Recent changes in a remote Arctic lake are unique within the past 200,000 years
- 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
- aInstitute of Arctic and Alpine Research and
- fDepartment of Geological Sciences, University of Colorado, Boulder, CO 80309;
- bGeology Department, University at Buffalo, Buffalo, NY 14260;
- cDepartment of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E3;
- dDepartment of Geosciences, University of Massachusetts, Amherst, MA 01003; and
- ePaleoecological Environmental Assessment and Research Laboratory, Department of Biology, Queen's University, Kingston, ON, Canada K7L 3N6
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Edited by Mark Brenner, University of Florida, Gainesville, FL, and accepted by the Editorial Board September 1, 2009 (received for review June 25, 2009)
Abstract
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.
Footnotes
- 1To whom correspondence should be addressed. E-mail: axford{at}colorado.edu
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Author contributions: Y.A., J.P.B., C.A.C., D.R.F., N.M., G.H.M., J.P.S., E.K.T., C.R.W., and A.P.W. designed research; Y.A., J.P.B., C.A.C., N.M., E.K.T., and C.R.W. performed research; Y.A., J.P.B., C.A.C., D.R.F., N.M., G.H.M., J.P.S., E.K.T., C.R.W., and A.P.W. analyzed data; and Y.A. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission. M.B. is a guest editor invited by the Editorial Board.
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See Commentary on page 18431.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0907094106/DCSupplemental.
