Featured Research

from universities, journals, and other organizations

Wind Shifts May Stir Carbon Dioxide From Antarctic Depths, Amplifying Global Warming

Date:
March 13, 2009
Source:
The Earth Institute at Columbia University
Summary:
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 man-made warming proceeds, a new article in the journal Science suggests.

This pictures shows the locations of cores showing Antarctic upwelling.
Credit: Robert Anderson, Lamont-Doherty Earth Observatory

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."

In addition to Anderson, the paper was coauthored by Simon Nielsen of Florida State University, and five Lamont-Doherty researchers: Shahla Ali, Louisa Bradtmiller, Martin Fleisher, Brenton Anderson and Lloyd Burckle. The study was funded by NOAA, the National Science Foundation, Norwegian Research Council and Norwegian Polar Institute.


Story Source:

The above story is based on materials provided by The Earth Institute at Columbia University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Wind-Driven Upwelling in the Southern Ocean and the Deglacial Rise in Atmospheric CO2. Science, March 13, 2009

Cite This Page:

The Earth Institute at Columbia University. "Wind Shifts May Stir Carbon Dioxide From Antarctic Depths, Amplifying Global Warming." ScienceDaily. ScienceDaily, 13 March 2009. <www.sciencedaily.com/releases/2009/03/090312140842.htm>.
The Earth Institute at Columbia University. (2009, March 13). Wind Shifts May Stir Carbon Dioxide From Antarctic Depths, Amplifying Global Warming. ScienceDaily. Retrieved August 28, 2014 from www.sciencedaily.com/releases/2009/03/090312140842.htm
The Earth Institute at Columbia University. "Wind Shifts May Stir Carbon Dioxide From Antarctic Depths, Amplifying Global Warming." ScienceDaily. www.sciencedaily.com/releases/2009/03/090312140842.htm (accessed August 28, 2014).

Share This




More Earth & Climate News

Thursday, August 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Big Waves, Minor Flooding from Hurricane

Big Waves, Minor Flooding from Hurricane

AP (Aug. 27, 2014) Thundering surf spawned by Hurricane Marie pounded the Southern California coast Wednesday, causing minor flooding in a low-lying beach town. High surf warnings were posted for Los Angeles County south through Orange County. (Aug. 27) Video provided by AP
Powered by NewsLook.com
Calif. Quake Underscores Need for Early Warning

Calif. Quake Underscores Need for Early Warning

AP (Aug. 26, 2014) Researchers at UC Berkeley are testing a prototype of an earthquake early warning system that California is pursuing years after places like Mexico and Japan already have them up and running. (August 26) Video provided by AP
Powered by NewsLook.com
Hurricane Marie Brings Big Waves to California Coast

Hurricane Marie Brings Big Waves to California Coast

Reuters - US Online Video (Aug. 26, 2014) Huge waves generated by Hurricane Marie hit the Southern California coast. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Brazil Tries Genetically Modified Mosquitoes to Fight Dengue

Brazil Tries Genetically Modified Mosquitoes to Fight Dengue

AFP (Aug. 25, 2014) A factory in the industrial state of Sao Paulo produces genetically modified mosquitoes to fight dengue, a deadly tropical disease more prevalent in Brazil than anywhere else in the world. Duration: 00:57 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins