Quaternary

Question 1

Crutzen (2002)

Answer 1

• anthropocene started late C18th - James Watt’s design steam engine 1784
• mankind geological force, will remain env force many millennia
• need guide society towards sustainable management

Question 2

Lowe and Walker (2015)

Chap 7

Answer 2

• Milankovitch cycles
• Glacial-interglacial cycles
• sub-orbital changes (OD cycles)
• last termination (last glacial maximum)
• Holocene climate - 11.7ka to today - warm episode after last glacial period (younger dryas) - 8.3ka event (climatic culling event in Greenland ice core) and Little Ice Age (cold interval C16th-C19th)
• ENSO, North Atlantic Oscillation (NAO)
• people and climate - greenhouse effect, GHGs, anthropocene

Question 3

Broecker (1995)

Answer 3

• potential for thermohaline circulation to change with climatic impacts
• Atlantic conveyor circulation currently keeps europe warm but pattern vulnerable to disruption by injections of excess freshwater into the North Atlantic - if conveyor stops, winter temp in North Atlantic and surrounding lands would fall 5 + degrees
• oceanic conveyor could come back to life but would take hundreds or thousands of years to regain salt and heat - even then it would likely be a different circulation pattern which would not keep europe warm - Rahmstorf suggests it would be a shallower circulation
• even slowing current circulation would impact abundance carbon 14 in ocean and atmosphere (more carbon 14 would mean that dating things would appear younger)
• believe previous shutdowns but momental - eg. Younger Dryas overall ocean circulation increased, which would be expected if cold snap were caused fault Atlantic conveyor - anticipate cause of such events as influx freshwater from ice caps - evidence of 8 invasions freshwater into North Atlantic - 7 icebergs; Lake Agassiz - 4 of which occurred at times corresponding to changes climate North Atlantic basin (eg. Lake Agassiz and onset Younger Dryas) - Heinrich layers - Greenland ice core evidence
• eg. after last Heinrich event 14,000 yrs ago Lake Lahontan in Nevada (West US) achieved greatest size - needed lot precipitation of magnitude of el nino winter 1982-3
• essentially earth’s climate has jumped before and likely link to oceans but not clear - need better understanding for future prediction

Question 4

Broecker (1997)

Answer 4

• last glacial period earth’s climate frequent large changes (ice and sediment records show) - appear reflect ocean’s thermohaline system take multiple modes operation - relevance for modern high CO2 world and a reorganisation of the climate system
• Atlantic conveyor keeps north europe warm
• North Atlantic surface waters saltiest - particularly sensitive to fresh water input - how much fresh water to shut down conveyor
• greenland ice cores show switch intense cold and moderate cold past 60,000 yrs each interval intense cold matched ice-rafting event N Atlantic and increased dust (dust reflecting change storminess Asia as from Gobi desert)
• could not make current models atmospheric circulation / climate reproduce the conditions seen cores - thus implies different system mode
• models show link CO2 build up, climatic changes and collapse thermohaline circulation - is this valid real world (model limitations) - need take seriously for now the potential of thermohaline and climate changes - need to improve knowledge of the deep water formation process to prepare for the buildup of atmosphere GHGs - need long records also to tell apart natural and human causes
• need energy supply not load atmosphere with CO2 - suggests answer is to separate hydrogen atoms contained fossil fuels by reacting them with steam (not advocate renewables)

Question 5

Ganopolski et al (2016)

Glacial Inception

Answer 5

• normally transition glacial marked reduced summer insolation boreal latitudes northern hemisphere - this is occurring but no new ice age
• Suggest missed glacial inception before beginning industrial revolution due to high late-holocene CO2 emissions and low orbital eccentricity earth
• current interglacial w/o humans would be long but CO2 emissions humans postponed it further
• models suggest if CO2 240ppm then rapid ice growth thousands of years before the present w large ice sheets now - would glacial if pre-industrial CO2 40ppm lower (is natural? pre-industrial land use said contribute in part to holocene high CO2)
• essentially holocene long IG without humans but humans extending it - esp with lag time and long lifetime anthropogenic CO2 in atmosphere
• 500 gigatonnes carbon (cumulative) (slightly above present value) = evolution northern hemisphere ice sheets affected tens of thousands years - 1500 makes glacial inception unlikely 100,000 years - all IPCC scenarios over 1000 - thus humans will make next ice age impossible over time period comparable to whole past glacial cycles

