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Tuesday, October 20, 2009

Yarrow Axford et al., PNAS, Recent changes in a remote Arctic lake are unique within the past 200,000 years

Proceedings of the National Academy of Sciences, published online before print October 19, 2009; doi: 10.1073/pnas.0907094106

Recent changes in a remote Arctic lake are unique within the past 200,000 years

  1. Yarrow Axforda,1, Jason P. Brinerb, Colin A. Cookec, Donna R. Francisd, Neal Micheluttie, Gifford H. Millera,f, John P. Smole, Elizabeth K. Thomasb, Cheryl R. Wilsone and Alexander P. Wolfec


The Arctic is currently undergoing dramatic environmental transformations, but it remains largely unknown how these changes compare with long-term natural variability. Here we present a lake sediment sequence from the Canadian Arctic that records warm periods of the past 200,000 years, including the 20th century. This record provides a perspective on recent changes in the Arctic and predates by approximately 80,000 years the oldest stratigraphically intact ice core recovered from the Greenland Ice Sheet. The early Holocene and the warmest part of the Last Interglacial (Marine Isotope Stage or MIS 5e) were the only periods of the past 200,000 years with summer temperatures comparable to or exceeding today's at this site. Paleoecological and geochemical data indicate that the past three interglacial periods were characterized by similar trajectories in temperature, lake biology, and lakewater pH, all of which tracked orbitally-driven solar insolation. In recent decades, however, the study site has deviated from this recurring natural pattern and has entered an environmental regime that is unique within the past 200 millennia.

Edited by Mark Brenner, University of Florida, Gainesville, FL, and accepted by the Editorial Board September 1, 2009 (received for review June 25, 2009) 

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