Azolla event talk june 2014 part 1

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

NATURE
June 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

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

for most of its history our planet had a greenhouse climate
a world with warm temperatures from pole to pole

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 Arctic
An ocean isolated from warm marine currents
present Arctic circulation

• basin is largely enclosed
• has little marine inflow

• basin is largely enclosed
• most input is from rivers

• the basin largely enclosed
• 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?

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
EPICA Dome C ice cores (Antarctic)

glacial-interglacial
cycles also show
strong CO2 cyclicity interglacial
glacial

280 ppm
but the maximum
approximates
280 ppm
glacial-interglacial
cycles also show
strong CO2 cyclicity

to the next glacial period?
So where are
we going now?

or another greenhouse world?

we need to go further
back in time
to get a better perspective

• 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
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

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

Azolla event talk june 2014 part 1

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Azolla event talk june 2014 part 1