Question 6

Ice cores EGs

Answer 6

1. Greenland ice sheet
   - GRIP (EU 1992) ice core - showed sub-milankovitch cycles
   - CISP (US 1993) ice core
   - 120,000 years
   - Operation Ice Bridge - scientists use radar data from NASA’s operation and earlier air campaigns built first comprehensive map layers deep inside ice sheet
2. Antarctica ice sheet
   - Vostok ice core record of 420,000 years

Question 7

Alley (2000)

Answer 7

Climate is like a drunk - when left alone, it sits; when forced to move, it staggers

Question 8

MacAyeal (1992)
vs
Bassis et al (2017)

Answer 8

Heinrich events = binge / purge cycles of ice sheets
- suggested ice sheet cyclical growth and decay was important for iceberg and freshwater flux to the ocean - which subsequently influences thermohaline circulation
- internal ice-sheet dynamics - grow ice sheet, more snow = gradual transition cold to warm
VS
- ice bergs released where warm ocean interacting with grounding line glacier - ice berg release = glacier thin and retreat = isostatic uplift of land in response

Question 9

Steven et al (2018)

Answer 9

Chinese loess record (Jingbian)

• depositional changes at site mark rapid env shifts East Asian desert margin
• showed dominant influence of ice volume on desert expansion
• East Asian Summer Monsoon variation matches ice volume - EASM not respond directly precessional forcing

Question 10

Lowe and Walker (2015)

Geomorphological Evidence

Answer 10

• landforms previous climates survived but to understand must understand process
• geomorphological mapping (landforms)
• reconstructing Quaternary history = determine altitude and differences altitude landforms to work out relative age
• remote sensing, aerial photography for landform patterns, satellite imagery, radar for ground surface roughness, sonar and seismic sensing (material goes through), digital elevation models / GIS
• Glacial landforms - palaeo-env indicators - thickness, extent, direction ice movement etc - end moraines, kame terraces, lateral and terminal moraine max positions glaciers - also periglacial features eg. ice wedges, patterned ground, pingos - may have been destroyed by later glacier though - streamlined features direction ice movement eg drumlins, striations from exposed bedrock (careful superimposed) - ice-sheet modelling
• sea level change - raised beaches, submerged landforms, reefs - note isostatic vs eustatic, tectonic etc - crustal deformation result of ice sheets - glaciologist-isostasy, hydro-isostasy - isostatic-recovery (rebound) - Norway still rising 1mm year
• River Terraces - evidence former river regimes - climate signals in records eg. DO oscillations and Little Ice Age
• Quat landforms low latitudes - arid playa lakes expand contract quat

Question 11

Lowe and Walker (2015)

Lithological Evidence

Answer 11

• SEDIMENT
• glacial sediments - former glacier types, mode deposition, ice-flow direction and source sediment supply - more widespread than landforms - sediment composition glaciers depends ice thickness, melting rate, topographic context, zone sediment accumulation -ice direction eg. erratics (foreign origin), till (orientated ice movement)
• periglacial sediments - freeze-thaw - ice wedges infilled show formally frozen ground (continuous permafrost Younger Dryas Britain / Ireland)
• Palaeosols - soil preserved as fossil soil buried under younger sediments - can deduce env conditions (problems of mixing and erosion tho)
• wind-blown sediments (loess) indicate former climate change and wind direction - Loess Plateau N China (sequence in sedimentary record of loss and palaeosols developed G/IG cycles)
• low-latitude lakes preserve sediment records - saline lakes, playa lakes, fluvial lakes - drainage basins may altered tectonics
• caves natural sediment traps, protected from weathering and erosion - carbonate deposits - speleothem layers carbonate (carbonate precipitation influenced climate conditions)
• lakes infilled sediment = mires and bogs - flora and fauna in deposits evidence past env conditions - glacial lakes can correlated IG/G cycles
• deep sea sediment - 018 and 16 values shells / skeletons reflect oceans 018/16 - G = 016 ice, 018 oceans
• ice-core - Greenland, Antarctica - thickness, trace gas, dust

Question 12

Local Quaternary Coastline

Answer 12

Northumberland coast / Easington Beach

- last glacial max marked by peat in Durham coast (G/IG env transition)

Question 13

Gibbard and Head (2009)

Quaternary type site

Answer 13

Cliff section at Monte San Nicola (Sicily, Italy) hosts golden spike or GSSP of the base Gelasian stage - now also defines base Quaternary and Pleistocene
- International Subcommission on Quaternary Stratigraphy now officially agreed Quaternary start 2.6Ma

Question 14

Walker et al (2009)

