Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New insights into causes and consequences of climate change

08.09.2005


An oxygen-free ocean from bottom to surface is probably the worst scenario that marine higher life can experience. Are processes and feedbacks linking the atmosphere to the deep ocean capable to cause a rapid change from an oxygen-rich to an oxygen-free deep ocean? And what are the consequences for the global carbon cycle that ultimately drive marine and terrestrial ecosystems and climate variation?



These are fundamental and burning questions on the society’s agenda. Hurricane Katrina and other natural catastrophes in recent years have shown how vulnerable mankind is in the face of nature. Professor Tom Wagner led a cross-disciplinary study of geological records combined with climate modeling to shed new light on the mechanisms and processes that led to repetitive rapid climatic change with major impact on the ocean during past greenhouse conditions.

By analysing sediments laid down on the ocean floor about 85m years ago in the Cretaceous, the research team found evidence that Cretaceous greenhouse climate was highly variable and repeatedly resulted in major changes in ocean chemistry and deep circulation causing disastrous consequences for marine ecosystems. These extreme conditions fostered massive burial of dead organic matter from marine species, such as algae and plankton, at the sea floor, leading to the formation of distinct sediments, "marine black shale", also well known as the world’s primary source for oil and gas.


Professor Wagner and colleagues uncovered evidence of the mechanisms that drove rapid and repetitive climate change by studying the quantity and content of proxy parameters in black shale in a core of sedimentary rock drilled out of the ocean bed, off Africa’s Ivory Coast, and comparing these results with data from a global climate model.

The model data were used to quantify the freshwater run-off from tropical Africa into the equatorial Atlantic, where the core has been drilled, and to specify the role of orbital configuration and the water cycle on climate and oceanographic variation. With these data, it was possible to explain the formation of the sedimentary succession of black shale and carbonate-rich sediments, indicating alternation between oxygen-depleted and oxygen-rich conditions in the deep ocean. All life other than simple organisms like bacteria would have been seriously depleted in the deeper ocean as oxygen became progressively scarce. On land, the climate variability would cause strong regional contrasts, with widespread deserts at mid-latitudes and extremely humid areas in the tropics.

Processes in the atmosphere driven by cyclic changes in the amount of energy from the sun entering the top of the atmosphere (insolation) have been identified to be the cause for the observed dramatic changes in ocean chemistry that resulted in the formation of black shale. This contributes to the current discussion on whether the atmosphere drives the oceans or vice-versa.

Higher rainfall would have caused increased amounts of fresh water running off the land, carrying large quantities of nutrients into the oceans, resulting in an increase in marine productivity and supporting oxygen depletion and a change in circulation patterns in the deep ocean.
Climate modeling identified that specific periods of extremely high river discharge occurred during maxima in seasonal contrasts when the northern equinox (when the sun is directly over the earth’s equator) coincided with perihelon (when the earth passes closest to the sun). It was only during this specific orbital configuration that freshwater run-off exceeded a certain threshold, finally to result in a rapid change to ocean anoxia.

The findings, reported in Nature, the international weekly journal of science, suggest that variations in the water cycle, once they have exceeded a certain threshold, are capable of inducing major environmental change in the oceans.

The researchers conclude: ’The results of this study demonstrate how sensitively and rapidly tropical marine areas close to continental margins react to even relatively moderate increases in continental freshwater discharge.

’The freshwater threshold required to shift sheltered and semi-enclosed areas of the modern ocean into an anoxic mode are unknown but the progressive emission of greenhouse gases to the modern atmosphere is gradually shifting Earth towards a greenhouse mode with an accelerated hydrological cycle.’

’At present it is hardly possible to estimate where we are on the long-term climate trend but once the freshwater threshold is passed, a substantial impact on biochemical cycling of continental margins may be expected.’
Commenting on the Nature paper, Professor Wagner said that the majority of the world’s population live in coastal areas, which were the most vulnerable to natural catastrophes as recorded in the geological record.

’Understanding the processes and feedbacks controlling carbon and nutrient cycling in the modern world and during past periods of extreme warmth is therefore critical to separate human impact on climate from natural variability and underpins the ability to adapt to future conditions,’ he said.

Professor Wagner, of the Institute for Research on Environment and Sustainability at Newcastle University, England, worked with colleagues from the Universities of Bremen and Cologne and the GEOMAR Leibniz Institute of Marine Sciences at Kiel, in Germany, and the Royal Netherlands Institute for Sea Research (NIOZ) at Texel, Netherlands.

Professor Tom Wagner | alfa
Further information:
http://www.newcastle.ac.uk

More articles from Ecology, The Environment and Conservation:

nachricht Value from wastewater
16.08.2017 | Hochschule Landshut

nachricht Species Richness – a false friend? Scientists want to improve biodiversity assessments
01.08.2017 | Carl von Ossietzky-Universität Oldenburg

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>