Insights into the Nature of Climate Variability During the Last Interglacial: A High-Resolution Multi-Proxy Record from the Fucino Basin, Central Italy.

Environmental reconstructions of the Last Interglacial (LIG, 129-116 ka) can enhance knowledge of natural climate variability under conditions of excess warmth. The LIG was characterised by a global mean temperature ~1˚C warmer than the pre-industrial era, pronounced Arctic warming, and elevated sea level (~6-9 m above present). The climate system response to a warmer background state can be explored through regional vegetation dynamics using combined pollen, charcoal, and stable isotope analyses. However, a lack of high-resolution palaeoclimatic archives employing a precise, independent, and robust chronological framework remains a primary limitation in investigating LIG climate variability and relating it to changes in other records.

Here, we present detailed palynological, charcoal, and isotope analyses of a thick lacustrine sedimentary sequence retrieved from the Fucino Basin, central Italy, covering the period from 139 to 107 ka. This key archive benefits from being very highly resolved with an independent chronology based on direct 40Ar/39Ar dating and geochemical fingerprinting of several tephra layers. Pollen and charcoal analyses were conducted at 4 cm intervals representing a sampling resolution of ~80-100 years, while stable isotopic analyses (δ18O and δ13C) were undertaken on lake carbonates every ~8 cm with an average resolution of ~180 years.

The detailed pollen sequence captures a vegetation succession reflecting several climatic phases throughout the LIG at the Fucino Basin. Interrupting this succession are a series of centennial- to millennial-scale contractions in temperate vegetation. The comparison between δ18O records from the Fucino Basin and an Italian stalagmite (Corchia Cave) suggests a strong hydrological contrast between summer evaporation and winter precipitation during the early LIG maximum (~129-127 ka). Further δ18O-inferred changes in temperature and moisture availability observed throughout the LIG at the Fucino Basin are concurrent with variations in forest composition and cover, fire activity, and δ13C-inferred terrestrial and aquatic productivity.