Holocene type site

Answer 14

• NGRIP Greenland ice core record mostly based to date GSSP for base holocene
• base holocene = first signs climatic warming at end Younger Dryas

Question 15

Walker and Lowe (2017)

Pollen record

Answer 15

Loch Ashik, Isle of Skye, NW Scotland

• basal gravel, clay gyttia and gyttia deposits = lateglacial interstadial (warming)
• silty-clay sediments loch lomond stadia (cold)
• holocene (warm)

Question 16

Taylor et al (2018)

Pollen Record

Answer 16

Starr Carr and Lake Flixton, Vale of Pickering (UK)

• record goes back 15,000 years
• pollen + other proxies show change palaeoenv conditions including human impacts
• lake large glacial max - surrounded ice sheers - becomes agricultural hot spot
• lake flixton shrinking lake (pollen record)
• reindeer antlers found

Question 17

Macleod et al (2011) / Coope and Rose (2008)

Answer 17

Croftamie - Younger Dryas type site UK

• C14 ages
• temp records from mutual climatic range of beetles

Question 18

Cosmogeic Surface Exposure Dating EG

Answer 18

Greenland ice sheet history

Question 19

Firestone et al (2007)

Answer 19

Bolide Impact

- linked meteorite to younger dryas - started to get warm, v cold point instead 1000 years

Question 20

External forcing - Solar EGs

Answer 20

• Little Ice Age cooling = decrease sunspots
• Medieval Warm Period = increased sunspots
  (lowe and walker, 2015 - extent solar cycles influenced holocene climate uncertain)

Question 21

IPCC (2018)

Answer 21

Must keep Global Warming below 1.5 degrees

Question 22

Maslin (2016)

Answer 22

• milankovitch linked to ice age cycles
• eccentricity = orbit circle / elliptical - 96,000 yrs
• obliquity = tilt earths axis - 41,000 years
• precession alters distance sun / earth - 21,000 years
• 1mn years ago 41,000 year cycles ice ages - past 8 100,000 years cycles

Question 23

Li and Born (2019)

Dansgaard - Oeschger events

Answer 23

• abrupt climate changes or large temp swings - cold / warm most evident N Atlantic
• cause overturning ocean circulation - freshwater trigger = overturn - stronger overturn, ocean more heat poleward
• see in greenland ice core records
• younger dryas cold (collapsing Laurentide ice sheet) - freshwater entry seas

Question 24

Bond et al (1993)

Answer 24

• D-O events - link ice sheets and ocean-atmosphere temp change - cycles culminating in iceberg discharge into N Atlantic (Heinrich event) = warmer climate
• ice-core temp cycles and heinrich events linked
• Younger Dryas - North Atlantic sea surface temp decrease, salinities dropped, icebergs from Labrador sea to North Atlantic (heinrich)
• Heinrich event occurs end D-O cycle bringing back warmth

Question 25

Li et al (2012) Lake Agassiz and 8.2 Leydet et al (2018 Younger Dryas

Answer 25

- freshwater pulses into North Atlantic (heinrich events) thought influence overturning circulation - trigger climate change eg. younger dryas, 8.2ka event - final drainage Lake Agassiz = 8.2 ka event in line with - overturn and cooling Younger Dryas due to freshwater outburst Glacial Lake Agassiz (Laurentide Ice sheet)

Question 26

Holden (2012)

Answer 26

- 2.6 mn yrs expansion / contraction glaciers - Glaciers and Glaciation - processes, landforms - Permafrost and periglacial environments - processes, landforms - Pleistocene (first epoch Quaternary 2.6mn to 11,700 yrs ago) - G/IG cycles (ocean cores) - Milakovitch cycles - eccentricity (orbit circular / elliptical, 100,000 yrs) - tilt 21 to 24 degrees 41,000 years - wobble axis = precession equinoxes, sun / moon gravity, determines where orbit season occur 19,000 and 23,0000 cycles - albedo, D-O events, bond cycles, heinrich events, Laurentide ice sheet drainage - env reconstruction - landforms (glacial, periglacial), river terraces, cave deposits, plants, insects - Dating methods - carbon dating, tree rings, sediments - Holocene (11,000 yrs to now - IG) - start transition from Younger Dryas (NGRIP) - Lake Aggiz into N Atlantic - Milakovitch cycles, sunspots 11-year cycle, ENSO, D-O cycles, Little Ice Age AD 1350-1900, retreating ice sheets, rising seas, Vikings, Medieval Warming Period, rise human civilisations and agriculture, deforestation, soil erosion, irrigation