Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Charcoal Evidence Tracks Climate Changes in Younger Dryas

30.01.2009
A new study reports that charcoal particles left by wildfires in sediments of 35 North American lake beds don't readily support the theory that comets exploding over the continent 12,900 years ago sparked a cooling period known as the Younger Dryas.

The study -- appearing online this week (Jan. 26-31) ahead of regular publication in the Proceedings of the National Academy of Sciences -- however, did find clear links between abrupt climate changes and fire activity during the transition between the last Ice Age and the warm interglacial period that began 11,700 years ago.

These links are also consistent with the impacts of climate-change conditions on wildfires during recent decades in North America, the researchers noted.

Charcoal particles, along with tree pollen, provide snapshots of types of vegetation and frequencies of wildfire activity in a given area, said study co-author Patrick J. Bartlein, a professor of geography at the University of Oregon. His doctoral student Jennifer R. Marlon led the collaborative study of 23 co-authors (including seven current or former UO students) at institutions in the U.S., Canada and Europe.

"The charcoal data don't support the idea of widespread fires at the beginning of the Younger Dryas interval," Bartlein said. "The results don't reject the comet hypothesis, but do suggest that one element of it -- widespread fires -- didn't occur. Instead, the data show that biomass burning tracked general climate changes closely. Biomass burning increased as conditions warmed during deglaciation until the beginning of the Younger Dryas cold interval at 12,900 years ago, leveled off during the cool interval, and then increased again as warming resumed after the end of the cold interval, about 11,700 years ago."

The fires that left the charcoal records reflect the impact of climate changes independent of potential contributions of early Paleoindians who may have been living on the continent. Proponents of the comet theory suggest Clovis culture may have been dramatically disrupted across the continent.

Marlon began the National Science Foundation-sponsored study of charcoal-pollen records soon after the comet theory was proposed in PNAS by an international team of 26 researchers led by Richard B. Firestone. A co-author of that study, UO archaeologist Douglas Kennett, in the Jan. 2 issue of Science, documented the existence of possible comet-triggered nanodiamond-rich soil at six North American sites dating to 12,900 years ago in apparent support of the hypothesis. The formation of nanodiamonds requires intense pressure and heat, much higher than those of biomass wildfires but possible in comet explosions.

"We had the data to look for widespread fires if they had occurred," Marlon said, "but what we saw instead was a general increase in biomass burning whenever the climate warmed."

The lakes containing the charcoal are in Alaska (3 sites), British Columbia (7), U.S. Pacific Northwest (6), the Sierra Nevada (3), northern U.S. Rocky Mountains (6), Southwest (4), Midwest (2), Northeast (3 sites in Quebec), and Southeast (1). Thirty of the samples came from the Global Charcoal Database; another five were drawn from more recent research by co-authors currently studying sediments from the Younger Dryas.

The new study's conclusion that climate is a major control of wildfires matched that of a study published last year in Nature Geosciences by the same researchers on global biomass burning over the last 2,000 years.

"Together," Bartlein said, "these studies suggest that episodes of global warming are accompanied by increases in wildfires."

Co-authors of the study were Marlon, Bartlein and Megan K. Walsh, all currently of the UO; Walsh is a postdoctoral researcher in Kennett's lab. Others were S.P. Harrison of the University of Bristol (UK); K.J. Brown of the Geological Survey of Denmark and Greenland and of the Royal British Columbia Museum in Victoria, B.C.; M.E. Edwards of the University of Southampton (UK) and University of Alaska; P.E. Higuera, C. Briles and C. Whitlock of Montana State University; M.J. Power and A. Brunelle of the University of Utah; R.S. Anderson and M. Daniels of Northern Arizona University; C. Carcaillet of the French National Centre for Scientific Research and University of Montpellier (France); Feng-Sheng Hu of the University of Illinois at Urbana-Champaign; M. Lavoie of Laval University in Quebec City; C. Long of the University of Wisconsin at Oshkosh; T. Minckley of the University of Wyoming; P.J.H. Richard of the University of Montreal; A.C. Scott of the University of London; D.S. Shafer of the Nevada System of Higher Education's Desert Research Institute; W. Tinner of the University of Bern, Switzerland; and C.E. Umbanhowar Jr. of St. Olaf College in Minnesota.

About the University of Oregon
The University of Oregon is a world-class teaching and research institution and Oregon's flagship public university. The UO is a member of the Association of American Universities (AAU), an organization made up of the 62 leading public and private research institutions in the United States and Canada. The University of Oregon is one of only two AAU members in the Pacific Northwest.

Sources: Jennifer Marlon, doctoral student, geography, 203-507-2462 (currently in New Haven, Conn.), jmarlon@uoregon.edu; Patrick Bartlein, professor of geography, 541-346-4967, bartlein@uoregon.edu

Links: Bartlein faculty page: http://geography.uoregon.edu/bartlein/; UO geography department: http://geography.uoregon.edu/

Jim Barlow | Newswise Science News
Further information:
http://www.uoregon.edu

More articles from Earth Sciences:

nachricht New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz

nachricht Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Subaru Telescope helps pinpoint origin of ultra-high energy neutrino

16.07.2018 | Physics and Astronomy

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides

16.07.2018 | Life Sciences

New research calculates capacity of North American forests to sequester carbon

16.07.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>