A new study has found a link between abrupt ocean warming at the end of the last ice age and the sudden onset of low-oxygen, or hypoxic, conditions that led to vast marine dead zones.
Results of the research, which was funded by the National Science Foundation (NSF), are published today in the journal Nature.
"This works tackles a long-standing debate about what causes expansion of Oxygen Minimum Zones, also known as dead zones, in the oceans," said Candace Major, a program director in NSF's Division of Ocean Sciences. "The results demonstrate a link between warming surface temperatures and dead zones at great depths. The findings also show that the response time between warming and dead zone expansion is quite fast."
Large-scale warming events at about 14,700, and again 11,500, years ago occurred rapidly and triggered loss of oxygen in the North Pacific, raising concern that low-oxygen areas will expand again as the oceans warm in the future.
Anomalous warmth that occurred recently in the Northeastern Pacific Ocean and the Bering Sea--dubbed "The Blob"--is of a scale similar to events documented in the geologic record. If such warming is sustained, oxygen loss becomes more likely.
Although many scientists believe that a series of low-oxygen "dead zones" in the Pacific Ocean off Oregon and Washington during the last decade may be caused by ocean warming, evidence confirming that link has been sparse.
Clear connection: Past ocean warming and dead zones
The new study, however, found a clear connection between two historic intervals of abrupt ocean warming that ended the last ice age with an increase in the flux of marine plankton sinking to the seafloor, ultimately leading to a sudden onset of low-oxygen conditions, or hypoxia.
"Our study reveals a strong link between ocean warming, loss of oxygen and an ecological shift to favor diatom production," said paper lead author Summer Praetorius of the Carnegie Institution for Science. "During each warming event, the transition to hypoxia occurred abruptly and persisted for about 1,000 years, suggesting a feedback that sustained or amplified hypoxia."
Warmer water, by itself, is not sufficient to cause diatom blooms, nor hypoxia, the researchers note.
Just as warming soda loses its fizzy gas, warmer seawater contains less dissolved oxygen, and this can start the oxygen decline. But it isn't until accelerated blooming of microscopic diatoms--which have large shells and tend to sink more rapidly than other smaller types of plankton--that de-oxygenation is increased.
Diatoms are known to thrive in warm, stratified water, but they also require sources of nutrients and iron, according to Alan Mix of Oregon State University, a co-author of the paper.
There are some competing effects, and the final story depends on which one wins. Warming may, for a time, decrease mixing from below, but if the major nutrients are there, as they are in the high North Pacific, then warming favors plankton growth.
"The high-latitude North Pacific is rich in common nutrients such as nitrate and phosphate, but it is poor in iron and that seems to be the key," Mix said. "A partial loss of oxygen causes a chemical reaction that releases iron previously trapped in continental margin sediments. That iron then fuels diatoms, which bloom, die and sink to the seafloor, consuming oxygen along the way."
Ocean response times a concern
The concern is how rapidly the ocean may respond, the researchers said.
"Many people have assumed that climate change effects will be gradual and predictable," Mix said, "but this study shows that the ecological consequences of climate change can be massive and can occur pretty fast with little warning."
Because the competing effects of mixing and iron may happen on different timescales, the exact sequence of events may be confusing.
On the scale of a few years, mixing may win, but on the scale of decades to centuries, the bigger effects kick into gear. The geologic record studied by the scientists emphasized these longer scales.
The new discovery was the result of a decades-long effort by numerous researchers at Oregon State University to collect marine sediment cores from the North Pacific, creating comprehensive, high-resolution records of climate change in the region.
The temperature records came from trace quantities of organic molecules, called biomarkers, produced by plankton.
In addition to "The Blob" of unusually warm ocean temperatures seen across the North Pacific, this year has had a record-breaking algae bloom dominated by a certain species of diatom.
"While it's too soon to know how this event ties into the long-term climate patterns that will emerge in the future," Praetorius said, "current conditions seem eerily reminiscent of past conditions that gave way to extended periods of hypoxia."
Cheryl Dybas | 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
24.10.2016 | Power and Electrical Engineering
24.10.2016 | Life Sciences
24.10.2016 | Life Sciences