moister refuges (e.g., forests or wetlands), where they adapted and evolved, potentially leading to new species in isolated habitats.

112
Q

How does the Aridity Refuge Model explain speciation in Africa?

A

Climate instability, such as periods of increased aridity, created isolated refuges, leading to genetic divergence and speciation as populations adapted to different environmental conditions.

113
Q

What role did aridity play in shaping evolutionary patterns according to the model?

A

Arid periods served as a trigger for the creation of habitat refuges where species survived, evolving differently from their counterparts in less arid regions.

114
Q

How do trade winds and ocean currents work together to affect African climate?

A

Trade winds push warm, moist air from the ocean over Africa, but during periods of climate instability, these winds might shift or weaken, reducing rainfall in some areas, while promoting the development of moister refuges elsewhere.

115
Q

What filled the deep ocean 100 million years ago?

A

Warm saline bottom water.

116
Q

Where did warm saline bottom water likely form 100 million years ago?

A

In the tropics or subtropics, flowing pole-ward and transferring heat.

117
Q

How is heat transferred through the deep ocean today?

A

By the formation of cold, dense water in polar regions and some warm saline water from the Mediterranean.

118
Q

What climatic periods can Sr concentrations indicate?

A

High Sr concentrations: Glacial periods (increased continental dust).

Low Sr concentrations: Interglacial periods (reduced dust transport).

119
Q

What are sapropels?

A

Layers of organic-rich sediment deposited in marine environments under low oxygen (anoxic) conditions.

120
Q

How do sapropels correlate with orbital climate cycles?

A

They form during periods of maximum summer insolation (increased solar radiation) in the Northern Hemisphere.
Linked to Earth’s precession cycle (~23,000 years).

121
Q

What do sapropels tell us about Mediterranean climate history?

A

Past episodes of intense river discharge from the Nile and other rivers.
Evidence of wetter climatic conditions in surrounding regions.

122
Q

What tools are used to study sapropels?

A

Core drilling in marine basins.
Geochemical analysis of sediment composition.
Radiometric dating methods like radiocarbon and uranium-thorium dating

123
Q

How are foraminiferal records better in the Atlantic?

A

Faster sedimentation rates lead to higher resolution records.
These allow detailed reconstructions of past climate changes, especially during the Pleistocene.

124
Q

What are the limitations of foraminifera as proxies?

A

Limited to carbonate sediments found at depths <4000 m.
Disturbances such as turbidity currents can disrupt sedimentary records.
Species-specific responses to environmental conditions may complicate interpretatations

125
Q

How do ocean circulation patterns affect sedimentation rates in the Atlantic?

A

The Atlantic’s thermohaline circulation enhances nutrient and particle transport, depositing more organic material and fine sediments. Turbidity currents also redistribute sediments.

126
Q

What is precession in Milankovitch cycles?

A

Precession refers to Earth’s axis wobbling, altering the distribution of solar radiation between hemispheres and changing summer insolation.

127
Q

How does precession affect δ¹⁸O levels?
A: H

A

Higher δ¹⁸O levels occur during glaciation as ice accumulates. Lower δ¹⁸O levels occur during ice melting due to increased summer insolation.

128
Q

How does precession influence glaciation?

A

Changes in summer insolation driven by precession can trigger ice sheet melting or growth, particularly in the Northern Hemisphere.

129
Q

What is obliquity in Milankovitch cycles?

A

Obliquity is the change in Earth’s axial tilt, varying between 22.1° and 24.5° over 41,000 years, affecting the intensity of seasons.

130
Q

How does obliquity affect glaciation?

A

Obliquity leads to more stable and longer-lasting ice sheet growth by maintaining colder seasonal conditions.

131
Q

How does eccentricity influence glaciation?

A

Ice sheets expand and retreat in response to changes in Earth’s distance from the Sun caused by eccentricity.

132
Q

How are Heinrich events related to δ¹⁸O patterns?

A

Heinrich events involve the rapid discharge of icebergs into the North Atlantic, lowering δ¹⁸O levels in ocean sediments due to the influx of ^16O.

133
Q

What are the effects of Milankovitch cycles on Earth’s climate system?

A

They cause periodic ice sheet growth, deglaciation, sea-level changes, and shifts in temperature patterns.

134
Q

What is a climate model?

A

A climate model is a complex mathematical simulation of the Earth’s climate system, using computer programs to represent interactions among the atmosphere, oceans, land, and ice.

135
Q

What are the main components of a climate model?

A

Atmosphere: Simulates temperature, wind, precipitation, and radiation.
Oceans: Tracks heat absorption and ocean currents.
Land: Models vegetation, soil moisture, and albedo (reflectivity).
Ice: Simulates glacier and sea ice changes.

136
Q

What are climate projections?

A

Climate projections are predictions about future climate patterns based on climate models, greenhouse gas emissions, natural variability, and feedback processes.

137
Q

What inputs are used to make climate projections?

A

Greenhouse gas emissions scenarios (CO₂, CH₄, etc.)
Solar variability
Volcanic activity

138
Q

How do climate models simulate climate processes?

A

Climate models simulate radiative forcing, energy balance, feedbacks (e.g., ice-albedo effect), and natural variability (e.g., El Niño).

139
Q

How do we validate climate models?

A

Comparing simulated data to historical climate trends.
Models accurately simulate warming trends and volcanic cooling effects.

140
Q

Why are climate models trusted?

A

They rely on well-established physical laws.
Multiple independent climate models show similar outcomes under the same scenarios.
Observations align with the models’ predictions (e.g., global warming, ice melting).

141
Q

What is the CMIP?

A

The Coupled Model Intercomparison Project (CMIP) compares climate models from independent research groups to ensure consistency and robustness.

142
Q

How are observed trends confirming climate projections?

A

Current trends like global warming, melting ice, and changing precipitation patterns match model predictions.

143
Q

WAIS Topography

A

Grounded below sea level. Much of it is grounded on fragmented bedrock composed of islands- few stabilising pinning points. Susceptible to MISI

144
Q

EAIS Topography

A

Grounded on high elevation continental bedrock. Much of it lies on mountainous regions which provide the ice sheet with more pinning points that stabilise the ice sheet and reduce ice flow

145
Q

Key hominid species evolutionary sequence?

A

A.Afarnesis-4-2.7 mya
Homo rudolfensis-2.4-1.6 mya
Homo Habilis- 2.4-1.4 mya
Homo erectus- 1.9 mya-110000 ya
Homo sapiens- 300,000 -present

146
Q

Key evolutionary trends- Hominids

A
  • Bipedalism emerges
  • Brain expansion
  • Migration and Adaptability
  • Cultural development
147
Q

Ways in which hominid evolution forced by climate change?

A
  • Changes in vegetation and climate = migration to savannas= bipedal locomotion
  • Glacial periods allowed expanded migration
148
Q

What forests played a role in African Mammalian evolution?

A

Indian Ocean coastal forests- provided climatic stability- served as a stable habitat

149
Q

What does the bipolar seesaw concept refer to?

A

The bipolar seesaw refers to the observed pattern of asynchronous climate change between the Northern Hemisphere (Greenland) and the Southern Hemisphere (Antarctica) over millennial timescales.

150
Q

What drives the bipolar seesaw mechanism?

A

Changes in thermohaline circulation, ice sheet melting, and atmospheric patterns disrupt heat distribution across the planet.

151
Q

What are the environmental consequences of the bipolar seesaw?

A
  1. Sea level rise
  2. Ocean circulation disruptions
  3. Changes in regional weather and ecosystems
152
Q

How is 87Sr produced?

A

87Sr is produced by the decay of 87Rb in older continental rocks

153
Q
A

Global Environmental Change (9 decks)

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