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.
Andreas Schmittner | EurekAlert!
Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union
UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences