Dendrochronology, 14C time-scale and mechanisms of rapid climate change during the last deglaciation

Full text: Our Euroclimate project 'Dendrochronology, 14C time-scale and mechanisms of rapid climate change during the last deglaciation' (Tree-14) is presented. In the collaboration we extend the radiocarbon calibration back into deglaciation, based on treering chronologies, and we obtain information on climate change events from treering proxies and 14C fluctuations. The tree-ring chronologies are being built in the tree-ring laboratories of Stuttgart-Hohenheim, Zurich and Aix-en-Provence. The absolutely dated chronology has been extended back to 12,593 years BP. For the Late Glacial well replicated, floating chronologies exist, starting at ca. 14,500 cal BP and extending for two centuries into Younger Dryas.We obtained decadal 14C ages of high precision (±25 years) for this interval. From a comparison to the marine 14C data set of the Cariaco basin we infer a substantial increase in the marine reservoir age for the tropical Atlantic, at least during Alleroed. Dendro-climatological evaluation is based on techniques to preserve long-term climate signals. Extensive fieldwork in Italy, Romania and Hungary has provided new finds of subfossil logs, with sequences dating into early Boelling, and even beyond the LGM. Using the common signal in the fluctuations of 14C in tree-rings and 10Be in ice cores will allow a comparison of the respective time-scales. (author)