Featured Research

from universities, journals, and other organizations

6,000-year climate record suggests longer droughts, drier climate for Pacific Northwest

Date:
February 23, 2011
Source:
University of Pittsburgh
Summary:
Researchers extracted a 6,000-year climate record from a Washington state lake showing that the American Pacific Northwest could not only be in for longer dry seasons, but also is unlikely to see a period as wet as the 20th century any time soon and will likely suffer severe water shortages.

Duration of dry and wet cycles by percentage over 6,000-year period.
Credit: Image courtesy of University of Pittsburgh

University of Pittsburgh-led researchers extracted a 6,000-year climate record from a Washington lake that shows that the famously rain-soaked American Pacific Northwest could not only be in for longer dry seasons, but also is unlikely to see a period as wet as the 20th century any time soon.

In a new report in the Proceedings of the National Academy of Sciences, the team linked the longer dry spells to the intensifying El Niño/La Niña climate pattern and concluded that Western states will likely suffer severe water shortages as El Niño/La Niña wields greater influence on the region.

The researchers analyzed a sediment core from Castor Lake in north central Washington to plot the region's drought history since around 4,000 BCE and found that wet and dry cycles during the past millennium have grown longer. The team attributed this recent deviation to the irregular pressure and temperature changes brought on by El Niño/La Niña. At the same time, they reported, the wet cycle stretching from the 1940s to approximately 2000 was the dampest in 350 years.

Lead researcher Mark Abbott, a Pitt professor of geology and planetary science, said those unusually wet years coincide with the period when western U.S. states developed water-use policies. "Western states happened to build dams and water systems during a period that was unusually wet compared to the past 6,000 years," he said. "Now the cycle has changed and is trending drier, which is actually normal. It will shift back to wet eventually, but probably not to the extremes seen during most of the 20th century."

Abbott worked with his former graduate student, lead author and Pitt alumnus Daniel Nelson, as well as Pitt professor of geology and planetary science Michael Rosenmeier; Nathan Stansell, a Pitt PhD graduate now a postdoctoral researcher at Ohio State University; and Pitt geology and planetary science graduate student Byron Steinman. The team also included Pratigya Polissar, an assistant research professor at Columbia University's Lamont-Doherty Earth Observatory; Joseph Ortiz, associate professor of geology at Kent State University; Bruce Finney, a professor of geology at Idaho State University; and Jon Riedel, a geologist at North Cascades National Park in Washington.

The team produced a climate record from the lake mud by measuring the oxygen isotope ratios of the mineral calcite that precipitates from the lake water every summer and builds up in fine layers on the lake floor. More calcite accumulates in wet years than in dry years. They reproduced their findings by measuring grayscale, or the color of mud based on calcite concentration, with darker mud signifying a drier year.

The record in the sediment core was then compared to the Palmer Drought Severity Index, which uses meteorological and tree-ring data to determine drought cycles dating back 1,500 years, Abbott explained. The Castor Lake core matched the Palmer Index reconstructed with tree-ring data and expanded on it by 4,500 years, suggesting that lakebeds are better records of long-term climate change, the authors contend.

Analysis of the sediment core revealed that the climate of the Pacific Northwest fluctuated more or less evenly between wet and dry periods for thousands of years, the researchers wrote. Droughts tended to be lengthier with 25 percent of dry periods during the past 6,000 years persisting for 30 years or more and the longest lingering for around 75 years. Wet periods tended to be shorter with only 19 percent lasting more than 30 years and the longest spanning 64 years.

But since around 1000 AD, these periods have become longer, shifted less frequently, and, most importantly, ushered in more extreme conditions, Abbott said. The two driest cycles the researchers detected out of the past 6,000 years occurred within only 400 years of each other -- the first in the 1500s and the second during the Great Depression. Wet periods showed a similar pattern shift with five very wet eras crammed into the past 900 years. The wettest cycle of the past 6,000 years began around the 1650s, and the second most sodden began a mere 300 years later, in the 1940s.

The change in cycle regularity Abbott and his colleagues found correlates with documented activity of El Niño/La Niña. When the patterns became more intense, wet and dry cycles in the Pacific Northwest became more erratic and lasted longer, Abbott said.


Story Source:

The above story is based on materials provided by University of Pittsburgh. Note: Materials may be edited for content and length.


Journal Reference:

  1. Daniel B. Nelson, Mark B. Abbott, Byron Steinman, Pratigya J. Polissar, Nathan D. Stansell, Joseph D. Ortiz, Michael F. Rosenmeier, Bruce P. Finney, Jon Riedel. Drought variability in the Pacific Northwest from a 6,000-yr lake sediment record. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1009194108

Cite This Page:

University of Pittsburgh. "6,000-year climate record suggests longer droughts, drier climate for Pacific Northwest." ScienceDaily. ScienceDaily, 23 February 2011. <www.sciencedaily.com/releases/2011/02/110222122725.htm>.
University of Pittsburgh. (2011, February 23). 6,000-year climate record suggests longer droughts, drier climate for Pacific Northwest. ScienceDaily. Retrieved September 23, 2014 from www.sciencedaily.com/releases/2011/02/110222122725.htm
University of Pittsburgh. "6,000-year climate record suggests longer droughts, drier climate for Pacific Northwest." ScienceDaily. www.sciencedaily.com/releases/2011/02/110222122725.htm (accessed September 23, 2014).

Share This



More Fossils & Ruins News

Tuesday, September 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Ice Age Wooly Mammoth Remains for Sale

Raw: Ice Age Wooly Mammoth Remains for Sale

AP (Sep. 23, 2014) — A rare, well-preserved skeleton of a woolly mammoth is going on sale at Summers Place Auctions hope the 11.5-foot tall, almost intact specimen will fetch between $245,000 to $409,000. (Sept. 23) Video provided by AP
Powered by NewsLook.com
Iconic 'Easy Rider' Chopper Bike to Go on Auction Block

Iconic 'Easy Rider' Chopper Bike to Go on Auction Block

AFP (Sep. 19, 2014) — The iconic Harley-Davidson motorbike ridden by Peter Fonda in the 1969 classic "Easy Rider" is to go under the hammer in California, and auctioneers predict it will make at least $1 million. Duration: 01:09 Video provided by AFP
Powered by NewsLook.com
Chocolate Museum Opens in Brussels

Chocolate Museum Opens in Brussels

AFP (Sep. 19, 2014) — Considered a "national heritage" in Belgium, chocolate now has a new museum in Brussels. In a former chocolate factory, visitors to the permanent exhibition spaces, workshops and tastings can discover derivatives of the cocoa bean. Duration: 01:00 Video provided by AFP
Powered by NewsLook.com
Egypt Denies Claims Oldest Pyramid Damaged in Restoration

Egypt Denies Claims Oldest Pyramid Damaged in Restoration

AFP (Sep. 17, 2014) — Egypt's antiquities minister denied Tuesday claims that the Djoser pyramid, the country's first, had been damaged during restoration work by a company accused of being unqualified to do such work. Duration: 00:56 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins