nature june 1, 2006 the cenozoic arctic ocean greenhouse to icehouse in 55 million years

NATURENATUREJune 1, 2006June 1, 2006

THECENOZOICARCTICOCEAN

Greenhouse to icehousein 55 million years

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

NATIONAL GEOGRAPHIC May 2005NATIONAL GEOGRAPHIC May 2005

NEW YORK TIMES November 30, 2004NEW YORK TIMES November 30, 2004

Need a picture of NYT page

Under All That Ice, Maybe Oil

THE AZOLLA STORYTHE AZOLLA STORY

IMPLICATIONS FORIMPLICATIONS FOR

CLIMATE CHANGECLIMATE CHANGEANDAND

ARCTIC SOURCE ROCKSARCTIC SOURCE ROCKS

PART 1PART 1

CLIMATE CHANGECLIMATE CHANGE

FROM GREENHOUSE TO ICEHOUSEFROM GREENHOUSE TO ICEHOUSE

MODERN ICEHOUSE WORLD

bipolar glaciation

MODERN ICEHOUSE WORLD

bipolar glaciation

Antarctic

Arctic

bipolar glaciation

geological rare

possibly unique

we think of this as ‘normal’…but

no previous bipolar glacial state is known from the geological record

icehouse world also characterized byicehouse world also characterized by

glacial – interglacial cycles

icehouse world also characterized byicehouse world also characterized by

high latitudinal thermal gradient

Mesozoic greenhouse worldMesozoic greenhouse world

• no bipolar glaciation

• low latitude thermal gradient

differed strongly from the modern icehouse world

determining the cause of climate changeis crucial today to

• understand the shift from greenhouse to icehouse

• understand the reasons for glacials and interglacials

and to understand where we are going next

so why is the modern icehouse world so why is the modern icehouse world geologically rare?geologically rare?

we need to look at two geological we need to look at two geological controls on long-term climate changecontrols on long-term climate change

PART 2PART 2

PLATE TECTONICS & MARINE GATEWAYSPLATE TECTONICS & MARINE GATEWAYS

isolate polar regions from warm marine currents

HOW TO MAKE AN ICEHOUSE WORLDHOW TO MAKE AN ICEHOUSE WORLD

STEP ONESTEP ONE

Antarctica landmass isolated from warm marine currents

Antarctica landmass isolated from warm marine currents

and centred on the South Pole

resulted from separation of Antarctica from Australia & South America

development of circum Antarctic current

initiation of moderncold deep-water oxygen-rich circulation

occurred during the Eocene to early Miocenewith a major step at the Eocene/Oligocene transition

ArcticAn ocean isolated from warm marine currents

centred on the North Pole

ArcticAn ocean isolated from warm marine currents

• basin largely enclosed

• single marine gateway

• freshwater input from rivers

• freshwater input from rivers

• locally lowering salinity

• preventing marine inflow into central Arctic

plate tectonics resulted in

isolated Arctic Ocean isolated Antarctic continent

thermal isolation of polar regions depended on unusual land-sea configuration at both poles at the same time

but this only provided the background needed to produce bipolar glaciation

for this to develop we also need to add the second major parameter to the story………

the atmosphere

PART 3

greenhouse gases

PART 3

greenhouse gases

• CO2 particularly important

• very significant

• today and in the past

now the focus of intense research

the debate is very controversial

atmospheric COatmospheric CO22

atmospheric COatmospheric CO2 2 through timethrough time

atmospheric COatmospheric CO2 2 through timethrough timeCharles Keeling – measured pCO2 over the past 50 years

atmospheric COatmospheric CO2 2 through timethrough time

1958 to present

Mauna Loa, Hawaii and la Jolla

and other locations worldwide

La Jolla Pier California

CO2 values measured in parts per million

due to northern spring drawdown

and autumn/fall CO2 release

annualcyclicityof 5ppm

increase from 320ppm to380ppm

we can look at older CO2 values using air trapped in ice cores

Source: Etheridge et al. 1996, 1998

can include the Keeling data

and rotate the graph

1958

Keeling data

Keeling dataice core data

how much is man made?

how much is natural cyclicity?

