Natural and anthropogenic climate change Lessons from ice cores - ESEU … · 2018. 7. 30. · Natural and anthropogenic climate change Lessons from ice cores Eric Wolff British Antarctic

Natural and anthropogenic climate change

Lessons from ice cores

Eric Wolff

British Antarctic Survey, Cambridge

[email protected]

ASE Annual Conference 2011; ESTA/ESEU lecture

Outline

• What is British Antarctic Survey (BAS), who

am I?

• Why the past, why ice cores?

• How do we collect ice cores?

• How do they work?

• 3 examples of what we have learnt

• Future plans

Climate: the polar regions are

• Iconic: undergoing changes visible at

planetary scale

Arctic sea ice decline

05 Sep 1980

14 Sep 2007

NOAA and NSIDC data

Climate: the polar regions are

• Iconic: undergoing changes visible at

planetary scale

• A centre of action: due to polar amplification

of climate

• At the root of important impacts (especially

sea level change)

• Vital sources of information about how the

climate system works

Palaeoclimate/palaeoatmosphereWhy do we need to understand the past?

• Curiosity – What? When? Why? Where?

• Processes – Observe how the climate/Earth

system responded under conditions

different to those of today

• Model validation – does the world behave

the way models suggest (in ways that matter

for the future)?

Criteria for sedimentary records

Essential

• Monotonic chronological

sequence

• Some feature of it that changes

in response to changes in the

parameter you want (for

example, temperature)

• Good signal to noise

(temperature is the dominant

factor controlling variability)

• Robust calibration/transfer

function

Desirable

• Good temporal resolution

• Length of record

• Geographical spread of

available records

• Cheap and simple collection

and analysis

Palaeo records• Historical records

• Tree rings

• Lakes - levels and sediments

• Peat

• Marine sediments

• Ice cores

• Other chronological sequences (e.g. corals)

Advantages and disadvantages to each

Ice coresisotopic content, gases, chemistry, precipitation

• Well-dated

• Annual resolution at some sites

• About 800 ka (Antarctic) and 120 ka (Greenland) available

• Atmospheric signals

• Many variables on same core

(1 ka = 1000 years)

• Dating becomes much

poorer in sites with low

snow accumulation rate

• Ice cores are

geographically limited and

deep cores are expensive

to obtain

Permanent ice cover, no significant melting, positive snow accumulation

i.e. Polar regions, high altitude mountain glaciers

Where can we collect ice cores?

Bedrock

Flow linesAccumulation zone

Ablation

The ice core record

One of many sedimentary records

Very good at recording the atmosphere

800,000 years (Antarctic) and 123,000 years (Greenland)

zone

Video courtesy of Lucia Simion

(not included in this version)

Signals in ice cores

1. The isotopic content of the water molecules themselves

(18O/16O and D/H) is determined mainly by the

temperature at the time of snowfall

The snow contains information about the

atmosphere in three forms:

2. Soluble and insoluble impurities are trapped at the

surface by falling snow, dry deposition and gaseous uptake

onto the surface

1883

1815

3. As the snow gets deeper,

pressure turns loose snow

into solid ice with trapped air

bubbles. The bubbles contain

a sample of stable gases from

the atmosphere: e.g CO2

The basic argument of

greenhouse warming

• Physics tells us that increasing the

concentrations of greenhouse gases traps

heat and causes climate on average to warm

• The concentration of major greenhouse

gases has increased significantly due to

human activities

CO2 has increased

280

320

360

400

1000 1200 1400 1600 1800 2000

Mauna Loa atmosphericLaw Dome (Etheridge et al., 1996)Siple (Friedli et al., 1986)EPICA DML (Siegenthaler et al., 2005)S. Pole (Siegenthaler et al., 2005)

Age / year AD

CO

2 /

pp

mv

And so has methane (CH4)

Etheridge et al 1998, JGR 103, 15979.

0

600

1200

1800

1000 1200 1400 1600 1800 2000

MacFarling Meure et al. (2006); Etheridge et al. (1998)Ice and firn airLine is Cape Grim air

Age / years AD

CH

4 /

ppb

v

Dome C

75ºS

3233 m asl

~25 kg m-2 yr-1

Mean T:-54.5ºC

DML

75ºS

2892 m asl

~64 kg m-2 yr-1

Mean T:-44.6ºC0km 1,000km 2,000km

80S°

70S°

60S°

Vostok

Dome F

Taylor

Dome

Byrd

Dronning

Maud Land

Siple Dome

Dome C

Law Dome

Berkner

Island

European Project for Ice Coring in Antarctica

(EPICA)

Dome C

• Depth reached 3270 m (bedrock 3275 m)

• Best estimate of useable age ~800 ka

-10

-5

0

5

0200400600800Age / thousands of years before present

Tem

pera

ture

rela

tive t

o

last

thou

san

d y

ea

rs /

°C

Estimated Antarctic temperature

EPICA Community Members, Nature, 429, 623-628, 2004; Jouzel et al., Science, 317, 793-796, 2007.

-10

-5

0

5


Tem

pera

ture

rela

tive t

o

last

thou

san

d y

ea

rs /

°C

Estimated Antarctic temperature

EPICA Community Members, Nature, 429, 623-628, 2004; Jouzel et al., Science, 317, 793-796, 2007.

