Featured Research

from universities, journals, and other organizations

Geologists: Opening Of Passage May Be Tied To Antarctic Cooling

Date:
April 21, 2006
Source:
University of Florida
Summary:
Ancient fish teeth are yielding clues about when Antarctica became the icy continent it is today, highlighting how ocean currents affect climate change.

Ancient fish teeth are yielding clues about when Antarctica became the icy continent it is today, highlighting how ocean currents affect climate change.

University of Florida geologists have used a rare element found in tiny fish teeth gathered from miles below the ocean surface to date the opening of a passage at the bottom of the globe between the Atlantic and Pacific. The opening, which occurred millions of years ago in a much warmer era, allowed the formation of an ocean current around the pole. That event preceded -- and may even have brought about -- Antarctica's transformation from a forested continent to an icy moonscape.

"We're saying we now have a date for the opening of the Drake Passage that looks like it's early enough that it may have contributed to the cooling," said Ellen Eckels Martin, a UF associate professor of geology.

Martin and H.D. Scher, a UF doctoral graduate now at the University of Rochester in New York, co-authored a paper on the research set to appear Friday in the journal Science.

Scientists have long puzzled over the rapid cooling that seemed to sweep over Antarctica more than 30 million years ago, replacing boreal pine forests with ice and snow. The cooling occurred in a very warm era when levels of carbon dioxide, the gas responsible for the greenhouse warming effect, were three to four times today's levels.

Theorists had suggested the plummeting temperatures could be related to the opening of the Drake Passage, a connection between the Atlantic and Pacific named after Sir Francis Drake, the English captain who circumnavigated the globe in the 16th century. But there has been a longstanding debate over when that passage opened. That's a key point because Antarctica is known to have been covered with ice by about 33.6 million years ago, meaning the circumpolar current would have had to be established before that event if it could be considered a cause of the cooling.

Estimates for the passage's opening have ranged from 15 million years to 49 million years ago. Martin and Scher's research confirms the older dates.

The scientists' source: neodymium isotopes retrieved from fish teeth the size of grains of sand -- teeth themselves retrieved from sediment cores recovered from the deep ocean bottom more than two miles beneath the surface.

Martin said neodymium has a chemical signature that varies depending on whether it came from the Atlantic or Pacific. Once the element erodes from rocks into the ocean, it becomes trapped in clays and minerals, which settle on the seabed. That means scientists can use it to determine the origin and movement of ocean currents, Martin said.

Fish teeth are composed of a mineral called apatite, which takes up neodymium on the seafloor. This is why the UF researchers focused on the teeth.

The geologists obtained the teeth from sedimentary cores retrieved from the South Atlantic ocean. The sediments were dated to more than 40 million years ago. Measurements using a technique called thermal ionization mass spectrometry revealed the teeth neodymium had a signature of the Pacific, indicating at least a surface connection between the oceans.

The presence of neodymium with a Pacific signature in the deep Atlantic suggests that Pacific surface waters flowed into the South Atlantic, where they cooled and sank.

Martin said the opening of the Drake Passage could have precipitated the plunge in temperatures because the newly developed circumpolar current would have isolated Antarctica from warm subtropical water carrying heat from the tropics. In addition, the circumpolar current sets up conditions leading to upwelling of cold, nutrient-rich water. This in turn may have spurred the growth of algae and higher forms of biological life, which consumed carbon dioxide, reducing levels and contributing to cooling the continent's climate, she said.

The UF researchers "proved that the formation of early ocean circulation patterns coincided with, and possibly caused, the initial buildup of ice in Antarctica," said Gabriel Filippelli, professor and chairman of the department of earth sciences at Indiana University-Purdue University Indianapolis.

Filippelli said the paper shows that ocean currents can have a big impact on the West Antarctic Ice Sheet, which would raise sea levels substantially if it were to melt. Some evidence already shows the sheet is becoming less stable due to warmer air and surface water temperatures, he said. "Circulation patterns and surface warmth of waters around Antarctica can be critical factors in the stability of the West Antarctic Ice Sheet, as they were in the buildup of ice around 40 million years ago," he said.


Story Source:

The above story is based on materials provided by University of Florida. Note: Materials may be edited for content and length.


Cite This Page:

University of Florida. "Geologists: Opening Of Passage May Be Tied To Antarctic Cooling." ScienceDaily. ScienceDaily, 21 April 2006. <www.sciencedaily.com/releases/2006/04/060420233450.htm>.
University of Florida. (2006, April 21). Geologists: Opening Of Passage May Be Tied To Antarctic Cooling. ScienceDaily. Retrieved September 17, 2014 from www.sciencedaily.com/releases/2006/04/060420233450.htm
University of Florida. "Geologists: Opening Of Passage May Be Tied To Antarctic Cooling." ScienceDaily. www.sciencedaily.com/releases/2006/04/060420233450.htm (accessed September 17, 2014).

Share This



More Earth & Climate News

Wednesday, September 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Man Floats for 31 Hours in Gulf Waters

Man Floats for 31 Hours in Gulf Waters

AP (Sep. 16, 2014) A Texas man is lucky to be alive after he and three others floated for more than a day in the Gulf of Mexico when their boat sank during a fishing trip. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Researchers Explore Shipwrecks Off Calif. Coast

Researchers Explore Shipwrecks Off Calif. Coast

AP (Sep. 16, 2014) Federal researchers are exploring more than a dozen underwater sites where they believe ships sank in the treacherous waters west of San Francisco in the decades following the Gold Rush. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Isolated N. Korea Asks For International Help With Volcano

Isolated N. Korea Asks For International Help With Volcano

Newsy (Sep. 16, 2014) Mount Paektu volcano in North Korea is showing signs of life and there's not much known about it. 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:
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