Epic Droughts of the Last 2000 Years: USGS science on climate change

3/24/2006, U.S. Geological Survey (USGS) scientists who study historic climate trends will be presenting new studies at a workshop held in Pacific Grove, California, March 26-29.

The recent six-year-long drought across much of the western United States and the extensive dust bowl of the Great Plains in the 1930s, the subject of John Steinbeck´s “The Grapes of Wrath,” are recent examples of droughts that have plagued western North America for centuries. These examples, and the associated costs to society, seem short and insignificant when compared to extensive warm and dry intervals that have been recorded over the past 2,000 years. These include a 16th century megadrought, which affected the culture of central Mexico, an extended period of dry summers which may have led to the abandonment of the Chaco Canyon culture in New Mexico, and a lengthy period between about A.D. 800 and 1350 known as the Medieval Warm Period. USGS scientists use a variety of tools to uncover evidence of these droughts, including tree ring patterns, lake and ocean sediments, geochemistry, and climate modeling. These extended periods of drought are the topic of the 22nd Pacific Climate Workshop (PACLIM) to be held March 26-29, 2006.

Partially organized and funded by the USGS, the conference brings together university and government scientists from around the country for presentations and discussions on various aspects of climate variability, from the impact of the current drought on seasonal snowpack in the Sierra Nevada and the role of sea surface temperature along the California coast, to evidence from tree rings in New Mexico supporting the influence of climate on the migration of Paleo-indian populations across the southwest. Other presentations cover drought and a wide variety of other climate-related topics including the role of climate variability in the types of fish caught in the eastern Pacific, evidence of solar variability from lake sediments, and the influence of volcanic activity on short-term cooling.

USGS scientists will be presenting the results on new analyses of the role of decadal variation in the temperature of the surface waters of the Atlantic and Pacific Oceans (McCabe and others), longer-period variations in water temperature and wind variability in the Gulf of California (Barron and Bukry), aridity patterns derived from microfossils in San Francisco Bay marshes (Starratt), the impacts of atmospheric circulation variability on the climate in Alaska (Anderson), rock glaciers as indicators of climate change in the eastern Sierra Nevada (Millar and others), and the role of climate change in the migration of Native Americans in the southwestern U.S. (Benson).

Highlights of USGS work presented at the Pacific Climate Workshop (PACLIM), Asilomar Conference Center, Pacific Grove, California, March 26-29, 2006, http://wrgis.wr.usgs.gov/wgmt/deserts/paclim/ are as follows:

ORAL PRESENTATIONS
All oral presentations will be in the Kiln Room, Asilomar Conference Center

Migrations of Western Native Americans in Response to 12th and 13th Century Droughts
Larry Benson (USGS, Boulder) Monday, March 27, 8:45 am

Drought Variability in Mountains and Arid Lands in the Western United States.
Hugo Hidalgo (UCSD-SIO), Dan Cayan (UCSD-SIO, USGS), and Michael Dettinger (UCSD-SIO, USGS) Tuesday March 28, 9:00 am

Sea-Surface Temperature Variability and Droughts
Greg McCabe (USGS, Denver), Julio Betancourt (USGS, Tucson), Stephen Gray (USGS, Tucson), Michael Palecki (Illinois State Water Survey), and Hugo Hidalgo (UCSD-SIO) Tuesday March 28, 9:30 am

POSTERS
All posters will be in the Oak Shelter Room, Asilomar Conference Center, and will be on display during the entire conference.

Atmospheric Circulation and Moisture in SW Yukon Territory
Lesleigh Anderson (USGS, Denver)

Gulf of California Microfossils Tell of Medieval Monsoons
John Barron (USGS, Menlo Park) and David Bukry (USGS, Menlo Park)

Sediment Records Indicate Atmospheric connections Between Atlantic and Pacific Oceans
Walt Dean (USGS, Denver)

625 Years of Salinas River Stream Flow Reconstructed from Blue Oak Tree-Rings
R. Daniel Griffin, David Stahle, Malcolm Cleaveland, and Jesse Edmondson (University of AR), and Michael Dettinger (UCSD-SIO, USGS)

SW Droughts Since 250 B.C.: Impacts on Early Cultures & Predictions of Future Climates
Thor Karlstrom (USGS)

Rock Glaciers in The Sierra Nevada: Mapping, Climate Relations and Water Monitoring
Connie Millar (USDA Sierra Nevada Research Center), David Clow (USGS, Denver), Jessica Lundquist (NOAA), and Robert Westfall (USDA Sierra Nevada Research Center)

Microfossils in SF Bay Marsh Sediments Identify Arid Periods
Scott W. Starratt (USGS, Menlo Park)

Diatoms from Lake Tahoe
Scott W. Starratt (USGS, Menlo Park)

Climate Variability and Mayan Migration
Dave Wahl (UGS, Menlo Park)

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Scott Starratt

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U.S. Department of the Interior, U.S. Geological Survey

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