need a bettergeological perspective

we need to go we need to go further back in timefurther back in time

almost half a million yearsalmost half a million years

Sources: Petit et al. (Nature 1999); Am Ass Adv Science November 2005; Science November 2005

using Vostok ice cores from the Antarctic

Vostok

note the change in CO2 scale

glacial

interglacialwe see strong fluctuations in CO2 that correlate closely with changes in temperature and glacial-interglacial cycles

glacial

temperature

glacials

with CO2 decreasing during glacials due to increased CO2 sequestration by the colder waters in the oceans

and peaking during interglacials as higher temperatures lead to CO2 release from the oceans

interglacial

glacialinterglacials

temperature

interglacial

glacial

Sources: Am Ass Adv Science November 2005;Science November 2005

glacial-interglacialphases initiallytriggered byMilankovitch cycles

interglacial

glacial



reinforced byresulting CO2

cyclicity due toocean dissolution


interglacial

glacial


reinforced byresulting CO2

cyclicity due toocean dissolution

with CO2 followingtemperature byabout 800 years

today’s situation differs

280

we are now at 380 ppm

380100 ppm higher than previous 280 ppm peaks

today’s situation differs

280

we are now at 280 ppm

380100 ppm higher than previous 280 ppm peaks

and CO2 appears to be leading temperature

let’s go let’s go further back further back in timein time

into theinto theMioceneMiocene

we now need to use proxies to estimate values of atmospheric CO2

CO2 determined fromboron 11 and alkenoid carbon isotopesbacked up by other data

poor data

note changein CO2 scale

poor data

Oligocene-mid Miocenevalues reach 600 ppm

600 ppm

poor data

extending further back into the Eocene

poor data

CO2 values exceed 1000 ppm

poor data

we see an abrupt fall in CO2 at the base Oligocene to below 1000 ppm

poor data

coincident with the onset of modern cold deep-water circulation

coincident with major development of cold bottom-water circulation

did this sequester CO2?

poor datamajor Antarctic glaciation

climate models also indicate that full Antarctic glaciation cannot occur unless CO2 ppm is less than 1000 ppm

poor data

minor glaciation

1200 ppm

1200 ppm

1200 ppm

poor data

1200 ppm

800 ppm

fall in CO2

800 ppm

increased glaciation

800 ppm

poor data

1200 ppm

800 ppm

600 ppm

fall in CO2

600 ppm

extensive continental glaciation

poor data

1200 ppm

800 ppm

600 ppm

can this be used to predict the effect of future increases in CO2

on Antarctic deglaciation?

poor data

preliminary data also indicate that middle-late Eocene values fluctuate strongly

poor data

was this a period of readjustment?

what were earlier CO2 values?

back into the early Eocene

Sources: Tripati et al. Nature July 2005Pagani et al. Science July 2005Pearson & Palmer Nature August 2000

Sources: Tripati et al. Nature July 2005Pagani et al. Science July 2005Pearson & Palmer Nature August 2000

CO2 values reach 3500 ppm

so we see a major decrease at base of the Middle Eocene from3500ppm to 600 ppm

what effect did thishave on temperature?

temperature changefrom greenhouseto icehouse

PART 4

Paleocene temperaturesPaleocene temperatures

greenhouse state inherited from the Mesozoic

Arctic centred on the North Pole

low latitudinal thermal gradient

warm Arctic temperatures

temperatures estimated by

• various marine and terrestrial markers

• oxygen isotopes

• climate models

we can therefore estimate Palaeocene Mean Annual Temperatures

11

23

11

11

23

11

2222

1916

12

2417

20 26

Source: Triparti et al. 2001

17

which indicate warm Arctic temperatures

11

23

11

11

23

11

2222

1916

12

2417

20 26

Source: Triparti et al. 2001

17

but with seasonality -resulting in Arctic environments totally unknown today

11

23

11

11

23

11

2222

1916

12

2417

20 26

17

- 24 hour summer daylight and 24 winter darkness

within a region of warm air and sea temperatures

11

23

11

11

23

11

2222

1916

12

2417

20 26

17

climate models indicate these temperatures required about x10 modern CO2 levels

= about 3500 ppm

climate models indicate these temperatures required about x10 modern CO2 levels

= about 3500 ppm

consistent with isotope data

we can also look at temperature change through the Cenozoic

cooler

warmer

using oxygen isotopes as a proxy for temperature

icehouse

greenhouse

these show the change from greenhouse to icehouse

and the Paleocene Eocene Thermal Maximum

and very high temperatures

including polar regions

which resulted in awhich resulted in asupergreenhouse worldsupergreenhouse world

Paleocene Eocene Thermal MaximumPaleocene Eocene Thermal Maximum

triggered by increased greenhouse gases from

• extensive volcanism (Greenland plume)

• release of methane clathrates (hydrates)

abundant greenhouse gases

high temperatures

supergreenhouse state continued supergreenhouse state continued through the early Eocenethrough the early Eocene

but early Eocene supergreenhousewas followed immediately by abrupt global cooling

what forced this change?

the massive decrease in

atmospheric CO2?

