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Extremely Large Variations of Atmospheric 14C Concentration During the Last Glacial Period
J. Warren Beck,1*David A. Richards,23*R. Lawrence ,Edwards,3Bernard W. Silverman,4Peter L. Smart,2Douglas J. Donahue,1Sofia Hererra-Osterheld,1George. S. Burr,1Leal Calsoyas,1A.
J. Timothy ,Jull,1Dana Biddulph1
A long record of atmospheric 14C concentration, from 45 to 11 thousand years ago (ka), was obtained from a stalagmite with
thermal-ionizationmass-spectrometric 230Th and accelerator
mass-spectrometric 14C measurements. This record reveals
highly elevated 14C between 45 and 33 ka, portions of
which may correlate with peaksin cosmogenic 36Cl and
10Be isotopes observed in polar ice cores. Superimposed on
thisbroad peak of 14C are several rapid excursions, the
largest of which occurs between44.3 and 43.3 ka. Between 26 and 11 ka,
atmospheric 14C decreased from ~700 to ~100 per mil,
modulated by numerous minorexcursions. Carbon cycle models suggest
that the major featuresof this record cannot be produced with solar or
terrestrial magneticfield modulation alone but also require
substantial fluctuationsin the carbon cycle.
1 NSF-Arizona Accelerator Mass Spectrometry
Facility, Department of Physics, University of Arizona, Tucson, AZ
85721, USA.
2 School of Geographical Sciences,
University of Bristol, Bristol, BS8 1SS, UK.
3 Minnesota Isotope Laboratory, Department of
Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA.
4 School of Mathematics, University of Bristol,
Bristol, BS8 1TW, UK.
*
To whom correspondence should be addressed. E-mail:
wbeck{at}physics.arizona.edu, David.Richards{at}bristol.ac.uk
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PERSPECTIVES
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[DOI: 10.1126/science.1058375] |Summary »|Full Text »
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14C between 45 and 33 ka, portions of
which may correlate with peaks in cosmogenic 36Cl and
10Be isotopes observed in polar ice cores. Superimposed on
this broad peak of 
