Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ancient ocean currents may have changed pace and intensity of ice ages

30.06.2014

Slowing of currents may have flipped switch

Climate scientists have long tried to explain why ice-age cycles became longer and more intense some 900,000 years ago, switching from 41,000-year cycles to 100,000-year cycles.


About 950,000 years ago, North Atlantic currents, Northern Hemisphere ice sheets underwent changes.

Credit: NASA

In a paper published this week in the journal Science Express, researchers report that the deep ocean currents that move heat around the globe stalled or may have stopped at that time, possibly due to expanding ice cover in the Northern Hemisphere.

"The research is a breakthrough in understanding a major change in the rhythm of Earth's climate, and shows that the ocean played a central role," says Candace Major, program director in the National Science Foundation (NSF)'s Division of Ocean Sciences, which funded the research.

... more about:
»Atlantic »NSF »Ocean »circulation »cycles »dioxide »neodymium

The slowing currents increased carbon dioxide (CO2) storage in the oceans, leaving less CO2 in the atmosphere. That kept temperatures cold and kicked the climate system into a new phase of colder, but less frequent, ice ages, the scientists believe.

"The oceans started storing more carbon dioxide for a longer period of time," says Leopoldo Pena, the paper's lead author and a paleoceanographer at Columbia University's Lamont-Doherty Earth Observatory (LDEO). "Our evidence shows that the oceans played a major role in slowing the pace of the ice ages and making them more severe."

The researchers reconstructed the past strength of Earth's system of ocean currents by sampling deep-sea sediments off the coast of South Africa, where powerful currents originating in the North Atlantic Ocean pass on their way to Antarctica.

How vigorously those currents moved can be inferred by how much North Atlantic water made it that far, as measured by isotope ratios of the element neodymium bearing the signature of North Atlantic seawater.

Like tape recorders, the shells of ancient plankton incorporate these seawater signals through time, allowing scientists to approximate when currents grew stronger and when weaker.

Over the last 1.2 million years, the conveyor-like currents strengthened during warm periods and lessened during ice ages, as previously thought.

But at about 950,000 years ago, ocean circulation slowed significantly and stayed weak for 100,000 years.

During that period the planet skipped an interglacial--the warm interval between ice ages. When the system recovered, it entered a new phase of longer, 100,000-year ice age cycles.

After this turning point, deep ocean currents remained weak during ice ages, and ice ages themselves became colder.

"Our discovery of such a major breakdown in the ocean circulation system was a big surprise," said paper co-author Steven Goldstein, a geochemist at LDEO. "It allowed the ice sheets to grow when they should have melted, triggering the first 100,000-year cycle."

Ice ages come and go at predictable intervals based on the changing amount of sunlight that falls on the planet, due to variations in Earth's orbit around the sun.

Orbital changes alone, however, are not enough to explain the sudden switch to longer ice age intervals.

According to one earlier hypothesis for the transition, advancing glaciers in North America stripped away soils in Canada, causing thicker, longer-lasting ice to build up on the remaining bedrock.

Building on that idea, the researchers believe that the advancing ice might have triggered the slowdown in deep ocean currents, leading the oceans to vent less carbon dioxide, which suppressed the interglacial that should have followed.

"The ice sheets must have reached a critical state that switched the ocean circulation system into a weaker mode," said Goldstein.

Neodymium, a key component of cellphones, headphones, computers and wind turbines, also offers a good way of measuring the vigor of ancient ocean currents.

Goldstein and colleagues had used neodymium ratios in deep-sea sediment samples to show that ocean circulation slowed during past ice ages.

They used the same method to show that changes in climate preceded changes in ocean circulation.

A trace element in Earth's crust, neodymium washes into the oceans through erosion from the continents, where natural radioactive decay leaves a signature unique to the land mass from which it originated.

When Goldstein and Lamont colleague Sidney Hemming pioneered this method in the late 1990s, they rarely worried about surrounding neodymium contaminating their samples.

