SignificanceA causality between millennial-scale climate cycles and the replacement of Neanderthals by modern humans in Europe has tentatively been suggested. However, that replacement was diachronous and occurred over several such cycles. A poorly constrained continental paleoclimate framework has hindered identification of any inherent causality. Speleothems from the Carpathians reveal that, between 44,000 and 40,000 years ago, a sequence of stadials with severely cold and arid conditions caused successive regional Neanderthal depopulation intervals across Europe and facilitated staggered repopulation by modern humans. Repetitive depopulation–repopulation cycles may have facilitated multiple genetic turnover in Europe between 44,000 and 34,000 years ago.

Abstract.Here we present a speleothem isotope record (POM2) from Ascunsȃ Cave (Romania) that provides new data on past climate changes in the Carpathian-Balkan region from 8.2 ka until the present. This paper describes an approach to constrain the effect of temperature changes on calcite δ 18 O values in stalagmite POM2 over the course of the middle Holocene (6-4 ka), and across the 8.2 and 3.2 ka rapid climate change events. Independent pollen temperature reconstructions are used to this purpose. The approach combines the temperature-dependent isotope fractionation of rain water during condensation and fractionation resulting from calcite precipitation at the given cave temperature. The only prior assumptions are that pollen-derived average annual temperature reflects average cave temperature, and that pollen-derived coldest and warmest month temperatures reflect the range of condensation temperatures of rain above the cave site. This approach constrains a range of values between which speleothem δ 18 O changes should be found if controlled only by surface temperature variations at the cave site. Deviations of the change in δ 18 O c_spel values from the calculated temperature-constrained range of change are interpreted towards large-scale variability of climate-hydrology.Following this approach, we show that an additional ∼ 0.6 ‰ enrichment of δ 18 O c in the POM2 stalagmite was caused by changing hydrological patterns in SW Romania across the middle Holocene, most likely comprising local evaporation from the soil and an increase in Mediterranean moisture δ 18 O. Further, by extending the calculations to other speleothem records from around the entire Mediterranean basin, it appears that all eastern Mediterranean speleothems recorded a similar isotopic enrichment due to changing hydrology, whereas all changes recorded in speleothems from the western Mediterranean are fully explained by temperature variation alone. This highlights a different hydrological evolution between the two sides of the Mediterranean.Our results also demonstrate that during the 8.2 ka event, POM2 stable isotope data essentially fit the temperatureconstrained isotopic variability. In the case of the 3.2 ka event, an additional climate-related hydrological factor is more evident. This implies a different rainfall pattern in the Southern Carpathian region during this event at the end of the Bronze Age.Published by Copernicus Publications on behalf of the European Geosciences Union.