Arctic Coring Expedition (ACEX)Arctic Coring Expedition (ACEX)

PART 5PART 5


• August – September 2004


• August – September 2004• first International ODP cruise into the Arctic• supported by Norwegian and Russian icebreakers

successfully cored the Lomonosov Ridge

ACEX resultsACEX results


• 1400 ft cored section

• good Paleocene Eocene section recovered


Azolla event

PETM

ACEX Azolla coreACEX Azolla core

• 8 to 20m metre ACEX core with >90% Azolla

• base not cored

• Azolla occurs as laminated layers

• indicates Azolla deposited in situ

• in a ‘marine’ setting away from shore

Age of the Azolla eventAge of the Azolla event

Azolla event also present in Arctic exploration wells

and transported south into Nordic seas

i

Brinkhuis et al., Nature, 2006

so we can establish the age of the Azolla event

base Middle Eocene

lasted about 800,000 years

coeval with onset of Arctic cooling

coeval with onset of Antarctic glaciation

coeval with massive fall in CO2

Azolla event: summaryAzolla event: summary

is this coincidence?

or is there a relationshipbetween Azolla and CO2?

modern and fossil Azollamodern and fossil Azolla

PART 6PART 6

what is Azolla?what is Azolla?

• floating aquatic freshwater fern

• known from Cretaceous to present

• so we can look at habitats of modern species

fossil Azolla from the Eocene Green River Formationfossil Azolla from the Eocene Green River Formation

is identical in morphology to modern Azollais identical in morphology to modern Azolla

what do we know about modern Azolla?what do we know about modern Azolla?

fastest growing plant on the planet!fastest growing plant on the planet!

doubles its biomass in 2 to 3 daysdoubles its biomass in 2 to 3 days

widely used as a green biofertilizer for rice fieldswidely used as a green biofertilizer for rice fields

why is it a fertilizer?why is it a fertilizer?

why does it have why does it have rapid growth?rapid growth?

how can it grow free-floating on water how can it grow free-floating on water without soil nutrients?without soil nutrients?

source: Carrapiço, 2002

the key is the key is Azolla’s leaf Azolla’s leaf structurestructure


its leaves are its leaves are characterised characterised by cavitiesby cavities


filled with nitrogen

inhabited by a nitrogen-fixing cyanobacterium (blue-green alga) Anabaena

leaf cavitiesleaf cavities

Azolla’s sporophyteAzolla’s sporophytesporocarpssporocarps

megasporocarpmegasporocarp

megasporocarp’s chambermegasporocarp’s chamber


fertilizationfertilization

new sporophytenew sporophyte

(Carrapiço, 2006)

Anabaena symbiont has been passed to successive generations via Azolla spores

Azolla’s sporophyteAzolla’s sporophytesporocarpssporocarps

megasporocarpmegasporocarp



fertilizationfertilization

new sporophytenew sporophyte

(Carrapiço, 2006)

for more than hundred million years!

providing a natural biofertilizer in the water for rice production

so Azolla-Anabaena can fix more than 1000 kg of atmospheric nitrogen per acre per year

the nitrogen is also available for rapid growth of the Azolla plant

which can then fix up to 6000 kg of atmospheric carbon per acre per year free-floating on water

it is the only known known symbiont of this kind

to summarize to summarize

• Azolla floating freshwater fern (no salinity tolerance)

• draws down large quantities of C & N

• doubles biomass in 2 - 3 days…….and

• temperature tolerant

• optimum growth 20 hours of daylight

i

PART 7PART 7

Arctic Eocene modelArctic Eocene model

i

what triggered the Azolla event?what triggered the Azolla event?

i

• Arctic Basin largely enclosed following the PETM


i

• Arctic Basin largely enclosed

• high temperature, rainfall & runoff


i



• widespread surface freshwater layer


i



• widespread surface freshwater layer

• atmosphere rich in C & N

• abundant nutrients flushed into basin


i

ideal conditions for opportunistic Azollaideal conditions for opportunistic Azolla

model of Azolla growth and deposition

local anoxia

variable water stratification and bottom water anoxia



Azolla deposited in anoxic conditions

and was therefore able to drawdown carbon

Azolla model of climate changeAzolla model of climate change

• AzollaAzolla blooms widespread in Arcticblooms widespread in Arctic

freshwater surface layersfreshwater surface layers

• occurred episodically for about 800,000 yearsoccurred episodically for about 800,000 years

resulting in massive resulting in massive

carbon drawdowncarbon drawdown

and the onset of coolingand the onset of cooling

triggering the shifttriggering the shift

from superfrom supergreenhousegreenhouse

towards the moderntowards the modern

icehouse state aticehouse state at

base Middlebase Middle EoceneEocene

• 6000 kg of carbon per acre each year6000 kg of carbon per acre each year

• = 6000,000 kg of carbon per acre in 1000 years= 6000,000 kg of carbon per acre in 1000 years

