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NATURE June 1, 2006 THE CENOZOIC ARCTIC OCEAN Greenhouse to icehouse in 55 million years NATIONAL GEOGRAPHIC May 2005 Great Green North “Was the icy Arctic once a warm soup of life?” NEW YORK TIMES November 30, 2004 Under All That Ice, Maybe Oil Need a picture of NYT page THE AZOLLA STORY IMPLICATIONS FOR CLIMATE CHANGE AND ARCTIC SOURCE ROCKS PART 1 CLIMATE CHANGE FROM GREENHOUSE TO ICEHOUSE MODERN ICEHOUSE WORLD bipolar glaciation MODERN ICEHOUSE WORLD Arctic bipolar glaciation Antarctic we think of this as ‘normal’…but bipolar glaciation geological rare possibly unique no previous bipolar glacial state is known from the geological record icehouse world also characterized by glacial – interglacial cycles icehouse world also characterized by high latitudinal thermal gradient Mesozoic greenhouse world differed strongly from the modern icehouse world • no bipolar glaciation • low latitude thermal gradient determining the cause of climate change is crucial today to • understand the reasons for glacials and interglacials • understand the shift from greenhouse to icehouse and to understand where we are going next so why is the modern icehouse world geologically rare? we need to look at two geological controls on long-term climate change PART 2 PLATE TECTONICS & MARINE GATEWAYS HOW TO MAKE AN ICEHOUSE WORLD STEP ONE isolate polar regions from warm marine currents Antarctic a landmass isolated from warm marine currents Antarctic a 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 modern cold deep-water oxygen-rich circulation occurred during the Eocene to early Miocene with a major step at the Eocene/Oligocene transition Arctic An ocean isolated from warm marine currents Arctic An ocean isolated from warm marine currents centred on the North Pole • 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 atmospheric CO2 now the focus of intense research the debate is very controversial atmospheric CO2 through time atmospheric CO2 through time Charles Keeling – measured pCO2 over the past 50 years atmospheric CO2 through 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 annual cyclicity of 5ppm due to northern spring drawdown and autumn/fall CO2 release increase from 320ppm to 380ppm 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 ice core data Keeling data how much is man made? how much is natural cyclicity? need a better geological perspective we need to go further back in time almost half a million years using Vostok ice cores from the Antarctic Vostok Sources: Petit et al. (Nature 1999); Am Ass Adv Science November 2005; Science November 2005 note the change in CO2 scale glacial we see strong fluctuations in CO2 that correlate closely with changes in temperature and glacial-interglacial cycles interglacial with CO2 decreasing during glacials due to increased CO2 sequestration by the colder waters in the oceans temperature glacials glacial and peaking during interglacials as higher temperatures lead to CO2 release from the oceans temperature interglacials glacial interglacial glacial-interglacial phases initially triggered by Milankovitch cycles glacial interglacial Sources: Am Ass Adv Science November 2005; Science November 2005 glacial-interglacial phases initially triggered by Milankovitch cycles reinforced by resulting CO2 cyclicity due to ocean dissolution Sources: Am Ass Adv Science November 2005; Science November 2005 glacial interglacial glacial-interglacial phases initially triggered by Milankovitch cycles reinforced by resulting CO2 cyclicity due to ocean dissolution with CO2 following temperature by about 800 years Sources: Am Ass Adv Science November 2005; Science November 2005 glacial interglacial today’s situation differs we are now at 380 ppm 100 ppm higher than previous 280 ppm peaks 280 380 today’s situation differs we are now at 280 ppm 100 ppm higher than previous 280 ppm peaks and CO2 appears to be leading temperature 280 380 let’s go further back in time we now need to use proxies to estimate values of atmospheric CO2 CO2 determined from boron 11 and alkenoid carbon isotopes backed up by other data into the Miocene note change in CO2 scale