REGIONAL OFFSET OF RADIOCARBON CONCENTRATION AND ITS VARIATION IN THE KOREAN ATMOSPHERE FROM AD 1650-1850

A series of annual tree-ring measurements has been performed in order to reconstruct the radiocarbon concentration variation in the Korean atmosphere from AD 1650 to 1850. The absolute ages of the samples were determined using dendrochronology. Alpha-cellulose extraction was applied to prepare the tree-ring samples for precise C-14 measurement. The C-14 concentrations of the tree rings were then plotted with the dendrochronological ages and showed that during the period AD 1650-1850, the discrepancy in C-14 concentration in the Korean atmosphere from IntCal data is small enough to use IntCal data without any further correction. This is nearly one third of the average offset of the 400 yr from AD 1250 to 1650. One of the probable causes for the regional offset around Korea is the contribution of C-14-depleted CO2 released from the northern Pacific Ocean, where old deep water upwells to the surface. It is likely that the release rate of C-14-depleted CO2 decreased due to the temperature change during the Little Ice Age.