Source: ACEX scientists preliminary unpublished data

we can estimate amount of carbon we can estimate amount of carbon from modern Azolla productionfrom modern Azolla production

carbon drawdown for Azolla eventcarbon drawdown for Azolla event

• TIME: up to 800,000 yearsTIME: up to 800,000 years

• AREA: up to 4,000,000 sq kmAREA: up to 4,000,000 sq km

carbon drawdown for Azolla eventcarbon drawdown for Azolla event

• TIME: up to 800,000 yearsTIME: up to 800,000 years

• AREA: up to 4,000,000 sq kmAREA: up to 4,000,000 sq km

easily sufficient to change COeasily sufficient to change CO22 from 3500 to 650 ppm from 3500 to 650 ppm

even with time and area strongly scaled downeven with time and area strongly scaled down

so the Azolla event couldso the Azolla event couldhave triggered the initial shift have triggered the initial shift

from a greenhouse world towards from a greenhouse world towards our modern icehouse planet!our modern icehouse planet!

PART 8PART 8

implications for Arctic petroleumimplications for Arctic petroleum

Arctic petroleum resources are Arctic petroleum resources are now becoming very significantnow becoming very significant

and controversial…..and controversial…..

TIME MAGAZINETIME MAGAZINEOctober 1 2007October 1 2007

Who Owns the Arctic?

Fight for the Top of the World

could the Azolla interval providecould the Azolla interval providea source for Arctic petroleum?a source for Arctic petroleum?

• large amount of C possibly deposited in Arctic Basin

• unusual source – includes cyanobacterial symbiont

Azolla event - implications for Arctic petroleumAzolla event - implications for Arctic petroleum

• occurs at ACEX location near central Arctic

• also present in numerous Alaskan and Canadian wells

Azolla event - implications for Arctic petroleumAzolla event - implications for Arctic petroleum

Canadian BeaufortCanadian Beaufort

northern Alaskanorthern Alaska

Chukchi SeaChukchi Sea

ACEXACEX

Bujak well databaseBujak well databaseextends data points extends data points beyond ACEXbeyond ACEX

• Canadian BeaufortCanadian Beaufort

• northern Alaskanorthern Alaska

• Chukchi SeaChukchi Sea

Canadian BeaufortCanadian Beaufort



ACEXACEX

in a variety of in a variety of environmentsenvironments

Canadian Beaufort: 28 wells in various deltaic facies

northern Alaska and Chukchi Sea

• 27 wells away from the delta

• various nearshore to offshore locations

Mik

kels

en 1

3-9-

19

4500'

4750'

5000'

5250'

5500'

5750'

6000'

6250'

6500'

Gamma Log(API)0 150

Alaska well

4460

T6

TEU4837.0

T4b

5100.0

T4a

Azolla5260.0

T3(iii)

5550

T3(ii)

5690.0

T3(i)

T2(ii) PETM6050.0

6642.0

T2(i)

Azolla and PETM events exactly the same age as in the ACEX cores based on palynological zones

Azolla event

PETM event

source Bujak unpublished data

Mik

kels

en 1

3-9-

19

4500'

4750'

5000'

5250'

5500'

5750'

6000'

6250'

6500'

Gamma Log(API)0 150

Alaska well

4460

T6

TEU4837.0

T4b

5100.0

T4a

Azolla5260.0

T3(iii)

5550

T3(ii)

5690.0

T3(i)

T2(ii) PETM6050.0

6642.0

T2(i)

both events are also characterised by distinctive high-gamma curves

Azolla event

PETM event

Canadian and Alaskan well dataCanadian and Alaskan well data

age and source rock potential are consistentwith preliminaryACEX results

indicates a possible Arctic-wide source rock

indicates a possible Arctic-wide source rock

gas prone with minor mixed oil/gas potential

TOC up to 5.5%

onset of maturationabout 0.8% Ro

but we don’t know its geographic extent

Canadian BMBCanadian BMB



ACEXACEX so we need to so we need to extend database extend database into other Arctic into other Arctic areasareas

and finally………..and finally………..

did Azolla really change the Earth from

a supergreenhouse to icehouse state?

the answer has important implications for

past & modern climate change -

which are crucially significant today

not only for not only for

the Arcticthe Arctic

but for the but for the

entire planetentire planet

thank youthank you

nature june 1, 2006 the cenozoic arctic ocean greenhouse to icehouse in 55 million years

Documents

icehouse slide

time slide

story slide

past slide

oil slide

normalbut slide

atmosphere slide

interglacials slide