poor data 600 ppm poor data Oligocene-mid Miocene values reach 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 coincident with major development of cold bottom-water circulation did this sequester CO2? coincident with the onset of modern cold deep-water circulation poor data climate models also indicate that full Antarctic glaciation cannot occur unless CO2 ppm is less than 1000 ppm poor data major Antarctic glaciation 1200 ppm 1200 ppm poor data minor glaciation 1200 ppm 800 ppm increased glaciation fall in CO2 800 ppm poor data 800 ppm 1200 ppm extensive continental glaciation fall in CO2 600 ppm 600 ppm poor data 800 ppm 1200 ppm can this be used to predict the effect of future increases in CO2 on Antarctic deglaciation? 600 ppm poor data 800 ppm 1200 ppm 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 2005 Pagani et al. Science July 2005 Pearson & Palmer Nature August 2000 CO2 values reach 3500 ppm Sources: Tripati et al. Nature July 2005 Pagani et al. Science July 2005 Pearson & Palmer Nature August 2000 so we see a major decrease at base of the Middle Eocene from 3500ppm to 600 ppm Why? what effect did this have on temperature? PART 4 temperature change from greenhouse to icehouse Paleocene 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 22 20 26 11 22 24 17 19 17 11 Source: Triparti et al. 2001 16 12 which indicate warm Arctic temperatures 11 23 22 20 26 11 22 24 17 19 17 11 Source: Triparti et al. 2001 16 12 but with seasonality resulting in Arctic environments totally unknown today 11 23 22 20 26 11 22 24 17 19 17 11 16 12 - 24 hour summer daylight and 24 winter darkness within a region of warm air and sea temperatures 11 23 22 20 26 11 22 24 17 19 17 11 16 12 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 these show the change from greenhouse to icehouse greenhouse and the Paleocene Eocene Thermal Maximum which resulted in a supergreenhouse world and very high temperatures including polar regions Paleocene Eocene Thermal Maximum triggered by increased greenhouse gases from • extensive volcanism (Greenland plume) • release of methane clathrates (hydrates) supergreenhouse state continued through the early Eocene abundant greenhouse gases high temperatures but early Eocene supergreenhouse was followed immediately by abrupt global cooling what forced this change? the massive decrease in atmospheric CO2? PART 5 Arctic Coring Expedition (ACEX) Arctic Coring Expedition (ACEX) • August – September 2004 Arctic Coring Expedition (ACEX) • August – September 2004 • first International ODP cruise into the Arctic • supported by Norwegian and Russian icebreakers successfully cored the Lomonosov Ridge ACEX results ACEX results • 1400 ft cored section • good Paleocene Eocene section recovered ACEX results Azolla event PETM ACEX 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 event Azolla event also present in Arctic exploration wells and transported south into Nordic seas so we can establish the age of the Azolla event i Brinkhuis et al., Nature, 2006 Azolla event: summary 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 is this coincidence? or is there a relationship between Azolla and CO2? PART 6 modern and fossil 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 Formation is identical in morphology to modern Azolla what do we know about modern Azolla? fastest growing plant on the planet! doubles its biomass in 2 to 3 days widely used as a green biofertilizer for rice fields why is it a fertilizer? why does it have rapid growth? how can it grow free-floating on water without soil nutrients? the key is Azolla’s leaf structure source: Carrapiço, 2002 its leaves are characterised by cavities source: Carrapiço, 2002 leaf cavities filled with nitrogen inhabited by a nitrogen-fixing cyanobacterium (blue-green alga) Anabaena source: Carrapiço, 2002 Anabaena symbiont has been passed to successive generations via Azolla spores sporocarps Azolla’s sporophyte megasporocarp new sporophyte megasporocarp’s chamber megasporocarp’s chamber fertilization (Carrapiço, 2006) for more than hundred million years! sporocarps Azolla’s sporophyte megasporocarp new sporophyte megasporocarp’s chamber