Azolla event talk june 2014 part 1
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Transcript of 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
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