The rise of consumer electronics has changed that.

"I used to say you could do sample processing for neodymium analysis in a parking lot," said Goldstein. "Not anymore."

Media Contacts
Cheryl Dybas, NSF, (703) 292-7734, cdybas@nsf.gov
Kim Martineau, LDEO, (845) 365-8708, kmartine@ldeo.columbia.edu

Related Websites
NSF Grant: Late Quaternary Variability of the Agulhas Thermohaline Valve from Nd Isotopes in Planktonic Foraminifera: http://www.nsf.gov/awardsearch/showAward?AWD_ID=1031198&HistoricalAwards=false
International Ocean Discovery Program: http://www.iodp.org/

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2014, its budget is $7.2 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives about 50,000 competitive requests for funding, and makes about 11,500 new funding awards. NSF also awards about $593 million in professional and service contracts yearly.

Cheryl Dybas | Eurek Alert!
Further information:
http://nsf.gov/news/news_images.jsp?cntn_id=131830&org=NSF

Further reports about: Atlantic NSF Ocean circulation cycles dioxide neodymium

More articles from Earth Sciences:

nachricht Ethanol refining may release more of some pollutants than previously thought
06.05.2015 | American Geophysical Union

nachricht Fjords are 'hotspots' in global carbon cycling
05.05.2015 | University of Otago

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Spray drying the precision particle under the virtual magnifying glass

Spray drying is a common manufacturing process, used in the production of ceramic granulate for technical components or dental prostheses as well as dissolvable medicinal substances, food additives and in the processing of milk into powder. Using computer simulation methodology developed by scientists at the Fraunhofer Institute for Mechanics of Materials IWM, a more comprehensible understanding can now be gained of the behavior of particles in solvent during the spray drying process. This allows powder and granulate manufacturers to specifically adjust the properties of their products while reducing waste.

Previously, it was unusual for granule and powder producers to use granulation simulations to improve their products. For new product development or process...

Im Focus: The random raman laser: A new light source for the microcosmos

Texas A&M University researchers demonstrate how a narrow-band strobe light source for speckle-free imaging has the potential to reveal microscopic forms of life

In modern microscope imaging techniques, lasers are used as light sources because they can deliver fast pulsed and extremely high-intensity radiation to a...

Im Focus: Pulsar with widest orbit ever detected

Discovered by high school research team

A team of highly determined high school students discovered a never-before-seen pulsar by painstakingly analyzing data from the National Science Foundation's...

Im Focus: Erosion, landslides and monsoon across the Himalaya

Scientists from Nepal, Switzerland and Germany was now able to show how erosion processes caused by the monsoon are mirrored in the sediment load of a river crossing the Himalaya.

In these days, it was again tragically demonstrated that the Himalayas are one of the most active geodynamic regions of the world. Landslides belong to the...

Im Focus: Through the galaxy by taxi - The Dream Chaser Space Utility Vehicle

A world-class prime systems integrator and electronic systems provider known for its rapid, innovative, and agile technology solutions, Sierra Nevada Corporation (SNC) is currently developing a new space transportation system called the Dream Chaser.

The ultimate aim is to construct a multi-mission-capable space utility vehicle, while accelerating the overall development process for this critical capability...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Green Summit 2015: the summit of the essential

05.05.2015 | Event News

HHL Energy Conference on May 11/12, 2015: Students Discuss about Decentralized Energy

23.04.2015 | Event News

“Developing our cities, preserving our planet”: Nobel Laureates gather for the first time in Asia

23.04.2015 | Event News

 
Latest News

Institutions of higher education spent more than Euro 46 billion in 2013

07.05.2015 | Statistics

Cotton fibres instead of carbon nanotubes

07.05.2015 | Health and Medicine

Expedition Genomics Lab: the mobile revolution in genetic analysis

06.05.2015 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>