The research team, overseen by Scripps geoscientist and study co-author Jeff Severinghaus, collected what may be the largest ice samples ever for a climate change study. The researchers cut away 15 tons of ice from a site called Pakitsoq at the western margin of the Greenland ice sheet to collect the ancient air trapped within. Methane exists in low concentrations in this air and only a trillionth of any given amount contains the carbon-14 isotope that the researchers needed to perform the analysis. Levels of carbon-14, which has a half-life of 5,730 years, were too high in the methane to have come from clathrates, the researchers concluded.
"This study is important because it confirms that wetlands and moisture availability change dramatically along with abrupt climate change," said Severinghaus. "This highlights in a general way the fact that the largest impacts of future climate change may be on water resources and drought, rather than temperature per se."
The burst of methane took place immediately after an abrupt transition between climatic periods known as the Younger Dryas and Preboreal. During this event, temperatures in Greenland rose 10 C (18 F) in 20 years. Methane levels over 150 years rose about 50 percent, from 500 parts per billion in air to 750 parts per billion.
In addition to Petrenko and Severinghaus, researchers from the Australian Nuclear Science and Technology Organisation (ANSTO), Oregon State University, the National Institute of Water and Atmospheric Research in New Zealand, the Technical University of Denmark and the Commonwealth Scientific and Industrial Research Organisation in Australia contributed to the report.
The work was supported by grants from the Natio
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University of California - San Diego