1300 years of climate variability in the northeastern Mediterranean from multiple tree-ring proxies of ancient Pinus heldreichii on Mt. Smolikas (northern Greece)
Principle Investigators
Jan Esper, Department of Geography, Johannes Gutenberg University Mainz (JGU)
Frank Keppler, Institute of Earth Sciences, Heidelberg University (HU)
PhD students
Philipp Römer, Department of Geography, Johannes Gutenberg University Mainz (JGU)
Anna Wieland, Institute of Earth Sciences, Heidelberg University (HU)
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Observational data and climate models predict the Mediterranean region to experience increasing drought risks over the 21st century, with negative impacts on 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, however, is severely constrained by the limited number of annually resolved reconstructions extending back over the past 1000+ years. One of the few Mediterranean sites to provide such reconstructions is the treeline ecotone at Mt. Smolikas (~2000 m asl) in northern Greece, where some of the oldest trees in Europe grow and the combination of living and relict wood samples enabled the development of a continuous tree-ring chronology extending back to the 5th century CE.
Tree-ring width (TRW) and maximum latewood density (MXD) measurements on ~400 living and relict Bosnian pines (Pinus heldreichii) allowed the establishment of a tree-ring chronology dating back to 468 CE, which represents the longest and (in the first centuries) best replicated timeseries from a high-elevation Mediterranean site. The TRW measurements have been used to reconstruct hydroclimate variability, while the MXD measurements permitted the development of late-summer temperature reconstructions back to 730 CE. However, the TRW- and MXD-based climate reconstructions, lack substantial low-frequency information due to the required detrending and pre-whitening procedures.
By measuring the stable (carbon, oxygen and hydrogen) isotopic composition of cellulose and lignin methoxy groups, and wood anatomical features at annual and intra-annual resolution, this projects aims to improve our understanding of past Eastern Mediterranean temperature and hydroclimate variability. Cross-comparison of the proxies will support the differentiation between complementary and redundant climatic information and will improve our understanding of the frequency and magnitude of climatic extremes, as well as long-term climatic changes over the past 1300 years. The 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.
Picture 1: Ancient Bosnian Pines at Mt. Smolikas.
Picture 2: Fieldwork 2021 - Extracting increment cores from a living tree.
Picture 3: Fieldwork 2021 – Relict pine stems at Mt. Smolikas.