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October 19th, 2009

Arctic lake sediment record shows warming, unique ecological changes in recent decades

A team of researchers from five universities, led by Yarrow Axford, discovered that biological and chemical changes occurring at a remote Arctic lake in recent decades are unprecedented over the past 200,000 years and likely are the result of human-caused climate change. The team's study is based on uniquely old sediment cores extracted from the bottom of a lake on eastern Baffin Island, which is several hundred miles west of Greenland.

The research team carefully sampled the sediments for indicators of past environmental change: algae, insects and geochemistry. They constrained the age of the core through radiocarbon and optically-stimulated luminescence dating. Their record of past environments goes back in time 80,000 years before the oldest reliable ice cores from Greenland and captures three interglacial periods, including the Holocene. Although the lake was overridden by glacier ice several times, the interglacial sediments were not eroded. Environmental changes during all three interglacial periods have been tightly linked to natural causes of climate change--including periodic, well-understood wobbles in Earth's orbit. But changes seen in the sediment cores since about 1950 show that expected natural climate cooling and related changes in the lake environment are being overridden by human activity like greenhouse gas emissions.

Team members included Jason Briner (former INSTAAR, now Univ. at Buffalo), Gifford Miller, and Alexander Wolfe (former INSTAAR post doc, now Univ. of Alberta). Their paper was the cover story for the November 3rd volume of the Proceedings of the National Academy of Sciences of the USA (PNAS).

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