Radiocarbon Ages of Annual Rings from Japanese Wood: Evident Age Offset Based on IntCal09

Abstract

To investigate the radiocarbon concentration of atmospheric CO 2 over the past few millennia in Japan, we measured the 14 C age of annual rings from 3 Japanese trees with calendar dates ranging from ~2000 yr old to present, and we compared the tree-ring 14 C age with the corresponding 14 C age from IntCal09. In some instances, the 14 C ages of the annual rings of Japanese trees are not consistent with the IntCal09 data sets. Often, the 14 C ages of tree rings are older than those from IntCal09, but younger than those from the SHCal04 data sets. The average shifts in the Nagoya 14 C age from IntCal09 data sets and 1σ errors were determined to be +26 ± 36, +24 ± 30, +16 ± 22, +5 ± 21, and +14 ± 22 14 C yr for the intervals AD 72- 382, 589-1072, 1413-1615, 1617-1739, and 1790-1860, respectively. The Japanese Archipelago is situated near the boundary of the Intertropical Convergence Zone in summer, and the 14 C concentration of atmospheric CO 2 over Japan can be influenced by air masses of the Southern Hemisphere with lower 14 C concentrations during periods of higher solar activity and heightened East Asian summer monsoons. Our results suggest that the Japanese Archipelago is located in a critical zone where it is difficult to calibrate the 14 C age of tree-ring samples using existing calibration data sets. It should be noted that calibration of the 14 C dates of Japanese samples with IntCal09 may induce additional systematic shifts of calibrated ages toward older ages by about 30 yr compared with the sample optimum calendar ages. © 2013 by the Arizona Board of Regents on behalf of the University of Arizona.