megasporocarp’s chamber fertilization (Carrapiço, 2006) so Azolla-Anabaena can fix more than 1000 kg of atmospheric nitrogen per acre per year providing a natural biofertilizer in the water for rice production 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 • 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 PART 7 Arctic Eocene model i what triggered the Azolla event? i what triggered the Azolla event? • Arctic Basin largely enclosed following the PETM i what triggered the Azolla event? • Arctic Basin largely enclosed • high temperature, rainfall & runoff i what triggered the Azolla event? • Arctic Basin largely enclosed • high temperature, rainfall & runoff i • widespread surface freshwater layer what triggered the Azolla event? • Arctic Basin largely enclosed • high temperature, rainfall & runoff i • widespread surface freshwater layer • atmosphere rich in C & N • abundant nutrients flushed into basin ideal conditions for opportunistic Azolla i model of Azolla growth and deposition model of Azolla growth and deposition local anoxia variable water stratification and bottom water anoxia model of Azolla growth and deposition Azolla deposited in anoxic conditions and was therefore able to drawdown carbon Azolla model of climate change • Azolla blooms widespread in Arctic freshwater surface layers • occurred episodically for about 800,000 years resulting in massive carbon drawdown and the onset of cooling triggering the shift from supergreenhouse towards the modern icehouse state at base Middle Eocene we can estimate amount of carbon from modern Azolla production • 6000 kg of carbon per acre each year • = 6000,000 kg of carbon per acre in 1000 years Source: ACEX scientists preliminary unpublished data carbon drawdown for Azolla event • TIME: up to 800,000 years • AREA: up to 4,000,000 sq km carbon drawdown for Azolla event • TIME: up to 800,000 years • AREA: up to 4,000,000 sq km easily sufficient to change CO2 from 3500 to 650 ppm even with time and area strongly scaled down so the Azolla event could have triggered the initial shift from a greenhouse world towards our modern icehouse planet! PART 8 implications for Arctic petroleum Arctic petroleum resources are now becoming very significant and controversial….. TIME MAGAZINE October 1 2007 Who Owns the Arctic? Fight for the Top of the World could the Azolla interval provide a source for Arctic petroleum? Azolla event - implications for Arctic petroleum • large amount of C possibly deposited in Arctic Basin • unusual source – includes cyanobacterial symbiont Azolla event - implications for Arctic petroleum • occurs at ACEX location near central Arctic • also present in numerous Alaskan and Canadian wells northern Alaska Canadian Beaufort Chukchi Sea Bujak well database extends data points beyond ACEX ACEX • Canadian Beaufort • northern Alaska • Chukchi Sea northern Alaska Canadian Beaufort Chukchi Sea ACEX in a variety of environments Canadian Beaufort: 28 wells in various deltaic facies northern Alaska and Chukchi Sea • 27 wells away from the delta • various nearshore to offshore locations Mikkelsen 13-9-19 Alaska well 4500' Gam ma Log 0 (API) 150 Azolla and PETM events exactly the same age as in the ACEX cores based on palynological zones 4460 T6 4750' TEU 4837.0 T4b 5000' 5100.0 T4a 5250' Azolla event Azolla 5260.0 T3(iii) 5500' 5550 T3(ii) 5690.0 5750' T3(i) 6000' PETM event T2(ii) PETM 6050.0 6250' T2(i) 6500' 6642.0 source Bujak unpublished data Mikkelsen 13-9-19 Alaska well 4500' both events are also characterised by distinctive high-gamma curves Gam ma Log 0 (API) 150 4460 T6 4750' TEU 4837.0 T4b 5000' 5100.0 T4a 5250' Azolla event Azolla 5260.0 T3(iii) 5500' 5550 T3(ii) 5690.0 5750' T3(i) 6000' PETM event T2(ii) PETM 6050.0 6250' T2(i) 6500' 6642.0 Canadian and Alaskan well data age and source rock potential are consistent with preliminary ACEX 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 maturation about 0.8% Ro but we don’t know its geographic extent northern Alaska Canadian BMB Chukchi Sea ACEX so we need to extend database into other Arctic areas 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 the Arctic but for the entire planet thank you