Raimund Muscheler

Variations in galactic cosmic rays reaching the Earth's atmosphere produce globally synchronous variations in the production rates of cosmogenic radionuclides. In consequence, they leave their imprint in tree-ring 14C and ice-core 10Be records. By identifying this signal and correcting for the known geochemical influences on the radionuclides, it is possible to compare and synchronize the tree-ring chronology and the Greenland ice-core time scale. Here, we compare the IntCal13 and the GICC05 time scales for the last 14,000 years via identification and synchronization of the common short-term variations in the ice-core 10Be and tree-ring 14C records most likely induced by variations in the solar modulation of galactic cosmic rays. We conclude that systematic time-scale differences have to be accounted for if ice-core and 14C-dated records are compared on decadal time scales. These are mostly within the uncertainties of the time scales and the method proposed here. However, for large parts of the mid to late Holocene (i.e. after 7000 yrs BP) the best agreement between ice-core 10Be and tree-ring 14C records is obtained for time shifts outside the stated errors of the respective time scales. A transfer function is proposed that can be applied to synchronize the GICC05 ice-core time scale to the radiocarbon time scale.