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Wednesday, February 23, 2011

Daniel B. Nelson et al., PNAS (February 2011), Drought variability in the Pacific Northwest from a 6,000-yr lake sediment record

Proceedings of the National Academy of Sciences, published online before print February 22, 2011; doi: 10.1073/pnas.1009194108

Drought variability in the Pacific Northwest from a 6,000-yr lake sediment record

  1. Daniel B. Nelsona,1
  2. Mark B. Abbotta,2
  3. Byron Steinmana,
  4. Pratigya J. Polissarb
  5. Nathan D. Stansella,c
  6. Joseph D. Ortizd,
  7. Michael F. Rosenmeiera
  8. Bruce P. Finneye, and 
  9. Jon Riedelf
+Author Affiliations
  1. aGeology and Planetary Science, University of Pittsburgh, 4107 O’Hara Street, Room 200, Space Research Coordination Center, Pittsburgh, PA 15260;
  2. bLamont–Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY 10964;
  3. cByrd Polar Research Center, Ohio State University, 1090 Carmack Road, Columbus, OH 43210;
  4. dDepartment of Geology, Room 334/336 McGilvrey Hall, Kent State University, Kent, OH 44242;
  5. eBiological Sciences and Geosciences, Idaho State University, Pocatello, ID 83209; and
  6. fUnited States Park Service, North Cascades National Park, Marblemount, WA 98267
  1. Edited by James P. Kennett, University of California, Santa Barbara, CA 93106, and approved January 18, 2011 (received for review June 28, 2010)
  • 1Present address: School of Oceanography, University of Washington, Box 355351, Seattle, WA 98195.


We present a 6,000-yr record of changing water balance in the Pacific Northwest inferred from measurements of carbonate δ18O and grayscale on a sediment core collected from Castor Lake, Washington. This subdecadally resolved drought record tracks the 1,500-yr tree-ring-based Palmer Drought Severity Index reconstructions of Cook et al. [Cook ER, Woodhouse CA, Eakin CM, Meko DM, Stahle DW (2004) Science 306:1015–1018] in the Pacific Northwest and extends our knowledge back to 6,000 yr B.P. The results demonstrate that low-frequency drought/pluvial cycles, with occasional long-duration, multidecadal events, are a persistent feature of regional climate. Furthermore, the average duration of multidecadal wet/dry cycles has increased since the middle Holocene, which has acted to increase the amplitude and impact of these events. This is especially apparent during the last 1,000 yr. We suggest these transitions were driven by changes in the tropical and extratropical Pacific and are related to apparent intensification of the El Niño Southern Oscillation over this interval and its related effects on the Pacific Decadal Oscillation. The Castor Lake record also corroborates the notion that the 20th century, prior to recent aridity, was a relatively wet period compared to the last 6,000 yr. Our findings suggest that the hydroclimate response in the Pacific Northwest to future warming will be intimately tied to the impact of warming on the El Niño Southern Oscillation.

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