July 7, 2014
History Of Volcanic Forcing Identified In Antarctic Ice Cores
Gerard LeBlond for redOrbit.com - Your Universe Online
A team of scientists from Reno, Nevada’s Desert Research Institute (DRI), led by Michael Sigl and Joe McConnell, has reconstructed historic volcanic sulfate emissions from the Southern Hemisphere. It is considered to be the most accurate and defined reconstruction to date, and was published in a manuscript in the online addition of Nature Climate Change.
“The collaboration between DRI, National Institute of Polar Research (NIPR), and RIKEN just started in the last year, and we were very happy to be able to use the two newly obtained ice core records taken from Dome Fuji, where the volcanic signals are clearly visible. This is because precipitation on the site mainly contains stratospheric components,” Yuko Motizuki from Japan’s largest comprehensive research institution said.
The team used data from numerous individual ice cores collected from various locations across Antarctica. This is the first annual record including data covering the last 2,000 years of human history.
“This (record) provides the basis for a dramatic improvement in existing reconstructions of volcanic emissions during recent centuries and millennia,” said Sigl, the report’s lead author.
According to the team, this was critical to accurately model simulations which are used to evaluate natural and anthropogenic climate forcing from the past. These models highlight the need for environmental policy decisions to regulate greenhouse gas and aerosol emissions and to diminish global warming.
Powerful volcanic eruptions are a major cause in climate inconsistency from the sulfur dioxide they release into the atmosphere. This leads to microscopic particles known as volcanic sulfate aerosols to develop. These particles reflect the sun’s radiation back into space, consequently cooling the Earth. The team measured sulfate deposits found in ice cores from past eruptions, and linked them to short-term regional cooling.
The team gathered data from the West Antarctic Ice Sheet (WAIS), along with other ice core sulfate data and put together the most extensive and detailed record of volcanic sulfate in the region. The study combined 26 precisely synchronized ice core records into an arrangement of 19 sites around Antarctica.
“This work is the culmination of more than a decade of collaborative ice core collection and analysis in our lab here at DRI,” said McConnell, who developed the continuous-flow analysis system used to analyze the ice cores.
Between 2007 and 2009, McConnell was a member of a team that collected cores from the Norwegian-American Scientific Traverse of East Antarctica and in 2011 the WAIS Divide project. “The new record identifies 116 individual volcanic events during the last 2000 years,” he said.
“Our new record completes the period from years 1 to 500 AD, for which there were no reconstructions previously, and significantly improves the record for years 500 to 1500 AD,” Sigl added.
DRI previously assisted with the international Past Global Changes (PAGES) effort and with the new record they added to it constructing a more detailed and accurate account of 2,000 years of global temperature for the individual continents.
Ice core observations were compared to simulations of volcanic sulfate transport combined with a coupled aerosol-climate model. They were used to investigate patterns of sulfate deposits in Antarctica.
“Both observations and model results show that not all eruptions lead to the same spatial pattern of sulfate deposition. Spatial variability in sulfate deposition means that the accuracy of volcanic sulfate reconstructions depends strongly on having a sufficient number of ice core records from as many different regions of Antarctica as possible,” said Matthew Toohey from the German institute GEOMAR Helmholtz Centre for Ocean Research Kiel.
The researchers were able to determine from the study that the two most recent eruptions in the region (Samalas in 1257 and Kuwae in 1458) deposited 30 to 35 percent less sulfate in Antarctica, meaning that they had a weaker effect on cooling of the global climate than previously thought.
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