Australia: The Land Where Time Began

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Early Younger Dryas - Variations of atmospheric 14C Derived from Tree Rings

Over the interval of the Younger Dryas, about 13,000 - 11,600 cal yr BP, variations in atmospheric radiocarbon reveal crucial information about linkages between climate, ocean circulation and carbon cycles, which makes them of immense scientific interest. According to the authors1 there is  no direct and reliable evidence available of atmospheric 14C that is based on tree rings for the entire Younger Dryas. The authors1 have presented in this paper high-precision measurements of 14 C, extending the absolute tree ring chronology from 12,400 to 12,550 cal yr BP and a high-precision, high-resolution record of atmospheric 14C that was derived from a 617 year tree ring chronology of Huon pine in Tasmania, Australia, that spans the early Younger Dryas. The current gap in European tree ring radiocarbon chronologies during the early Younger Dryas is bridged by the new 14C records, which links the floating late glacial pine record to the absolute tree ring timescales. The result is a continuous, reliable atmospheric 14C record that covers the past 14,000 cal yr BP, including the Younger Dryas. It is indicated by the new records that the abrupt atmospheric Δ14C rise associated with the onset of the Younger Dryas occurs at about 12,760 cal yr BP, which is about 240 years later than that recorded in the Cariaco varves, with a smaller magnitude of about 40 ‰, which was followed by several centennial Δ14C variations of 20-25 ‰. When the tree ring Δ14C is compared to Δ14C that is marine-derived and modeled Δ14C, that is based on ice core 10Be fluxes, the authors1 concluding that ocean circulation changes and production rate of Δ14C were responsible for variations of the atmospheric Δ14C for the remainder of the Younger Dryas.


Sources & Further reading

  1. Hua, Quan, Mike Barbetti, David Fink, Klaus Felix Kaiser, Michael Friedrich, Bernd Kromer, Vladimir A. Levchenko, et al. "Atmospheric 14c Variations Derived from Tree Rings During the Early Younger Dryas." Quaternary Science Reviews 28, no. 2526 (12// 2009): 2982-90.


Author: M. H. Monroe
Last updated: 03/04/2013

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