• ~100 ka cycles of warm and cold (warm is short)

• Tendency to stronger cycles in later part of period

• Every warm period is different!

• CO2 responsible for 30-50% of the glacial-interglacial warming

• probably controlled mainly through processes in the Southern Ocean

-10

-5

0

5


Tem

pera

ture

rela

tive to

last th

ousand y

ears

/ °

C

200

250

300C

O2 / p

pm

v Lüthi et al 2008

What does CO2 do in a changing climate?

But we are out of the range of the last 800 ka

200

250

300

350

400

CO

2 / p

pm

v

-10

-5

0

5


Tem

pera

ture

rela

tive to

last th

ousand y

ears

/ °

C

• In rate as well as concentration:

– Last termination rate was ~20 ppmv/1000 years

– 20 ppmv increase in last 11 years

Dome C

detailed CO2Updated from Monnin et al

(2001) Science 291, 112-114

Phasing is

consistent with CO2

as an amplifier

200

220

240

260

280

CO

2 / p

pm

v

-10

-5

0

900012000150001800021000Age / years before present

Te

mp

era

ture

re

lative

to la

st

10

00

yrs

/ °

C

For CH4 (methane) also

400

600

800Loulergue et al 2008

CH

4 /

pp

bv

-10

-5

0

5

0200400600800

Jouzel et al 2007

Age / thousands of years before present

Te

mp

era

ture

re

lative

to

la

st

tho

usa

nd

ye

ars

/ °

C

-10

-5

0

5


Te

mp

era

ture

rela

tive

to

la

st

tho

usa

nd

ye

ars

/ °

C 400

600

800

1000

1200

1400

1600

1800C

H4 /

pp

bv

Many other things we can measure – but

ice cores are only part of the picture

2.5

3.0

3.5

4.0

4.5

LR04 benthic stackδ

18O

marine / ‰

-450

-420

-390

02004006008001000

EPICA Dome C


δD

ice / ‰

-450

-420

-390

0200400600800

EPICA Dome C


δD

ice / ‰

2.5

3.0

3.5

4.0

4.5

LR04 benthic stack

δ18O

marine / ‰

0

25

50

75

100 Tenaghi Philippon, GreeceA

rbore

al

polle

n / %

-450

-420

-390

0200400600800

9°C

EPICA Dome C


δD

ice /

‰EPICA Community Members, Nature, 429, 623-628, 2004;

Jouzel et al, Science, 317, 793-796, 2007

And Antarctica is only part of the picture

Greenland

Rapid Climate Change

-45

-40

-35

0255075100125

NorthGRIP

Age / kyr BP

δ1

8O

/ ‰

-450

-425

-400

-375

Dome C

δD

/ ‰

-45

-40

-35

-30

0306090120

NorthGRIP Project Members 2004


δ18O

/ ‰

-45

-40

-35

-30


δ18O

/ ‰

Discovery of rapid (in a

human lifetime) climate shifts

from a Greenland ice core(Dansgaard-Oeschger events)

North GRIP Project Members 2004

~10ºC

WARM

COLD

Footprint of D-O events

throughout northern hemisphere

• Greenland

• Atlantic SSTs

• Santa Barbara Basin

• Cariaco Basin (Venezuela)

• Arabian Sea

• ?Tropical wetlands (methane)

• ?China (dust to Greenland)

Clues to the mechanism

Blunier and Brook 2001

(Science)

Antarctica vs the

north

Beware:

time running

in reverse

Ideas about mechanism

• Freshwater (ice or lake drainage) to North Atlantic

�Changes density structure of ocean, reducing sinking

�Collapsed or reduced meridional overturning circulation (MOC)

�Cooling and atmospheric circulation changes in NH (northern hemisphere)

� Some warming in south (Bipolar seesaw)

• Restart of MOC spontaneous or forced by freshwater in Southern Ocean

Significance of D-O events

• Rapid change has occurred in the past, but

as far as we know only when there are large

ice sheets

• But models for the future do suggest

changes in thermohaline circulation

• Need to better understand past changes and

test models against them

Future ice core researchInternational Partnership in Ice Core Science (IPICS)

• Longer records – Dome C and beyond (1.5 Ma?)

• Older ice in Greenland (full interglacial)

• Detailed regional pattern for transition and Holocene around Antarctica and Arctic

• Spatial pattern of climate change over last 2000 years (global) 0km 1,000km 2,000km

80S°

70S°

60S°

Vostok

Dome F

TaylorDome

Byrd

Dronning

Maud Land

Siple Dome

Dome C

Law Dome

Berkner

Island

Context: longer-term cooling

Age / Ma

Based on Zachos et al 2001

3

4

5


δ18O

/ ‰

3

4

5


δ1

8O

/ ‰

Changing amplitude and period

From marine sediments (Lisiecki and Raymo 2005 [LR04])

40 ka 100 ka

Summary – ice core records

• A fantastic archive of our past

• Have provided our only clear record of recent

greenhouse gas increases, as well as data on

natural forcings

• Over longer periods shown strong link between

climate and greenhouse gases

• Revealed existence of past rapid climate change

• Shows us how Earth works: needed for future

prediction

Thank you

Documents

Natural and anthropogenic climate change Lessons from ice cores - ESEU … · 2018. 7. 30. · Natural and anthropogenic climate change Lessons from ice cores Eric Wolff British Antarctic