Intra-Annual Radiocarbon (14C) Offsets, Chronology and Paleoclimate

This project specifically aims to test whether small growing-season-related Carbon-14 offsets exist for two Mediterranean-type areas comprised of the East Mediterranean-Middle East (EMME) and the Southwest United States (SW USA), as well as one humid sub-tropical area Southeast United States (SE USA), and, if identified, quantify their scale and paleoclimate relevance. Carbon-14 is relevant to many temporally-dependent investigations in paleoclimate and related fields, as well as a key tracer for a number of carbon-cycle models central to paleoclimate research. Recent studies have revealed a distinct seasonal cycle in atmospheric Carbon-14. With high-precision measurement it seems plausible that plants growing at substantially different times of the year may reflect different portions of this seasonal Carbon-14 cycle. This research has the potential to advance knowledge in the fields of paleoclimate, paleoecology, and archaeology. Precise age-depth modelling is critical to establishing the timing of past events, and the research will attempt to improve radiocarbon age calibration by investigating the potential impacts of seasonal phenological differences in annual radiocarbon uptake by plants and how those biases may impact calibration based on widely used but spatially-biased northern hemisphere calibration curve. Until recently, analytical precision precluded exploring such differences since they were below measurement detection but advances in analytical measurements now make this inquiry possible. Although small, these analytical differences could have significant effects on carbon-related dating, especially at times of reversals and plateaus in the Carbon-14 calibration curve. The potential Broader Impacts include involving undergraduates in dendrochronology research at both Cornell University and the University of Georgia while also supporting an early career scientist at Georgia. The project would also support a PhD student who will develop outreach materials for the public. Research results will be distributed during International Archaeology Day and outreach to middle school students through the Expanding Your Horizons (EYH) program in Ithaca, New York. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.