Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Earth Science News .




ICE WORLD
Researchers document acceleration of ocean denitrification during deglaciation
by Staff Writers
Corvallis OR (SPX) Jun 06, 2013


File image.

As ice sheets melted during the deglaciation of the last ice age and global oceans warmed, oceanic oxygen levels decreased and "denitrification" accelerated by 30 to 120 percent, a new international study shows, creating oxygen-poor marine regions and throwing the oceanic nitrogen cycle off balance.

By the end of the deglaciation, however, the oceans had adjusted to their new warmer state and the nitrogen cycle had stabilized - though it took several millennia. Recent increases in global warming, thought to be caused by human activities, are raising concerns that denitrification may adversely affect marine environments over the next few hundred years, with potentially significant effects on ocean food webs.

Results of the study have been published this week in the journal Nature Geoscience. It was supported by the National Science Foundation.

"The warming that occurred during deglaciation some 20,000 to 10,000 years ago led to a reduction of oxygen gas dissolved in sea water and more denitrification, or removal of nitrogen nutrients from the ocean," explained Andreas Schmittner, an Oregon State University oceanographer and author on the Nature Geoscience paper. "Since nitrogen nutrients are needed by algae to grow, this affects phytoplankton growth and productivity, and may also affect atmospheric carbon dioxide concentrations."

"This study shows just what happened in the past, and suggests that decreases in oceanic oxygen that will likely take place under future global warming scenarios could mean more denitrification and fewer nutrients available for phytoplankton," Schmittner added.

In their study, the scientists analyzed more than 2,300 seafloor core samples, and created 76 time series of nitrogen isotopes in those sediments spanning the past 30,000 years. They discovered that during the last glacial maximum, the Earth's nitrogen cycle was at a near steady state. In other words, the amount of nitrogen nutrients added to the oceans - known as nitrogen fixation - was sufficient to compensate for the amount lost by denitrification.

A lack of nitrogen can essentially starve a marine ecosystem by not providing enough nutrients. Conversely, too much nitrogen can create an excess of plant growth that eventually decays and uses up the oxygen dissolved in sea water, suffocating fish and other marine organisms.

Following the period of enhanced denitrification and nitrogen loss during deglaciation, the world's oceans slowly moved back toward a state of near stabilization. But there are signs that recent rates of global warming may be pushing the nitrogen cycle out of balance.

"Measurements show that oxygen is already decreasing in the ocean," Schmittner said "The changes we saw during deglaciation of the last ice age happened over thousands of years. But current warming trends are happening at a much faster rate than in the past, which almost certainly will cause oceanic changes to occur more rapidly.

"It still may take decades, even centuries to unfold," he added.

Schmittner and Christopher Somes, a former graduate student in the OSU College of Earth, Ocean, and Atmospheric Sciences, developed a model of nitrogen isotope cycling in the ocean, and compared that with the nitrogen measurements from the seafloor sediments. Their sensitivity experiments with the model helped to interpret the complex patterns seen in the observations.

.


Related Links
Oregon State University
Beyond the Ice Age






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





ICE WORLD
Ancient trapped water could explain timing of Earth's first ice age
Pilbara, Australia (UPI) Jun 5, 2013
Tiny bubbles of ancient water trapped in quartz grains in Australia may hold the key to understanding what caused the Earth's first ice age, scientists say. Researchers at the University of Manchester in England, along with French colleagues, analyzed the amount of ancient atmospheric argon gas isotopes dissolved in the bubbles and found levels were very different to those in the air we ... read more


ICE WORLD
More radioactive leaks reported at Fukushima plant

Japan disaster cash spent on counting turtles: report

Agreement over Statue of Liberty security screening

No health risk from Fukushima radiation: UN

ICE WORLD
Atom by atom, bond by bond, a chemical reaction caught in the act

Dense hydrogen in a new light

Another American High Frontier First: 3-D Manufacturing in Space

Charred micro-bunny sculpture shows promise of new material for 3-D shaping

ICE WORLD
To save corals, save the forests: study

Is enough being done to make drinking water safe

Catastrophic climatic events leave corals facing a decade-long fight for recovery

Monsoon rains arrive in India, bring cheer to farmers

ICE WORLD
Researchers document acceleration of ocean denitrification during deglaciation

New map reveals secrets of Antarctica below the ice

Arctic current flowed under deep freeze of last ice age

Russian scientists make rare find of 'blood' in mammoth

ICE WORLD
Investigators link poultry contamination on farm and at processing plant

Agricultural innovation offers only path to feed Africa and the world

Improving 'crop per drop' could boost food and water security

Researchers help threatened wheat crops in Asia

ICE WORLD
Merkel pledges aid amid flood surge

'Flood tourists' inundate deluged Czech capital

Ten dead, thousands evacuated as floods sweep Europe

Strong quake kills two, injures 21 in Taiwan

ICE WORLD
Now is the time to invest in Africa: Japan's Abe

Japan, eyeing China, pledges $14 bn aid to Africa

Climate change drowning the 'Venice of Africa'

Outside View: Somalia's Jubaland

ICE WORLD
Scientists say fossil from China is oldest primate skeleton yet found

Study: African terrain may have pushed humans into walking on two feet

170,000 living in subdivided flats in Hong Kong: study

Monkey teeth help reveal Neanderthal weaning




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement