THE AZOLLA STORY

HOW AN AMAZING PLANT CHANGED

OUR CLIMATE 50 MILLION YEARS AGO

(FIRST HALF OF THE TALK)

DR JONATHAN BUJAK

THE TALK IS SPLIT DUE TO ITS LENGTH

THIS IS THE FIRST HALF OF THE TALK

NATUREJune 1, 2006

THE

CENOZOIC

ARCTIC

OCEAN

Greenhouse to

icehouse

in 55 million years

NEW YORK TIMES November 30, 2004

Need a picture of NYT page

Under All That Ice, Maybe Oil

Great Green North“Was the icy Arctic once a warm soup of life?”

NATIONAL GEOGRAPHIC May 2005

THIS IS THE STORY OF THE EVENTS

BEHIND THESE HEADLINES

PART 1

CLIMATE CHANGE

FROM GREENHOUSE TO ICEHOUSE

this is our

beautiful planet

a rare world

that is teaming

with life

it is a world with glaciation at both poles

that geologists call

a bipolar icehouse world

glacial

interglacial

a world that flips

between glacial and

interglacial phases

we think of our climate as being normal

but it is very rare

and we last see this in the early Eocene just over 50 million years ago

we know of no previous time when our planet had bipolar glaciation

and we last see this in the early Eocene just over 50 million years ago

for most of its history our planet had a greenhouse climate

a world with warm temperatures from pole to pole

and we last see this in the early Eocene just over 50 million years ago

we last saw this in the early Eocene just over 50 million years ago

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lush forests grew on Ellesmere Island just a few hundred kilometres

from the North Pole where temperatures rarely climb above freezing today

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pole

Ellesmere

icehouse

and then, 50 million years ago the climate

abruptly shifted towards an icehouse state

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icehouse

to understand why we need to first look

at the land – sea configuration at the poles

which results from plate tectonics

PART 2

PLATE TECTONICS & MARINE GATEWAYS

Arctic: isolate an ocean

Antarctic: isolate a landmass

isolate polar regions from warm marine currents

HOW TO MAKE AN ICEHOUSE WORLD

STEP ONE

The Antarctic:a landmass isolated from warm marine currents

present Antarctic

circulation

the plate tectonic

separation of Antarctica

from Australia and

South America…..

….. isolated the Antarctic

landmass, permitting the

development of the

circum Antarctic current

due to the Earth’s rotation

and initiation of modern

deep-water circulation*

during the

Eocene-Oligocene

(*the Oceanic Conveyer

first recognized by

Wally Broecker)

this set the stage for

subsequent changes

in oceanic circulation

during the Cenozoic

leading to today’s

circulation system

The ArcticAn ocean isolated from warm marine currents

present Arctic circulation

• basin is largely enclosed

• has little marine inflow

• basin is largely enclosed

• has little marine inflow

• most input is from rivers

• the basin largely enclosed

• has little marine inflow

• most input from rivers

• so salinity is locally lowered

But the Arctic was already

isolated by the Paleocene

….. and it had much warmer

temperatures than today

WHY?

PART 3

greenhouse gases

greenhouse gases

are very significant

and CO2 is

particularly important

now the focus of intense research

many studies currently in progress

others are published but controversial

atmospheric CO2

for example -

a 1000 year

record from

ice cores

Source: Etheridge et al. 1996, 1998

which has been

used to distinguish

pre- and post

industrial values

pre post

here is the same

CO2 curve

rotated through

ninety degrees

pre industrial

values average

280 parts per

million (ppm)

but interpretations

of post industrial

values are

controversial

how much is man

made?

and how much is

due to natural

cyclicity?

how much is man

made?

how much is

natural cyclicity?

need a better

geological

perspective

extending

back into

Pleistocene

Sources: Am Ass Adv Science November 2005;

Science November 2005

EPICA Dome C ice cores (Antarctic)

Note change in CO2 scale

Sources: Am Ass Adv Science November 2005;

Science November 2005

EPICA Dome C ice cores (Antarctic)

glacial-interglacial

cycles also show

strong CO2 cyclicityinterglacial

glacial

Sources: Am Ass Adv Science November 2005;

Science November 2005

280 ppm

but the maximum

approximates

280 ppm

glacial-interglacial

cycles also show

strong CO2 cyclicity

So where are

we going now?

to the next glacial period?

