A paleoprecipitation and paleotemperature reconstruction of the Last Interglacial in the southeastern Alps

The Last Interglacial (LIG, ∼130-116ka) was one of the warmest interglacials of the past 800000 years and an important test bed for future climate conditions warmer than today. LIG temperature reconstructions from marine records and paleoclimate models show that middle and high northern latitudes were considerably warmer (by about 2 to 5°C) compared to today. In central Europe, the LIG has been widely studied using pollen and more recently chironomids preserved in lake sediments. While these bio-archives document temperature changes across the LIG, they are commonly poorly constrained chronologically. Speleothems and fluid inclusions contained therein offer superior age control and provide information on past climate, including qualitative and partly also quantitative records of temperature and precipitation. Here, we present a precisely dated fluid-inclusion record based on seven speleothems from two caves in the southeastern Alps (Obir and Katerloch) and use a δ2H/T transfer function to reconstruct regional LIG temperatures. We report a temperature change across the glacial-interglacial transition of 5.2±3.1°C and peak temperatures at ∼127ka of 2.4±2.8°C above today's mean (1973-2002). The fluid-inclusion δ2H record of these speleothems exhibits millennial-scale events during the LIG that are not well expressed in the δ18Ocalcite. The early LIG in the southeastern Alps was marked by an important climate instability followed by progressively more stable conditions. Our record suggests that the southeastern Alps predominantly received Atlantic-derived moisture during the early and middle LIG, while more Mediterranean moisture reached the study site at the end of the LIG, buffering the speleothem δ18Ocalcite signal. The return towards colder conditions is marked by an increase in δ13C starting at ∼118ka, indicating a decline in the vegetation and soil activity.