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Climate > Week 18 > Flashcards

Week 18 Flashcards

1
Q

When was the LGM?

A

18ka BP

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2
Q

When was the last interglacial (aka)

A

12.5ka BP

aka

Younger Dryas
Emian

MIS 5e

Ipswichian

Sangamon

= numbering system where cold = even no. warm = odd no.

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3
Q

COLD: 18O, soil, pollen (European)

A

Low 18O in ice cores

Low clay/C in soil

Pollen = 100% herbs

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4
Q

WARM: 18O, soil, pollen (European)

A

High 18O in ice cores

High clay/C in soil

Pollen = 100% trees

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5
Q

Correlating marine and terrestrial records

A

Poor chronologies = broad range 11-23ka

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6
Q

Terrestrial dating

A

U-Th in stalagmites for low latitude climate change

13C decreases = increase in bio productivity
Growth hiatus
13C increases = decreasing bioproductivity

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7
Q

EPICA; facts

A

Record 6 glacial cycles

3.2km of ice core

650,000 years of record

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8
Q

EPICA; results

A

Modern CO2 conc = 30% higher than any point last 650,000 years

CO2 + T strongly coupled

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9
Q

Other evidence that agrees with epica’s coupling of CO2 and T

A

Vostok - last 450ka

Taylor Dome - last 15ka

Instrumental - last 40yr

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10
Q

Problems with ice cores

A
  1. RECORD T AND CO2
    - closure depth = depth of ice necessary to close ice from atmosphere
    - CO2 still mixing when T set = younger
  2. NICK SHACKLETON (18O sed cores) - (18O ice cores)
    - = G timing vs CO2/T
    - CO2/T changed 1st then ice
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11
Q

Current paradigm

A

T changes ~800 years before CO2

CO2 1st responds to T/deglaciation

?CO2 then drives +ve feedback

CO2 PROBABLY DRIVES BUT DOES NOT INITIATE

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12
Q

Evidence for increase in CO2

A

Deep sea sed cores = light (biogenic) C influx at G-termination

Interglacial C+80ppmv
= 170 GtC
= 60% fossil fuel burning C 180-1997

(BUT glacial world = very low biomass system???

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13
Q

Explanations for CO2 increase

A
  1. OCEAN DEGASSING
  2. IRON FERTILISATION HYPOTHESIS
  3. SHIFT IN TERRESTRIAL BIOMASS
  4. OCEAN CIRCULATION CHANGES
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14
Q
  1. Ocean degassing
A

Not primary source

MgCO3(s) < > Mg2+ + CO32-

CaCI3(s) < > Ca2+ + CO32-

H3O+ + CO32- < > HCO3- + H2O

H3O+ + HCO3- < > CO2(aq) + 2H2O

CO2 (aq) < > CO2(g)

CO2 more soluble in colder water

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15
Q
  1. Iron fertilisation hypothesis
A

“High Nutrient Low Chloropyll” (HNLC) in parts of S Ocean = Fe limiting agent on bio productivity

G = dust influx = alleviates
= increase CO2 uptake/exported to seafloor
= decreases atmospheric CO2

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16
Q

Pros for iron fertilisation hypothesis

A

Modern experiments show Fe fertilisation = phytoplankton blooms/CO2 sequestered

Explains increase in foraminerferal 13C in G

17
Q

Cons for iron fertilisation hypothesis

A

Dust flux timing doesn’t correspond with low CO2 timing

Would only account for ~50%

Initial change to cause dust input???

18
Q
  1. Shift in terrestrial biomass
A

G = fewer C sinks (less terrestrial biomass)
= CO2 lingers longer in atmosphere

IG = C stored in biospheric resources (peat/boreal forest)
= low T

19
Q
  1. Ocean circulation changes
A

Accounts for <50% CO2 G-IG variability

Decreases during g
As increase = released substantial deep ocean CO2 to atmosphere

20
Q

Other biological pump theories

A

Whole Ocean Nutrient Increase Theory

Nutrient Utilisation

CaCO3/Corg rain ratio

Silica leakage hypothesis

21
Q

Dansgaard Oeschger (DO) Events

A 
Sawtooth
Rapid increase in T
Gradual decrease in T
Millenial scale
23 between 110-23ka BP

= ?initiated by ice rafting events
= ice raft debris (IRD)

22
Q

Heinrich Events

A

H1-H6

Defined by grain ratios in N Atlantic sediment
Massive iceberg events
Initiate warming

23
Q

Glacial Lake Missoula; forming the hypothesis

A

J Harlen Bretz 1927 = channeled scablands/giant ripple marks due to FLOOD

Joe Pardee mapped area to E of channeled scablands as huge glacial lake = SOURCE

24
Q

What happened to Glacial Lake Missoula

A

Formed behind southern extension of Cordillera Ice Sheet - Purcell Lobe

Water deep enough = ice dam floated up
= water beneath escaped
= lake drains (10 x combined flow of world’s rivers)

Ice readvanced + refilled/emptied x 55 from 15ka bP

25
Q

Deglacial meltwater releases

A

MELTWATER PULSE 1A

YOUNGER DRYAS

8.2KA EVENT

26
Q

MELTWATER PULSE 1A

A

~14ka BP

+25M sl IN 500 YEARS

?Greenland/Antarctica

27
Q

G-IG asymmetry

A

G end quickly

IG end slowly

Involves carbon cycle

28
Q

YOUNGER DRYAS

A

Proglacial Lakes Agassiz/Ojibway = freshwater discharge

29
Q

8.2KA EVENT

A

100 x Lake Missoula

Proglacial Lakes Agassiz/Ojibway = freshwater discharge

Southern fringes of Laurentide ice sheet = dome over present day Hudson Bay
= 5 x freshwater of modern day great lakes

Dome collapsed

= 4.67x10^13 m3 through Hudson Strait to N Atlantic

Sl +0.5m w/in 2 days

30
Q

Climate before the 8.2ka event

A

Warm water went N with Gulf Stream
Separated into N Atlantic Drift
Cool/sink (NADW)
Flowed back to low lats

= conveyer

  • warm to N
  • cold to S

= Ireland = wet

31
Q

Climate caused by 8.2ka event

A

+low density freshwater = no sinking/NADW

= warmer water no longer flows to higher latitudes
= colder, drier

8’C max cooling
5’C N hemispheric cooling
Proxy; drier through N Atlantic

Climate (11 decks)

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