Featured Research

from universities, journals, and other organizations

Ice Age Ocean Circulation Reacted To, Did Not Cause, Climate Change At Glacial Boundaries

Date:
May 1, 2005
Source:
Lamont-Doherty Earth Observatory
Summary:
Scientists from the Lamont Doherty Earth Observatory (LDEO) have provided new evidence that ocean circulation changes lagged behind, and were not the cause of, major climate changes at the beginning and end of the last ice age (short intervals known as glacial boundaries), according to a study published in the March 2005 issue of Science magazine.

Great Ocean Conveyer Belt.
Credit: Image courtesy of Lamont-Doherty Earth Observatory

Scientists from the Lamont Doherty Earth Observatory (LDEO) have provided new evidence that ocean circulation changes lagged behind, and were not the cause of, major climate changes at the beginning and end of the last ice age (short intervals known as glacial boundaries), according to a study published in the March 2005 issue of Science magazine.

Related Articles


Both ice sheet volume and the “global carbon budget,” the amount of carbon stored in deep ocean reservoirs compared to that on the earth’s surface, changed before ocean circulation patterns changed, according to evidence from deep sea cores taken from the South Atlantic. Thermohaline (heat and salt) ocean circulation changes were found to have occurred 1,000-3,000 years after carbon shifts in each case.

The Lamont Doherty Earth Observatory team, which included Steve Goldstein, Alexander Piotrowski (now a postdoctoral student at Cambridge University), Sidney Hemming, and Richard Fairbanks, identified a chemical marker, isotopes of the rare earth element neodymium (Nd), that they believe reveals the progression of ancient ocean circulation changes more unequivocally than did carbon isotope ratios used to study the chronology of these ancient climate changes previously.

The Nd markers provided evidence that changes in the ocean’s thermohaline circulation rate came later than both carbon budget shifts and changes in ice sheet volume at the start and end of the last ice age. In other words, the ocean’s “conveyor belt” system did not trigger the changing conditions of cold and ice on the surface of Earth but rather responded to them.

“This was an unusual use of neodymium (Nd) isotopes, which are more often applied to magnetism and continent-mantle evolution studies,” explains co-author Steve Goldstein. “Our study illustrates its great potential for the study of the history of climate change.” Goldstein is a geochemist who is Associate Professor of Earth and Environmental Sciences and Senior Researcher at LDEO.

Ice ages are driven by changes in the amount of heat that arrives at the poles from the sun. The carbon cycle shifts were likely caused by the decline of plant life on the planet’s surface because of the cold and the advancing ice sheets. The ocean’s circulation system amplifies the effect of the sun’s heat through warmth brought to high latitudes by the Gulf Stream, whose saltiness affects how fast it sinks and begins the deep water arm of the global ocean “conveyor belt” circulation back to the South.

Ocean circulation changes “amplified” the climate trends that started the advance of continental ice sheets 70,000 years ago, making it colder in the high latitudes, as well as those that caused the retreat of ice sheets that ended the most recent ice age about 15,000 years ago, making it warmer.

The deep sea core showed that ocean circulation also changed during several smaller abrupt periods of warming during the last ice age, but these showed no obvious time sequence among the proxies for ice sheet growth, carbon cycle, and ocean circulation, leaving open the possibility that ocean circulation changes could in fact have been the trigger of these warmings.

The neodymium in ocean water comes from weathering of the continental rock. The isotope ratios of dissolved neodymium “dye” the ocean water, Goldstein explains, and the Nd in the Pacific (where more molten rock is brought up from the earth’s mantle in volcanic activity) has a different signature than that in the Atlantic. The amount of North Atlantic Deep Water, as determined by Nd isotopes in a deep sea sediment core, can thus be used to trace ocean circulation. The team plans to continue to investigate the usefulness of neodymium as a proxy for ocean circulation in studying the history of climate change, using cores from other locations and depths.


Story Source:

The above story is based on materials provided by Lamont-Doherty Earth Observatory. Note: Materials may be edited for content and length.


Cite This Page:

Lamont-Doherty Earth Observatory. "Ice Age Ocean Circulation Reacted To, Did Not Cause, Climate Change At Glacial Boundaries." ScienceDaily. ScienceDaily, 1 May 2005. <www.sciencedaily.com/releases/2005/04/050428180401.htm>.
Lamont-Doherty Earth Observatory. (2005, May 1). Ice Age Ocean Circulation Reacted To, Did Not Cause, Climate Change At Glacial Boundaries. ScienceDaily. Retrieved December 19, 2014 from www.sciencedaily.com/releases/2005/04/050428180401.htm
Lamont-Doherty Earth Observatory. "Ice Age Ocean Circulation Reacted To, Did Not Cause, Climate Change At Glacial Boundaries." ScienceDaily. www.sciencedaily.com/releases/2005/04/050428180401.htm (accessed December 19, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Friday, December 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Lava on Track to Hit Hawaii Market

Raw: Lava on Track to Hit Hawaii Market

AP (Dec. 19, 2014) Lava from an active volcano on Hawaii's Big Island slowed slightly but stayed on track to hit a shopping center in the small town of Pahoa. (Dec. 19) Video provided by AP
Powered by NewsLook.com
Navy Unveils Robot Fish

Navy Unveils Robot Fish

Reuters - Light News Video Online (Dec. 18, 2014) The U.S. Navy unveils an underwater device that mimics the movement of a fish. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Arctic Warming Twice As Fast As Rest Of Planet

Arctic Warming Twice As Fast As Rest Of Planet

Newsy (Dec. 18, 2014) The Arctic is warming twice as fast as the rest of the planet, thanks in part to something called feedback. Video provided by Newsy
Powered by NewsLook.com
Prenatal Exposure To Pollution Might Increase Autism Risk

Prenatal Exposure To Pollution Might Increase Autism Risk

Newsy (Dec. 18, 2014) Harvard researchers found children whose mothers were exposed to high pollution levels in the third trimester were twice as likely to develop autism. Video provided by Newsy
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:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

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