1300 years of climate variability in the northeastern Mediterranean from multiple tree-ring proxies of ancient Pinus heldreichii on Mt. Smolikas (northern Greece)

• Applicants: Professor Dr. Jan Esper; Professor Dr. Frank Keppler
• Subject Area: Physical Geography
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 428565501

Observational data and climate models indicate the Mediterranean region to experience increasing drought risks, which will adversely impact regional ecology, economy, and human well-being. Our ability to place these dynamics into a long-term context, and to relate current climate variability with pre-instrumental changes and extremes, including the naturally forced Medieval Warm Period, is constrained by the limited number of annually resolved reconstructions extending back over the past 1000+ years, however. One of the few Mediterranean sites to provide such reconstructions is the tree-line ecotone at Mt. Smolikas in northern Greece, where some of the oldest trees in Europe grow, and where the combination of samples from living trees with dead wood on the ground enabled the development of a chronology extending back to the 6th century CE.Here, we apply for funding to explore the full paleoclimatic potential of these ancient Pinus heldreichii trees by combining the work forces of two groups specialized in stable isotope analyses and climate reconstructions from tree-ring proxies. One PhD student will be based in Heidelberg in the group of Frank Keppler to produce d2H and d13C chronologies from lignin methoxyl groups reaching back over the past 1300 years. These will be the longest such proxy records developed so far. A second PhD student will be based in Mainz in the group of Jan Esper to produce chronologies of d18O from wood cellulose as well as cell lumen and cell wall metrics over the same time period.The combination and joint interpretation of these proxies will provide insight into the (i) climate during the Medieval Warm Period in the northeastern Mediterranean, (ii) importance of drought events and association with temperature fluctuations in this vulnerable region, and (iii) magnitude and frequency of climatic extremes back into the first millennium CE. We particularly expect new evidence from the assessment of co-variance among the proxies to reconstruct short-to-long term hydroclimate and radiative (cloud cover and sunshine) variability. Evidence from these new proxies will be combined with reconstructions of regional summer temperature variability derived from maximum latewood density measurements of the same Pinus heldreichii trees. Outcome from this project will be beneficial to climate modelers studying the forcing of natural climate variability, historians evaluating the vulnerability of Mediterranean societies to climate extremes, ecologists analyzing biocenosis sensitivity on longer timescales, and paleoclimatologists accessing spatial patterns of climate variability at European to hemispheric scales.

• DFG Programme: Research Grants