In the January 5 issue of the journal Science, the researchers from the University of California, San Diego, the National Center for Scientific Research (CNRS) and the University of Grenoble in France report that the chemical fingerprint of fallout from past eruptions reveals how high the volcanic material reached, and what chemical reactions occurred while it was in the atmosphere.
The work is particularly relevant because the effect of atmospheric particles, or aerosols, is a large uncertainty in models of climate, according to Mark Thiemens, Dean of UCSD’s Division of Physical Sciences and professor of chemistry and biochemistry.
“In predictions about global warming, the greatest amount of error is associated with atmospheric aerosols,” explained Thiemens, in whose laboratory the method, which is based on the measurement of isotopes—or forms of sulfur—was developed. “Now for the first time, we can account for all of the chemistry involving sulfates, which removes uncertainties in how these particles are made and transported. That’s a big deal with climate change.”
Determining the height of a past volcanic eruption provides important information about its impact on climate. If volcanic material only reaches the lower atmosphere, the effects are relatively local and short term because the material is washed out by rain. Eruptions that reach higher, up to the stratosphere, have a greater influence on climate.
“In the stratosphere, sulfur dioxide that was originally in the magma gets oxidized and forms droplets of sulfuric acid,” said Joël Savarino, a researcher at the CNRS and the University of Grenoble, who led the study. “This layer of acid can stay for years in the stratosphere because no liquid water is present in this part of the atmosphere. The layer thus acts as a blanket, reflecting the sunlight and therefore reducing the temperature at ground level, significantly and for many years.”
To distinguish eruptions that made it to the stratosphere from those that did not, the researchers examined the isotopes of sulfur in fallout preserved in the ice in Antarctica. The volcanic material is carried there by air currents. Thiemens, Savarino and two of their students traveled to Antarctica and recovered the samples by digging snow pits near the South Pole and Dome C, the new French/Italian inland station.
Sulfur that rises as high as the stratosphere, above the ozone layer, is exposed to short wavelength ultraviolet light. UV exposure creates a unique ratio of sulfur isotopes. Therefore the sulfur isotope signature in fallout reveals whether or not an eruption was stratospheric.
To develop the method, the team, which also included Mélanie Baroni, the first author on the paper who is a postdoctoral fellow working with Savarino, and Robert Delmas, a research director at the CNRS, focused on two volcanic eruptions. Both eruptions, the 1963 eruption of Mount Agung in Bali and the 1991 eruption of Mount Pinatubo in the Philippines, were stratospheric according to the isotope measurements.
“Young volcanoes have the advantage of having been documented by modern instruments, such as satellites or aircraft,” said Savarino, who began his investigations into sulfur isotope measurements when he was a postdoctoral fellow working with Thiemens. “We could therefore compare our measurements on volcanic fallout stored in snow with atmospheric observations.”
Not only did their isotope measurements match the atmospheric observations, they were also able to distinguish the Pinatubo eruption from the eruption of Cerro Hudson that occurred the same year. Cerro Hudson did not send material as high as the stratosphere and the fallout had a different sulfur isotope fingerprint than the fallout from Pinatubo.
Volcanic material from more ancient eruptions is preserved in Antarctica, but the older, deeper seasonal layers of ice are extremely thin as a result of the pressure from the overlying ice. Therefore, it is not currently feasible to extract enough fallout from the ice to apply the isotope method to all past volcanoes. However, data from eruptions in the recent past reveal what chemical reactions of sulfates occur in the upper atmosphere.
Some scientists have proposed that if global warming becomes severe, sulfates could be injected into the stratosphere in order to block some of the incoming solar radiation and reduce the temperature. Thiemens explained that understanding the chemical reactions of sulfates in the stratosphere is critical to determining if this approach would be effective.
“Sulfates can cause warming or cooling depending on how they are made,” he said. “They are usually white particles, which tend to reflect sunlight, but if they are made on dark particles like soot, they can absorb heat and worsen warming.”
The study was funded by the French Polar Institute (IPEV) and the National Science Foundation Office of Polar Programs.
Sherry Seethaler | EurekAlert!
Monitoring lava lake levels in Congo volcano
16.05.2018 | Seismological Society of America
Ice stream draining Greenland Ice Sheet sensitive to changes over past 45,000 years
14.05.2018 | Oregon State University
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.
Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...
A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.
Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
18.05.2018 | Power and Electrical Engineering
18.05.2018 | Information Technology
18.05.2018 | Information Technology