So where are

we going now?

or another greenhouse world?

to the next glacial period?

we need to go further

back in time

to get a better perspective

to the next glacial period?

going back

to the Paleogene

• CO2 determined from

boron 11 isotope in forams

• isotope changes reflect shifts in

surface water acidity and

atmospheric CO2

going back

to the Paleogene

poor data

note change

in CO2 scale

Oligocene-mid Miocene

values reach 600 ppm

600

ppm

poor data

into the Eocene

poor data

we see an abrupt fall in

CO2 at the end of the

Eocene to values

below 1000 ppm

poor data

major Antarctic glaciation

The onset of Antarctic

glaciation was previously

related to thermal

isolation of Antarctica

poor data

major Antarctic glaciation

but GCM studies now

show that Antarctic

glaciation cannot

occur unless CO2 ppm

is less than 1000 ppm

poor datamajor Antarctic

glaciation

1200 ppm

poor data

1200 ppm

800 ppm

fall in CO2

major Antarctic

glaciation

poor data

1200 ppm

800 ppm

600 ppm

fall in CO2

major Antarctic

glaciation

poor data

GCM studies agree with the

geological record of major

Antarctic glaciation in the

earliest Oligocene

major Antarctic

glaciation

poor data

1200 ppm

800 ppm

600 ppm

can this be used to predict the

effect of future increases in CO2 ?

poor data

middle-late Eocene values fluctuate

was this a period of readjustment?

back into the early Eocene

Sources: Trapiti et al. Nature July 2005

Pagani et al. Science July 2005

Pearson & Palmer Nature August 2000

Paleocene - early Eocene

values reach 3500 ppm

we see a major decrease at

the base of the Middle Eocene

from 3500ppm to 600 ppm

Why?

temperature change

from greenhouse

to icehouse

PART 4

Paleocene

the greenhouse climate was

inherited from the Mesozoic

• low latitudinal thermal gradient

• warm Arctic temperatures

• yet Arctic largely enclosed

temperatures estimated by

• various marine and terrestrial markers

• oxygen isotopes

• Global Climate Models

so we can estimate Palaeocene Mean Annual Temperatures (MAT)

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Source: Triparti et al. 2001

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note the warm Arctic Mean Annual Temperatures

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Source: Triparti et al. 2001

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these values agree with

General Climatic Models (GCMs)

which calculate MAT’s with

different levels of atmospheric CO2

Arctic MAT

(observed

Mean Annual

Temperatures)

GCM’s

indicate at least

x 6 modern

pre industrial

CO2 values

in the early

Eocene

cooler

warmer

The oxygen isotope curve is also

now well-established for the

Cenozoic (Zachos et al. 2001)

icehouse

greenhouse

shows the change from greenhouse to icehouse

and the Paleocene Eocene Thermal Maximum

and the extremely warming,

including polar regions

Paleocene Eocene Thermal Maximum [PETM]

supergreenhouse state triggered by increased greenhouse gases from

• extensive volcanism

• release of methane clathrates

this is coeval with

maximum activity

of the Greenland

Mantle Plume

which also increased

isolation of the

Arctic Basin

PETM was followed by early Eocene supergreenhouse

• Arctic Basin largely enclosed

• abundant greenhouse gasses following PETM

• high temperatures

but Early Eocene supergreenhouse

was followed immediately

by abrupt global cooling

What forced this change?

the massive

decrease in

atmospheric

CO2

but why did

atmospheric CO2 fall so

dramatrically

50 million years ago?

the answer finally came in 2004

when the Integrated Ocean

Drilling Project (IODP) was

finally able to drill

in the Arctic due to

reduced ice cover…..

1979

2004

1979

end of the first half of the talk

1979