Purdue researchers part of volcanic eruptions study

July 8, 2015  

WEST LAFAYETTE, Ind. — A Purdue University professor was part of an international study that found volcanic eruptions have been responsible for cooling extremes recorded since early Roman times.

Marc Caffee, director of the Purdue Rare Isotope Measurement Laboratory, or PRIME lab, and Thomas Woodruff, a postdoctoral researcher, used accelerator mass spectrometry to perform measurements critical to the research.

The study, which was led by scientists at the Desert Research Institute, reconstructed the timing and associated radiative forcing of nearly 300 individual volcanic eruptions within the past 2,500 years. The researchers found that large volcanic eruptions were a dominant driver of climate variability, as the volcanic sulfate and ash ejected into the upper atmosphere shielded the Earth's surface from incoming solar radiation. The eruptions led to widespread summer cooling extremes and climate change that has been tied to pandemics and famines in the 6th century, Caffee said.

The researchers studied the volcanic sulfate and other chemicals in ice cores taken from ice sheets in Greenland and Antarctica.

The paper was published in the journal Nature on July 8 and is available online.

Caffee, who is a professor of physics, used a tandem electrostatic accelerator to perform measurements of beryllium-10 in individual layers of ice within the ice core.

The PRIME lab is one of only two laboratories in the nation capable of performing the ultra-sensitive measurements necessary for this work, he said.

"Anomalies in the deposition of beryllium-10 in the ice layers allowed us to establish a more precise timeline than was possible with previous studies," Caffee said. "This ice core chronology, in turn, was used to precisely date the volcanic eruptions. What is exciting about this work is the ability to date events nearly to the year. This gives us the real opportunity to look for cause and effect relationships."

Beryllium-10 is a radioactive isotope formed from the interaction of cosmic rays with oxygen in the atmosphere. When trapped in ice, beryllium-10 begins to decay at a known rate. The researchers analyzed the amount of remaining beryllium-10 in the ice core samples to determine how long ago each layer was deposited, he said.

A link to the Desert Research Institute news release is available online

Writer: Elizabeth K. Gardner, 765-494-2081, ekgardner@purdue.edu

Source: Marc Caffee, 765-494-5381, mcaffee@physics.purdue.edu 

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