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Abstract:
Investigating climatic and environmental changes during past interglacials is crucial to improve our understanding of the mechanisms that govern changes related to current global warming. Among the numerous proxies that can be used to reconstruct past environmental and climatic conditions, pollen allows quantitative reconstructions of annual, warmest month and coldest month air temperatures as well as precipitation sums, and Chironomidae larvae are widely used to infer past summer air temperature. Chironomidae have mostly been used for reconstructing Holocene and Late Weichselian summer temperatures whilst there are only four sites in Europe with chironomid-based summer air temperature reconstructions for the Late Pleistocene and no such records for any Middle Pleistocene warm period as of the writing of this paper. In this study we present the first quantitative palaeoclimate reconstruction for the post-Holsteinian (Marine Isotope Stage – (MIS) 11b) in Central Europe based on both pollen and fossil chironomid remains preserved in palaeolake sediments recovered from Krępa, southeastern Poland. Besides being used for the palaeoclimatic reconstruction, pollen analysis provides the biostratigraphic framework and a broader perspective of climate development at the end of Holsteinian Interglacial. Fossil Chironomidae assemblages at Krępa consist mainly of oligotrophic and mesotrophic taxa (e.g. Corynocera ambigua, Chironomus anthracinus-type) while eutrophic taxa (e.g. Chironomus plumosus-type) are less abundant. The chironomid-based summer temperature reconstruction indicates July air temperatures between 15.3 and 20.1 °C during the early post-Holsteinian, while pollen-based temperature reconstructions (using MAT and WA-PLS methods) indicate temperature values from 15 to 19 °C. Pollen-derived mean temperature of the coldest month (MTCO) and mean annual precipitation sum vary from −13.2 to −9.6 °C and between 500 and 900 mm respectively. In any case, results from Krępa prove that conducting Chironomidae analysis is feasible for periods as early as the Middle Pleistocene, improving our understanding of the mechanisms that control present-day climatic and environmental changes.
