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Great flood disrupted ocean currents, cooled climate, finds new research
mongabay.com
June 29, 2006
Ocean circulation changes caused at the end of the past glacial period were more extensive than previously thought, according to new research scientists at the University of East Anglia and Cardiff University.
The findings, published in the June 30 issue of the journal Science, indicate that the catastrophic freshwater release from glacial lakes in North America slowed ocean circulation and cooled the climate some 8200 years ago.
According to a release from the University of East Anglia, the "research increases our understanding of the complex link between ocean circulation and climate change and highlights the sensitivity of the Atlantic overturning circulation to freshwater forcing."
Christopher Ellison and Dr Mark Chapman, of the University of East Anglia's School of Environmental Sciences, and Dr Ian Hall, of Cardiff University's School of Earth, Ocean and Planetary Sciences used a sediment core drawn from the North Atlantic seabed to come to their conclusions.
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"The core contains sediments representing the warm interval since the last Ice Age," said Dr. Ellison of the University of East Anglia. "The sediment includes a variety of small animals called foraminifera that record surface water conditions in their shells when living. We analysed changes in the abundance of different species of foraminifera and the chemistry of the shells to examine past patterns of climate change. We also analysed the sediment grain size to gauge the speed of deep ocean currents and therefore the strength of ocean circulation."
The researchers said the findings provide the first direct evidence of both the freshwater forcing and the climate response to the event.
"The 8200-year-old event is the most recent abrupt climate change event and by far the most extreme cooling episode in the last 10,000 years, but up until now we knew comparatively little about its impact, if any, on the ocean circulation," explained Dr. Chapman. "Our records show a sequenced pattern of freshening and cooling of the North Atlantic sea surface and an associated change in the deep ocean circulation, all key factors that are involved in controlling the state of northern hemisphere climate."
"These findings have important implications for future research because they aid our understanding of the magnitude of forcing involved in rapid climate changes and the mechanisms involved," Dr Hall added. "This provides a useful target for assessing the models that are used to predict future patterns of climate change"."
This article is based on a release from the University of East Anglia.
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