Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Evidence of glaciation in 'super greenhouse' world

14.01.2008
Ice sheets existed when alligators lived in the Arctic

Large ice-sheets existed on Earth about 91 million years ago, during one of the warmest periods since life began, an international team of scientists reports this week.

The findings, published in the journal 'Science', challenges the popular assumption that large glaciers could not have existed in the 'super greenhouse' climate, when tropical surface ocean temperatures reached as high as 35-37C (95-98.6F) and alligators lived in the Arctic.

Scientists from the USA, UK, Germany and Netherlands found evidence of an approximate 200,000 year period of widespread glaciation during the Turonian 'super-greenhouse' period of the Cretaceous, with ice sheets about 60 per cent the size of the modern Antarctic ice cap.

The team obtained their evidence from detailed analyses of sediments that were deposited in the western Equatorial Atlantic Ocean at that time.

The sediments, recovered by drilling into the ocean floor off Suriname in South America, contained fossil shells of tiny sea creatures, foraminifera, that lived in the Cretaceous seas.

These shells 'captured' chemicals that were present at the time, providing the researchers with clues about the temperature, composition and salinity of the seawater. Scientists at the Scripps Institution of Oceanography in the USA were able to use this information to reconstruct sea temperature, both at the surface and at depth.

Meanwhile, a European team at Newcastle University in the UK, the University of Cologne in Germany and the Royal Netherlands Institute for Sea Research (NIOZ), studied the composition of organic molecules in the same sediments, providing separate evidence about the temperature of the surface water during this period of time.

By combining these two lines of data, the team was able to identify temperature and chemical changes in the ocean that are consistent with periods of glacial formation.

Professor Thomas Wagner, of the School of Civil Engineering and Geosciences and the Institute for Research on Environment and Sustainability at Newcastle University, said: 'Speculation about whether large ice caps could have formed during short periods of the Earth's warmest interval has a long history in Geology and climate research, but there has never been final conclusive evidence.

'This uncertainty remained, as there is very little direct evidence from high latitude rocks supporting or disproving the concept; also computer simulations have difficulties to accurately model climate conditions at polar latitudes during past greenhouse conditions'.

'Our research from tropical marine sediments provides strong evidence that large ice sheets indeed did exist for short periods of the Cretaceous, despite the fact that the world was a much hotter place than it is today, or is likely to be in the near future'.

Professor Jaap S. Damste from the Royal NIOZ added: 'The results are consistent with independent evidence from Russia and the USA that sea level fell by about 25-40 metres at this time. Sea level is known to fall as water is removed from the oceans to build continental ice-sheets and to rise as ice melts and returns to the sea. Today, the Antarctic ice cap stores enough water to raise sea level by about 60 metres if the whole mass melted and flowed back into the ocean.'

Dr Andre Bornmann, who led the research at Scripps Institute of Oceanography, University of California, together with Professor Richard Norris, and who has since moved to Leipzig University in Germany, said it was not clear where such a large mass of ice could have existed in the Cretaceous period or how ice growth could have started. 'This study demonstrates that even the super-warm climates of the Cretaceous Thermal Maximum were not warm enough to always prevent ice growth. Certainly, ice sheets were much less common during the Cretaceous Thermal Maximum than they are during more recent 'Icehouse' climates, allowing tropical plants and animals like breadfruit trees and alligators to frequent the high arctic. However, paradoxically past greenhouse climates may actually have aided ice growth by increasing the amount of moisture in the atmosphere and creating more winter snowfall at high elevations and high latitudes,' he said. The findings of this study provide compelling support for another related study published by Fletcher and co-authors from The University of Sheffield and Yale in the January 2008 issue of the journal, Nature Geoscience (first published online, 9 December 2007). In their study, Fletcher and co-authors reconstructed atmospheric carbon dioxide concentrations for the Mesozoic and early Cenozoic below the simulated threshold for the initiation of widespread glaciation on several occasions and speculated on the repetitive occurrence of cold intervals in a general greenhouse world.

Technical notes on methodology:

The research team obtained their evidence from detailed geochemical and isotopic analyses of organic carbon-rich sediments that were deposited in the western Equatorial Atlantic at Demerara Rise off Surinam during the Cretaceous.

The sediments were recovered during the Ocean Drilling Program Leg 207 and contained glassy carbonate shells of tiny sea creatures, foraminifera, that lived in the Cretaceous seas. The fossil shells consist of pristine carbonate, which contain oxygen and other elements. By analysing the different types of oxygen atoms (isotopes) in these shells scientists at the Scripps Institution of Oceanography in the USA were able to reconstruct sea temperature, both at the surface and at depth. Meanwhile, a European team at the Universities of Newcastle and Cologne in the UK and Germany, and the Royal Netherlands Institute for Sea Research (NIOZ) in the Netherlands studied the composition of organic molecules of membrane lipids from archea in exactly the same sediments, providing an independent temperature record of surface waters for the Cretaceous western tropical Atlantic. Because the growth of continental ice enriches seawater in oxygen-18 (the isotope of oyygen with an atomic mass of 18), the " oxygen-18 chemistry, when constrained by biomarker temperature estimates, was used to estimate the size of continental ice sheets. By combining these two lines of data, the team was able to show that differences in the records of the tropical oceans were consistent with periods of glacial formation.

Mick Warwicker | EurekAlert!
Further information:
http://www.ncl.ac.uk

More articles from Earth Sciences:

nachricht Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute

nachricht Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>