Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Wind shifts may stir CO2 from Antarctic depths

13.03.2009
Releases may have speeded end of last ice age -- and could act again

Natural releases of carbon dioxide from the Southern Ocean due to shifting wind patterns could have amplified global warming at the end of the last ice age--and could be repeated as manmade warming proceeds, a new paper in the journal Science suggests.

Many scientists think that the end of the last ice age was triggered by a change in Earth's orbit that caused the northern part of the planet to warm. This partial climate shift was accompanied by rising levels of the greenhouse gas CO2, ice core records show, which could have intensified the warming around the globe. A team of scientists at Columbia University's Lamont-Doherty Earth Observatory now offers one explanation for the mysterious rise in CO2: the orbital shift triggered a southward displacement in westerly winds, which caused heavy mixing in the Southern Ocean around Antarctica, pumping dissolved carbon dioxide from the water into the air.

"The faster the ocean turns over, the more deep water rises to the surface to release CO2," said lead author Robert Anderson, a geochemist at Lamont-Doherty. "It's this rate of overturning that regulates CO2 in the atmosphere." In the last 40 years, the winds have shifted south much as they did 17,000 years ago, said Anderson. If they end up venting more CO2 into the air, manmade warming underway now could be intensified.

Scientists have been studying the oceans for more than 25 years to understand their influence on CO2 levels and the glacial cycles that have periodically heated and chilled the planet for more than 600,000 years. Ice cores show that the ends of other ice ages also were marked by rises in CO2.

Two years ago, J.R. Toggweiler, a scientist at the National Oceanic and Atmospheric Administration (NOAA), proposed that westerly winds in the Southern Ocean around Antarctica may have undergone a major shift at the end of the last ice age. This shift would have raised more CO2-rich deep water to the surface, and thus amplified warming already taking place due to the earth's new orbital position. Anderson and his colleagues are the first to test that theory by studying sediments from the bottom of the Southern Ocean to measure the rate of overturning.

The scientists say that changes in the westerlies may have been triggered by two competing events in the northern hemisphere about 17,000 years ago. The earth's orbit shifted, causing more sunlight to fall in the north, partially melting the ice sheets that then covered parts of the United States, Canada and Europe. Paradoxically, the melting may also have spurred sea-ice formation in the North Atlantic Ocean, creating a cooling effect there. Both events would have caused the westerly winds to shift south, toward the Southern Ocean. The winds simultaneously warmed Antarctica and stirred the waters around it. The resulting upwelling of CO2 would have caused the entire globe to heat.

Anderson and his colleagues measured the rate of upwelling by analyzing sediment cores from the Southern Ocean. When deep water is vented, it brings not only CO2 to the surface but nutrients. Phytoplankton consume the extra nutrients and multiply.

In the cores, Anderson and his colleagues say spikes in plankton growth between roughly 17,000 years ago and 10,000 years ago indicate added upwelling. By comparing those spikes with ice core records, the scientists realized the added upwelling coincided with hotter temperatures in Antarctica as well as rising CO2 levels.

In the same issue of Science, Toggweiler writes a column commenting on the work. "Now I think this really starts to lock up how the CO2 changed globally," he said in an interview. "Here's a mechanism that can explain the warming of Antarctica and the rise in CO2. It's being forced by the north, via this change in the winds."

At least one model supports the evidence. Richard Matear, a researcher at Australia's Commonwealth Scientific and Industrial Research Organisation, describes a scenario in which winds shift south and produce an increase in CO2 venting in the Southern Ocean. Plants, which incorporate CO2 during photosynthesis, are unable to absorb all the added nutrients, causing atmospheric CO2 to rise.

Some other climate models disagree. In those used by the Intergovernmental Panel on Climate Change, the westerly winds do not simply shift north-south. "It's more complicated than this," said Axel Timmermann, a climate modeler at the University of Hawaii. Even if the winds did shift south, Timmermann argues, upwelling in the Southern Ocean would not have raised CO2 levels in the air. Instead, he says, the intensification of the westerlies would have increased upwelling and plant growth in the Southeastern Pacific, and this would have absorbed enough atmospheric CO2 to compensate for the added upwelling in the Southern Ocean.

"Differences among model results illustrate a critical need for further research," said Anderson. These, include "measurements that document the ongoing physical and biogeochemical changes in the Southern Ocean, and improvements in the models used to simulate these processes and project their impact on atmospheric CO2 levels over the next century."

Anderson says that if his theory is correct, the impact of upwelling "will be dwarfed by the accelerating rate at which humans are burning fossil fuels." But, he said, "It could well be large enough to offset some of the mitigation strategies that are being proposed to counteract rising CO2, so it should not be neglected."

Kim Martineau | EurekAlert!
Further information:
http://www.columbia.edu

More articles from Earth Sciences:

nachricht Welcome Committee for Comets
19.07.2019 | Technische Universität Braunschweig

nachricht Sea level rise: West Antarctic ice collapse may be prevented by snowing ocean water onto it
18.07.2019 | Potsdam-Institut für Klimafolgenforschung

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Better thermal conductivity by adjusting the arrangement of atoms

Adjusting the thermal conductivity of materials is one of the challenges nanoscience is currently facing. Together with colleagues from the Netherlands and Spain, researchers from the University of Basel have shown that the atomic vibrations that determine heat generation in nanowires can be controlled through the arrangement of atoms alone. The scientists will publish the results shortly in the journal Nano Letters.

In the electronics and computer industry, components are becoming ever smaller and more powerful. However, there are problems with the heat generation. It is...

Im Focus: First-ever visualizations of electrical gating effects on electronic structure

Scientists have visualised the electronic structure in a microelectronic device for the first time, opening up opportunities for finely-tuned high performance electronic devices.

Physicists from the University of Warwick and the University of Washington have developed a technique to measure the energy and momentum of electrons in...

Im Focus: Megakaryocytes act as „bouncers“ restraining cell migration in the bone marrow

Scientists at the University Würzburg and University Hospital of Würzburg found that megakaryocytes act as “bouncers” and thus modulate bone marrow niche properties and cell migration dynamics. The study was published in July in the Journal “Haematologica”.

Hematopoiesis is the process of forming blood cells, which occurs predominantly in the bone marrow. The bone marrow produces all types of blood cells: red...

Im Focus: Artificial neural network resolves puzzles from condensed matter physics: Which is the perfect quantum theory?

For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.

Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...

Im Focus: Extremely hard yet metallically conductive: Bayreuth researchers develop novel material with high-tech prospects

An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".

The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

 
Latest News

Heat flow through single molecules detected

19.07.2019 | Physics and Astronomy

Heat transport through single molecules

19.07.2019 | Physics and Astronomy

Welcome Committee for Comets

19.07.2019 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>