Synchronizing ice cores from the Renland and Agassiz ice caps to the Greenland ice core chronology

Four ice cores from the Agassiz ice cap in the Canadian high arctic and one ice core from the Renland ice cap in eastern Greenland have been synchronized to the Greenland Ice Core Chronology 2005 (GICC05) which is based on annual layer counts in the DYE-3, GRIP and NGRIP ice cores. Volcanic reference horizons, seen in electrical conductivity measurements (ECM) have been used to carry out the synchronization throughout the Holocene. The Agassiz ice cores have been matched to the NGRIP ice core ECM signal, while the Renland core has been matched to the GRIP ice core ECM signal, thus tying the cores to GICC05. Furthermore, it has been possible to synchronize the Renland ice core to NGRIP-GICC05 in the glacial period back to 60,000 years b2k (years before A. D. 2000), on the basis of a matching of transitions between stadials and interstadials. This work brings the total number of ice core records that have been rigorously tied to the GICC05 timescale up to nine. Renland annual layer thicknesses are increasing with depth during the period from 7 to 8.5 ka b2k, a highly unusual observation only matched by a similar thickness increase in the glacial section of the Renland core some 60 ka ago. Annual layer thicknesses in the Agassiz ice cores point to a well-developed Raymond bump in the Agassiz ice cap.