A combined pollen and δ18OSphagnum record of mid-Holocene climate variability from Dürres Maar (Eifel, Germany)

Abstract

In this study we investigate pollen and oxygen isotopes of moss cellulose from the peat bog ‘Dürres Maar’ in the Eifel low mountain range, Germany (450 m a.s.l.) to quantitatively infer mid-Holocene climate change for the period between ~7000 and 3800 cal. BP. Pollen was analysed on the same samples from which Sphagnum leaves were isolated to extract cellulose for the determination of its oxygen isotope composition (δ18O Sphagnum). To quantitatively estimate January and July temperature and annual precipitation from the pollen data, we applied a probabilistic indicator taxa method (‘pdf-method’). The pollen-based reconstructions indicate July temperatures ~1°C higher around 6000 cal. BP than after ~5500 cal. BP, which is consistent with a ~1‰ decrease in δ18O Sphagnum during the same period. While the pollen-based climate reconstructions indicate little variability in summer temperature after ~5500 cal. BP, winter temperature shows several pronounced cold excursions of ~2–4°C in this period, which was likely accompanied by changes in precipitation patterns. Test reconstructions leaving out specific taxa indicate that not only larger climate trends, but also relatively small-scale climate variability can robustly be reconstructed with the pdf-method. This is of particular importance for reliable reconstructions of climate variability not only during the Holocene, but also in former interglacials, for which archives are rare and pollen is often the only suitable proxy in terrestrial records. The stable isotope values agree with the reconstructions based on pollen for the time between ~4500 and 3500 cal. BP, but not for the period before 4500 cal. BP. We explain this difference by atmospheric circulation patterns being different in the mid and late Holocene, respectively.